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Abstract: A miniaturized dual‐band filter using novel triple‐folded substrate‐integrated waveguide (TFSIW) resonators is proposed in this paper. The proposed TFSIW is enabled by specially designed folding structures, which leads to significant size reduction. The 2 lowest resonant modes, namely folded TE102 mode and folded TE101 mode in the TFSIW cavity, are utilized to achieve a dual resonance response with a small frequency ratio. To validate the design concept, a dual‐band filter operating at 1.91 and 2.32 GHz is designed, fabricated and characterized. Good agreement has been achieved between the simulation and measurement results. Moreover, the size of the proposed TFSIW resonator has been reduced for 86% compared with the conventional SIW resonator (assuming the same frequency ratio). [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, we present a dual-band sequential power amplifier (SPA) to provide high efficiency at power back-offs and maximum output power at two separate working frequencies. The proposed SPA, including a carrier amplifier, a peaking amplifier, a power divider, and a combing coupler, is fabricated on Isola I-TeraMTRF boards with 3.45 dielectric constant, 0.0028 loss tangent, and 0.508 mm substrate thickness. The SPA provides 48 and 62% drain efficiency (DE) at 6 dB output back- off (OBO) and maximum output power at 1.1 GHz (first design frequency), and it also provides 52 and 65% DE at 6 dB OBO and maximum output power at 1.5 GHz (second design frequency). The designed SPA achieves above 39 dBm output powers at two working frequencies with about 10 dB gain and ±1.3 dB gain flatness. To the best of the authors' knowledge, it is the first time that a dual-band SPA is reported and demonstrated experimentally. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:99-102, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, we present a simplified Doherty power amplifier (DPA) architecture for the easy implementation of dual-band operation. The proposed DPA structure eliminates the 35 Ω quarter wavelength impedance inverters used in the conventional DPAs by matching the output impedances of the carrier and peak amplifiers of the DPA to other values (e.g., 100 Ω). The electrical lengths of the offset line and the phase compensation line are carefully chosen to enhance the Doherty effect (high efficiency at back-off power level) at two assigned frequency bands. Broadband matching networks are also designed to increase the operation bandwidths at the two designed bands. To prove the design concept, a dual-band DPA is designed and measured. In the first frequency band (550-650 MHz), the designed DPA provides 60.6-76.3% drain efficiency (DE) at full output power, 46-54.9% DE at 6 dB of output power back-off (OBO); in the second frequency band (950-1050 MHz), the designed DPA provides 51.4-61.2% DE at full output power, 35-38% DE at 6 dB of OBO. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:953-956, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents a novel approach to shrink the size of the conventional phased array antenna fed by Butler matrix. The proposed size reduction of the phased array antenna is obtained by designing the whole system to operate at dual frequency bands. Due to the dual-band operation, an N-element phased array antenna can be used to generate 2N radiation beams, leading to a great size reduction. To verify this design concept, a dual-band feed network is built based on a dual-band 4 × 4 Butler matrix. By integrating this dual-band feed network with a four-element antenna array, eight distinct radiation beams can be realized. An experimental prototype operating at 5 and 8 GHz is designed and fabricated. It can achieve the same function as the conventional phased array antenna system using single-band 8 × 8 Butler matrix, realizing a great size reduction. The simulated and measured results show good agreement with the design theory. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1391-1396, 2014 [ABSTRACT FROM AUTHOR]

We propose a dual-band microwave device to detect the dielectric changes in polydimethylsiloxane microfluidic channels. Such a device, which consists of two dual-band Wilkinson power dividers (working at 2 and 5 GHz) and two 90° dual-band microstrip lines (providing 180° phase difference at two operating frequencies), is very sensitive for identifying dielectric material changes. Moreover, by operating at two frequencies simultaneously, it can improve the measurement stability/robustness. Compared with other existing microwave microfluidic sensors, the proposed device features enhanced measurement stability with the same level of measurement sensitivity (up to −80 dB cancellation level). © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2691-2694, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27188 [ABSTRACT FROM AUTHOR]