| 摘要 |
In a multi-band radio frequency tuning system, typified by a television tuning system including UHF and VHF signal paths (14,36,44), each such path is tuned by a tuning voltage (VT) and coupled to a common signal path (50,60) by a diplexer (20). In order to attenuate UHF signals so to not cause interferences with a VHF channel signal which has been selected, the UHF filter (14) is detuned when a VHF channel is selected. Detuning the UHF filter is accomplished by filter control (15) which modifies the tuning voltage (VT) for the UHF filter (14) responsive to the VHF band-switching voltage (VB 12). The filter 14 is described in detail (Figs. 3 or 4) and includes varactor diodes (CD42, CD44). <IMAGE> |
