Yi-Chyun Chiou

Broadband quasi-Chebyshev bandpass filters with multimode stepped-impedance resonators (SIRs)

Planar broadband bandpass filters of order up to 9 are synthesized based on the multimode property of stepped-impedance resonators (SIRs). Based on the transmission line theory, the modal frequencies of the SIRs are calculated based on the impedance and length ratios of its hi- and low-Z segments. In the synthesis, the SIR coupling schemes are determined by the split mode graphs. Using one, two, two, three, and three dual- or triple-mode SIRs, quasi-Chebyshev filters with four, six, six, eight, and nine transmission poles, respectively, are synthesized with a fractional bandwidth (BW) Delta=50%. Emphasis is placed not only on designing the I/O coupling structures for matching the external Q (Qext) and the circuit BW, but also on matching the resonant peaks of the circuit with the nominal Chebyshev poles. Measured results of experimental circuits show good agreement with simulated responses

Miniaturized Rat Race Coupler With Suppression of Spurious Passband

A new hybrid ring coupler design is devised for circuit miniaturization based on the periodic stepped-impedance ring resonator structure. The circuit has an area of 21.5% of a conventional rat race coupler and no passband up to the sixth harmonic of the design frequency. The designs are validated by comparing measured four-port parameters with the simulated results

New Miniaturized Dual-Mode Dual-Band Ring Resonator Bandpass Filter With Microwave

A new miniaturized dual-mode dual-band ring resonator bandpass filter is implemented by a cascade of several microwave C-sections. Each C-section is used to substitute a transmission line section of designated electrical length. Through proper design of input/output coupling configuration, two transmission zeros can be created on both sides of each passband. Two circuits with four and six microwave C-sections are fabricated for confirmation. They occupy less than 30% of the area of a traditional ring resonator filter. Measured responses agree very well with the simulation.

C

Performance of a fully planar four-port crossover coupler is investigated. This bisymmetric circuit consists of a ring and two inner orthogonal sections connecting the diagonal ports. Based on the transmission line theory, analysis equations are formulated and design curves are presented. Two crossover junctions are fabricated and measured for validity confirmation. The measured data have good agreement with simulation.

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Quadruple-mode coupled-ring resonator is used to design quasi-elliptic function bandpass filters (BPFs) with a relatively wide bandwidth. The resonator consists of a pair of coupled rings with two open stubs symmetrically tapped to the inner ring. The stubs are used to move a transmission zero near the center frequency to lower transition band. It is believed that it is the first ring resonator BPF based on the coupled-ring to create four transmission poles and four transmission zeros. Two filters with relative bandwidths of 10% and 15% are fabricated and measured. Good agreement between simulation and measurement is obtained.

Design of Compact Symmetric Four-Port Crossover Junction

Based on microwave C-sections, rat-race coupler is designed to have a dual-band characteristic and a miniaturized area. The C-section together with two transmission line sections attached to both of its ends is synthesized to realize a phase change of 90° at the first frequency, and 270° at the second passband. The equivalence is established by the transmission line theory, and transcendental equations are derived to determine its structure parameters. Two circuits are realized in this presentation; one is designed at 2.45/5.2 GHz and the other at 2.45/5.8 GHz. The latter circuit occupies only 31% of the area of a conventional hybrid ring at the first band. It is believed that this circuit has the best size reduction for microstrip dual-band rat-race couplers in open literature. The measured results show good agreement with simulation responses.

Quadruple-Mode Coupled-Ring Resonator Bandpass Filter With Quasi-Elliptic Function Passband

Parallel-coupled line filters with Chebyshev passbands are synthesized based on the insertion-loss functions derived by converting the composite ABCD matrices of all coupled stages. With the synthesis, both the electromagnetic simulation and measurement results have accurate in-band response and bandwidth. Simultaneous equations for Chebyshev filters of order N les 9 are derived for determining geometric parameters of the coupled stages. The tradeoff between circuit bandwidth and ripple level is discussed. In experiments, three planar or quasi-planar structures, including the coupled-line with aperture in the ground plane, the three-line microstrip, and the broadside-coupled lines, are employed to realize the end stages for implementing the high coupling levels. Experimental filters of order up to nine with fractional bandwidth of 30% or 40% are fabricated and measured. The results show good agreement with predictions by the theory and simulation.

New miniaturized dual-band rat-race coupler with microwave C-sections

Rat-race coupler is designed to have dual-band operation, a miniaturized area, and arbitrary power division using microwave C-sections. With a C-section and two transmission line sections attached to both of its ends, an elementary two-port is designed to play the role of a quarter-wave section in a conventional rat-race. It is designed to possess phase changes of 90° and 270° at the first and second frequencies, respectively. Transcendental equations are derived for calculating its structure parameters. Two circuits operating at 2.45/5.8 GHz with various output power ratios are fabricated and measured. Both couplers have only 31% area of conventional rat-race at the first band. It is believed that these circuits have the best size reduction for microstrip dual-band rat-race with arbitrary power division in open literature. Measured results agree well with their simulation counterparts.

New Synthesis of Parallel-Coupled Line Bandpass Filters With Chebyshev Responses

Miniaturization of microstrip rat race coupler is implemented by incorporating a broadside-coupled structure and stepped-impedance line sections into the design. The former is used to replace the 3lambda/4-section and the latter is to substitute the lambda/4-line in the conventional circuit. No lumped-element is required in the circuit. One of the experimental circuits occupies only 18.3% of the area of a traditional 6lambda/4-rat race. It is believed that it has the best size reduction in comparison with those in open literature. In addition to a wideband characteristic, total inband power loss is better than 3.2%. Measurement results are shown to validate the design and theoretical prediction.

Dual-band rat-race coupler with arbitrary power divisions using microwave C-sections

A microstrip-to-coplanar waveguide broadside-coupled section is used to replace a 34-section of the conventional dual-mode 1-ring resonator filter for circuit area miniaturization. It is believed that it is a new idea to incorporate the broadside-coupled section into a ring resonator filter for size reduction. For design purpose, some important characteristics of the broadside-coupled lines are investigated. In experiments, two realized circuits show only 19.4% of the area of a uniform ring. Measured responses show good agreement with simulation.