Self test circuit for multichannel radio receivers

A self test circuit providing a simultaneously amplitude modulated and frequency modulated carrier signal for each frequency channel of a multichannel radio receiver having a substantially equal frequency separation between channels, comprising in combination:

• circuit means providing a periodic signal having a predetermined sloping leading edge adapted to control the operating state of an electronic switch device and having a frequency equal to the frequency separation between channels;
• an electronic switch device operable between first and second operating states coupled to said circuit means and being driven into one of said operating states by said periodic signal;
• bias means coupled to said switch device for causing said switch device to switch to said one operating state at a selected point on said leading edge of said periodic signal intermediate the extremities thereof;
• a modulation signal source coupled to said switch device for causing said switching to selectively vary about said selected point and thereby generate an intermediate output signal having a waveform including an abrupt changing leading edge which varies both in amplitude and phase;
• and
• circuit means coupled to said switch device and being responsive to said intermediate output signal to pass the high frequency components of said waveform as an output signal to said receiver, said output signal having a harmonic frequency component at every channel which is both simultaneously amplitude modulated and frequency modulated.