Carrier frequency regulating circuit - is for pulse modulated signal and transforms error frequency oscillations into rectangular current pulses

摘要

The carrier frequency regulating circuit for a pulse modulated signal e.g. transmitted by a radar transponder, includes a bandpass filter (2), with a centre frequency coinciding with the required carrier frequency coupled to the signal source (1). The filter (2) is coupled to a mixer circuit (3) including a local oscillator (4) with a fixed reference frequency (Fo). The output of the mixer circuit (3) comprises a pulse modulated signal with a frequency corresponding to the frequency difference between the source and the local oscillator. The error frequency oscillations are connected into rectangular pulses via an amplifier (5) and pulse former (6), to obtain a current pulse signal which is integrated and supplied to regulating means for adjusting the carrier frequency until the DC signal reaches zero.