Research On The Distributed Circuit Parameters Of Non-uniform Microstrip Line And On The Miniaturised Microstrip Bandpass Filters

Microwave circuits are widely used in radar, avigation and spaceflight areas. Now, the development of the modern communication systems, especially for the satellite communication and mobile telecommunication, can not be separated away from microwave circuit. However, comparing to the circuits working at low frequency and in digital state, microwave circuits working at high frequency and have many specialties in materials, configures, circuit structure, elements and design methods, so it is necessary to study microwave circuit deeply. This is the main reason of this thesis to select non-uniform microstrip line and bandpass microstrip filters as the research subjects. The main works and the innovative parts of this thesis are summarized as following:1. The Generalized Transmission Line Equations are employed to analyze the circuit parameters of the non-uniform microstrip lines. The static distributed capacitances and inductances of the 90°bent microstrip lines are extracted.2. By comparing the differences between the port's S-parameters respectively obtained by the extracted static circuit parameters using circuit method and by the Method of Moment directly, the applicable frequency range of the extracted static distributed circuit parameters is found. The results show that the extracted static circuit parameters can be used in a certain frequency band3. The problem of the moment method when used in analysis of structures with small reflection is studied. With the method of minus two results respectively obtained from the bent microstrip and the straight microstrip with the same length, the small mismatch due to the termination loads employed in moment method can be eliminated. The results by this method are in agreement with those obtained by analytical method.4. Coupling comb unit and separated electrical and magnetic coupling paths unit are chosen to construct our innovative filters'resonator units. Comparing with the traditional comb filter, this new filter has smaller size.5. By using the technique of slotting on the middle metal plate, the horizontal coupling on one layer is changed into vertical coupling between two layers. This result in a miniaturized filter with satisfying performance.