| 摘要 |
The invention relates to a method for controlling a phase-locked loop in a locking situation, and to a phase-locked loop. The loop comprises a phase detector (13), a loop filter (14) and a voltage-controlled oscillator (15) connected in succession, a feedback path being established from the output of the oscillator to a second input (12) in the phase detector. In response to a change causing a currently used input signal to become inadequate for locking, the signal connected from the loop filter (14) to the oscillator (15) is frozen to a constant value, and in response to a change causing a currently used signal to become again adequate for locking, the freezing is removed. In the method, in order that the locking would take place directly, without any sudden phase changes, (a) the output signal of the loop filter (14) is additionally maintained substantially at said constant value by means of the feedback loop (25; 45) in response to a change causing the currently used input signal to become inadequate for locking; and (b) the control provided by said feedback loop for the loop filter (14) is frozen substantially at its current value in response to a change causing the signal to become again adequate for locking. |
