Research And Design Of Microstrip Dual-mode Filters With Square Patch Resonators

Microwave filters are very important constituting elements of wireless communication systems. With the rapid development of communication systems, the requirement for the researching and performance of microwave filters becomes more stringent. All this time micro-strip filters are much accounted since they are light and easy to integrate. In some communication systems, we need to design small-sized filters. Dual-mode filters are better way to design miniaturized filters. As a new and developing technique in domain of micro-strip filters, micro-strip dual-mode filters have the advantage that one dual-mode resonator can be regarded as two resonant circuits. Thus, the number of the resonators will be reduced to half. So we can use dual-mode resonators to design compact and small-sized filters.The dual-mode pass-band filter is based on dual-mode resonator within the degenerate mode. Use perturbation approach to separate the degenerate mode and to couple to each other. In this dissertation, the characteristics of a square patch resonator are analyzed, and then improve design for the deficiencies are given. The main work carried out the following:1. The key technologies and common design procedures of micro-strip dual-mode filters are discussed.2. The characteristics of square patch resonator are researched. On the basis of perturbation theory, we present and analyze perturbation method about the square patch resonators. A novel dual-mode band-pass filter is presented and fabricated. The result shows that it is identical to simulation and measurement.3. It introduces the spur-line in output port to improve suppression performance.4. The cascade dual-mode filter that consists of two dual-mode resonators is studied. A four-stage pass-band filter with high performance is designed.