| 摘要 |
A front end for a radio frequency tuner, for example for connection to a cable distribution network, comprises an input connected to a signal path comprising an LNA 9 connected via an AGC stage 10 to a signal splitter 11. The input path has a bandwidth sufficiently wide to pass all of the channels in an input signal and has a substantially constant voltage standing wave ratio over the bandwidth. The splitter 11 supplies identical signals to several filtering paths, each of which comprises a fixed filter 12, 13. The paths are selectable one at a time and the filters 12, 13 divide the input frequency band into a plurality of contiguous or slightly overlapping sub-bands. The output of the front end is supplied to, for example, a double conversion arrangement comprising an upconverter 2, 3 and a downconverter 5, 6 with first and second IF filters 4, 7. <IMAGE> |
