Design Of Compact Microstrip Multiband Filter

With the rapid development of wireless communication, the wireless terminal products as well as its passive circuits needs to meet the requirements of miniaturization and high performance . The band pass filters ( BPFs ) as a transceiver system essential for a module of passive circuit elements components play important role in wireless communication system, which directly influences the performance and the size of small RF transceiver system performance. The microstrip bandpass filter with novel structure, high performance, small sizes were analyzed thorough research.Firstly, this article introduces the background and trend of development of filter. Due to the need for filter performance from communication and military industry. Filter design method developed from the original " Wagner filter" design method and image parameter method, to the development of the modern network theory. Now along with the application of computer technology, electromagnetic simulation software has spread to the filter design process, greatly saving time and cost. As a result of new materials production and filter theory unceasing development, now filter is turning to high performance, integration and miniaturization.Thereafter, it introduces microstrip line theory and the basic principle of the filter. Simple explanation of the main characteristics of the ideal filter, low-pass filter main prototype is given and show the frequency change from the low-pass filter to bandpass filter method. Based on the above theory, a half wavelength resonator parallel coupled bandpass filter design method is given.Then, the article introduces the design methods of multiple-band filter, such as synthetic method, a multi-mode resonator method, parallel passband method and so on.Also for the dual-band filter, the paper summarizes the SLR, double resonator method, dual-mode structure, SIR spurious band method. In addition, also it in detail discusses the SIR principle, basic structure, the resonance conditions and spurious band design method. Finally, tow new multiple frequency filters are introduced, which includes a dual-band bandpass filter and the triple-band bandpass filter. For the filter, coupled in parallel transmission structure foundation, introduced into the parallel resonant structure, the 5.7G band is realized.Based on SIR theory in the third chapter , 2.4GHZ band is realized. Two structures in the stopband mutual inhibition, achieve a better out-band rejection performance. By adding a low-pass filter structure, the article realizes a good upper stopband performance. In addition, based on the above filter structure, a triple-band bandpass filter is proposed.This article focuses on bandpass filter, the most commonly used element in RF circuit, which has a certain significance for the telecommunications industry development.