| 摘要 |
In a receiver the input signal is converted by a mixer into two quadrature IF signals. The quadrature IF signals are amplified by an amplifier and filtered by a filter. A polyphase filter suppresses signals having frequencies above a predetermined frequency. A second mixer converts the filtered IF signal into a second IF signal. This second IF signal is filtered by a second polyphase filter which suppresses signals having a frequency below a predetermined frequency. In this way a band-pass transfer function is obtained having a first edge defined by the first polyphase filter and having the second defined by the second polyphase filter. In an embodiment of the invention, the cut off frequencies of the polyphase filters are equal to zero, resulting in a transfer function for the complete receiver having cut off frequencies independent from the component values use in the polyphase filters.
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