| 摘要 |
PURPOSE:To make the quantity of a change in an oscillated frequency of a local oscillator constant by providing a means supplying a control voltage in response to the phase difference between an output of a reference frequency generating means and an output of a variable frequency division means to the local oscillator. CONSTITUTION:With a keyboard 14 is operated, a CPU 16A varies the frequency division ratio P of a programmable divider 10 in response to an operation signal. Then the oscillating frequency fl of the local oscillator 4 changes and the intermediate frequency f2 and the detected output voltage V are changed attended therewith. The CPU 16A fixes once a frequency division ratio P of the programmable divider 10 so as to monitor whether the output of voltage comparators 7h, 7l is of the same sign or the different sign. When the outputs of the voltage comparators 7h, 7l are of the different sign, the fixed frequency division ratio P is released. On the other hand, when the outputs of the comparators 7h, 7l are of the same sign, the voltage setting data fed to a D/A converter 25 is changed and the fixed frequency division ratio is released when the output of the comparator 7h reaches an 'L' level and the output of the comparator 7l reaches an 'H' level.
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