Study And Design Of UWB Bandpass Filter

As an essential components of communication system, filter, plays a very important role in the entire field of wireless, is to be recognized as the crucial part in the process of designing work. With the unceasing development of society's informatization, people ask for more higher requirements on communication system, meanwhile with very demanding stringent requirements for the design norm of filter. This paper mainly studied the design philosophy and method of UWB Band-pass filter. For the first step, it summarized the existing design method of UWB filter, based on which a few new types of design methods were analyzed. These filters are promising for engineering application with the features of small volume, tight structure and excellent performance.Analysis the multimode features of SIR(Stepped independence resonators) and their application scenarios as well. For the multimode resonators, it analyzed the relationship between structural parameters and resonant frequency adjustability of resonant characteristics and frequency firstly. And then studied the transmission characteristics of parallel coupling line secondly. Finally a new type of band-pass filter was designed with the multimode resonator for basis, which was proved to be correct by actual processing.Study the impedance parameters of shunted short parallel coupled line, through which the theory that the transmission zero of filter is generated from shunted short parallel coupled line was pointed out. The transmission zero is decided by coupling strength of coupling line. In accordance with this theory, a new type of UWB filter was designed with little improvements been carried out later on for changing the double parallel coupling line to triple ones, by which the coupling coefficient was increased and the bandwidth of filter was expanded.The designing method of filters based on Signal-Interference Techniques isintroduced. Two types of band-passed filters were designed and debugged in accordance with this technique. First of all, it analyzed the resonant characteristics of ring resonator and the adjustment between filter BW and parameters. On that basis, a new band-pass filter with the width only for 50% was schemed out. In addition, it studied the transmission parameters of parallel coupling line for both ends shorted. A new UWB band-pass filter was designed by parallel connection of the coupling line with another transmission line. It studied the pole-zero distributing regularity and adjusting parameter of this filter and also the impact for variation of its physical parameters to S-parameters. Finally, the design was proved to be correct through experiment.Conclusion of this paper and outlook for the next forthcoming works to be carried out.