| 摘要 |
PURPOSE:To eliminate a narrow band disturbing signal mixed on the way of a transmission system by generating a continuous wave whose phase is intersected orthogonally with that of a carrier from an intermediate frequency signal, applying synchronization detection to the intermediate frequency signal and controlling a narrow band filter interposed between the intermediate frequency signal and the output in response to the output of the detector. CONSTITUTION:An IF signal is given to an IF carrier oscillator 5, a synchronization detector 7 and a variable trap filter 8, and the oscillator 5 generates a continuous wave cosomegact. The continuous wave is shifted by 90 deg. at a phase shifter 6 and a continuous wave sinomegact whose phase is intersected orthogonally with that of the carrier is obtained. The output voltage (v) of a converter 10 is given to the variable trap filter 8 and the trap frequency is varied. When the capacitance of variable capacitors c1, c2 is controlled by a voltage corresponding to frequencies fc+DELTAf and fc-DELTAf, the frequency f1 of a disturbing wave and a component of a side band conjugated and opposite thereto are eliminated from the IF signal. |
