GB1315533A - Vehicle monitoring radar apparatus - Google Patents

Abstract

1315533 Pulse radar PYE Ltd 24 June 1971 [24 June 1970] 30695/70 Heading H4D A vehicle monitoring pulse radar provides an output indicative of a characteristic of the vehicle or its motion only when an echo pulse is coincident with a timing pulse generated a predetermined time after the transmitted pulse. In a radar speed trap generator 50 produces pulses spaced at 2 Ás. which are fed to shaper 52 which diverts them along a delay line 54 whose length is determined by the position of switches 28, 30, 32 which earth respective taps on the line. The shaper output thus comprises the generated pulse followed by a timing pulse reflected from the short circuit. The pulse pair passes to a p.i.n. switch 56 which modulates the output of a Gunn diode oscillator 58. The transmitted pulses are coupled into the receiving antenna 26. If a reflected signal is coincident with a timing pulse detector 60 passes the signal to mixer 62 which extracts the Doppler signal. The timing pulse spacings selected by delay line 54 are chosen to correspond to echoes from the near, centre or far lanes of a three-lane carriageway. The Doppler signal passes through a zero-crossing detector 72 to gate 70 which is enabled by a monostable 68 triggered by detector 66. The pulsed output of the gate 70 is counted and provides a direct reading of the vehicle velocity on a three figure seven segment display. The apparatus is aligned at precisely 45 degrees to the carriageway using the following procedure. At a convenient point the radar is aligned along the traffic flow and flux gate magnetometer 78 rotated until a null output is indicated by lamp 44. The magnetometer is then rotated through 45 degrees. At the measuring station (i.e. at a more discrete point) the radar apparatus is rotated until the magnetometer output is nulled. The magnetometer also provides an inhibit signal to gate 68 if the apparatus is incorrectly aligned. Switches are provided for enabling transmission or display and also for providing a continuous signal to the modulator which signal acts as a test signal equivalent to a vehicle travelling at 30 m.p.h.