| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that receiving sensitivity is deteriorated due to shift of a resonant frequency generated due to a stray capacity when a discriminator is connected to a detection IC in configuring an FM/FSK receiver of a weak radio or small power facility using the detection IC. SOLUTION: A discriminator circuit 6b consists of a piezoelectric resonator X1, a resistor R1, a capacitance C1, a varactor diode VC and a capacitance C2. A level detecting circuit 8 for monitoring detection output is connected to an AF-OUT terminal of a detection Ic7. A control voltage to be applied to the varactor diode VC is changed while the level detecting circuit 8 is monitoring the detection output of the AF-OUT terminal in a state where a high-frequency signal of a constant level is input from an RF input terminal, and the control voltage at which the detection level is the maximum is stored in a memory 9. The control voltage stored in the memory 9 is applied to the varactor diode VC1 via the resistor R1 simultaneously with operation start of a receiver 110. COPYRIGHT: (C)2006,JPO&NCIPI
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