Target detecting system

• US 3,975,729 A
• Filed: 05/31/1957
• Issued: 08/17/1976
• Est. Priority Date: 05/31/1957
• Status: Expired due to Term

• Current Assignee: Aeronutronic Ford Corporation
• Original Assignee: Aeronutronic Ford Corporation
• Inventors: Ringer, Hayden N.
• Primary Examiner(s): Tubbesing, T.H.
• Application Number:
  US03/662,944
• Time in Patent Office: 7,018 Days
• Field of Search: 343/5, 343/7, 343/10, 343/11, 343/13, 343/17.1, 343/7 PF, 343/13 R, 343/17.1 R, 343/5 PD, 328/111, 328/133, 328/139, 328/141
• US Class Current: 342/82
• CPC Class Codes: G01S 13/22 using irregular pulse repetition frequency G01S13/12 takes precedence

Abstract

1. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses having a width equal to a/nf_r, where a and n are integers and f_r is the pulse repetition frequency, means for projecting said energy pulses into space, receiver means for receiving target reflected echoes of said projected pulses, said receiver means including a heterodyne mixer, a bandpass circuit connected to the output of said heterodyne mixer, and means for supplying received echo signals to said mixer, means for supplying pulses corresponding to said generated pulses in pulse repetition frequency, pulse width and frequency to said heterodyne mixer as a local oscillator signal, said bandpass circuit having a passband centered at the frequency nf_r, the width of said passband being not greater than f_r.

Claims

1. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses having a width equal to a/nf_r, where a and n are integers and f_r is the pulse repetition frequency, means for projecting said energy pulses into space, receiver means for receiving target reflected echoes of said projected pulses, said receiver means including a heterodyne mixer, a bandpass circuit connected to the output of said heterodyne mixer, and means for supplying received echo signals to said mixer, means for supplying pulses corresponding to said generated pulses in pulse repetition frequency, pulse width and frequency to said heterodyne mixer as a local oscillator signal, said bandpass circuit having a passband centered at the frequency nf_r, the width of said passband being not greater than f_r.

2. A radar detection system comprising means for generator time spaced pulses of high frequency energy, said pulses having a width equal to 1/nf_r, where n is an integer, and f_r is the pulse repetition frequency, means for projecting said energy pulses into space, receiver means for receiving target reflected echoes of said projected pulses, said receiver means including a heterodyne mixer, a bandpass circuit connected to the output of said heterodyne mixer, and means for supplying received echo signals to said mixer, means for supplying said generator pulses to said heterodyne mixer as a local oscillator signal, said bandpass circuit having at least one passband, each passband being an integral multiple including the first of the frequency nf_r, the width of each passband being not greater than f_r.

3. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses recurring at the frequency f_r, means for projecting said energy pulses into space, receiver means for receiving target reflected echoes of said projected pulses, said receiver means including a heterodyne mixer and a bandpass circuit connected in cascade and means for supplying received echo signals to said mixer, means for supplying pulses corresponding to said generated pulses in pulse repetition frequency, pulse width and frequency to said heterodyne mixer as a local oscillator signal, said bandpass circuit having a passband centered at the frequency nf_r, where n is an integer, the width of said passband being not greater than f_r, and means connected to said pulse generator means and to said receiver means at a point following said;

mixer for maintaining the width of said generated pulses at the value a/nf_r, where a is an integer.

4. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses recurring at the frequency f_r, means for projecting said energy pulses into space, receiver means for receiving target reflected echoes of said projected pulses, said receiver means including a heterodyne mixer and a bandpass circuit connected in cascade and means for supplying received echo pulses to said mixer, means for supplying said generated pulses to said mixer as a local oscillator signal, said bandpass circuit having a passband centered at the frequency nf_r, when n is an integer, the width of said passband being not greater than f_r, and means connected to said pulse generator means and to said receiver means at a point following said mixer for maintaining the width of said generated pulses at the value 1/nf_r.

5. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses having a width equal to 1/nf_r, where n is an integer, and f_r is the pulse repetition frequency, means for projecting said energy pulses into space, receiver means including a heterodyne mixer, a bandpass circuit connected to the output of said heterodyne mixer, and means for supplying received echo signals to said mixer, means for supplying said generated pulses to said heterodyne mixer as a local oscillator signal, said bandpass circuit having a single passband centered at the frequency nf_r, the width of said passband being not greater than f_r, and means for comparing the phase of the component of said signals in the output of said bandpass circuit with the component nf_r of said generated pulses thereby to provide an indication of the range to the target reflecting said echo pulses.

6. An object proximity indicating system comprising a transmitting antenna for projecting signals into space in a predetermined pattern, a receiving antenna for receiving echoes of said projected pulses reflected from objects within said pattern, the spacing between said antennas being small compared to the distance between said object and said system at which detection occurs, means for generating time spaced pulses of high frequency energy, said pulses recurring at the frequency f_r, means connecting the output of said generating means to said transmitting antenna, a receiver means including a heterodyne mixer and a bandpass circuit connected in cascade, said mixer having a signal input and a local oscillator input means connecting said signal input of said mixer to said receiving antenna, means connecting said local oscillator input of said mixer to the output of said pulse generating means, said bandpass circuit having a passband centered at the frequency nf_r, where n is an integer, the width of said passband being not greater than f_r, and means connected to said pulse generator and to said receiver means at a point following said mixer for maintaining the width of said generated pulses at the value 1/nf_r.

7. An object proximity indicating system comprising a transmitting antenna for projecting signals into space in a predetermined pattern, a receiving antenna for receiving echoes of said projected pulses reflected from objects within said pattern, the spacing between said antennas being small compared to the distance between said object and said system at which detection is to occur, means for generating time spaced pulses of high frequency energy, said pulses recurring at the frequency f_r, means connecting the output of said generating means to said transmitting antenna, a receiver means including a heterodyne mixer and a bandpass circuit connected in cascade, said mixer having a signal input and a local oscillator input, said bandpass circuit having a passband center at the frequency nf_r, where n is an integer, the width of said passband being not greater than f_r, means connecting said signal input of said mixer to said receiving antenna, means connecting said local oscillator input of said mixer to the output of said pulse generating means, and an automatic width control circuit connected to said pulse generating means and to said receiver means at a point following said bandpass circuit, said automatic width control circuit being responsive to the phase of the signal at frequency nf_r at the output of said bandpass circuit for controlling the width of said generated pulses, thereby to maintain the signal at frequency nf_r at minimum amplitude.

8. An object proximity indicating system comprising a transmitting antenna for projecting signals into space in a predetermined pattern, a receiving antenna for receiving echoes of said projected pulses reflected from objects within said pattern, the spacing between said antennas being small compared to the distance between said object and said system at which detection occurs, means for generating time spaced pulses of high frequency energy, said pulses recurring at a frequency f_r, the width of said pulses being determined by the characteristics of selected signals supplied to said pulse generating means, means connecting the output of said generating means to said transmitting antenna, a receiver means including a heterodyne mixer, a bandpass amplifier, and a detector connected in cascade, said mixer being provided with a signal input and a local oscillator input, said bandpass amplifier having a passband centered at the frequency nf_r, where n is an integer, the width of said passband being not greater than f_r, means connecting the signal input of said mixer to said receiving antenna, means connecting the local oscillator input of said mixer to the output of said pulse generating means, an automatic width control circuit connected between the output of said detector and said pulse generator means, said automatic width control circuit comprising a source of periodic signal connected to said pulse generating means for modulating the width of said pulses, filter means connected to the output of said detector, said filter means having a narrow passband centered at the frequency of said last-mentioned signal source, phase detector means having first and second inputs connected to said source of periodic signal and to said filter means, respectively, said phase detector means providing an output signal indicative of the relative phases of the signals supplied by said periodic source and said filter, and means connecting the output of said phase detector means to said pulse generating means to control the width of said generated pulses.

