Automatic balancer for high frequency mixer in spectrum analyser

摘要

The balancer (54) in a single-pulse HF mixer (52) mixes the HF input signal (53) with the LO-energy local oscillator signal (55) to achieve an intermediate frequency signal. It is connected to an in-phase conductor (58) and an out-phase conductor (59) and through these the signals pass to a difference amplifier (62) which inputs their amplitude and to a difference phase shifter (64). A signal combiner (66) combines the amplitude and phase inputs from the in-phase and out-phase signals, determined and controlled by a microprocessor. This intermediate frequency circuit is inexpensive to make. It almost completely neutralises local oscillator shunt and thus ensures cost-effective accurate spectrum analysis.