| 摘要 |
PURPOSE:To decrease the frequency deviation more by adopting a primary frequency correction stage and a secondary frequency correction stage for the stages the controlling searching frequency of a variable frequency local oscillator in an FM demodulator or the like for satellite communication. CONSTITUTION:A controller 3 calculates a primary setting frequency FS1 of a 1st local oscillation signal 6 corresponding to a channel number designated via a frequency designation terminal 4, controls a variable frequency local oscillator 1 by a frequency data 2 based on the result of calculation and outputs a 2nd intermediate frequency signal fS1 of an output signal 12. Then the controller 3 counts the signal fS1 by a frequency counter 9, obtains a DELTAfS1 being a deviation of a 2nd intermediate frequency from a center frequency f0 (fixed value), calculates a 1st local oscillation secondary setting frequency FS2 to be closed to the frequency f0 and outputs a frequency data 2 subject to secondary correction to the variable frequency local oscillator 1 (secondary setting). In this case, the 2nd intermediate frequency is fS2, the frequency deviation DELTAfS2 is suppressed within a frequency deviation being + or -1 bit of the frequency data 2 set secondarily by the controller 3. |
