| 摘要 |
<p>Proposed is a switchable loop filter structure which allows a dual mode operation. A low bandwidth mode is used during acquisition of a channel. In case of high rate reception the low bandwidth synthesizer loop is combined with a high bandwidth carrier recovery loop. This combination allows steps of the synthesizer which are tracked in the carrier recovery loop. The tuner steps are used to compensate input signals frequency drift. An algorithm is proposed which allows acquisition in a low synthesizer loop bandwidth mode and switching to a high bandwidth synthesizer loop mode while maintaining frequency lock. This allows the use of a high bandwidth synthesizer loop and a low bandwidth carrier recovery loop. This combination is best for reception of low rate input signals. The synthesizer loop compensates for residual FM of the tuner Local Oscillator.</p> |
