| 摘要 |
The tuner in a digital TV receiver converts received signal to a penultimate intermediate-frequency signal. Penultimate local oscillations are supplied i n a first phasing and in a second phasing in quadrature therewith, for heterodyning wi th the penultimate IF signal in first and second mixers respectively to generate re al and imaginary components of an ultimate intermediate-frequency signal. The first andsecond mixers are of a switching type, switching in respective response to the penultimate local oscillations as supplied in first and in second phasing. F irstanalog-to-digital conversion circuitry containing a number N of analog-to-digital converters digitizes the real component of the ultimate IF signal on an N-phase basis, N being at least one. Second analog-to-digital conversion circuitry, which contains a n umber N of analog-to-digital converters, digitizes the imaginary component of the ul timate IF signal on an N-phase basis. A complex digital carrier signal is generated at thefrequency of the radio carrier wave as Translated to the ultimale IF signal band, Synchrodyning circuitry respondj to the complex digital carrier signal suppl ied as ultimate local oscillations, and to the digital samples of the real and imag inary components of the ultimate IF signal, for recovering in-phase and quadrature -phase components of baseband signal.
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