Patent GB-1075348-A (GB)
Title: Radar system simulators
IPC: G01S7/40
Filed: 1964-06-26
Abstract: 1,075,348. Radar simulators. V. I. MJAGKOV, N. I. GRIGORJEV, V. A. GROSMAN, E. A. DURNOV, V. L. KOBLOV, M. V. KOZLOVA, and G. N. SHTAPEL. June 26, 1964, No. 26487/64. Heading H4D. In a trainer for an airborne radar system, provision is made for simulating (a) the system used for determining the aircraft's drift angle; (b) echo signals corresponding to an oncoming aircraft, thunder clouds, mountains, ground echoes, active jamming sources and random noise; and (c) the operation, including faults therein, of the receiver-transmitter and antenna systems. Simulation of the antenna system and the drift angle measuring system.-In the embodiment of Figs. 2 and 3 (not shown), an antenna system simulator (22) comprises a motor-driven shaft (78) scanning through 180 degrees and coupled to selsyn-receivers (CC2, CC4, CC5, CC6, CC7) and a rotary transformer (79). The rotary transformer (79) generates sine and cosine waveforms which are fed to the deflection coils of pilot'sand navigator's displays (1 and 2). A selsyn receiver (CC1) electrically coupled to selsyn (CC2), controls a servomotor (25) to vary the frequency of an oscillator (38). Simulated ground echo signals and signals from the oscillator (38) are fed to a modulation and mixing circuit (39a) and thence to the displays (1 and 2). The aircraft's drift angle, as measured by a trainee, corresponds to a minimum beat frequency between the simulated echo signals and the signals from oscillator (38) and is represented by the angle position of selsyn (CC2). A selsyn-transmitter (CC3) on an instructor's control console (23) is set to represent the true drift angle and an output signal appears on selsyn (CC1) when the true and measured drift angles differ. The servomotor (25) is actuated to minimize the difference and moves an indicator (27) to indicate the error in degrees between the true and measured drift angles. Simulation of echo signals and interference.- A phantastron (29) drives four multivibrators (30, 31, 32 and 35). Multivibrators (30), (31) and (32) drive two blocking oscillators (33 and 34) whose output pulses are mixed with the output from multivibrator (35) and shaped to simulate ground echo signals which are fed to the mixing circuit (39a). Mountain echo signals are simulated by phantastrons (45, 46 and 47) and fed to the mixing circuit (39a). Signals from an oncoming aircraft are simulated by a phantastron in a pulse-shaping circuit (62) and fed to the mixing circuit (39a). Echo signals from thunderstorm clouds are simulated by phantastrons (52), (53) and (55) and fed to the mixing circuit (39a). The azimuth positions at which the simulated mountain, thunderstorm and aircraft echoes appear on the displays (1, 2) are set up in the control console (23); the echo display being controlled by the selsyn-receivers (CC4), (CC5) and (CC6), the output signals from which are used to gate amplifiers (L 2 ), (L 7 ) and (L 10 ) respectively. The range positions at which the simulated echoes appear are set up on potentiometers (R6, R8, R11), on the instructor's control console (23), which vary the timing of pulses from the phantastrons (47), (55) and (62) respectively. Fading of the echoes with increasing range is simulated by adjustment of potentiometers (R5), (R7) and (R10) which control respective modulation circuits (44), (51), (L 10 ) for varying the amplitude of the echo pulses from the phantastrons (45), (52) and (53), and (62) respectively. Variation of the intensity of the echo signals with antenna direction and tilt is simulated by adjustment of potentiometers (R4), (R9), (R12) which control the gain of respective amplifiers (L 4 ), (L 8 ), (L 15 ) and hence control the amplitude of the echo pulses from the phantastrons (45), (53) and (62) respectively. To simulate an active jamming source, three voltage waveforms, mutually phase-displaced by 60 degrees, are taken from the selsyn receiver (CC7), fed through amplifiers (L 21 , L 22 , L 23 ) to the mixing circuit (39a), mixed with a simulated receivernoise signal from a thyratron noise-generator (37a), and appear on the displays (1 and 2) as three broad sectors filled with noise. The simulated range of this jamming source is set up on a potentiometer (R25) which varies the gain of amplifiers (L 21 , L 22  and L 23 ) and hence the width of the sectors. If it is required to simulate several mountains, thunderstorms or aircraft, more than one of each such simulator may be provided. Simulation of the receiver-transmitter system.- A circuit (72) simulates a klystron oscillator and includes a bridge circuit (R15, R16, R17, D2) from which potentials representing klystron current and a mixer crystal current are derived, these potentials being applied through a selector switch (73) to an indicator (67). A neon oscillator circuit (69) generates a sawtooth waveform to simulate an AFC circuit in the transmitterreceiver system, the waveform being applied to the indicator (67) and also to the mixing circuit (39a). A switch (71) simulates switchover from AFC to manual frequency control. Magnetron current and transmitter case pressure are simulated by units (64) and (65).