| 摘要 |
A tuner is provided for selecting a channel for reception from a multiple channel input signal. The tuner has a signal path which converts a selected channel, for example in a frequency changer, to a standard intermediate frequency and supplies this to a demodulator. The signal path has at least one controllable variable gain stage. The tuner also comprises a controller which periodically operates the tuner in a channel mapping mode. In this mode, a look-up table is provided by determining from the signal at the input which channels are occupied, together with other data relating to each occupied channel. During the normal reception mode of the tuner, the controller 8 selects a channel for reception and then controls the or each variable gain stage in accordance with the occupancy of channels adjacent the selected channel. |
