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In this letter, we present a new negative coupling structure applicable to a substrate-integrated waveguide (SIW) resonator filter structure. Unlike conventional negative coupling structure, the proposed coupling structure can achieve a negative coupling value without employing an additional substrate or slots on ground planes. To demonstrate the new negative coupling structure, we designed, fabricated, and measured a fourth-order K -band SIW resonator filter with a pair of transmission zeros. [ABSTRACT FROM PUBLISHER]

This paper reports the first co-design configuration of a power amplifier (PA) in cascade with a high-Q bandpass filter. By matching the filter's input port directly to the transistor's drain node, the conventional output matching network (OMN) of a PA is entirely eliminated. This leads to smaller size/volume, minimized loss, and enhanced overall performance. To enable this co-design method, the matching-filter synthesis theory is proposed and investigated in detail in this paper. Based on this theory, a 3% bandwidth (centered at 3.03 GHz) two-pole filter, implemented using high-Q evanescent-mode cavity resonators, is designed as the PA OMN to provide optimized fundamental and harmonic impedances for a commercial 10-W GaN transistor. Simulation and measured results show that the co-designed PA-filter module yields a desired Chybeshev filter behavior while maintaining excellent PA performance in the passband with 72% efficiency, 10-W output power, >10-dB gain, and 60-dBm output third-order intercept point. This co-designed module experimentally presents a 8% higher overall efficiency compared to a control group developed using a conventional independent PA and filter, which further validates the effectiveness of this method. [ABSTRACT FROM PUBLISHER]

This paper describes an analytic design procedure for microstrip tunable filters. Step-impedance resonators are employed and loaded with varactors for achieving agility in the filter response. Fixed lumped capacitors are utilized as admittance inverters in order to minimize the number of varactors in the filter. An analytic approach for filter design makes it possible to achieve a tunable filter showing the same frequency response when the center frequency is adjusted. A two-pole microstrip tunable filter whose center frequency can be adjusted from 1.1 to 1.5 GHz is designed to demonstrate the validity of design theory. A prototype tunable filter operating from 2.1 to 2.7 GHz is also designed and measured. A good agreement between the measured and simulated results is shown. Finally, three- and four-pole tunable filters are designed to show straightforward application of the presented design method to higher order tunable filter design. [ABSTRACT FROM AUTHOR]

This paper deals with a simple method to extract the coupling matrix of a 10th-order dual-mode asymmetric canonical filter. The coupling matrix of an asymmetric canonical filter is obtained by applying a plane rotation technique to the coupling matrix of a symmetric canonical filter. This paper gives a list of pivots and rotation angles to obtain the coupling matrix of an asymmetric canonical-structure filter. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 64–68, 2003 [ABSTRACT FROM AUTHOR]

Presents a method of determining resonant frequencies of cylindrical and ring dielectric resonators (DR). Effective dielectrical constants in the dielectric waveguide model; Axial and radial attenuation constants; Calculation of resonant frequencies in cylindrical and ring DR in a microwave integrated-circuit environment.

This work, for the first time, presents an absorptive frequency-tunable substrate-integrated waveguide (SIW) filter. For the filter design, an absorptive bandpass filter prototype tailored to an SIW structure has been formulated. The proposed absorptive bandpass filter prototype is capable of having a return loss larger than 20 dB at all frequencies although it has a simple matching circuit. The filter prototype has been attained by comprehensive formula-based synthesis of a new matching circuit equivalent to an existing one. To validate our filter prototype, a second-order absorptive bandpass filter that can alter its center frequency has been designed, fabricated, and measured. This article demonstrates approaches to find physical dimensions by comparing each section of the filter structure with the corresponding part of the prototype. The fabricated absorptive bandpass filter has a compact structure by virtue of its simple matching section. The frequency-tunable SIW resonators allow our absorptive bandpass filter to adjust its center frequency from 1.76 to 2.69 GHz while having absorptive performance. The measured reflection of the filter centered at 2.50 GHz is smaller than −10 dB between 1.56 and 3.27 GHz (2.10:1). It is shown that theory, simulation results, and measured responses are in good agreement. [ABSTRACT FROM AUTHOR]

This letter reports an accurate and rigorous design method for a distributed‐element reflectionless bandpass filter capable of producing a reflectionless response at two ports simultaneously. The design method relies on novel transmission‐line reflectionless filter prototypes. This work presents a stub‐based reflectionless filter prototype and its design formulas in terms of a target transmission response. It also provides a stub‐less coupled‐line reflectionless filter prototype equivalent to the stub‐based prototype in case where stubs are not feasible. A second‐order bandpass filter has been designed and fabricated to verify the design method. Reasonable agreement between the measured performance and the simulated one has been obtained, confirming that the proposed design is valid. [ABSTRACT FROM AUTHOR]