A capacity loaded dual-mode satellite band-pass filter

In the current C-band satellite communication applications, usually added one band pass filter with wally stop-band attenuation characteristic between the satellite receiving antenna and LNB (low-noise down converter) to suppress the microwave interference and pulse interference at the receiving end, band-pass filter´s performance direct impact on the overall performance of the receiver. Meanwhile, in order to match the system installation, the filter length are subject to limitations. If we don´t add the transmission zero to the filter, we can only design the filter in the traditional way with over ten cavities and large size, which can not be used in the satellite communication. So we use the miniaturization technology to solve the problem. And in order to get high inhibition out of the pass-band and small size, we should add several transmission zeros to the filter. In a result, a capacity loaded dual-mode filter is designed in this paper. We can get S11 is less than -19dB in the pass band and S21 is less than -40dB in the suppression frequency band of 3.4GHz to 3.6GHz and less than -60dB from 4.27GHz to 5GHz. In a word, this kind of the filter has a higher suppression out of the pass band.