| 摘要 |
Some of the capacitors in an RC N-path bandpass filter (fig. 4) may be omitted (S34) from the switching sequence in order to alter the ratio N between the centre frequency and the clock frequency. In multi-band radio receiver arrangements where the ADC clock is derived from the local oscillator by division by a band-dependent integer, the technique allows a notch filter frequency to be matched to the ADC sampling frequency while using a simple divider chain to derive the ADC and filter clocks from the local oscillator signal. Variation in the gain of the bandpass filter due to variation in N, and hence reduction in the depth of the notch, may be reduced by scaling, dependent on N, the output of the bandpass filter prior to combination with the input signal.
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