Research Of Microstrip Antennas Based On LTCC Metamaterial Substrate

Recently, the applications of metamaterials in microwave/RF circuits design havebecome very popular because of its unusual electromagnetic properties. Microstripantennas have attracted increasing interest due to their light weight, small volume, lowprofile, good integration and easy feed. LTCC (Low Temperature Co-fired Ceramic) asan important technology for passive integration is well suitable for high-densitymicrowave passive component integration and SIP (System-In-Package). Therefore,researches on microstrip antennas using LTCC metamaterials are attractive andsignificant for both scientific and engineering disciplines.In this thesis, microstrip antennas based on LTCC metamaterial substrate havebeen investigated. The main contributions of the thesis are listed below.Firstly, the basic theory and method of analyzing metamaterials and microstripantennas have been established. The physics mechanisms including microstrip antennasminiaturization using high permeability metamaterial or left-handed metamaterial,achieving high-gain microstrip antennas and mutual coupling suppression of microstripantenna arrays by using negative permeability metamaterial to eliminate surface wavesare studied, separately.Then, tridimensional Split Ring Resonators (SRRs) using multi-layer LTCCsubstrates are designed for high permeability metamaterial, left-handed metamaterialand negative permeability metamaterial. Simulations illustrate that the size of the patchantenna is reduced to22.5%and25.1%with the high permeability metamaterialsubstrate. Based on left-handed metamaterial, the electrical length of the patch antennais successfully reduced to0.28λg, breaks through the limitation of half-wave length ofconventional patch antennas. By utilizing negative permeability metamaterial, the gainof negative permeability metamaterial microstrip antenna is enhanced by1.5dB, andgreater than15-dB peak isolation is achieved between two adjacent microstrip antennas.Lastly, negative permeability metamaterials are presented to suppress the mutualcoupling between adjacent microstrip lines on LTCC Substrate. The physicalmechanism of the mutual coupling model is analyzed as a symmetrical four-port network by the even and odd modes method. The characteristic impedances andpropagation constant of the transmission line are investigated. The even mode electricallength exhibits strong dispersion around the resonance frequency of the metamaterial,which leads to counteraction of the even mode coupling and the odd mode coupling andresults in prominent mutual coupling suppression. Experimental results indicate amaximum20-dB suppression of broadside coupling between two adjacent50microstrip lines.