| 摘要 |
<p>PURPOSE:To suppress power consumption of a battery especially by operating intermittently a PLL local oscillation circuit of the FSK receiver in response to a phase locking state. CONSTITUTION:A modulation wave is mixed with a 1st local oscillating frequency generated by a VCO 112, a loop filter 119 and a PLL circuit 113 at a 1st mixer 104 and mixed with a 2nd local oscillating frequency generated by a local oscillation circuit 120 at a 2nd mixer 106 and the mixed signal is demodulated by a detection circuit 109 and a base band signal is extracted by a low frequency filter 110 and a comparator circuit 111. Its output is detected as a DC voltage at an integration circuit 114 and fed to a comparator circuit 115 via a sample-and-hold circuit 116 and compared with a succeeding detected DC voltage. Only when the value exceeds a prescribed value and the frequency fluctuation is deviated from the synchronization lock state, the operation of the PLL circuit is activated by a PLL intermittent operation circuit 117, and the operation is inactivated in other cases except initial synchronization locking to use a free run output of the VCO.</p> |
