| 摘要 |
<p>A method and apparatus for controlling a radio receiver provided with a local frequency reference (2) and a closed loop control system with a loop filter (5) for tuning the receiver's operating frequency to a received radio signal by altering the local frequency reference based on the received signal. On first receiving a radio signal from a given source, the characteristic of the loop filter (5) is fixed to a predetermined value. Subsequently, the characteristic of the loop filter (5) is changed after successive signal samples taken from the received signal so as to progressively increase the settling or alignment time of the receiver. Preferably the signal samples correspond to those portions of the received signal with a quality which exceeds, or alternatively equals or exceeds, a predetermined threshold value of signal quality. After a predetermined number of signal samples have been taken, the loop characteristic is fixed once more to provide a relatively slower settling time for the control loop.</p> |
