| 摘要 |
PURPOSE:To carry out a fine adjustment for the received frequency of a wide band for an electronic channel selector using the frequency synthesizer system, by forming a timing pulse to vary the dividing ratio of a programmable divider every time when the dividing ratio passes the received frequency value. CONSTITUTION:Dividing ratio setting data is set to U/D counters 32-36 to set a channel, and fine adjustment data equivalent to the shift of an IF delivered from an electronic tuner 21 is formed by a fine adjustment signal producing circuit 37. The fine adjustment data is applied to the counters 32-36 to be added to or subtracted from the dividing ratio setting data. The result of this addition or subtraction is supplied to a designated input terminal of a programmable divider 23. Then a pulse forming circuit 44 is provided to form a timing pulse to reduce the dividing ratio of the divider 23 or the dividing ratio setting speed. Then the timing pulse given from the circuit 44 is supplied to the circuit 37 and a channel selection controlling circuit 28. |
