Patent GB-1416504-A (GB)
Title: Harmonic radar detecting and ranging system for automotive vehicles
IPC: G01S13/931
Filed: 1973-06-22
Abstract: 1416504 Aerials; radar; transponders RCA CORPORATION 22 June 1973 [30 June 1972] 29663/73 Headings H4D H4A and H4L A vehicle-mounted detecting and ranging system includes a transmitter with an associated directional aerial for propagating waves of given frequency and polarization in the direction of travel of the vehicle, a receiver with an associated directional aerial for received waves returned along said direction of travel, and means for comparing the transmitted and received waves in order to obtain information about objects in the direction of travel. The receiver and its aerial are constructed to respond substantially solely to waves whose frequency and polarization are both different from those of the transmitted waves. As described a transmitter 12, Fig. 1, on an equipped vehicle has one output to a directional aerial 14 and another output on a line 20 to a receiver 16. A directional aerial 18 is provided for waves returned from a target, and has an output to the receiver 16. Signal processing and output circuitry 24 receives output on a line 22 from the receiver 16. The frequency of the received signal is a harmonic (e.g. the second harmonic) of the frequency of the transmitted signal, and mixing is effected either in one stage, when the signal on the line 20 is first subjected to frequency multiplication in the receiver 16, or in two stages, when a further output from the transmitter 12 is taken on a line 21 to the circuitry 24. Output from the circuitry 24 may provide indications of the distance and relative speed of a target and be used to operate a safety device, such as an air bag, in anticipation of a collision. An aerial structure, 40, Fig. 2, for fixing in front of the vehicle comprises a low-loss circuit board 46 upon which two arrays of parallel dipoles are formed by a printed circuit process. The first, for transmission of vertically polarized waves, has a plurality of vertical dipoles 44, and a horizontal central feed line 48. The second, for reception of horizontally polarized waves having a frequency which is twice that of the waves transmitted from the first aerial, has a plurality of horizontal dipoles 51, and a vertical central feed line 52. Said first and second arrays correspond, respectively, to the aerials 14 and 18 of Fig. 1. A target, for installation upon a co-operating vehicle, comprises a similar aerial structure 40, Fig. 2, which in this case is fixed at the rear of the vehicle, the array of dipoles 44 being used for reception, and the array of dipoles 51 being used for transmission. Said arrays correspond, respectively, to the aerials 32 and 37 of Fig. 1, and they are coupled together via a passive harmonic generator 34 (such as a zero-bias silicon Schottky barrier diode) and a filter 36. The transmitter 12, Fig. 1, may comprise a voltage controlled oscillator 108, Fig. 6, with an associated sawtooth oscillator 106. In the receiver, a mixer 122 has one input from a frequency doubler 118, which is coupled to the transmitter line. The output from the mixer 122 has a frequency which corresponds to range and may be coupled through high- and low-pass filters 124, 128 to signal processing and output circuitry 130, so that said circuitry is only effective over a predetermined portion of said range. Relative velocity may be determined by differentiation of the frequency of the input to the circuitry 130, and a ground speed sensor 134 may provide another input thereto.