Vehicle collision anticipating method and device

• US 4,143,370 A
• Filed: 06/24/1977
• Issued: 03/06/1979
• Est. Priority Date: 05/20/1972
• Status: Expired due to Term

• Current Assignee: Toyooki Kogyo Kabushiki Kaisha, Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Toyooki Kogyo Kabushiki Kaisha, Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Sato, Kazuo, Kato, Takayuki, Ozeki, Osamu, Bito, Minoru, Yamanaka, Teruo
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US05/809,878
• Time in Patent Office: 620 Days
• Field of Search: 343/9, 343/7 VM, 343/112 CA
• US Class Current: 342/72
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/932 using own vehicle data, e.g. ground speed, steering wheel direction
• CPC Class Codes: G01S 2013/93271 in the front of the vehicles

Abstract

An improvement of a vehicle collision anticipating method and device using transmitted and reflected frequency-modulated continuous waves is provided. A low frequency wave is produced by mixing a part of transmitted wave and a reflected wave from the object. The low frequency wave and a Doppler signal obtained from the low frequency wave are signal processed so as to generate signals. A predetermined distance range is obtained by multiplying a time which is determined by the distance between the vehicle and object and the velocity of said object with respect to the vehicle obtained from the Doppler signal, by a relative velocity of the object with respect to the vehicle. A collision of the object against the vehicle is anticipated by detecting the object entering the predetermined distance range in front of the vehicle.

Claims

1. A vehicle collision anticipating method comprising establishing a predetermined distance range S in front of said vehicle, S representing a time, which is the ratio of the distance R of said object from said vehicle to the apparent velocity v_r of said object as viewed from said vehicle, multiplied by the real relative velicity v which is the magnitude of the relative velocity vector of the object with respect to the vehicle (vR/v_r),

transmitting a wave to an object,

receiving a wave reflected from said object,

generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of difference frequencies,

separating said components by frequency-responsive means,

obtaining the distance R from the ratio of the amplitude of said first component to that of said second component

determining the Doppler angular velocity from said low frequency wave,

determining from said Doppler angular velocity the apparent velocity v_r,

determining v from said Doppler signal components when R is sufficiently large so that v_r and v are substantially equal, and

detecting the object entering said predetermined distance range in front of the vehicle by comparing S with a distance obtained as the object approaches said vehicle by taking a time which is the ratio of the determined R to the determined v_r and multiplying said time by the determined v,

thereby anticipating a collision of the object against the vehicle.

2. A vehicle collision anticipating method comprising establishing a predetermined distance range S in front of said vehicle, S representing a time, which is the ratio of the distance R of said object from said vehicle to the apparent velocity v_r of said object as viewed from said vehicle, multiplied by the real relative velocity v which is the magnitude of the relative velocity vector of the object with respect to the vehicle (vR/v_r),

transmitting a wave to an object,

receiving a wave reflected from said object,

generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

separating said components by frequency-responsive means,

obtaining the distance R from the ratio of the amplitude of said first component to that of said second component,

determining the Doppler angular velocity from said low frequency wave,

determining from said Doppler angular velocity the apparent velocity v_r,

determining from said Doppler signal the real relative velocity v, and

detecting the object entering said predetermined distance range in front of the vehicle by detecting a value representative of vR/v_r using said determined v, R and v_r,

thereby anticipating a collision of the object against the vehicle.

3. The vehicle collision anticipating method of claim 2, wherein the real relative velocity v is the relative vector velocity equal to the sum of the velocity vector of the object and the negative of the velocity vector of the vehicle.

4. The vehicle collision anticipating method of claim 2, further comprising the step of activating a protective device when a collision of the object against the vehicle is anticipated.

5. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on a vehicle, and for generating a low frequency wave by mixing said transmitted and reflected, waves said low frequency wave containing a Doppler signal having first and second components of different frequencies,

frequency-responsive means for separating said Doppler signal components,

means for determining the distance R of said object from said vehicle from the ratio of the amplitude of said first component to said second component,

means for determining the Doppler angular velocity of said low frequency wave,

means for determining from said Doppler angular velocity the apparent velocity v_r of said object with respect to said vehicle,

means for substantially determining from said Doppler signal components the real relative velocity v of the object at a predetermined distance from the vehicle, said real relative velocity being taken as said apparent velocity at said predetermined distance, said real relative velocity being the magnitude of the relative velocity vector of the object with respect to the vehicle, and

collision state decision means including means for setting a predetermined distance range S in front of said vehicle, said range S being represented by the expression vR/v_r, where R/v_r has the dimension of time, and means for determining when said object is entering said predetermined distance range S in front of said vehicle from the expression vR/v_r, using the determined values v, R and v₄,

thereby anticipating a collision of the object against the vehicle.