9. A system for generating pulses having a repetition frequency f_r and a pulse width equal to 1/nf_r where n is an integer, said system comprising a pulse generator circuit for providing pulses at a repetition rate f_r, said generator circuit being responsive to a potential supplied to a control input thereof to vary the width of the pulses generated thereby, a signal adder circuit having first and second inputs and an output, means connecting the output of said signal adder circuit to said control input of said pulse generator circuit, a source of oscillatory signals having a frequency low compared to f_r, said source being connected to said first input of said signal adder, thereby to produce a modulation in the width of said pulses at the frequency of said oscillatory signal, a bandpass circuit coupled to the output of said pulse generator circuit, said bandpass circuit having a passband centered at the frequency nf_r, the frequency width of said passband being not greater than f_r, means coupled to the output of said bandpass circuit for detecting the modulation at the frequency of said oscillatory signal present on the signal passed by said bandpass circuit, and phase detector means connected to said source of oscillatory signal and said modulation detection means, said phase detector providing an output signal having a polarity dependent upon the phase of said detected modulation relative to said oscillatory signal, and an amplitude indicative of the amplitude of said detected modulation, the output of said phase detector means being connected to said second input of said signal adder means.

10. A system for detecting in a signal which includes as a component thereof a periodic series of pulses of repetition frequency f_r and pulse width b, the presence of a simultaneously occurring series of pulses of repetition frequency f_r and pulse width a, where b is different from a and is equal to 1/nf_r, where n is an integer, said system comprising a bandpass circuit having at least one passband, each passband being centered at an integral multiple including the first of the frequency nf_r, each passband having a frequency width not greater than f_r, means for supplying said signal to said bandpass circuit, and detecting means connected to the output of said bandpass circuit for detecting signals passed by said bandpass circuit.

11. An object proximity indicating system comprising a transmitting antenna for projecting signals into space in a predetermined pattern, a receiving antenna for receiving echoes of said projected pulses reflected from objects within said pattern, the spacing between said antennas being small compared to the distance between said object and said system at which detection occurs, means for generating time spaced pulses of high frequency energy, said pulses recurring at a frequency f_r, the width of said pulses being determined by the characteristic of a selected signal supplied to a first input of said pulse generating means, means connecting the output of said pulse generating means to said transmitting antenna, a receiver means including a heterodyne mixer, a bandpass circuit, and a detector connected in cascade, said mixer being provided with a signal input and a local oscillator input, said bandpass circuit having a passband centered at the frequency nf_r, where n is an integer, the width of said passband being not greater than f_r, means connecting the signal input of said mixer to said receiving antenna, means connecting the local oscillator input of said mixer to the output of said pulse generating means, an automatic width control circuit connected between the output of said detector and said pulse generator means, said automatic width conrol circuit comprising a harmonic generator circuit having its input circuit connected to an output of said pulse generator means, a phase detector circuit having first and second inputs and an output, said phase detector circuit providing at said output a signal having a selected characteristic which is indicative of the relative phases of signals supplied to the two inputs thereof, said first input of said phase detector circuit being coupled to the output of said harmonic generator, said second input of phase detector circuit being coupled to the output of said bandpass circuit, and said output of said phase detector being coupled to said first input of said pulse generating means.

12. A system for detecting variations in the pulse width of a periodic series of pulses having an average pulse width approximately equal to 1/nf_r, where f_r is the repetition frequency of said pulses and n is an integer, said system comprising a bandpass circuit having a single passband centered at the frequency equal to 1/T_p, where T_p is the average time width of said pulses, said passband having a frequency width not greater than f_r, means for supplying said series of pulses to the input of said bandpass circuit, a source of an oscillatory reference signal, means responsive to said oscillatory reference signal for causing the width of said pulses to vary about said average value at the frequency of said oscillatory reference signal, a phase detector circuit having a first input coupled to the output of said bandpass circuit at the frequency of said reference signal, means for supplying said reference signal to a second input of said phase detector circuit, said phase detector circuit providing an output signal which is indicative of the relative phases of the signal supplied to the two inputs thereof, said output signal of saiid phase detector being indicative of the difference between the average width of said pulses and 1/nf_r.

