| Defected Ground Structure (DGS) is a periodic or nonperiodic defected pattern etched on the ground plane of microwave circuit, which is extended from Photonic Band-Gap (PBG) Structure. DGS has many characteristics that are single pole and low pass, slow wave and high effective characteristic impedance and so on. If it is applied in microwave plane circuits reasonably, it may greatly improve the performance of microwave integrated circuits (MIC), such as suppressing harmonic response, enlarging stopband bandwidth and reducing size and so on, so DGS is becoming a research hotspot of MIC design domain in recent years.Firstly, the main work of this thesis is analyzing the transmission characteristic of DGS. According to the DGS characteristic of single pole and low pass and the theory of the LC equivalent circuit, the LC equivalent circuit of DGS is researched and validated by electromagnetic simulations and circuit simulations. With the help of 3-D electromagnetic simulation software and the LC equivalent circuit, the effect of changing several parameters of dumbbell shaped DGS is discussed and summarized particularly. .The drawback of DGS is analyzed by simulation too, etching DGS may lead electromagnetic radiation to the ground plane and have an impact on the surrounding circuit, so a new improved type of DGS with the snake-like gap is proposed.Then DGS is applied in the design of microstrip passive circuits in detail. Based on the DGS characteristic of single pole and low pass, a microstrip low-pass filter which is composed of four different cascaded DGS units and a new microstrip diplexer which is consist of asymmetric DGS are designed; Using the DGS characteristic of high effective characteristic impedance, a 1:4 unequal power divider is proposed and realized. And the designed filter and power divider are processed in accordance with their models and sizes, the good agreement between simulation and test results shows the validity and feasibility of the application of DGS in the circuits. |
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