6. A vehicle collision anticipating method comprising establishing a predetermined distance range S in front of said vehicle, S representing a time, which is the ratio of the distance R of said object from said vehicle to the apparent velocity v_r of said object as viewed from said vehicle, multiplied by the real relative velocity v which is the magnitude of the relative velocity vector of the object with respect to the vehicle (vR/v_r),

transmitting a wave to an object,

receiving a wave reflected from said object,

generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

separating said components by frequency-responsive means,

obtaining the distance R from the ratio of the amplitude of said first component to that of said second component,

determining the Doppler angular velocity from said low frequency wave,

determining from said Doppler angular velocity the apparent velocity v_r,

determining the real relative velocity v of said object with respect to said vehicle from said Doppler signal at a distance where v_r is substantially independent of the approach angle between said object and said vehicle,

detecting the object entering said predetermined distance range in front of the vehicle from substantially the expression vR/v_r, using said determined v, R and v_r,

thereby anticipating a collision of the object against the vehicle.

7. A vehicle collision anticipating method comprising establishing a predetermined distance range S in front of said vehicle, S representing a time, which is the ratio of the distance R of said object from said vehicle to the apparent velocity v_r of said object as viewed from said vehicle, multiplied by the real relative velocity v which is the magnitude of the relative velocity vector of the object with respect to the vehicle (vR/v_r),

transmitting a wave to an object,

receiving a wave reflected from said object,

generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

separating said components by frequency-responsive means,

obtaining the instantaneous distance R from said vehicle from the ratio of the amplitude of said first component to that of said second component,

determining the Doppler angular velocity from said low frequency wave,

determining from said Doppler angular velocity an apparent velocity v_r between said object and said vehicle at each said distance R,

determining from said Doppler angular velocity the real velocity v of the object with respect to the vehicle at a predetermined distance from the vehicle at which the apparent velocity v_r is substantially independent of the approach angle between said object and said vehicle by setting v as the apparent velocity v_r substantially at said predetermined distance, and

detecting the object entering said predetermined distance range in front of the vehicle by continuously comparing S with a distance obtained as the object approaches the vehicle by taking a series of times which are each the ratios of the determined instantaneous R to the determined instantaneous v_r and multiplying each such time by the determined set v,

thereby anticipating a collision of the object against the vehicle.

60. The vehicle collision anticipating method of claim 7, wherein said predetermined distance from said vehicle is at least two times the width of said vehicle.

8. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on the vehicle, and for generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

frequency-responsive means for separating said Doppler signal components,

means for determining the instantaneous distance R of said object from said vehicle from the ratio of the amplitude of said first component to that of said second component,

means for determining the Doppler angular velocity of said low frequency waves,

means for determining from said Doppler angular velocity the instantaneous apparent velocity v_r of said object with respect to said vehicle,

means for substantially determining from said Doppler signal a real relative velocity v, which is the magnitude of the relative velocity vector of the object with respect to the vehicle, by setting v at a value of v_r selected to be substantially independent of the approach angle between said object and said vehicle, and

collision state decision means including means for setting a predetermined distance range S in front of the vehicle represented by the expression vR/v_r where said distance range S is dependent on the approach angle between said object and said vehicle and is independent of the determined values of v and v_r, and means for detecting the object entering said predetermined distance range in front of said vehicle by detecting values representative of vR/v_r using said determined v, R and v_r.

9. A vehicle collision anticipation method comprising

establishing a predetermined distance range S in front of said vehicle, S representing a time, which is the ratio of the distance R of said object from said vehicle to the apparent velocity v_r of said object as viewed from said vehicle, multiplied by the real relative velocity v which is the magnitude of the relative velocity vector along the absolute direction of movement of said object between said object and the line normal to the absolute direction of movement of said object which passes through said vehicle (vR/v_r), whereby S is dependent on the approach angle of said object to said vehicle and independent of the real relative velocity therebetween,

transmitting a wave to an object,

receiving a wave reflected from said object,

generating a low frequency wave by mixing said transmitted and reflected wave, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

separating said components by frequency-responsive means,

obtaining the instantaneous distance R from the ratio of the amplitude of said first component to that of said second component,

determining the Doppler angular velocity from said low frequency wave,

determining from said Doppler angular velocity the instantaneous apparent velocity v_r,

determining v from said Doppler signal, and

detecting an object entering said predetermined distance range S in front of said vehicle by detecting values representative of vR/v_r using said determined v, R and v_r,

thereby anticipating a collision of the object against the vehicle.

10. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on the vehicle, and for generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

frequency-responsive means for separating said Doppler signal components,

means for determining the instantaneous distance R of said object from said vehicle from the ratio of the amplitude of said first component to that of said second component,

means for determining the Doppler angular velocity of said low frequency wave,

means for determining from said Doppler angular velocity an instantaneous apparent velocity v_r of said object with respect to said vehicle,

means for dividing each said determined R by a corresponding determined v_r,

means for determining a real relative velocity v which is the magnitude of a relative velocity vector along the absolute direction of movement of the object between the object and the line normal to the absolute direction of movement of the object which passes through the vehicle,

means for multiplying each result of said division by said determined v, and

collision state decision means including means for establishing a predetermined distance range S representing the expression vR/v_r, S being dependent on the approach angle between said object and said vehicle and independent of relative velocity therebetween, and

means for detecting the object entering said predetermined range S from a series of results from said multiplication.

