| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a heterodyne receiver in which a fixed frequency is changed by following to the case that the frequency of the input received signal changes and an intermediate frequency of constant frequency is generated. <P>SOLUTION: A local oscillator 4 is constituted with a PLL circuit. The output of a voltage controlled oscillator 4g is not returned to be input to a comparison frequency divider 4c, but a signal of intermediate frequency F3 is input in which a mixture 5 outputs. And, in the state that the received signal is not received, the voltage controlled oscillator 4g is not oscillated by the loop of the PLL circuit but on the basis of a reference voltage Vref. When the received signal is received, the voltage controller oscillator 4g is oscillated by the loop of the PLL circuit. Consequently, even if the signal of different frequency is made into the received signal, the intermediate frequency F3 of the output signal of the mixer 5 is locked up for a short time, and it can become a predetermined frequency (10.7 MHz). <P>COPYRIGHT: (C)2006,JPO&NCIPI |
