| 摘要 |
A radio receiver comprises an input (10) coupled to first and second quadrature related low-IF frequency translation stages (20, 21) generating IF signals at substantially half the channel bandwidth or channel spacing. The IF signals which may be optionally filtered in a pre-filter (28), for example a polyphase filter, are applied to first and second cross-coupled continuous time, low pass Sigma-Delta modulators (30) comprising for example transconductor-capacitor integrators, all but the first integrators of which are cross-coupled by gyrators set to resonate at the IF frequency. Outputs of the Sigma-Delta modulators (30) comprise 1 bit oversampled signals. The oversampled signals in one embodiment are filtered in first decimation stages (32, 34) which provide anti-aliasing. The decimated signals are derotated (38, 40) and decimated in a second decimation means (42, 44) to provide outputs at base band. The outputs are equalised and demodulated to provide an output (48). The input signal may be frequency translated to zero IF and then filtered in low pass filters.
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