S-band Mini Filter Design And Development

In the development of electronic technology and wireless communications, communication equipment which had the capability of small size, lightweight, reliability, multifunctional, and portable gradually came into people’s daily lives. In such a trends, as an essential device of an communication system, filter was bound to have the capability both small size and high-quality. Aiming at designing miniaturized and good frequency selectivity,a series of studies such as the introduction of cross-coupled filter,SIR structure, was used in the design of filters and diplexer.Through the design and make of the filter and diplexer a lot of experience in design and debugging was summed up. The main contents are on the following:Firstly, the development trends and the history of the development of the filter and design theory as well as the coupling matrix derivation was given. Secondly, a fourth-order SIR cross-coupling filter which had two additional finite transmission outside the pass-band and good frequency selectivity was designed.The insertion loss and return loss of the filter meet the design requirements. The correctness of the design was vertfied.Based on the design of the filter, a diplexer was designed which had good frequency selectivity, low insertion loss and return loss. Thirdly, a micro-strip dual band-pass filter which was combined by two parallel filters feed by coupled line, and its frequency selectivity was improved by introducing the coupling between the source and the load was designed. The two pass band of the filter can be choose freely.Lastly, because of the significant advantages of LTCC devices in miniaturization, a pass-band LTCC filter which had a good frequency selectivity by creating two additional finite transmission outside the pass-band was designed. Through the design and physical test of the filter, the correctness of the design was vertfied.