| 摘要 |
PROBLEM TO BE SOLVED: To shorten a time until defining a communication frequency by intermediately tuning the next frequency without processing after digital modulation concerning a frequency discriminated to have not reached a regulated level yet by an IF level discriminating circuit. SOLUTION: A tuning control circuit 2 sends a frequency control signal to a tuning circuit 1 for tuning a frequency. The circuit 1 which has received the frequency control signal converts the frequency of a received RF signal to an IF band. The circuit 1 transmits the converted IF signal to an IF level discrimination circuit 3 and a digital demodulation circuit 4. Since the frequency is non-signal, the IF signal of the output of the circuit 1 is also non-signal. When the circuit 3 detects that the IF level of the IF signal inputted from the circuit 1 has not reached a regulated level yet, the circuits 3 sends the detecting result to the circuit 2 to tune another frequency.
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