| 摘要 |
PURPOSE:To make the tracking adjustment of each stage possible, by oscillating the preceding stage side of a multistage tuning RF amplifying circuit and using this oscillation output to perform the tracking adjustment for the succeeding stage side of this RF amplifying circuit. CONSTITUTION:The oscillation output from an RF amplifying circuit 121 of the first stage part and an RF tuning part RFT1 which are adjusted already is used as a reference signal. Then, a signal of the differential frequency between the oscillation frequency of the RF amplifying circuit 121 and the local oscillation frequency of a local oscillator OSC is outputted from the output terminal of a mixer 13. A level detector 24 detects this signal and supplies it to a control voltage controlling circuit 25. The control voltage controlling circuit 25 gives a control voltage to a varactor diode provided in the RF tuning part RFT1 to change the tuning frequency of the RF tuning part RFT1 and holds such control voltage that the output of the level detector 24 is maximum. Thus, the tracking adjustment is terminated, and similar operations are performed for the next and following stages successively. |
