| 摘要 |
PROBLEM TO BE SOLVED: To enable linear control and reduce the power consumption by outputting a control signal which controls a gain according to the signal level of a receive signal to a local oscillator and controlling the level of a signal outputted by the local oscillator. SOLUTION: A low-noise amplifying circuit 2 directly amplifies the received signal and outputs it to a mixer 3, which multiplies the signal oscillated by teh local oscillator 6' by the signal inputted from the low-noise amplifying circuit 2 and outputs the result to an amplifying circuit 4. Then the amplifying circuit 4 amplifies and outputs the signal to the outside and also to an input level detecting circuit 5, which detects the level of the inputted signal and feeds it back to an AGC circuit 1' as a received electric field intensity signal. Then AGC circuit 1' outputs the control signal to a buffer amplifier 65 of the local oscillation circuit 6' and the buffer amplifier 65 amplifies the oscillated signal with an amplification factor almost in proportional to the control signal and outputs the amplified signal to a PLL circuit 62 and a multiplier 66, which multiplies the amplified signal to a mixer 3. |
