Patent GB-1057656-A (GB)
Title: Target simulating apparatus
IPC: G01S7/40
Filed: 1964-05-13
Abstract: 1,057,656. Radar. CANADIAN PATENTS & DEVELOPMENTS Ltd. May 13, 1964 [May 24, 1963], No. 19947/64. Heading H4D. Relates to a simulator for the radar system disclosed in Specifications 1,042,821 and 1,047,431 in which the launching or landing point of a projectile is determined by extrapolation of the line joining the points of intersection of the trajectory with two vertically-superposed horizontal fanshaped scans of a radar pencil-beam. Signals corresponding to the echoes returned in the upper and lower scans are simulated in the following manner. The range sweep signals RS (# 8000 c/s.) of the type-B display, a D.C. voltage RPP, and low-slope triangular wave voltage ASR (# 1 c/s.) are applied to a Schmitt trigger VC1 which gives an output signal when the range sweep voltage RS exceeds the sum of the D.C. voltage RPP and the triangular wave voltage ASR (Fig. 8, not shown). The output signals are fed to a blocking oscillator BO to produce a first series of range pulses RA1 in which, for that part of the triangular wave having a positive slope, successive pulses occur progressively later in relation to the beginning of each range sweep. (For a negative slope, the pulses occur progressively earlier.) The pulses RA1 are fed through a delay line DL1 to provide a second series of range pulses RA2. Similarly, a Schmitt trigger VC2 compares the azimuth sweep signals ASG (# 40 c/s.) with the sum of a D.C. voltage APP and a low-slope triangular wave voltage ASA (# 1 c/s.) to obtain two azimuth pulse series AZ1 and AZ2 from a multivibrator MV and delay line DL2. A selected one of the two range pulse series (RA1 or RA2) is gated by a selected one of the two azimuth pulse series (AZ1 or AZ2) to provide a range-azimuth pair of co-ordinates RAa, AZa which is fed as a first input signal to the display and represents the echo returned in one of the two scans. A second selected pair of co-ordinates RAb, AZb represents the echo returned in the other scan. For example, the combination RA1, AZ1 selected to provide the first input signal and the combination RA2, AZ2 to provide the second input signal will simulate a target moving with increasing range and from left to right (Fig. 10, not shown), the simulated range and azimuth increments being dependent upon DL1 and DL2 which may be varied. A 12-way aspect selector switch ASS (detailed in Fig. 7, not shown) enables any two such range-azimuth combinations to be selected as the first and second displayed signals and thus enables the simulation of a target moving in any direction. The input signals to the display are fed through respective gates AG5 and AG6 which are opened in a sequence determined by logic circuitry shown on the right-hand side of Fig. 6. A bi-stable flip-flop FF1, with feedback through a push-pull integrator PP1 and voltage comparators CPR1 and CPR2, provides timing pulses for the logic circuitry. The low-slope triangular waveforms ASA and ASR are derived from the integrator PP1, which has two antiphase outputs, and may be chosen with a positive, negative or zero slope by means of selector switch ASS. The simulated target velocity depends on the slopes of these triangular waveforms and is controlled by varying the time constants in the integrator PP1. The simulated initial target range and azimuth are controlled by varying the D.C. voltages RPP and APP. In order to distinguish between rising and falling projectiles, the upper or lower scan is identified by passing the signals representing the echo in that scan both directly, and through a gated delay circuit D (Fig. 3, not shown), to the display, thus giving a double-image for that scan on the screen of the display.