PURPOSE: To effect sweeping while forming a phase locked loop by sequentially setting a clock rate for each sweeping step frequency unit to a frequency divider in a DDS(Direct Digital Synthesizer) by means of a controller, thereby, eliminating the need of analog voltage in the sweeping.
CONSTITUTION: The inner clock rate of a DDS 33 is set sequentially for each sweeping step frequency unit by means of a controller 32 and a variable sweeping frequency is outputted thus realizing a sweeping function. The variable frequency is fed to one input of a phase comparator 36 and the output from an YTO(YIG-tuned Oscillator) 38 is fed to a frequency divider 37 where the frequency is divided by N. It is then fed to the other input of the phase comparator 36 and an output signal therefrom is employed in oscillation frequency control of the YTO 38 thus locking the phase. Consequently, the oscillation frequency of the YTO 38 is outputted stepwise while being phase locked at all times.
ANNO NAOYA
FUKUI TAKAMASA
