| 摘要 |
A saw-tooth waveform signal generating circuit (3) generates a saw-tooth waveform signal d in response to a timing signal b derived from a reference clock a. A voltage comparator (4) slices the saw-tooth waveform signal with a reference voltage to shape the waveform thereof, thereby producing a synthesizer output e having a rectangular waveform. A counter (5) adds or subtracts a predetermined value every time a reference clock arrives. The count of the counter (5) is converted to an analog value by a DAC (6) and then is applied to, for example, the saw-tooth waveform signal generating circuit as a bias. As a result, the voltage for causing the saw-tooth waveform signal to start rising or falling is manipulated to allow the voltage comparator to slice the saw-tooth waveform signal at any desired timing. Hence, a synthesizer output can be produced in any desired phase.
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