Study On The Design Of Coplanar Waveguide Microwave Filter

Coplanar waveguide (CPW), which has been taken more and more attention for its advantages such as easy connections in series and shunt, insensitivity to substrate thickness, and low dispersion effect in the design of microwave and millimeter wave circuits. And the microwave filter using CPW could highly improve the filters'performance and the systematic integration. This paper sums up the research status and the study hotspot of the CPW filter by reading and studying mass of references. The research work focuses on the coupling matrix synthesis methods for microwave filters. And several high performance dual passband fiters and wide stopband fitlers, which are achieved by coplanar waveguide, are designed and analyzed. The primary work is concluded as follows:Firstly, in order for the following design of the CPW microwave filters, the basic design theory of the microwave filters is research. By using the software MATLAB, the synthesis of butterworth, chebyshev function and the cross-coupled matrix is achieved. A useful filter synthesis design kit is presented. And the validity of the execute results is finally verified by the software Advanced Design System (ADS).And then we taken attention to the designed of CPW dual passband filter. Based on the split-modes of the loaded stub square loop resonators, a novel dual passband filter, which is achieved by the CPW loaded stub square loop, is proposed and fabricated. Following the general theory of coupling, a CPW dual passband filter using hybrid microstrip open loop and CPW slotline resonators is presented. The external quality factor and coupling coefficient of each passband are achieved from numerical simulation. And high performance CPW dual passband filters are designed and measured. Besides, according to the theory of coupled resonator circuits, a CPW dual passband filter using hybrid microstrip split ring and coplanar waveguide quarter wavelength resonators is proposed. Its equivalent RLC circuit model is introduced and its parameters are also extracted from the theoretical analysis. And the electromagnetic, equivalent circuit simulated results and measured results are offered to validate the design approach.Finally, the design approach of CPW wide stopband filter is research. A cell of CPW quarter wavelength SIR is proposed. It bandstop characteristics are demonstrated. And using this structure, a wide stopband CPW low pass filter is proposed by cascading three tapered quarter wavelength SIR and a CPW spurline resonator. Wide stopband performance could be achieved by suitable adjusting its seven controllable frequency attenuations. On the other hand, an asymmetric CPW bandpass filter is presented. And by leading the CPW quarter wavelength SIR into it, its stopband will be broaden up to its seventh harmonics frequency, while have rarely influence on its passband. These filters are fabricated and measured. The measured results have good agreement with the simulation.