| 摘要 |
The tuner in a digital TV receiver converts received signal to a penultimate intermediate-frequency signal. Penultimate local oscillations are supplied in a first phasing and in a second phasing in quadrature therewith, for heterodyning with t he penultimate IF signal in first and second mixers respectively to generate real a nd imaginary components of an ultimate intermediate-frequency signal. The first and second mixers are of a switching type, switching in respective response to the penultimate local oscillations as supplied in first and in second phasing. First analog-to-digital conversion circuitry containing a number N of analog-to-digita l converters digitizes the real component of the ultimate IF signal on an N-phase basis, N be ing at least one. Second analog-to-digital conversion circuitry, which contains a numbe r N of analog-to-digital converters, digitizes the imaginary component of the ultima te IF signal on an N-phase basis. A complex digital carrier signal is generated at the frequency of the radio carrier wave as Translated to the ultimale IF signal band , Synchrodyning circuitry respondj to the complex digital carrier signal supplied as ultimate local oscillations, and to the digital samples of the real and imaginar y components of the ultimate IF signal, for recovering in-phase and quadrature-pha se components of baseband signal.
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