Study And Design Of Microstrip Ring Resonator Filters

Filters are an essential part of telecommunications and are key items in the performance and cost of such systems, especially in the increasingly congested spectrum. There has been a particularly marked growth in the cellular communications industry since the 20 th century. This has contributed to both research of microwave filters and their commercial applications. Since the 21 th century, kinds of novel communications require high isolations between congested spectrums, low insertion loss and high performance in systems, such very demanding performance specifications for filters and the commercial pressures for low cost promote the development of microwave filters further more. Microstrip filters based on ring resonators have garnered a lot of attention over the few past years due to their inherent characteristic of multiple modes. Through an investigation into and a subsequent implementation of microstrip ring resonator filter theory, new microstrip ring loaded resonator used to produce optimal filter performance for a class of filters such as dual-band, tri-band, wideband, and ultra-wideband bandpass filters is developed in this thesis. The primary work of this thesis is outlined as follows:1. This thesis presents an entire design process for microstrip ring resonator filters, from an investigation of the basic theory through to the development of implementation method for multi-band and wideband bandpass filters. Subsequently, detailed analysis on resonant characteristics of the loaded resonator is provided and corresponding design figures are plotted. Based on the concept of ring resonator and loaded resonator, a novel ring loaded resonator is put forward to design dual-band, tri-band, wideband and ultra-wideband bandpass filters.2. Detailed procedures about multi-band bandpass filter with high rejection skirt utilizing ring loaded resonator are studied. Finally, the designed filters are fabricated and the comparison of the simulated results with the measured ones verifies the correct method.3. Wideband bandpass filter is proposed based on the resonant characteristic and coupling characteristic of the ring loaded resonator which is the basic cell of the wideband bandpass filter. Two kinds of wideband bandpass filter, i.e., one with asymmetric high out-of-band attenuation and one with expanded bandwidth, are designed in detail. The proposed filter realized the minimal circuit size of the ring resonator filters.4. Microstrip ultra-wideband bandpass filter is studied, and new structures for miniaturized ultra-wideband bandpass filter are introduced. Two novel miniaturized ultra-wideband bandpass filters based on ring resonator are presented. Comparison of the proposed filter with other UWB filters show that the proposed ultra-wideband bandpass filters has the advantages of simple structure, miniaturized circuit size, and high performance.