Frequency agile signal generator for emulating communications environments

摘要

A frequency agile signal generator provided for emulating a communication signal of predetermined frequency and modulation characteristics including frequency hopping. The signal generator includes a digital controller such as a microprocessor or microcomputer for generating digital command signals specifying the desired characteristics of the output signal. In response to the digital command signals, a base digital frequency signal representing the desired base or center frequency of the output signal is generated by a number controlled oscillator in response to a digital frequency control signal. The digital command signals also control the generation of an analog modulation signal having desired modulation characteristics. For frequency modulation, the analog modulation signal is converted to a digital signal in the frequency domain and is algebraically summed with the frequency control signal to control the frequency of the number controlled oscillator output signal as a function of both the digital frequency control signal and the digital modulation signal. The number controlled oscillator output signal is converted to analog form to provide an analog output signal. The analog output signal can be amplitude modulated and/or attenuated as commanded by the digital command signals. For amplitude modulation, the analog modulation signal in the time domain is used directly under the control of the digital command signals as a mixer input to amplitude modulate the analog output signal or for on/off keying.