| 摘要 |
In a double conversion tuner for a television receiver including a first local oscillator and a first mixer for converting the RF signal corresponding to a selected channel to a first IF signal and a second local oscillator and a second mixer for converting the first IF signal to a second IF signal, control apparatus is coupled to one of the local oscillators for offsetting its frequency and correspondingly the carriers of the first IF signal relative to the passband of a first IF filter coupled between the two mixers. In this manner the amplitude or phase of the carriers of the first IF signal can be controlled. An AFT signal is coupled to the other one of the local oscillators to compensate for the frequency offset of the carriers of the first IF signal in order to tune the carriers of the second IF signal to their nominal frequencies.
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