Study On Microstrip Multi-mode Resonators And Their Application To Filters

With the rapid development of communication industry, multi-frequency communication system has become a research hotspot. As an important part of communication system, the size and performance of the multi-frequency filter affect the quality of the entire communication system directly. Therefore, the high-performance and miniaturization of multi-frequency filter is the focus of the current issues. Resonator is the core component of the filter. Multi-mode resonator(MMR) has many advantages, such as small size, rich mode and low insertion loss. It plays an important role in reducing the cost of equipment, reducing the volume of equipment and increasing the channel capacity. So it has been widely used. Multi-mode resonators with high-performance are great helpful for the realization of high-performance filters.In this thesis, based on the study of multi-mode resonator and coupled with the appropriate coupling structure, we design the multi-mode resonators to achieve micro and high-performance filters.The main contents of this thesis are as follows:1. The basic theory of microwave filter is studied, including the structure and parameters of the microstrip line, and the basic design parameters of the microwave filters. The odd-even method and the general Chebyshev filter are studied. The theory of microwave filters is the theoretical basis for the design of the filters.2. The structure and resonance characteristics of resonators with high-performance and multi-mode are analyzed. First, based on the step impedance resonator(SIR), the structure and resonant characteristics of the type gl/ 4 and the type gl/ 2 with two segment step impedance resonators and the three segment step impedance resonators are analyzed. Second, based on the stub loaded resonator(SLR), the structure and resonant characteristics of the short circuited stub loaded resonator, the open stub loaded resonator and the crossed resonator are analyzed. And simulation graphs are given.3. A combined resonator composed of two resonators is designed. The advantage of the resonator is that the four resonant frequencies can be controlled independently. At the same time, a parallel coupled feeder with a suitable external coupling is designed for the two pass bands through the physical topology of the composite resonator structure. The center frequency and bandwidth of the dual-band filter can be controlled independently. The dual-band filter with 1.5GHz and 2.4GHz has been realized. The measurement results show that the insertion loss at the center frequency of the two pass band of the filter is 0.5d B and 0.6d B, and the return loss is better than 17 d B and 18 d B.4. A four mode resonator is designed. The resonator can generate four resonant frequencies, so that the filter can further realize miniaturization. In addition, the source-load coupling is introduced, which increases the transmission zeros between the two passbands, and greatly improves the isolation between the two passbands. The dual-band filter with 3.5GHz and 2.4GHz has been realized. The measurement results show that the insertion loss at the center frequency of the two pass band of the filter is two 1.0d B and 0.5dB, and the return loss is better than 20 dB and 18 dB.