11. A vehicle collision anticipating method comprising establishing a predetermined distance range S in front of said vehicle at each of first and second spaced points thereon, S representing a time, which is the ratio of the distance R of said object from said vehicle at said point to the apparent velocity v_r of said object as viewed from said vehicle at said point, multiplied by the real relative velocity v which is the magnitude of the relative velocity vector of the object with respect to said vehicle (vR/v_r),

transmitting first and second waves from said spaced points respectively to an object,

receiving first and second waves reflected from said object at said first and second points respectively,

generating first and second low frequency waves by mixing said transmitted and reflected first waves and mixing said transmitted and reflected second waves respectively, said first and second low frequency waves each containing a Doppler signal having first and second components of different frequencies,

separating said components by frequency responsive means,

obtaining the distance R from the ratio of the amplitude of the first component of each Doppler signal to that of the second component thereof,

determining first and second Doppler angular velocities from said first and second low frequency waves,

determining from said first and second Doppler angular velocities the respective first and second apparent velocities v_r,

determining from said Doppler signals the real relative velocity v, and

detecting the object entering each of said predetermined distance ranges in front of the vehicle by detecting a value for each predetermined distance range representative of vR/v_r using said determined v, R and v_r associated with each,

thereby anticipating a collision of the object against the vehicle.

12. A vehicle collision anticipating method comprising establishing a predetermined distance range S in front of said vehicle, S representing a distance from a location on said vehicle represented by the relationship R'"'"'/cos θ

'"'"' = C₂, where C₂ is a constant, R'"'"' is the distance from said location on said vehicle to the periphery of said predetermined distance range at each point on said periphery, and θ

'"'"' is the approach angle of the object relative to the vehicle at each point of said periphery corresponding to R'"'"',

transmitting a wave to an object,

receiving a wave reflected from said object,

generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency waves containing a Doppler signal,

determining the instantaneous distance R between said location on the vehicle and said object from said Doppler signal,

determining a value substantially representation of the instantaneous cos θ

where θ

is the actual approach angle of the object relative to the vehicle, and

detecting the object entering said predetermined distance range in front of the vehicle by detecting a value representative of R/cos θ

using said determined R and cos θ

,

thereby anticipating a collision of the object against the vehicle.

13. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on the vehicle, and for generating a low frequency wave by mixing said transmitting and reflected waves, said low frequency wave containing a Doppler signal,

means for determining the instantaneous distance R of said object from said vehicle from said Doppler signal,

means for determining a value substantially representative of cos θ

, where θ

is the instantaneous approach angle of the object relative to the vehicle, and

collision state decision means including means for setting a predetermined distance range S in front of said vehicle, range S being represented by the expression C₂ = R'"'"'/cos θ

'"'"', where C₂ is a constant, R'"'"' is the distance from said receiving antenna on said vehicle to each point on the periphery of said predetermined distance range and θ

'"'"' is the approach angle of the object relative to the vehicle at each point on the periphery of the predetermined distance range corresponding to R'"'"', and means for determining when said object is entering said predetermined distance range S in front of said vehicle from the expression R/cos θ

using the instantaneous determined values of R and cos θ

,

thereby anticipating a collision of the object against the vehicle.

14. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on a vehicle, and for generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

frequency-responsive means for separating said Doppler signal components,

means for determining the instantaneous distance R of said object from said vehicle from the ratio of the amplitude of said first component to that of said second component,

means for determining the Doppler angular velocity of said low frequency wave,

means for determining from said Doppler angular velocity the instantaneous apparent velocity v_r of said object with respect to said vehicle which is the relative velocity along the direct line between the object and vehicle,

means for substantially determining the real relative velocity v of the object relative to said vehicle, which is the magnitude of the relative velocity vector of the object with respect to the vehicle by setting v substantially at the value of v_r at a predetermined distance from said vehicle at which said apparent velocity v_r is substantially independent of the approach angle between said object and said vehicle, and

collision state decision means including means for setting a predetermined distance range S in front of said vehicle represented by the expression vR/v_r and means for continuously dividing the instantaneous determined R by the corresponding instantaneous determined v_r and multiplying each result by the set determined v to detect said object entering said predetermined distance range S,

thereby anticipating a collision of the object against the vehicle.

15. The vehicle collision anticipating device of claim 14 wherein said wave processing means comprises an osciallator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means.

