GB1480587A - Radar systems - Google Patents

Abstract

1480587 Radar PLESSEY CO Ltd and I D LONGSTAFF 18 July 1974 [4 Aug 1973] 37123/73 Heading H4D In a pulse radar, especially an altimeter, the use of the trigger pulse A, Fig. 2, to define the start of the ranging period and the use of the echo pulse D at the receiver 6, Fig. 1, output to define the end of the ranging period, ignores the delay T1 between the trigger pulse and the actual transmitted pulse B and the delay T2 between the echo C as received at the antenna and the pulse D. As T1 and T2 are randomly temperature dependant, this produces large errors at very small ranges (altitudes). It is therefor proposed to use the leakage pulse E of the transmitted pulse to define the start of the ranging period, said pulse E being delayed the required amount T3=T1+T2 from the trigger pulse. During an assumed time of reception of the leakage pulse E, the receiver 6 has its gains increased and a leakage integrator 16 is bought into circuit by the closure of switches 18 and 19. The leakage integrator output resets at ¢ v. and is compared at 10 with a sawtooth voltage from 5 synchronous with the transmitted pulses. Equality in the comparator 10 enables range gate 9 which produces a positive signal increasing the integrator output if the pulse E is not acquired and a negative signal if it is. The integrator output is varied until the pulse E is acquired whereby its output at one input of differential amplifier 23 represents T3. During the remainder of the ranging period, switches 20, 21 close and 18, 19 open, giving a change over to integrator 14 resetting at 10 v. The integrator output is controlled by the gate 9 output until the echo pulse D is acquired whereby said output, at the second input to differential amplifier 23, produces the required error free output therefrom.