| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a communication apparatus which accurately measures the signal strength of a demodulated signal. <P>SOLUTION: Two local oscillators are provided, a local oscillator 22 is used to perform demodulation processing for obtaining a demodulated signal, and a local oscillator 33 is used to perform signal level detection processing. In the signal level detection processing, a DC component Δ is extracted by an LPF 27 from the demodulated signal containing, as the DC component Δ, a difference between a frequency fc' of a carrier wave of a reception signal and a frequency fc of a first local oscillation signal of the first local oscillator 22. An AFC 32 detects the difference of the frequencies in accordance with the DC component Δ, and outputs, to the local oscillator 33, a control signal of a correction frequency δf that cancels the frequency. A mixer 34 mixes a corrected second local oscillation signal outputted from the local oscillator 33 and the reception signal, and supplies the mixed result to a BPF 35. A signal level detector 37 measures the signal strength of a signal, selected by the BPF 35, having a passband of the same or narrower bandwidth as or than that of the reception signal. <P>COPYRIGHT: (C)2010,JPO&INPIT |
