| 摘要 |
PURPOSE:To eliminate a hit that is caused during the swtching and to prevent the deterioration of signal quality due to the hit, by setting a phase shifter into an output circuit of an intermediate frequency, and controlling the phase shifter in response to the phase difference of the signal applied to an intermediate switch. CONSTITUTION:The outputs of intermediate frequency filters 6 and 6' pass through phase shifters 21 and 21', primary intermediate frequency amplifiers 23 and 23', and intermediate frequency branching circuits 25 and 25'. Then one of signals obtained by an intermediate frequency switch 27 is delivered through an output terminal 28. The switch 27 is driven by a control signal obtained by comparing the bias voltages of AGC circuits 24 and 24' added to the amplifiers 23 and 23' respectively through a controller 22. Some of the signals branched by the circuits 25 and 25' is wave detected by a phase difference detector 26, and the phase difference between input signals is detected by the output voltage of the detector 26. Therefore the phase of the shifter 21 or 21' is advanced or delayed by pi when the phase difference between input signals has a >=pi/2 shift. Thus a hit which is caused during the switching can be prvented. |