16. The vehicle collision anticipating device of claim 14 further comprising an amplifier connected to receive said low frequency wave, a first bandpass filter and a high pass filter connected to the output of said amplifier, a source of oscillations, a mixer connected to said source of oscillation and said high pass filter, a second bandpass filter connected to the output of said mixer, and first and second AC-DC converters connected to the outputs of said first and second bandpass filters respectively.

17. The vehicle collision anticipating device of claim 16 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, wherein said signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second high pass filter connected to the output of said mixer, a first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively, and wherein said collision state decision means comprises a first divider connected to receive said first and second analog signals, a first frequency to voltage converter connected to receive one of said Doppler signals, a second divider connected to receive the outputs of said first divider and first voltage to frequency converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signals, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said second frequency to voltage converter, and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the outputs of said multiplier with said second reference potential to produce an output signal.

18. The vehicle collision anticipating device of claim 14, wherein said predetermined distance is at least two times the width of said vehicle.

19. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on a vehicle, and for generating a low frquency wave by mixing said transmitted and reflected waves,

analog signal processing means for signal processing said low frequency to provide first and second Doppler signal components and first and second analog signals corresponding respectively, to said first and second Doppler signal components, and

collision state decision means for setting a predetermined distance range S in front of the vehicle by processing said signals, said predetermined distance range being represented by the relation vR/v_r, where v is the magnitude of the relative velocity vector of the object with respect to the vehicle denoted the real relative velocity, R is the distance between the vehicle and object and v_r is the apparent velocity, of the object relative to the vehicle as seen from the vehicle, for determining the instantaneous distance R from the ratio of said first and second analog signals, for determining the Doppler angular velocity of said Doppler signal components and the instantaneous apparent velocity v_r therefrom, for setting v as the value of v_r at a predetermined distance of said object from said vehicle, and for detecting the object entering said predetermined distance range in front of the vehicle substantially from the expression vR/v_r using the determined values of R and v_r and the set value of v to produce an output signal in response to such entering,

thereby anticipating a collision of the object against the vehicle.

20. The vehicle collision anticipating device of claim 19 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means.

21. The vehicle collision anticipating device of claim 19 wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second bandpass filter connected to the output of said mixer, and first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and said first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively.

22. The vehicle collision anticipating device of claim 21 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, wherein said signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled tp the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second high pass filter connected to the output of said mixer, a first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively, and wherein said collision state decision means comprises a first divider, connected to receive said first and second analog signal components, a first frequency to voltage converter connected to receive one of said Doppler signal components, a second divider connected to receive the outputs of said first divider and first voltage to frequency converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signal components, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said second frequency to voltage converter, and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the outputs of said multiplier with said second reference potential to produce an output signal.

23. The vehicle collision anticipating device of claim 19, wherein said collision state decision means comprises a first divider connected to receive said first and second analog signals, a first frequency to voltage converter connected to receive one of said Doppler signal components, a second divider connected to receive the outputs of said first divider and first frequency to voltage converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signal components, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said second frequency to voltage converter and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the output of said multiplier with said second reference potential to produce an output signal.

24. The vehicle collision anticipating device of claim 23 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frquency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, and wherein said signal processing means comprises an amplifier connected to receive said low frequency wave, a first bandpass filter and a high pass filter connected to the output of said amplifier, a source of oscillations, a mixer connected to said source of oscillations and said high pass filter, a second bandpass filter connected to the output of said mixer, and first and second AC-DC converters connected to the output of said first and second bandpass filters respectively.

25. The vehicle collision anticipating device of claim 19, wherein said collision state decision means comprises a low pass filter coupled to receive one of said Doppler signal components, an AC-DC converter coupled to the output of said low pass filter, comparing means connected to compare the ratio of said first and second analog signals with a reference voltage, multiplier means coupled to multiply one of said output signals with a voltage inversely proportional to the velocity of a detected object at a determined distance from said device upon detection of a comparison in said first comparator, and a second comparator coupled to compare the output of said AC-DC converter with the output of said multiplier means to produce an output voltage.

26. The vehicle collision anticipating device of claim 25 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, and wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first band pass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillations and said high pass filter, a second bandpass filter connected to the output of said mixer, and first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and said first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively.

27. The vehicle collision anticipating device of claim 19 wherein said collision state decision means comprises a high pass filter coupled to receive one of said Doppler signal component, an AC-DC converter connected to the output of said high pass filter, a first comparator for comparing the ratio of said first and second analog signals with a reference potential, multiplier means connected to multiply the output of said AC-DC converter with a voltage inversely proportional to the velocity of an object at a determined distance from said device when a comparison is detected in said first comparator, and a second comparator connected to compare the output of said multiplier means with one of said analog signals to produce an output voltage.

28. The vehicle collision anticipating device of claim 27 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, and wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first band pass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillations and said high pass filter, a second bandpass filter connected to the output of said mixer, and first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and said first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively.

