Design Analysis And Application Of New Type Broadband Filter

In modern wideband communication system, the development of communication technology has close relationship with the progress of filter technology. Based on the rapid development and growing demand of satellite communications, electronic warfare and personal mobile communications, wrieless communication technology is moving toward high speed, high capacity, multiple bands etc. Beacause filter is a key components of RF/ microwave circuit transceiver system, its complanation and miniaturization have been attracting more and more attention. With the development of wireless communication technology, RF circuits and communication systems have become increasingly complex, the required space is also becoming smaller and smaller, so there are electromagnetic mutual interferences among the interconnection and nodes of different dielectric layer circuits. Due to the advantages of higher immunity to common mode signal and lower electromagnetic interference, wideband balanced/differential circuit become more important in mordern communication systems. The research for planar filter structure with high performance has a higher potential for practical application. In this thesis, in orde to realize the microwave filter with good stopband characteristics and high selectivity, combined with dual-mode ring resonator and a parallel coupled line, the following work has mainly been carried out:1. The analysis and design of wideband bandpass filter based on ransversal signal-interference concepts:the signal interference technique was applied to the design of wideband bandpass filter, by the superimposing and cancellation of the signal in two paths,3 and/or 7 transmission zeros were realized in stopband. The purpose of using signal interference technology to improve stopband rejection properties has been achieved, ensuring that the transmission characteristic in band can be kept unchanged basically, and the circuit size is also reduced.2. The analysis and design of wideband bandpass filter based on ring resonators: analyze the principle of transmission zero for the dual-mode ring resonator, Two novel microstrip bandpass filters with improved selectivity based on dual-mode ring resonators were proposed. Two and/or four transmission zeros close to the passband were realized to improve the selectivity for the passband. The transmission zeros near the passband can be adjusted conveniently by changing the characteristic impedances of the coupled lines.3. Analysis and design of balanced/differential bandpass filter based on ring resonators:introduce the basic concepts of differential extraction procedure of the hybrid S parameter. Two novel balanced filters with wideband common mode suppression using dual-mode ring resonators were proposed. Two and/or four transmission zeros close to the passband were realized to improve the selectivity for the differential mode. In addition, over 20-dB common mode suppression can be realized. The theoretical and measured results agree well.