| 摘要 |
A filter assembly is disclosed. The filter assembly is for filtering a radio frequency signal and comprises: a first filter having a first filter pass band and a first filter stop band, the first filter being operable to receive the radio frequency signal and to provide a first filtered radio frequency signal; a coupler operable to receive the first filtered radio frequency signal and to provide a second filtered radio frequency signal; and a pair of filtered reflective loads coupled with the hybrid coupler to receive the first filtered radio frequency signal and to provide the second filtered radio frequency signal, each filtered reflective load comprising a second filter and an impedance device, each second filter having a second filter pass band which overlaps with the first filter stop band. Selecting the pass-band of the filtered reflective loads to overlap with the stop-band of the filter causes two effects. The first is that the portion of the filtered signal within the pass-band of the filtered reflective load is dissipated by the impedances, which provides a deep and broad transmission zero. It will be appreciated that by carefully arranging the position of the pass-bands and stop-bands of the filters, the position and breadth of the transmission zero can be controlled. Secondly, the radio frequency signal within the filtered signal in the pass-band of the filter will not be dissipated by the impedance device, but instead will be reflected back to the coupler to provide an output radio frequency signal. This means that high power does not flow through the filter within the filtered reflective loads and so smaller and less robust components can be used for that filter which reduces its size. |
