Study On Microwave And Millimeter-Wave LTCC Key Techniques

Multichip-Module(MCM) is an effective method reducing the volume and weight and improving the performance of a microwave system. MCM traditionally applied in the areas of military, aviation, large-scale computer, and has already expanded to electronic system products, such as automobiles, communications, industry equipments, instruments and medical equipments. In recent years, because of its low-loss, high-integration and low-cost predominance in microwave and millimeter-wave frequencies, Low Temperature Cofired Ceramic(LTCC) technique is becoming more and more prosperous. With the increasing requirements of miniaturization and high integration of the microwave and millimeter-wave system modules, the passive circuit design and system packaging of LTCC have become the essential techniques to realize its advantages.In this thesis, the key problems of the applications of the LTCC technique in microwave and millimeter wave have been studied. Some useful conclusions have been drawn as well. The main research works are as the following:1. The interconnections between LTCC microwave and millimeter-wave modules: The area interconnection is used to realize high-density vertical interconnecting between two multichip modules, in which fuzz buttons are adopted as the metal connectors. The interconnecting characteristic of the three-button connectors has been analyzed in this thesis. The performance of this kind of connectors has been improved by applying the inductance and capacitance compensation. For the interconnecting in millimeter-wave frequencies, with the advantages of LTCC substrates, a novel interconnecting structure based on fuzz-button connectors has been proposed. An interconnection of substrate-integrated waveguide (SIW) to coaxial cable transition has been realized by using LTCC substrates and fuzz-button connectors. A wide-band interconnection has been constructed with a Y-branch SIW structure.2. Broadband transition structure: Due to the limitation of the LTCC process, it is difficult to manufacture substrates with irregular shapes. In addition, it is important to realize a sealed and highly reliable packaging. Traditional transitions, such as microstrip-probe transition and ridged-waveguide transition are not suitable for standard LTCC process. In this thesis, two kinds of novel transitions have been proposed. One is using slot coupling and patch resonators to realize waveguide-to-microstrip transition. This structure has also been improved by adding two extra connectors embedded in the substrates in order to expand the bandwidth. Measurement results have been carried out, which present a very good performance. The other proposed transition structure has realized a novel transition to waveguide in millimeter-wave frequencies using SIW structures. This kind of transition can be easily manufactured in LTCC substrates.3. Modeling of LTCC vertical interconnections: With the increment of packaging density, the discontinuity of LTCC interconnections becomes the bottleneck of the system performance. Thus, the modeling of the vertical interconnections is important in MCM design. In this thesis, support vector machine (SVM) regression method has been introduced to realize microwave modeling for the first time. Detailed explanation of the SVM theory has been included. Comparison of SVM regression method with artificial neural network (ANN) method has been given out in this thesis to present the advantages of the SVM. Two structures of a layer-to-layer interconnection and a board-to-board interconnection have been modeled by using SVM regression method, which show that modeling using SVM is more feasible and has more advantages than conventional methods such as ANN.4. LTCC system design: The most remarkable advantage of MCM especially that using LTCC technique is that it can realize a highly integrated system packaging in a single cofired substrate. The design of a dual-channel front-end of millimeter-wave receiver is presented in the thesis. The improvements have been finished according to the processing methods. The feasibility of this system has been validated as well.