| 摘要 |
PURPOSE:To prevent the generation of a spurious component in a transmission band by inserting a wind-band phase shifter into one of two intermediate frequency circuits, and then controlling the phase shifter by detecting a phase difference between branched intermediate frequency signals. CONSTITUTION:Received signals from antennas 31 and 31' are passed through branching filters 32 and 32', converted by frequency converters 33 and 33', and amplified by intermediate frequency amplifiers 35 and 35'; one signal is supplied to a phase shifter 37, and the other is supplied to a branching circuit 38 through an absolute delay time equalizer 36. The output of the phase shifter 37 is supplied to the branching circuit 38'. Outputs of the circuits 38 and 38' are supplied partially to a phase difference detector 40 through amplitude limiters 39 and 39'. The detector 40 sends out a phase error signal of 0 when a difference in phase between those two signals is pi/2 or a phase error signal of positive or negative polarity to control the phase shifter 37 through a driving circuit 41 so that the phase difference between those two signals supplied to the detector 40 is pi/2. The remainders branched by the circuits 38 and 38' are synthesized in phase by a pi/2 synthesizer 42 and amplified by an IF amplifier 43 equipped with an AGC circuit 44 to a constant level before being outputted. |
