| 摘要 |
PROBLEM TO BE SOLVED: To output only a received electric field intensity signal by a desired wave in an IF(intermediate frequency) filter used by various receivers. SOLUTION: A first automatic gain control amplifier 1 executes prescribed amplitude limit to an input signal large than a gain range. In addition, a band- pass filter 3 gives prescribed attenuation to an interference wave, connects the output it a second automatic gain control amplifier 2 with a prescribed gain range, a gain control signal adding circuit 4 adds the gain control signals of the first and second automatic gain control amplifiers 1 and 2 to generate the received electric field intensity signal, a comparator 5 compares the gain control signal of the second amplifier 2 and the detected level threshold value of a input terminal 15 with each other, and a switch circuit 6 outputs the received electric field intensity signal obtained by the adder circuit 4 only when the gain control signal of the second amplifier 2 is larger then the detected level threshold value. |
