| 摘要 |
A communications receiver architecture characterized by a relatively low intermediate frequency (IF) and a polyphase filter. The receiver includes an input amplifier coupled to a carrier signal. Respective I and Q demodulators are coupled to the output of the input amplifier. A quadrature local oscillator (LO) generator provides respective LO_I and LO_Q inputs to the I demodulator and LO_Q inputs to the I demodulator and to the Q demodulator. The quadrature LO generator is driven by a phase-locked LO, and the LO frequency is such that an IF of, in one embodiment, approximately 1 MHz results. The I demodulator and Q demodulator outputs are applied through respective AID converters to a polyphase filter. The polyphase filter outputs are then processed by a digital I/Q demodulator. Although a low IF is not generally understood to promote the image rejection performance of a receiver, substantial image rejection is afforded by the polyphase filter, thereby enabling the receiver to be realized almost entirely as a monolithic integrated semiconductor device.
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