| 摘要 |
A modem tuner of ZIF or NZIF type comprises a mixer which receive first and second inputs via a multiplexer in different frequency ranges from different sources such as cable and satellite. A local oscillator supplies signals via a bandswitch which switches the local oscillator frequency range in synchronism with the selection of inputs by the multiplexer. The mixer converts the selected incoming data stream to zero or near-zero intermediate frequency and this signal is filtered exclusively by a variable bandwidth low-pass filter before being converted to the digital domain and demodulated.
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