| 摘要 |
PURPOSE:To attain the sure phase locked loop establishment by alternately crossing the frequency pull-in range from upward or from downward with a bias voltage at the time of turning on the power source and at the time of changing the set frequency. CONSTITUTION:When the power source is turned on or when a set frequency fS of a frequency setter 15 is largely changed, the phase locked loop is instantaneously or naturally out. In the condition, a microprocessor 23 sends a frequency setting command (h) to a voltage width preparing means 21a of a bias voltage generating part 22. At such a time, after a time t0, a bias voltage VB is impressed from a bias voltage generating part 22 through a voltage adder 5 to a VCO 8 as a control voltage VC. Consequently, after a time t1 when the bias voltage VB exceeds a lower limit voltage V2 of the frequency pull-in range, the phase locked loop is established and a frequency f0 of an output signal (c) is controlled to a set frequency fS. Thus, when the bias voltage VB crosses a frequency pull-in range (V2 to V3) from downward or from downward, the chance to execute the phase locked loop establishment is given. |
