| 摘要 |
The invention provides a bandpass filtering method in which two frequency transpositions are performed in parallel on an input signal for filtering using respective first and second upstream mixing signals that are substantially in phase quadrature, and two respective downstream mixing signals, and the sum or the difference of the two signals obtained in this way is taken, the frequency of the downstream mixing signals is selected to be different from the frequency of the first and second mixing signals so that the output signal is transposed into a desired frequency range, the method being characterized in that a common oscillator is used which is coupled with a first phase shifter to produce the upstream mixing signals and which is coupled with a second phase shifter to produce the downstream mixing signals, and in that the phase shifters are used in opposite manner on the first and second signals so that each of said first and second signals receives the phase-advanced output signal from one of the two phase shifters and the phase-delayed output signal from the other of the two phase shifters.
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