| 摘要 |
PROBLEM TO BE SOLVED: To avoid an inaccurate input signal by allowing a low pass recursive filter to obtain a comparison value between a power of an output signal and a permitted power of a control loop signal so as to form an initializing signal to enhance the gain control. SOLUTION: An input signal IF 2 amplified automatically by an amplifier circuit 10 is given to an A/D converter 11. Then in order to avoid an inaccurate value due to a saturated output or a too weak output of the A/D converter, the input signal IF2 tuned to a dynamic range of the input of the A/D converter. Then a power of an output signal IF3 of the A/D converter 11 is measured by a measurement circuit 12 in an automatic gain control loop. The circuit 12 is composed of a circuit 20 using an absolute value of a signal IF 3, a recursive LPF 22 forming a mean power P of the signal IF 3, and a comparator 24 that compares the measured average powder P with a window reference power permitted between a maximum value Pmax and a minimum value Pmin. The measured value is enhanced to provide an initial value enhancing the gain control. |
