Design And Research Of Cavity Band Stop Filter

The radio spectrum has become extremely crowded recently due to the rapid growth of wireless systems. Due to interference by other systems which are spectrally close to the desired communication system, it is challenging to achieve optimum performance of a system. In order to mitigate the effects of co-site interference, it is desirable to have a band-stop filter in the front-end of a receiver. Moreover, there has been a demand for rejecting all unwanted signals such as spurious responses and image frequencies from active devices as well as co-site interference. In addition, in order for the front end filter to provide flexible suppression of co-site interference and other undesirable RF signals, it is necessary for the band-stop filter to have the ability to change its center frequency. Areconfigurable receiver front-end without a frequency-agile design presents complexity, large size, and extra loss from the switches for rejecting undesired frequencies. Also, a reconfigurable receiver front-end with high power millimeter wave band-stop filters will be a more challenging design.By reading a large number of domestic and foreign literatures, on the basis of in-depth study of the microwave/millimeter wave filters,this paper presents a kind of band-stop filter with well rejection capability、low pass-band loss and the good adjustability. The mainly work of the thesis includes:Firstly, the basic theory of designing microwave filters has been analyzed, which Butterworth, Chebyshev and other basic low-pass prototype filter by Kuroda transformation from lumped parameter elements to distribution parameter element transformation theory is introduced.Secondly, by simulation design E-plane inductance coupling and H-plane capacitance coupling two cavity band-stop filter, it introduced a short-circuit stubs and resonant mode as the designing scheme to construct the band-stop filter.Finally, design of a cavity band-stop filter to achieve the large-scale in the structure, extent to reduce the difficulty of the debugging task and makes a certain degree of discussion on the high frequency of the filter design problem.