| 摘要 |
A filter system includes a low pass filter, a first summer circuit, a second low pass filter and a second summer circuit. The first low pass filter includes an input, an output, a storage means, a switching means and a control means. An input signal is placed on the input. An output signal is generated on the output. The storage means provides storage of a signal sample over time. The switching means, when closed, electrically couples the input to the first end of the storage means. The switching means, when open electrically isolates the input from the first end of the storage means. The control means controls the switching means. The control means generates a switching control signal. The switching control signal has a sampling frequency. A maximum cutoff frequency of the low pass filter is dependent on a value of a capacitance provided by the storage means, the sampling frequency, and a pulse width of the switching control signal. The first summer circuit subtracts the output signal from the input signal to produce a high pass output signal. The second low pass filter receives the high pass output signal and produces a bandpass filtered output. The second summer circuit subtracts the bandpass filtered output from the input signal to produce a notch filtered output.
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