Design of two microstrip slow-wave structures and short-circuit terminated stepped-impedance resonator dual-band filters
This dissertation consists of two parts. First, two types of microstrip slow-wave structure are proposed. The first one has the signal strips and the inserted ground strips periodically loaded in the internal part of the conventional microstrip line. The inserted ground strips increase the per-unit-length capacitance. The per-unit-length inductance is increased by decreasing the line widths on the two sides of the microstrip line. Therefore, the slow-wave factor increases so that the circuit size can be significantly reduced. The second type comprises a meander line and a shunt open-circuited stub. The per-unit-length inductance is mainly attributed to the meander line, and the per-unit-length capacitance is primarily controlled by the shunt open-circuited stub. The main property of this slow-wave line is that it has independently controlled structural parameters to realize the required slow-wave factor and characteristic impedance. This facilitates the circuit design. These two slow-wave structures are used in many miniaturized circuits. Second, a dual-band filter with the analytical design method is proposed. The structural parameters of the short-circuit terminated half-wavelength stepped-impedance resonator (SIR) are first determined by the filter specifications. Then, the K-inverter is used to control the coupling between resonators. Due to the completely analytical equations of the SIR and K-inverter, the dual-band filter design becomes easier and much more efficient.
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