| 摘要 |
PROBLEM TO BE SOLVED: To allow the gain controller to have both a low noise characteristic and a high adjacent disturbance suppressing characteristic in spite of a small circuit scale, and to need no adjustment. SOLUTION: When an IF automatic gain control(AGC) control signal 112 is smaller a delay point, a 1st loop filter 105 receives an output signal agcerr of a signal level detector. Thus, the IF AGC control signal 112 with a value in response to a signal level of an IF signal is fed black to an IF AGC amplifier 608 that conducts automatic gain control. On the other hand, a 2nd loop filer 106 receives '0' when the output of a 2nd comparator 108 is '0' or receives a fixed value -rfdump when the output of the 2nd comparator 108 is not '0', and the 2nd loop filter is converged when the output is '0'. Thus, an RF AGC control signal 113 fed to the RF AGC amplifier 602 is '0' so that the gain of the RF AGC amplifier 602 is fixed to a maximum value. |
