The Study Ofsatellite Band Pass Filter In C Band

Satellite band pass filter in C band is quite important in modern satellite communication, which directly affects the whole receiver’s indexes. Microwave interference and pulse interference which come from satellite communication receiverseriously affect the quality of the signal reception and interrupt the received signal,resulting in a significant impact to the communication work. These interfering signals generally come from the C-band satellite transmission stations, pulse interference terrestrial interference and various radar systems. A band pass filter is used between the satellite receiving antenna and the low noise converter to suppress the interference signals. The original filter can’t satisfy the stop band characteristics now.In addition, due to the limited volume of the satellite receiver, the total length of the filter requires less than 200 mmand the interface is waveguide. So the band pass filter is not only asked for steep outer band rejection and wide stop band characteristics, but also its shorter length to connect and miniaturize the system easily.Aiming at the indexes of satellite band pass filter in C band, this paper presents two kinds of solutions after studying and researching. One is to design the filter with several transmission zeros by using short band branch sections. And it is built, simulated and optimized by the software CST. This kind of band pass filter has an advantage of only using four cavities, which can get several transmission zeros to achieve steep outer band rejection and shorter the filter’s length. The other is using dual-mode waveguide structure to get transmission zeros to design the filter with steep outer band rejection. In order to miniaturize the band pass filter, the paper uses the capacitance loaded technology to have the filter with shorter length. Meanwhile, it is also built, simulated and optimized by CST. By comparing the results from the two kinds of filters, we can get that the latter one is better at the indexes and size and use Autocad to draw the filter to process and test. In the end, the tested results are basically the same as the simulated results. The insertion loss is less than 0.5 dB from 3.7GHz to 4.2GHz and the VWSR is less than 1.33. The outer band rejection is 40 dB from 3.4GHz to 3.6GHz and 50 dB from4.25 GHz to 5.0GHz.