Study On Microstrip Filters Based On Multi-mode Resonators

Filter has been studied as one of the most significant component in RF and wireless communication due to its advantages such as compact size, simple physical layout, low cost, good compatibility with active device and so on. Through designing novel multi-mode resonators(MMR) and adding appropriate feeding structures, several novel microstrip filters have been proposed.The main work in this thesis can be summarized as follows:1. Proposed a novel MMR. Through using even-odd mode method, the resonant frequencies of the MMR are calculated. Based on this MMR, a novel ultra-wide band(UWB) filter is proposed.2. Improving the MMR, a novel MMR which owns a transmission zero is proposed. Based on this MMR, a novel dual-band bandpass filter is proposed. The passband of the dual-band bandpass filter can be adjusted individually. By changing the physical parameter such as the length and the off-center distance of the loaded open-circuited stub, the dual passbands can be adjustable.3. Adjusting the structure of the feeding, improving the rolloff factor of the upper band of the first pass band and the lower band of the second passband. It makes the performance of the dual band bandpass filter more excellent. An improved dual-band multi-mode bandpass filter is designed and fabricated, and the measurement of the filter shows good performance for both in-band matching and outside rejections of the desired dual passbands.