Study Of Defected Ground Structure With Low Radiation And Its Application In Microwave Circuits

Defected Ground Structure (DGS) is realized by etching periodic or non-periodic defected patternin the ground plane. The etched defect in ground plane disturbs the shield current distribution in theground plane. This disturbance can increase the effective capacitance and inductance of a transmissionline respectively. DGS has been applied to microwave circuits because it has several excellent circuitperformance, such as stopband characteristics,high impedance characteristics and slow-wave factor.But DGS makes the ground incomplete, so it will produce larger radiation, and then the performance ofthe circuit around will be affected. It is meaningful to design new Defected Ground Structures whichhave lower radiation.Focusing on the DGS with lower radiation, the research works in this paper are presented asfollows:1. The performance of the Defected Ground Structure is analysed in details. Thus, a parallel LCresonant circuit is represented to be equivalent to DGS unit, and the equivalent circuit parameters areextracted by using a simple circuit analysis method. Then the basic knowledge of the electromagneticcompatibility and analysis of how to reduce the near field radiation are introduced. Finally, simulateand analyse the near field radiation of the traditional Defected Ground Structures when they have thesame circuit performance.2. Two DGSs with lower near field radiation are designed, and they are called the jagged shapedDGS with low radiation and the DGS of high impedance characteristics with low radiation. Then thecircuit and radiaton performance of the two DGSs are analysed in details. Finally, the two DGSs arecompared with the traditional DGSs, and the results show that the two new designed DGSs havelower near field radiation when they have the same circuit performance.3. The crosstalk of the proposed DGSs are analysed, and they are compared with the traditionalDGSs when they have the same circuit performance. The results show that the two proposed DGSshave lower crosstalk voltages.4. The two proposed DGSs are applied to microwave circuits. A stopband filter is designed andthe second harmonic of a parallel coupled line bandpass filter is suppressed using the the jagged shapedDGS with low radiation. A4:1Wilkinson power divider using the DGS of high impedancecharacteristics with low radiation is designed.