Digitally controlled signal simulator

Abstract

A signal simulator for generating a simulated target signal useful in testing the receiver and data processing portions of radar systems is disclosed. Input signals to the signal simulator include a multi-pulsed synchronizing signal having substantially the same duty cycle and PRF (pulse repetition frequency) as the RF output signal of the radar transmitter normally used in conjunction with the receiver, digital signals specifying the acceleration, the initial velocity and the initial range of the target to be simulated. A target range calculator circuit utilizes the acceleration, initial velocity and initial range signals to calculate the range of a simulated target. A plurality of delay circuits are sequentially initialized by the synchronizing signal to generate a trigger signal delayed from the synchronizing signal with the delay corresponding to the range of the simulated target. The pulse width of each pulse of the synchronizing signal is measured and stored. A pulse generator circuit in response to the trigger signal reads the stored values corresponding to the width of the pulses of the synchronizing signal and generates a delayed synchronizing signal having the same PRF and duty cycle as the synchronizing signal with the delay corresponding to the range of the simulated target. The target range calculator also generates a signal which determines the amplitude and a signal which determines the frequency of the simulated target signal. These signals are coupled as input signals to a signal synthesizer. The output signal of the synthesizer and the delayed synchronizing signal are coupled to a signal generator to generate the simulated target signal.