| 摘要 |
A frequency synthesizing apparatus comprising a reference generator (1) and a phase locked loop containing a phase detector (3) of the sample-hold type, a loop filter (4) a VCO (5) and a frequency divider (6) in the loop. The frequency divider (6) can be set at different numbers (N) so that the VCO sends different frequencies. In accordance with the invention a synchronizing unit (2) is connected between the reference generator (1) and the phase detector (3). The synchronizing unit switches reference generator (1) and the frequency divider means simultaneously to the phase locked loop during the locking phase and switches these out during a working phase, when the VCO (5) sends an output signal of the desired frequency (f). The loop filter can then be dimensioned with a wide bandwidth for rapid locking. |
