| 摘要 |
A feedback circuit for amplification of the output signal of an analog front end and suppression of its DC and low frequency components comprises a variable gain amplification unit ( 2 ) controlled by a gain control signal and a reverse path unit ( 6 ) comprising a filter unit ( 8 ) with variable time constant. A control unit ( 13 ) produces the gain control signal as well as a reverse path control signal (S) which causes adaptation of variable resistances ( 12 ) and capacitances ( 10 ) in such a way that the time constant of the filter unit ( 8 ) varies essentially proportionally with the gain of the variable amplifier unit ( 2 ). Thereby the gain of the feedback circuit as a function of the frequency retains its shape with varying gain. As the reverse path control signal (S) can be produced from different inputs selectable by selectors ( 20 a , 20 b) in the control unit ( 13 ) and due to the adaptability of the reverse path unit ( 6 ) and other features the analog base band unit is suited for the processing of signals of various types, e.g. signals pertaining to GPS and mobile telecommunication systems.
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