| 摘要 |
PURPOSE:To widen a dynamic range even when a transmission area is expanded and to realize reception with superior sensitivity, by amplifying a weak signal by controlling amplification degree by a first demodulator, and outputting a strong signal by suppressing the amplification degree by a second demodulator. CONSTITUTION:The first demodulator I is provided with an AGC function, therefore, it is formed so that the amplification degree of an intermediate frequency amplifier 105 can be controlled by outputting an AGC signal corresponding to a detector I108 with superior detecting efficiency which detects the weak signal and a signal to be inputted to the detector I108. The second demodulator II is constituted of a simple and inexpensive envelope detector in which a diode D, a capacitor C, and a resistor are combined, etc. In such a way, a signal being damped and weakened because of transmission from a remote place is amplified by the demodulator I, and the strong signal from a near place is amplified by the demodulator II. Therefore, the signal emitted both from the remote place or the near place can be received with high sensitivity.
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