Resonant Photonic Crystals In Microstrip Antenna Applications

Photonic Crystal is a new type periodic structure which has frequency bandgaps, and the propagation of electromagnetic waves whose frequencies are within the bandgaps is forbidden. According to the different formation mechanism of band-gap, photonic crystals can be divided into two types which are Bragg scattering-type and resonant-type. This dissertation studies resonant-type photonic crystal in microwave band and its application in microstrip antenna.This dissertation focuses on the electromagnetic characteristics of High impedance surface (HIS) which is a representative of resonance-type photonic crystals and the application in microstrip antenna. First of all, the concept of photonic crystal, classification, analysis method and overview of its current application are reviewed. Then the basic theory of photonic crystals, effective medium model of HIS photonic crystal and the basic principles of the microstrip antenna are Described. On this basis, the primary work is as follows:(1) For HIS photonic crystal, the cells with Square patches are Studied in detail. Some parameters which can affect the bandgap characteristics of the HIS have been studied, including cell size, gap width, Via size, thickness and dielectric constant of substrate.(2) Miniaturization of HIS photonic crystal is achieved in 2.45GHz frequency band using three-layer structure.(3) The photonic crystals have been applied in microstrip antennas. Simulation results show that the gain of the main radiation direction with PBG structures is increased and the sidelobe level is reduced, the mutual coupling between antennas is reduced also. The results also show that the performance improvement of the microstrip antenna is more obvious when the surface wave power is larger.All of the computed results are acquired by simulation. The job is done by the commercial software HFSS.