29. The vehicle collision anticipating device of claim 19 in which said analog signal processing means further comprises means providing a third analog signal component corresponding to said first Doppler signal, and wherein said collision state decision means comprises a first multiplier connected to multiply said first analog voltage with a voltage proportinal to the inverse of the velocity of an object at a determined distance from said device, first, second and third coefficient multiplying means connected to receive the output of said multiplier, and said third and second analog signals respectively, adding means coupled to add the output of said first and second coefficient multiplying means, and a comparator connected to compare the output of said adding means with the output of said third coefficient multiplier means to produce an output signal.

30. The vehicle collision anticipating device of claim 29 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, and wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first band pass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a first low pass filter coupled to the output of said mixer, a second low pass filter coupled to the output of said first bandpass filter, and first, second and third AC-DC converters connected respectively to the output of said first band pass filter, said second low pass filter and said first low pass filter, whereby said first and second Doppler signal components are derivable from the outputs of said first band pass filter and first low pass filter respectively, said first and second analog signals are derivable from the outputs of said first and third AC-DC converters respectively, and said third analog signal is derivable from the output of said second AC-DC converter.

31. The vehicle collision anticipating device of claim 29 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, and wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first band pass filter and a first high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillations and said first high pass filter, a second high pass filter coupled to the output of said first bandpass filter, a second bandpass filter coupled to the output of said mixer, and first, second and third AC-DC converters coupled respectively to the output of said second high pass filter, said first bandpass filter and said second bandpass filter, whereby said first and second Doppler signal components are derivable from the outputs of said second high pass filter and said second bandpass filter, said first and second analog signals are derivable from the outputs of said first and third AC-DC converters respectively, and said third analog signal is derivable from the output of said second AC-DC converter.

32. The vehicle collision anticipating device of claim 19 further comprising a direction detecting means for detecting the direction of relative movement of the object with respect to the vehicle and for generating a signal when the object approaches the vehicle, and decision means for generating a signal when said, collision state decision means and direction detecting means simultaneously produce output signals, said direction detecting means comprising a D-type flip-flop, means applying said first and second Doppler signal components to the clock and D-input terminals of said flip-flop respectively, an integrator circuit connected to the output of said flip-flop, a comparator havinhg a first input connected to the output of said integrator, and a reference voltage source connected to the other input terminal of said comparator, said decision unit comprising an AND circuit having a first input connected to the output of said collision state decision means and a second input connected to the output of said comparator.

33. The vehicle collision anticipating device of claim 32 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said freqeuncy modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second high pass filter connected to the output of said mixer, a first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and said first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively, and wherein said collision state decision means comprises a first divider connected to receive said first and second analog signals, a first frequency to voltage converter connected to receive one of said Doppler signals, a second divider connected to receive the outputs of said first divider and first voltage to frequency converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signals, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said second frequency to voltage converter, and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the outputs of said multiplier with said second reference potential to produce an output signal.

34. A vehicle collision anticipating device comprising wave processing means for transmitting a wave by a transmitting antenna installed at a predetermined position on a vehicle, for receiving a reflected wave from the object by a receiving antenna installed at a predetermined position on the vehicle, and for generating a low frequency wave by mixing said transmitted and reflected waves, said low frequency wave containing a Doppler signal having first and second components of different frequencies,

signal processing means including frequency-responsive means for separating said Doppler signal components, means for determining the distance R of said object from said vehicle from the ratio of the amplitude of said first component to that of said second component, means for determining the Doppler angular velocity of said low frequency wave, means for determining from said Doppler angular velocity the apparent velocity v_r of said object with respect to said vehicle, and means for substantially determining from said Doppler signal the magnitude v of the real relative velocity of said object with respect to said vehicle which is the magnitude of the relative velocity vector of the object with respect to the vehicle, and

collision state decision means including means for setting a predetermined distance range S in front of said vehicle, range S being represented by the expression vR/v_r, where R/v_r has the dimension of time, and means for determining when said object is entering said predetermined distance range S in front of said vehicle from the expression vR/v_r using the determined values of v, R and v_r and for producing a signal respresentative of such entering,

thereby anticipating a collision of the object against the vehicle.

35. A vehicle collision anticipating device as set forth in claim 34, further comprising

direction detecting means for detecting a direction of a relative movement of the object with respect to the vehicle, and for generating a signal when the object approaches the vehicle, and

decision means for generating a signal when said collision state decision means and direction detecting means simultaneously generate their respective signals.

36. A vehicle collision anticipating device as set forth in claim 34, further comprising

minimum level detecting means for detecting an intensity of a Doppler signal obtained from said low frequency wave so as to detect the object entering a predetermined minimum intensity range determined by positions and angles of the transmitting and receiving antennas installed on the vehicle, and for generating a signal when said intensity reaches a predetermined minimum level, and

decision means for generating a signal when said collision state decision means and minimum level detecting means simultaneously generate their respective signals.

37. The vehicle collision anticipating device of claim 34, wherein the real relative velocity v is the relative vector velocity equal to the sum of the velocity vector of the object and the negative of the velocity vector of the vehicle.

