Patent ID: 8233864

Claim:
A signal receiving apparatus comprising: resonance means for receiving an input signal at a variable resonance frequency; signal supplying means for supplying an electrical signal having a frequency set at a value equal to a desired reception frequency to said resonance means; mixture means for mixing a resonance signal, which is output by said resonance means when said resonance means receives said electrical signal from said signal supplying means, with a switching signal having a frequency set at a value equal to said desired reception frequency; and control means for changing a resonance characteristic of said resonance means and measuring the phase of a mixed signal output by said mixture means before said resonance characteristic is changed as well as said phase of said mixed signal output by said mixture means after said resonance characteristic has been changed in an operation to control said resonance frequency of said resonance means in order to change said resonance frequency in a direction to reduce a difference between said phase of said mixed signal output by said mixture means before said resonance characteristic is changed and said phase of said mixed signal output by said mixture means after said resonance characteristic has been changed.