Ltcc-based Transmission Line Characteristics Of Study

The packaging technology, Low Temperature Co-fired Ceramic (LTCC), is now widely used in various microwave system front ends to reduce the circuit size and lower the cost. As a transmission line, stripline (symmetrical or asymmetrical) is often used in LTCC. In practice, the conductors of stripline may deviate from the center of two ground-plates for various reasons, so the analysis of the asymmetric stripline and asymmetric edge-coupled stripline is of much importance. Some complicated circuits are realized by interconnecting circuit components with striplines and their line discontinuities in microwave integrated circuits (MICs), therefore the analysis of discontinuities for asymmetric stripline is valuable.Firstly, based on basic transmission theory and strict numerical methods, this thesis have obtained the excess capacitance formula of asymmetric stripline open-end by curve-fitting in this paper. Compared with IE3D, the average error of this formula is less than 2%. And then successfully applying our formula and the equivalent circuit model obtained by the authors before to analyse the different discontinuities of asymmetric stripline, such as open circuit, step, right-angle bend and T-junction, and then three practical circuit components constructed by the various asymmetric stripline discontinuities, such as a low-pass filter, a branch-line coupler, and an edge-coupled stripline band-pass filter. Compared with numerical results, the average error of S parameters is less than 2%, and which checks the practicability of the equivalent circuit model and formula.Secondly, multiconductor transmission lines system is analysed to extract their capacitance matrix and inductance matrix via the moment method, which is foundation of obtaining CAD formulas.Finally, this article have obtained simple CAD formulas for the even-odd mode capacitances of asymmetric edge-coupled stripline and the capacitance matrix of asymmetric broadside coupled stripline via synthetic asymptote on the basis of the moment method (MoM), which is good for the design of asymmetric microwave circuits, such as, filters, couplers, power dividers and so forth. Compared with numerical results, the average error of S parameters is less than 2%.