38. The vehicle collision anticipating device of claim 34, further comprising a protective device activatable by a signal from said collision state decision means when a collision of the object against the vehicle is anticipated.

39. The vehicle collision anticipating device of claim 34, wherein said means for determining v is a means for measuring v_r at a distance between said object and said vehicle great enough so that v is essentially equal to v_r.

40. The vehicle collision anticipating device of claim 34, wherein said means for determining v includes means for establishing a predetermined Doppler signal intensity value, and

means for storing the maximum value of said Doppler signal intensity commensing when said Doppler intensity reaches said predetermined intensity value, the maximum stored value of v_r being taken as v.

41. A vehicle collision anticipating device as set forth in claim 34, further comprising

relative velocity detecting means for generating a signal when said apparent velocity of the object reaches a predetermined level, and

decision means for generating a signal when said collision state decision means and relative velocity detecting means simultaneously generate their respective signals.

42. A vehicle collision forecasting device as set forth in claim 41, wherein

said relative velocity detecting means comprises

a frequency-voltage converter,

a potentiometer for setting a reference voltage to determine said predetermined apparent velocity level, and

a comparator, and

said decision means comprises

an AND circuit for generating a signal when said collision state decision means and said relative velocity detecting means simultaneously generate each signal.

43. A vehicle collision anticipating device as set forth in claim 34, further comprising

means for determining the ground speed V of said vehicle,

means for determining the intensity of said Doppler signal,

protecting means for detecting a relative characteristic of vehicle and object selected from the group including the apparent velocity of the vehicle relative to the object, the position of the vehicle relative to the object and the intensity of a Doppler signal, weighting said selected characteristic by said ground speed V and generating a signal when said weighted characteristic reaches a predetermined value, and

decision means for generating a signal when said collision state decision means and protecting means simultaneously generate their respective signals.

44. The vehicle collision anticipating device of claim 43 wherein said protecting means comprises a relative velocity detecting unit and a ground speed detecting unit, said relative velocity detecting unit comprising a first voltage to frequency converter, and said ground speed detecting unit comprising an electromagnetic pickup for producing a signal corresponding to the ground speed of said device, a second frequency to voltage converter coupled to said electromagnetic pickup, first and second reference voltage sources, first and second voltage generators for producing voltages of different amplitude, a first comparator for comparing the output of said second frequency to voltage converter with said first reference voltage, a NOT circuit, first and second gate circuits having input terminals coupled to receive the outputs of said first and second voltage generators respectively, and control terminals coupled to said first comparator and said NOT circuit respectively, a multiplier having a first input terminal coupled to said first frequency to voltage converter and a second input terminal coupled to the outputs of said first and second gate circuits, and a second comparator coupled to compare the outputs of said multiplier and said second reference voltage source, and said decision means comprising an AND circuit coupled to said collision state decision means and said second comparator for providing an output when each of said collision state decision means and second comparator generates an output signal.

45. The vehicle collision anticipating device of claim 44 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, wherein said analog signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second high pass filter connected to the output of said mixer, a first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and said first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively, and wherein said collision state decision means comprises a first divider connected to receive said first and second analog signals, a first frequency to voltage converter connected to receive one of said Doppler signal components, a second divider connected to receive the outputs of said first divider and first voltage to frequency converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signal components, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said second frequency to voltage converter, and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the outputs of said multiplier with said second reference potential to produce an output signal.

46. A vehicle collision anticipating device as set forth in claim 34, wherein

said wave processing means comprises at least two wave processing units each of which comprises at least one transmitting antenna installed on the vehicle in transversely spaced apart relation from the other transmitting antenna for transmitting a wave to the object, and at least one receiving antenna installed on the vehicle in transversely spaced apart relation from the other receiving antenna for receiving a reflected wave from the object,

said signal processing means comprising at least two signal processing units for signal processing the low frequency wave from each wave processing unit and the Doppler signal contained in said low frequency wave,

said collision state decision means comprising at least two collision state decision units each connected to a signal processing unit and setting a predetermined distance range S in front of the vehicle and determining when said object is entering the associated predetermined distance range to generate a signal, and further comprising

decision means for generating a signal when said at least two collision state decision units simultaneously generate their respective signals,

thereby anticipating a collision of the object against the vehicle.

47. A vehicle collision anticipating device as set forth in claim 46, further comprising

maximum level detecting means comprising at least two maximum level detecting units, one associated with each wave processing unit designated respectively as the right and left unit, for detecting an intensity of a Doppler signal obtained from said low frequency wave so as to detect the object entering right and left predetermined maximum intensity ranges determined by positions and angles of the right and left transmitting and receiving antennas installed on the vehicle, and for generating a signal when said intensity reaches a predetermined maximum level, and wherein

said decision means generates a signal when said at least two collision state decision units or one of said maximum level detecting units generates a signal.

