摘要 |
<P>PROBLEM TO BE SOLVED: To provide a radio transmitter and receiver capable of detecting a free channel by accurately detecting the signal level of a reception signal. <P>SOLUTION: When a free channel is detected, a control unit 1 varies the frequency of a local oscillation signal oscillated by a local oscillator 3 to detect the level of a signal detected by a mixer 10. Consequently, the output signal of the mixer 10 is not affected by self-mixing of homodyne reception, so the signal level of the reception signal is accurately detected to accurately detect the free channel. <P>COPYRIGHT: (C)2008,JPO&INPIT |