Abstract: A synthesizer combines frequencies for multiple targets, accumulating the phase components separately and allowing the targets to change velocity separately. The amplitude of the simulated signal at the phase secified is generated using a method that combines coarse and fine angle components of the desired angle signal allowing small high speed memories to be used. A first ROM is addressed by high order bits of the phase component and a second ROM by the lower order bits. The outputs of the first and second ROM's are multiplied and then added to the output of the first ROM producing the amplitude of the desired phase. The system also allows the amplitude of the signal being synthesized to be modulated by multiplying the synthesized digital value by an amplitude modulator. The synthesized amplitudes for each frequency are combined. Digital zero order hold correction removes amplitude distortion from the output spectrum.

Abstract: The present invention provides a radar simulation system with at least two counters. The first counter is a coarse counter 20/30 that counts a transmit pulse interpulse periods to provide a coarse return delay at the beginning of a radar look. The second counter is a fine counter 22/36 which counts, after the coarse counter has counted down to zero, from each subsequent transmit pulse to the time for the return pulse. Once the coarse counter has finished counting, the fine counter, which can be reset and reloaded during the look responsive to each transmit pulse, can provide return targets repeating at the same distance at the pulse repetition frequency. A cyclic counter 24 can also be added that produces the return pulses by cyclically counting the interpulse period one the fine counter has timed out. If the cyclic counter is used the fine counter is not reloaded during the look.