| 摘要 |
PURPOSE:To simplify the controller and to reduce the cost by sweeping and detecting a carrier area so as to obtain a valid carrier number and selecting a reference value of a transmission level based thereon so as to implement level control. CONSTITUTION:A sweep signal generator 7 generates a sweep local oscillation signal repetitively at a period T so as to cover a signal frequency band including a carrier of a transmission signal branched at a branch circuit 3. A mixer 6 mixes a sweep frequency and a carrier and converts the result into a difference and a sum signal of the both. When a component of the difference of the converted signals is coincident with a band pass frequency, a band pass filter 8 passes through it and outputs the result to a detector 9. A difference between each carrier and a sweep frequency is coincident with the band frequency of the filter 8, and then the detector 9 generates a pulse in the timing. A valid carrier number is recognized by counting the pulse number at a counter 10. Thus, a high frequency section detects the carrier number even in the system where the carrier number is timewise fluctuated and the controller is simplified. |
