Simple frequency converter - has multiplier receiving local carrier via variable resistance controlled by detector

摘要

The converter has a modulator (4) receiving an input signal and a local sinusoidal carrier wave (from a local oscillator (6)) and producing an output signal transposed in frequency w.r.t. the input signal. The modulator is a multiplier. The carrier wave is passed to the multiplier via a variable resistance (8) controlled by a control signal. The multiplier's output is bandpass filtered (10) and passed to processing circuitry (12) (e.g. an amplifier). A part of the output of the processing circuitry is separated out by e.g. a differential transformer (14) and passed to a detector (16) that produces the control signal which sets the variable resistance.