Research And Design Of Ultra-wide Band Multiple-mode Filters

As a key component in RF front-end of Ultra-wideband (UWB) wireless communication system, UWB filters play important and essential roles in enhancing the overall system performance. As a result, high performance UWB filter design have been becoming a challenging research filed which attracts both domestic and overseas scholars.This thesis mainly concerns on analysis and design of UWB bandpass filter based on multiple-mode method. Meanwhile, odd-even mode method, based on transmission line theory, is implemented to analyze the resonate frequency of multiple-mode resonator. By introducing open or short circuit stub, the resonate frequencies of resonator, which can be separately adjusted, are roughly allocated within the desired passband. In this thesis, four applicable UWB multiple-mode filter are designed and fabricated.The main work and the contributions in this thesis can be summarized as follows:1. A UWB bandpass filter (BPF) with source/load coupling and triple-mode resonator is proposed. The in-band even-mode resonate frequencies of this resonator can be simply adjusted. The filter with the fractional bandwidth 76% not only shows good in-band performance but also has wide upper-stopband and steep rejection skirt.2. A novel quadruple-mode resonator is proposed and analyzed based on odd-even mode method. By properly adjusting the geometric parameters,the first four resonant frequencies can be allocated in the UWB passband of almost equally. Therefore, a UWB quadruple-mode filter with fractal bandwidth 114% is achieved.3. A compact quintuple-mode UWB BPF is proposed. The folded resonator can meet the needs of miniaturization. Moreover, the short-circuit stubs are introduced to add a resonate frequency and improve lower harmonic suppression. Despite of miniaturization, the proposed UWB BPF also shows good in-band and out-of-band performance.4. A high performance quintuple-mode UWB BPF with ultra-wide upper-stopband extended to 27GHz is also proposed. Meanwhile, this quintuple-mode BPF has the characteristic of good in-band performance and steep rejection skirt.