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Title: Doppler radar for forecasting collision
Claims: What we claim is: 1. A Doppler radar for forecasting collision comprising a microwave oscillator provided with a frequency modulator, the bias voltage to said frequency modulator being consecutively switched at a constant interval in the order of voltage level V.sub.B1, V.sub.B2, V.sub.B3, V.sub.B1, . . . , to consecutively switch the oscillation frequency of said microwave oscillator in the order of f.sub.1, f.sub.2, f.sub.3, f.sub.1, . . . , where f.sub.1 < f.sub.3 < f.sub.2, f.sub.2 - f.sub.1 = .DELTA.f.sub.21, f.sub.3 - f.sub.1 = .DELTA.f.sub.31, .DELTA.f.sub.21. l.sub.max .sbsb.1 < 150 MHz.m, .DELTA.f.sub.31. l.sub.max .sbsb.2 < 75 MHz.m, l.sub.max .sbsb.1 being the maximum detection distance required for the Doppler radar to detect l.sub.max .sbsb.2 being the maximum detectable distance of the Doppler radar, the output of said microwave oscillator being coupled through an isolator and a directional coupler for radiating from a transmitting antenna provided at the center of car front and also for partly coupling to a mixer, Doppler signals d.sub.1, d.sub.2 and d.sub.3 corresponding respectively to the frequencies f.sub.1, f.sub.2 and f.sub.3 being obtained by mixing in said mixer the microwave oscillator output partly coupled through the directional coupler and a reflected wave output produced from a receiving antenna also provided at the center of the car front and receiving reflected wave reflected at an object, means for detecting the distance of the object from the antennas from the phase difference between the Doppler signals d.sub.1 and d.sub.2, detecting the residual time left for the object to reach the antennas from a time length corresponding to said phase difference and determining an instant when the detected residual time becomes equal to a preset residual time from said time length, and means for determining the sense of relative velocity of the object relative to the antennas from the phase difference between the Doppler signals d.sub.1 and d.sub.3. 2. A Doppler radar for forecasting collision according to claim 1, which further comprises means for detecting and memorizing the residual time T.sub.1 ' left for the object to reach a reference point on a line connecting the object and center of the car front and behind and at distance l = l.sub.0 from the center of the car front at an instant when the object reaches a point ahead of and at distance l = l.sub.1 from the center of the car front and monitoring subsequent residual time T' left for the object to reach said reference point for forecasting the occurrence of collision if T' satisfies ##EQU44## where ##EQU45## a being the car width, and l.sub.2 ' in (l.sub.0 + l.sub.2 ')cos .theta. = l + l.sub.0 when the maximum value of l .sin .theta. is a/2, .theta. being - .pi./2 .ltoreq. .theta. .ltoreq. .pi./2. 3. A Doppler radar system for use on a vehicle, comprising: a microwave oscillator; means for sequentially modulating said microwave oscillator to generate microwave frequencies f.sub.1, f.sub.2 and f.sub.3, where f.sub.1 < f.sub.3 < f.sub.2, in the order f.sub.1, f.sub.2, f.sub.3, f.sub.1, . . . ; antenna means coupled to said microwave oscillator to transmit said microwave frequencies f.sub.1, f.sub.2 and f.sub.3 and to receive portions of the transmitted frequencies reflected from an object having a relative velocity to said vehicle; means coupled to said oscillator and antenna means for mixing at least a portion of said transmitted and received microwave frequencies to obtain Doppler signals d.sub.1, d.sub.2 and d.sub.3 corresponding to said frequencies f.sub.1, f.sub.2 and f.sub.3, respectively; means coupled to said mixing means for separately amplifying and filtering each of said Doppler signals d.sub.1, , d.sub.2 and d.sub.3 ; distance detecting means coupled to said amplifying and filtering means for detecting the distance between said object and said antenna means from the phase difference between said Doppler signals d.sub.1 and d.sub.2, said distance detecting means including means for comparing the detected distance with a preset reference distance; residual time detecting means coupled to said amplifying and filtering means for detecting the residual time left for said object to reach said antenna means, said residual time detecting means including means for comparing said detected residual time with a preset reference residual time; direction determining means coupled to said amplifying and filtering means for determining the direction of movement of said object relative to said antenna means from the phase difference between said Doppler signals d.sub.1 and d.sub.3 ; and means coupled to said distance detecting means, said residual time detecting means, and said direction determining means for generating an output signal only when the detected distance between said object and said antenna means is not greater than said reference distance, the detected residual time is not greater than said reference residual time and said direction determining means has determined that the direction of relative movement of said object and antenna means is toward each other. 4. The Doppler radar system according to claim 3, wherein said distance detecting means comprises means for counting pulses from a clock signal generator during a period corresponding to the phase differene between said Doppler signals d.sub.1 and d.sub.2 and means for generating an output signal when the number of counted clock pulses is not greater than a predetermined reference number of pulses corresponding to said predetermined reference distance. 5. The Doppler radar system according to claim 4, wherein said residual time detecting means includes: memory means coupled to said distance detecting means and said direction determining means for counting and storing clock pulses from said clock signal generator during a period corresponding to the phase difference between said Doppler signals d.sub.1 and d.sub.2 upon the generation of said output signal from said distance detecting means and after said direction determining means has determined that the direction of relative movement of said object and said antenna means is toward each other; counter means coupled to said distance detecting means and direction determining means for counting clock pulses from said clock signal generator only after the generation of said distance detecting means output signal and only after said direction determining means has determined that the direction of relative movement of said object and said antenna means is toward each other; and means coupled to said memory means and said counter means for generating an output signal only when the difference between the number of clock pulses stored in said memory means and the number of clock pulses stored in said counter means is not greater than a predetermined reference value. 6. The Doppler radar system according to claim 4, further comprising a collision forecasting circuit including: memory means coupled to said distance detecting means and said direction determining means for counting and storing clock pulses from a second clock signal generator, generating pulses of a different frequency from those generated by the first clock signal generator, during a period corresponding to the combined periods of signals corresponding to said Doppler signals d.sub.1 and d.sub.2 upon the generation of said output signal from said distance detecting means and after said direction determining means has determined that the direction of relative movement of said object and said antenna means is toward each other; counter means coupled to said distance detecting means and direction determining means for counting clock pulses from said first clock signal generator during said period corresponding to said combined periods and only after the generation of said distance detecting output signal and only after said direction determining means has determined that the direction of relative movement of said object and said antenna means is toward each other; and means coupled to said memory means and said counter means for generating an output signal only when the number of clock pulses counted by said counting means is not greater than the number of clock pulses stored in said memory means. Other info: Inventors: Watanabe, Masahiro (Sagamihara, JA) Shibuya, Hideo (Sagamihara, JA) Sakai, Yasuhide (Kawasaki, JA) Hori, Ryuji (Yokohama, JA) Kamiharako, Mistuaki (Yokohama, JA) Sato, Kazuo (Toyota, JA) Application Number: 442240 Filing Date: 1974-02-13 Publication_date: 1976-04-20 Assignee: Matsushita Electric Industrial Co., Ltd. (Osaka, JA); Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota, JA) Primary Class(es): 342/112 342/72, 342/114 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Hubler, Malcolm F. Assistant Examiner: Attorney: Stevens, Davis, Miller & Mosher |
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