Serrodyning system employing an adjustable phase shifting circuit

Claim 1

A phase shifting circuit for producing an output signal adjustably shifted in phase relative to an input alternating frequency signal, comprising in combination: a first signal path having an input terminal receptive of said input signal and having a first output terminal, said first signal path comprising a first adjustable level signal translating device including a first level control terminal, said device being positioned intermediate said input terminal and output terminal; a second signal path having an input terminal receptive of said input signal and having a second output terminal, said second signal path comprising a second adjustable level signal translating device including a second level control terminal; means for effecting a 90° relative phase shift in one signal path relating to the other; means coupled to said first and second output terminals for producing said output signal which is the vector sum of the signals appearing at said first and second output terminals; means coupled to said first and second control terminals for respectively applying control signals thereto for controlling the level of signal produced respectively at said first and second output terminals for controlling the phase of said output signal by any amount between 0° and 90° relative to said input signal; means for selectively shifting said output signal by N·90° where N=0, 1, 2, or 3 for thereby effecting a 0° to 360° phase shift relative to said input signal; and means for providing to said phase shifting circuit a signal at a given frequency f 1 , means for continuously and uniformly shifting the phase of said signal in said phase shifting circuit between 0° and 360° and means responsive to said output signal from said phase shifting circuit for producing a signal at frequency f 2 where f 2 differs from f 1 by an amount determined by the rate at which said phase shift occurs in said phase shifting circuit.