| 摘要 |
PURPOSE:To allow the circuit to lock a correct frequency by locking a frequency with a frequency apart from a lock frequency by + or -fs and discriminating the frequency to be a correct lock frequency when an output locked to a lock frequency is larger than an output locked to either of both extreme frequencies. CONSTITUTION:When a lock detection section 4 detects the lock state, an output of a reception level detection section 10 at that time is written in a register M, a frequency control section 5 increases the frequency of a VCO 6 by fa from the lock frequency and an output of the reception level detection section 10 at that time is written in a register U. Moreover, the frequency control section 5 decreases the frequency of the VCO 6 by fa from the lock frequency and an output of the reception level detection section 10 at that time is written in a register L. A reception level comparison section 12 compares contents of the registers L, M, U and when the content of the register M is largest, the lock frequency written in the register M is selected as a correct lock frequency. |
