Researches Of LTCC Circuits Based On Substrate Integrated Waveguide

In recent years, microwave and millimeter-wave technology has issued unprecedented challenges on the miniaturization and high integration of circuits and systems. In this background, Low Temperature Cofired Ceramic (LTCC) technology, possessing many advantages such as small size, low weight, low loss and low cost in mass manufacturing, has developed rapidly and been applied widely in many fields such as modern wireless communication and military application. Since traditional transmission structures such as planar transmission lines and metal wave-guides etc have the limitations of big size and high cost, it is difficult to apply them in LTCC multi-layered circuits. Thus, one of the research hotspots of LTCC technology lies in studying and developing various kinds of low-loss transmission and resonate structures, mainly novel substrate integrated waveguide, which are applicable to the characteristics of LTCC circuits and can satisfy their needs as well. On the other hand, the circuit structures and electromagnetic characteristics of LTCC circuits are usually complicated, so traditional design methods based on full wave electromagnetic field simulation become more and more inadequate to meet the design demands of complicated circuit structures. Hence, another key problem LTCC technology studies needs to tackle is to develop more efficient optimization methods whose target is to shorten the design period of LTCC circuits.This dissertation has conducted researches on novel LTCC low-loss transmission structures and explored the application of Space Mapping algorithm to the optimization of LTCC circuit design. The main researching works are as follow:1. SIW, HMSIW and FSIW have been studied, and a series of LTCC circuits with wide applications have been realized. Traditional planar transmission lines such as microstrip and stripline have the disadvantages of high loss and low Q value, and although metal waveguide has the advantages including high Q value, it is hard to be used in multilayer integrated circuits with high density. Compared with these traditional transmission lines, SIW have these favorable characteristics of low loss, high Q value, and small size. This dissertation firstly presents the partial equivalent circuit model of SIW by adopting the equivalent model method, then analyzes and validates the electromagnetic characteristics of SIW, and realizes LTCC filter with multilayer structures. To further achieve miniaturization and low loss of LTCC circuits, on the basis of SIW, the characteristics of HMSIW and FSIW have been explored. HMSIW transition and FSIW power divider have also been implemented.2. By adopting the similar methods as analyzing SIW, this dissertation has researched into the electromagnetic characteristics of SICC, and LTCC circuits such as filter and duplexer have been realized. SICC can be as easily integrated as SIW, and in addition, it can provide a more flexible circuit topological layout. On the basis of SICC, this dissertation has put forward a brand-new HSICC resonator, and also designed and implemented a series of LTCC circuits such as HSICC resonator, HSICC filter and HSICC power divider. Thus, the feasibility of the application of HSICC to LTCC circuits is verified. LTCC circuits with HSICC structure, when compared with the ones with SICC structure, are found to have the flexibility in adjusting the positions of input/output ports, and besides this advantage, it has also reduced the circuit size by half.3. In this dissertation, pertinent researches on applying space mapping method to the optimization of LTCC circuit have been carried out. Traditional method of full wave simulation will cause high cost and low efficiency, so it has become the choke point for a fast optimization of LTCC circuit. This dissertation takes the H-plane waveguide filter as a case, and by adopting space mapping method, it has been optimized. Also, the discontinuity structure which exists widely in LTCC circuits has also been analyzed pertinently. In the optimization process, both EM simulation and circuit simulation have been adopted. By doing so, the efficiency of optimization has been promoted remarkably, which is a rewarding effort for exploring the application of space mapping method to highly efficient optimization of LTCC circuit.