FREQUENCY SWEEP METHOD AND CIRCUIT

PROBLEM TO BE SOLVED: To perform hige-speed sweep without causing the generation of a repetitious frequency signal by a stepped waveform, and to control a frequency stably without being influenced by environmental conditions such as temperatures.SOLUTION: A loop for feeding back an output from VCO1 via a programmable counter 14, PFD 16, a stabilization filter 17, and a gradient control filter 18 is formed. Within a frequency acquisition time based on a control signal at a present frequency point from the programmable counter 14, a control signal at a next frequency point is output to the PFD 16 to perform a continuous sweep of frequencies without passing through a phase synchronized state. The gradient control filter 18 controls a gradient of a change in frequency during the sweep.