48. A vehicle collision anticipating device as set forth in claim 47, wherein

each of said maximum level detecting units comprises a comparator and a reference voltage source set to a voltage corresponding to said predetermined maximum intensity level, and

said decision means comprises an OR circuit for generating a signal when said at least two collision state decision units or one of said maximum level detecting units generates a signal.

49. A vehicle collision anticipating device as set forth in claim 46, further comprising

approaching angle detecting means for detecting an approaching angle of the object with respect to the vehicle, and for generating a signal when said approaching angle of the object reaches a predetermined angle, and wherein

said decision means generates a signal when said at least two collision state decision units and approaching angle detecting means simultaneously generate their respective signals.

50. The vehicle collision anticipating device of claim 49 wherein said approaching angle detecting means comprises first and second counters, means applying a Doppler signal component from each said signal processing unit to one of said counters, first and second RS flip-flops connected to the outputs of said first and second counters respectively, an OR circuit having separate inputs connected to the outputs of said first and second counters, an AND circuit having first and second inputs connected to the outputs of said first and second flip-flops respectively, a delay circuit having an input connected to the output of said OR circuit and an output connected to reset said first and second counters, and a D-type flip-flop having a D terminal connected to the output of said AND circuit and a clock terminal connected to the output of said OR circuit, and wherein said decision means comprises means for generating an output signal when said two collision state decision means and said D-type flip-flop simultaneously generate output signals.

51. The vehicle collision anticipating device of claim 50 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, wherein said signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second high pass filter connected to the output of said mixer, a first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal component are derivable from the outputs of said first and second bandpass filters respectively, and first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively, and wherein said collision state decision means comprises a first divider connected to receive said first and second analog signals, a first frequency to voltage converter connected to receive one of said Doppler signal components, a second divider connected to receive the outputs of said first divider and first voltage to frequency converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signal components, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said frequency to voltage converter, and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the outputs of said multiplier with said second reference potential to produce and output signal.

52. A vehicle collision anticipating device as set forth in claim 46, further comprising

maximum level detecting means comprising at least two maximum level detecting units one associated with each wave processing unit designated respectively as right and left units for detecting an intensity of a Doppler signal obtained from said low frequency wave so as to detect the object entering right and left predetermined maximum intensity ranges determined by positions and angles of the right and left transmitting and receiving antennas installed on the vehicle, and for generating a signal when said intensity reaches a predetermined maximum level,

approaching angle detecting means for detecting an approaching angle of the object with respect to the vehicle, and for generating a signal when said approaching angle of the object reaches a predetermined angle,

protecting means including means for detecting a signal representative of the ground speed V of the vehicle and means for detecting a relative characteristic of the vehicle and object selected from the group including the apparent velocity of the vehicle relative to the object, the position of the vehicle relative to the object and the intensity of a Doppler signal, weighting said selected characteristic by said ground speed V and generating a signal when said weighted signal reaches a predetermined value,

direction detecting means for detecting a direction of a relative movement of the object with respect to the vehicle, and for generating a signal when the object approaches the vehicle,

minimum level detecting means for detecting an intensity of a Doppler signal obtained from said low frequency wave so as to detect the object entering a predetermined minimum intensity range determined by positions and angles of the transmitting and receiving antennas installed on the vehicle, and for generating a signal when said intensity reaches a predetermined minimum level, and wherein

said decision means generates a signal when said at least two collision state decision units or one of said maximum level detecting units generates a signal, and said approaching angle detecting means, protecting means, direction detecting means, and minimum level detecting means simultaneously generate their respective signals.

53. A vehicle collision anticipating device as set forth in claim 52, further comprising

relative velocity detecting means for generating a signal when said apparent velocity of the object reaches a predetermined level, and wherein

said decision means generates a signal when said at least two collision state decision units or one of said maximum level detecting units generates a signal, and said approaching angle detecting means, protecting means, direction detecting means, minimum level detecting means and relative velocity detecting means simultaneously generate their respective signals.

54. The vehicle collision anticipating device of claim 52 wherein each of said maximum level detecting units comprises a reference voltage source set to a voltage corresponding to said predetermined maximum intensity level, and comparator means connected to compare the output of said reference voltage source with said Doppler signal obtained from said low frequency wave.

55. The vehicle collision anticipating device of claim 54 wherein said approaching angle detecting means comprises first and second counters each connected to receive a separate Doppler signal component from one of said signal processing units, first and second RS dlip-flops connected to the outputs of said first and second counters respectively, an OR circuit having first and second inputs connected to the outputs of said first and second counters respectively, an AND circuit having first and second inputs connected to the outputs of said first and second flip-flops respectively, delay means connected to reset said first and second counters from the output of said OR circuit, and a D-type flip-flop having a D terminal connected to the output of said AND circuit and a clock terminal connected to the output of said OR circuit.

