Radar system for detecting distance, mutual speed and azimuth of a target obstacle

• US 5,757,307 A
• Filed: 09/27/1996
• Issued: 05/26/1998
• Est. Priority Date: 09/28/1995
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Sasaki, Kunihiko, Mizuno, Hiroshi, Fujita, Akihisa, Hazumi, Hiroshi, Nakatani, Hiroto, Naganawa, Hiroshi
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/721,453
• Time in Patent Office: 606 Days
• Field of Search: 342/70, 342/71, 342/72, 342/107, 342/113, 342/114, 342/115, 342/133, 342/135, 342/139, 342/140, 342/146, 342/196, 342/116
• US Class Current: 342/70
• 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 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/44 Monopulse radar, i.e. simultaneous lobing
• CPC Class Codes: G01S 13/583 using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/93271 in the front of the vehicles
• CPC Class Codes: G01S 7/2883 using FFT processing

Abstract

Receivers 14 and 16 comprise mixers 14b and 16b for mixing reception signals of receiver antennas 14a and 16a with a transmission signal to generate beat signals B1 and B2, respectively. Signal processing section 20 performs the Fourier transformation of beat signals B1 and B2 supplied from receivers 14 and 16 to obtain the phases of beat signals B1 and B2 and then obtain the azimuth based on the difference of these phases.

Claims

1. A radar system comprising:

transmitting means for generating a transmission signal having a predetermined frequency and sending out a radar wave carrying said transmission signal toward a target;

receiving means having at least two antennas for receiving said radar wave when said radar wave is reflected from said target; and

signal processing means for detecting the azimuth of said target based on signals simultaneously received by said at least two antennas of said receiving means, wherein

said transmitting means transmits continuous wave,

said receiving means comprises mixing means for mixing reception signals of said antennas with said transmission signal to produce beat signals,

said signal processing means comprises analysis means for performing the Fourier transformation of each beat signal to obtain a frequency spectrum of each beat signal, peak detecting means for detecting a peak in the frequency spectrum and specifying a frequency corresponding to the detected peak, detection value specifying means for specifying at least one of the phase and the amplitude of the frequency component corresponding to said peak as a detection value resultant from the analysis of said analysis means, and azimuth calculating means for calculating the azimuth of said target based on the difference between detection values for respective beat signals specified by said analysis means, said peak detecting means and said detection value specifying means.

2. The radar system in accordance with claim 1, wherein

the transmission signal generated from said transmitting means comprises a plurality of frequency components,

said receiving means comprises a separating means for producing said beat signal for each of said plurality of frequency components of said transmission signal,

said analysis means, said peak detecting means, and said detection value specifying means cooperatively specify the detection value for each beat signal and for each of said plurality of frequency components of said transmission signal, and

said azimuth calculating means calculates the azimuth of the target based on the difference of detection values specified for respective beat signals with respect to the same frequency component of said transmission signal.

3. The radar system in accordance with claim 1 wherein,

said transmitting means generates the transmission signal having an ascending part and a descending part through frequency modulation by a modulation signal with a triangular waveform,

said receiving means comprises separating means for producing the beat signal for each of said ascending part and said descending part of the transmission signal,

said analysis means, said peak detecting means, said detection value specifying means cooperatively specify said detection value for each beat signal and for each of said ascending part and descending part of said transmission signal, and

said azimuth calculating means calculates the azimuth of the target based on the difference of detection values specified for respective beat signals with respect to one of said ascending part and descending part of said transmission signal.

4. The radar system in accordance with claim 1, wherein

said receiving means comprises at least three antennas aligned in line,

said mixing means produces said beat signal for each of the reception signal of each antenna, and

said system further comprises beat signal selecting means for selecting a pair of beat signals based on the reception signals of any two neighboring antennas.

5. The radar system in accordance with claim 1, wherein

said receiving means comprises at least three antennas aligned in line,

said receiving means further comprises reception signal selecting means for selecting a pair of reception signals of any two neighboring antennas from the reception signals of said antennas, and

said mixing means produces the best signal for each of the reception signals selected by said reception signal selecting means.

7. The radar system in accordance with claim 1, wherein said receiving means comprises:

band limiting means for limiting the frequency band of each beat signal supplied to said signal processing means;

signal switching means for selectively supplying said band limiting means a reference signal or the beat signal corresponding to said band limiting means,

said signal processing means comprises correction value memorizing means for memorizing said detection value obtained by said signal processing means as a correction value when said signal switching means supplies said reference signal to said band limiting means; and

said azimuth calculating means corrects the detection value specified for each beat signal using the correction value memorized in said correction value memorizing means and calculates the azimuth of the target using the corrected detection value.

8. The radar system in accordance with claim 7, wherein one of beat signals generated from said mixing means is used as said reference signal.

9. The radar system in accordance with claim 7, wherein signal generating means is provided for generating a signal having a frequency component substantially identical with said beat signal, and the signal generated from said signal generating means is used as said reference signal.