13. A system for detecting variations in the pulse width of a periodic series of pulses having an average width approximately equal to 1/nf_r, where f_r is the repetition frequency of said pulses and n is an integer, said system comprising a bandpass circuit having a single passband centered at the frequency equal to 1/T_p, where T_p is the average time width of said pulses, said passband having a frequency width not greater than f_r, means for supplying said series of pulses to the input of said bandpass circuit, means for generating a signal having a frequency nf_r and a preselected fixed phase, a phase detector circuit having one input coupled to the output of said bandpass circuit, means for supplying said reference signal to a second input of said phase detector circuit, said phase detector circuit providing an output signal which is indicative of the relative phases of the signals supplied to the two inputs thereof, said output signal of said phase detector being indicative of the difference between the average width of said pulses and 1/nf_r.

14. A system for detecting in a composite signal which includes as one component thereof a periodic series of pulses of repetition frequency f_r and a pulse width b, the presence of a second component comprising a simultaneously occurring series of pulses of repetition frequency f_r and pulse width a, where b is different from a and is equal to 1/nf_r, where n is an integer, said system comprising filtering means which passes only signal components having frequencies within the range nf_r +f_r /2 and nf_r -f_r /2, means for supplying said composite signal to the input of said filtering means, and means for detectiing the signals passed by said filtering means.

15. In conjunction with a system which provides a first series of pulses having a pulse repetition frequency f_r and a pulse width a and a second periodic series of pulses having a pulse repetition rate nf_r, where n is an integer greater than one, and a pulse width b, means for measuring the difference in said pulse widths a and b comprising means for phasing said two series of pulses so that one edge of each pulse in said first series is in time coincidence with one edge of a pulse in said second series, means for extracting the component mf_r from each series where m is an integral multiple of n and means for measuring the phase difference of said two extracted components.

16. In conjunction with a system which provides a first periodic series of pulses having a pulse repetition frequency f_r and a pulse width a, and a second periodic series of pulses having the same pulse repetition rate f_r and a pulse width b, means for measuring the difference in said pulse widths, said means comprising means for phasing said series of pulses so that one edge of each pulse in one series is in time coincidence with one edge of a pulse in the other series, means for extracting the component mf_r from each series, where m is an integer, and means for measuring the phase difference of said two extracted components.

17. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses having a width equal to a/nf_r, where a and n are integers and f_r is the pulse repetition frequency, means for projecting said energy pulses into space, receiver means for receiving target refelected echoes of said projected pulses, said receiver means including a heterodyne mixer, a bandpass circuit connected to the output of said heterodyne mixer, and means for supplying received echo signals to said mixer, means for supplying pulses corresponding to said generated pulses in pulse repetition frequency, pulse width and frequency to said heterodyne mixer as a local oscillator signal, said bandpass circuit having a single passband centered at the frequency nf_r, the width of said passband being not greater than f_r.

18. A radar detection system comprising means for generating time spaced pulses of high frequency energy, said pulses having a width equal to 1/nf_r, where n is an integer, and f_r is the pulse repetition frequency, means for projecting said energy pulses into space, receiver means for receiving target reflected echoes of said projected pulses, said receiver means including a heterodyne mixer, a bandpass circuit connected to the output of said heterodyne mixer, and means for supplying received echo signals to said mixer, means for supplying said generated pulses to said heterodyne mixer as a local oscillator signal, said bandpass circuit having a single passband centered at the frequency nf_r, the width of said passband being not greater than f_r.

19. A system for detecting variations in the pulse width of a periodic series of pulses having an average pulse width approximately equal to 1/nf_r, where f_r is the repetition frequency of said pulses and n is an integer, said system comprising a bandpass circuit having a single passband centered at a frequency equal to 1/T_p, where T_p is the average time width of said pulses, said passband having a frequency width not greater than f_r, means for supplying said series of pulses to the input of said bandpass circuit, a source of signals of reference phase which have a frequency equal to nf_r, and phase detector means having first and second inputs, means coupling the output of said bandpass circuit to said first input of said phase detector means and means coupling said source of signals of reference phase to said second input of said phase detector means, said phase detector means being responsive jointly to signals supplied to said inputs thereof to provide an output signal which is indicative of the relative phases of the signals supplied to the two inputs thereof.