| 摘要 |
PURPOSE:To improve the separation, by keeping a constant level regardless of the receiving level fot the sum signal of an AM stereo receiver through which the carrier wave received an angle modulation by the differential signa receives an amplitude modulation by the sum signal. CONSTITUTION:The received AM stereo signal is applied to a mixer 2 via an RF amplifier 1 to receive a conversion of frequency, and the IF signal is selectively amplified by an IF amplifier 4. The output of the amplifier 4 is applied to an RF amplifier 1 as well as to the amplifier 4 after the AGC voltage is produced by an AGC voltage generating circuit 5. At the same time, a part of the output of the amplifier 4 is applied to sum signal wave detector 6 and a limiter 7. The detector 6 comprises a voltage control type variable gain amplifier 61, a multiplier 62 functioning as an AM wave detector, and a control voltage generator 63, and produces a certain sum signal. The differential signal is obrained from a PLL circuit 8 and separated to the right and left signals through a matrix circuit 9. |
