| 摘要 |
The performance of filter 14 is adapted, after testing the operation of the filter, by applying at least one portion of a sheet material 24 (e.g. a dielectric such as polyimide) to the filter, altering its operation. An actual parameter (e.g. limit values for frequency) of the filter 14 is compared with the required value, the material being applied after an unacceptable comparison. The filter may be formed on a PCB and the sheet material may be selected to have particular dimensions, such that it covers only a certain part of the filter as in the figure, or so that a certain thickness (e.g. in the range 30-60 microns) is used. A set with differing dimensions may be available and a reference table used to select them, based on the comparison. The filter may be used for reception of digital television services e.g. in conjunction with Low Noise Blocks (LNBs). |
