| 摘要 |
PURPOSE:To stabilize the 2nd intermediate frequency without giving the compensation of temperature to the 2nd local oscillator and a filter, by securing the same variation factor due to the variance of ambient temperatures, etc. between the 1st and 2nd local oscillation frequencies. CONSTITUTION:The 1st local oscillation frequency f1 is divided by a fixed frequency divider 12 and a variable frequency divider 14 and then undergoes a phase comparison through a phase comparator 15 with the signal obtained by dividing the oscillation frequency f2 of the 2nd local oscillator 6. Then the frequency f1 of the 1st local oscillator 3 is controlled with the signal corresponding to the phase difference obtained from said comparison. Therefore the temperature variance DELTAf1 of the frequency f1 is set at f1XDELTAf2/f2 (DELTAf2: variance of frequency f2), and the variance DELTAf=¦DELTAf1-DELTAf2¦ of the frequency f of the 2nd intermediate frequency signal is set at ¦f1-f2¦XDELTAf2/f2. As a result the variance component can be reduced. |