56. The vehicle collision anticipating device of claim 55 wherein said protecting means comprises a relative velocity detecting unit and a ground speed detecting unit, said relative velocity detecting unit comprising a first voltage to frequency converter, and said ground speed detecting unit comprising an electromagnetic pickup for producing a signal corresponding to the ground speed of said device, a second frequency to voltage converter coupled to said electromagnetic pickup, first and second reference voltage sources, first and second voltage generators for producing voltages of different amplitude, a first comparator for comparing the output of said second frequency voltage converter with said first reference voltage, a NOT circuit, first and second gate circuits having input terminals coupled to receive the outputs of said first and second voltage generators respectively, and control terminals coupled to said first comparator and said NOT circuit respectively, a multiplier having a first input terminal coupled to said first frequency to voltage converter and a second input terminal coupled to the outputs of said first and second gate circuits, and a second comparator coupled to compare the outputs of said multiplier and said second reference voltage source, said direction detecting means comprising a D-type flip-flop having a D input terminal connected to receive one of said Doppler signal components of a signal processing unit and a clock input connected to receive the other of said Doppler signal components of said signal processing unit, an integrator connected to the output of said D-type flip-flop, a source of reference voltage and a comparator connected to compare the output of said integrator with the output of said last mentioned reference voltage source, wherein said minimum level detecting means comprises a reference voltage source set to such a voltage that the farthest point of the predetermined minimum intensity range is at least 2 meters from the vehicle, and a comparator connected to compare the output of said last mentioned reference voltage source with a corresponding Doppler signal.

57. The vehicle collision anticipating device of claim 56 wherein said two wave processing units, two signal processing units and two collision state decision circuits correspond to two channels, and wherein said decision means comprises a first OR circuit having inputs connected to the outputs of the comparators of the maximum level detecting units of each channel, a second OR circuit connected to the outputs of the comparators of the minimum level detecting means of each of said channels, a first AND circuit having separate inputs connected to the outputs of the collision state decision units of each of said channels, said signal processing units further comprising means for providing first and second analog signals corresponding to said first and second Doppler signals respectively, and means for comparing the first and second analog signals, said decision means further comprising third OR gate means connected to said last mentioned comparator means of each channel, a second ANd gate having separate inputs connected to the outputs of said first AND gate and said second OR gate, a third AND gate having separate inputs connected to the outputs of said first and third OR gates, a fourth OR gate connected to the outputs of said second and third AND gates, and a fourth AND gate for producing an output signal and having an input connected to the output of said fourth OR gate.

58. The vehicle collision anticipating device of claim 46 wherein said wave processing means comprises an oscillator, a frequency modulator for modulating the output of said oscillator, transmitting and receiving antennas, an isolator connected to said transmitting antenna, mixing means, and coupling means connected to couple said frequency modulator to said isolator, to couple said receiving antenna to said mixing means, and to couple a portion of the output of said frequency modulator to said mixing means, whereby said low frequency wave is derived at the output of said mixing means, wherein said signal processing means comprises an amplifier connected to receive said low frequency signal, a first bandpass filter and a high pass filter coupled to the output of said amplifier, a source of oscillations, a mixer connected to receive the output of said source of oscillation and said high pass filter, a second high pass filter connected to the output of said mixer, a first and second AC-DC converters coupled to the outputs of said first and second bandpass filters, whereby said first and second Doppler signal components are derivable from the outputs of said first and second bandpass filters respectively, and said first and second analog signals are derivable from the outputs of said first and second AC-DC converters respectively, and wherein said collision state decision means comprises a first divider connected to receive said first and second analog signals, a first frequency to voltage converter connected to receive one of said Doppler signals, a second divider connected to receive the outputs of said first divider and first voltage to frequency converter, first and second sources of adjustable reference voltages, first comparator means connected to compare the output of said first divider with said first reference voltage, a second frequency to voltage converter connected to receive one of said Doppler signals, a monostable multivibrator coupled to the output of said first comparator, a sample and hold circuit having an input terminal coupled to the output of said second frequency to voltage converter, and a control terminal coupled to the output of said monostable multivibrator, a multiplier circuit connected to receive the outputs of said second divider and said sample and hold circuit, and a comparator coupled to compare the outputs of said multiplier with said second reference potential to produce an output signal, said two transmitting and receiving antennas are inclined inwardly in the longitudinal direction of the vehicle as a toe-in on the front wheels of a vehicle so that a radiation signal of the wave beams may be limited within 10°

-30°

, said two antennas are spaced apart from each other by a predetermined distance of the order of 50-140 cm.

59. A vehicle collision anticipating device as set forth in claim 36, wherein

said minimum level detecting means comprises a comparator and a reference voltage source set to such a voltage that the farthest point of the predetermined minimum intensity range is at least 2 meters from the vehicle, and

said decision means comprises an AND circuit for generating a signal when said collision state decision means and said minimum level detecting means simultaneously generate each signal.