6. A radar system comprising:

transmitting means for generating a transmission signal having a predetermined frequency and sending out a radar wave carrying said transmission signal toward a target;

receiving means comprising;

at least two antennas for receiving said radar wave when said radar wave is reflected from said target;

signal multiplexing means for performing the time division multiplexing of a plurality of reception signals,

mixing means mixing the reception signal multiplexed by said signal multiplexing means with said transmission signal,

signal separating means operated in synchronism with said signal multiplexing means for separating the output of said mixing means, and

signal reproducing means for restoring a discontinuous waveform of each signal separated by said signal separating means to a continuous waveform, thereby producing beat signals,

whereby said mixing means is commonly used for said plurality of reception signals, and

signal processing means for detecting the azimuth of said target based on an output signal of said receiving means, wherein

said transmitting means transmits continuous wave, and

said signal processing means comprises frequency analysis means for performing the Fourier transformation of each beat signal to obtain a frequency spectrum of each of the beat signals, peak detecting means for detecting a peak in the frequency spectrum and specifying a frequency corresponding to the detected peak, detection value specifying means for specifying at least one of the phase and the amplitude of the frequency component corresponding to said peak as a detection value resultant from the analysis of said analysis means, and azimuth calculating means for calculating the azimuth of said target based on the difference between detection values for respective beat signals specified by said analysis means, said peak detecting means and said detection value specifying means.

10. A radar system comprising:

a transmitter generating a transmission signal having a predetermined frequency and sending out a radar wave carrying said transmission signal toward a target;

a receiver having at least two antennas for receiving said radar wave when said radar wave is reflected from said target; and

a signal processing section detecting the azimuth of said target based on signals simultaneously received by said at least two antennas of said receiver, wherein;

said transmitter transmits continuous wave;

said receiver comprises a mixer for mixing reception signals of said antennas with said transmission signal to produce beat signals;

said signal processing section means comprises a frequency analysis section for performing the Fourier transformation of each beat signal to obtain a frequency spectrum of each beat signal, a peak detecting section for detecting a peak in the frequency spectrum and specifying a frequency corresponding to the detected peak, detection value specifying means for specifying at least one of the phase and the amplitude of the frequency component corresponding to said peak as a detection value resultant from the analysis of said frequency analysis section, and an azimuth calculating section for calculating the azimuth of said target based on the difference between detection values for respective beat signals specified by said frequency analysis section, said peak detecting section and said detection value specifying means.

11. The radar system in accordance with claim 10, wherein the transmission signal generated from said transmitter comprises a plurality of frequency components;

said receiver comprises a separating means for producing said beat signal for each of said plurality of frequency components of said transmission signal;

said frequency analysis section, said peak detecting section, and said detection value specifying means cooperatively specify the detection value for each beat signal and for each of said plurality of frequency components of said transmission signal; and

said azimuth calculating section calculates the azimuth of the target based on the difference of detection values specified for respective beat signals with respect to the same frequency component of said transmission signal.

12. The radar system in accordance with claim 10 wherein:

said transmitter generates the transmission signal having an ascending part and a descending part through frequency modulation by a modulation signal with a triangular waveform;

said receiver comprises separating means for producing the beat signal for each of said ascending part and said descending part of the transmission signal;

said analysis section, said peak detecting section, said detection value specifying means cooperatively specify said detection value for each beat signal and for each of said ascending part and descending part of said transmission signal; and

said azimuth calculating section calculates the azimuth of the target based on the difference of detection values specified for respective beat signals with respect to one of said ascending part and descending part of said transmission signal.

13. The radar system in accordance with claim 10, wherein:

said receiver comprises at least three antennas aligned in line;

said mixer produces said beat signal for each of the reception signal of each antenna; and

beat signal selecting means provided to select a pair of beat signals based on the reception signals of any two neighboring antennas.

14. The radar system in accordance with claim 10, wherein:

said receiver comprises at least three antennas aligned in line;

said receiver further comprises reception signal selecting means for selecting a pair of reception signals of any two neighboring antennas from the reception signals of said antennas; and

said mixer produces the beat signal for each of the reception signals selected by said reception signal selecting means.

15. The radar system in accordance with claim 10, wherein said receiver comprises:

signal multiplexing means for performing the time division multiplexing of a plurality of reception signals;

signal separating means operated in synchronism with said signal multiplexing means for separating the output of said mixing means; and

signal reproducing means for restoring a discontinuous waveform of each signal separated by said signal separating means to a continuous waveform, thereby producing the beat signal;

whereby said mixer is commonly used for said plurality of reception signals.

16. The radar system in accordance with claim 10, wherein said receiver comprises:

band limiting means for limiting the frequency band of each beat signal supplied to said signal processing section;

signal switching means for selectively supplying said band limiting means a reference signal or the beat signal corresponding to said band limiting means;

said signal processing section comprises correction value memorizing means for memorizing said detection value obtained by said signal processing section as a correction value when said signal switching means supplies said reference signal to said band limiting means; and

said azimuth calculating means corrects the detection value specified for each beat signal using the correction value memorized in said correction value memorizing means and calculates the azimuth of the target using the corrected detection value.

17. The radar system in accordance with claim 16, wherein one of beat signals generated from said mixer is used as said reference signal.

18. The radar system in accordance with claim 16, wherein signal generating means is provided for generating a signal having a frequency component substantially identical with said beat signal, and the signal generated from said signal generating means is used as said reference signal.