| 摘要 |
PURPOSE:To realize the process of the intermediate frequency amplified signal for a quadrature wave detecting circuit which is used for an AM receiver, by applying the bias voltage to a switching transistor receiving application of the 90 deg.-phase shift signal at its base via a tank circuit. CONSTITUTION:The AM broadcast signal is amplified through an RF input stage 1 and then mixed with the local oscillation signal produced at a local oscillating circuit 3 through a frequency mixing circuit 2 to be applied to an intermediate frequency amplifying stage 4 after conversion of frequency. Then an output obtained from an AM wave detector after detection of wave is supplied to matrix circuit 15 and an AGC filter 6. At the same time, the intermediate frequency amplified signal supplied from the stage 4 is applied to a limiter amplifier 7 to exclude the amplitude modulated component, and this output is supplied to the circuit 15 via a quadrature wave detecting circuit 8, an LPF9, an AGC circuit 10 and a muting circuit 14 respectively. In such constitution, the bias voltage is applied to a switching transistor in the circuit 8 via a tank circuit. |
