Waveguide Inductive Strip Filter Embedded in LTCC

Microwave filters are generally designed with microwave transmission lines. However these filters are typically lossy. The waveguide filters using conventional inductive elements such as metal rods and transverse diaphragm have some disadvantages such as complicated structure, high cost and they can be hard to mass produce. But they also have many advantages such as the capability of high power transmission, a non-radiating structure, and their thermal efficiency. A novel waveguide inductive strip filter embedded in LTCC is introduced in this paper where the disadvantages of the conventional waveguide filters are eliminated. By using LTCC technology, the cost will typically be lower, it can easily be mass produce, and these designs can also be tested easily. The equivalent T-network parameters of the inductive strip mounted in a waveguide and embedded in LTCC substrate were derived. A new iterative technique was used based on the Variation principle. The design formulas and curves of the filter were presented. The design method of the filter was derived by applying the equivalent network of the inductive strip to the usual method of the filter design. A complete set of new curves relating the various filter parameters were introduced. Similar curves can be derived to design similar filters for any frequency band using any dielectric material. Three-dimensional electromagnetic field modeling and simulation was carried out using HFSS (High Frequency Structure Simulator). An optimization process was done for the designed filter. The modeling and the optimization S-parameters curves are shown. This paper introduces a new methodology of designing waveguide inductive strip filters embedded in LTCC. The design methodology was derived and presented with formulas and curves. The design steps are explained and verified by examples and results.