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ABSTRACT This article presents a dual-band amplifier with flexible frequency ratios. The amplifier features novel Wilkinson power divider/combiner with dual-band property that allows large frequency ratio (2.16-4.9) between its first and second operating bands. The measured combining efficiency on a stand-alone combiner is 97% at 2.25 GHz and 75% at 5.25 GHz. A 2.25/5.5 GHz prototype amplifier is tested to verify dual-band functionality. Measured linear gains are 12.85 dB and 12.07 dB at the first and second frequency bands, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2242-2247, 2015 [ABSTRACT FROM AUTHOR]

A parallel-strip line fed antenna with very wide bandwidth is presented in this article. This wideband antenna is designed as a combination of two individual antenna elements that are connected in a way inspired by the log-periodic antenna array technique. To miniaturize the size of the structure, metamaterial-based antennas are used as the basic radiating elements. The proposed antennas are designed on FR4 substrate and measured results show that it has a very wide bandwidth from 0.68 to 120 GHz with a VSWR < 3 for frequency range from 0.68 to 3.2 GHz and VSWR < 2 for the remaining bandwidth, with relative stable radiation characteristics. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2646-2650, 2012; this online at wileyonlinelibrary.com. DOI 10.1002/mop.27150 [ABSTRACT FROM AUTHOR]

In this paper, a new fully symmetrical four-port microstrip crossover and its dual-frequency application are presented. The proposed single-band crossover has a simple structure and an easily controlled bandwidth; and its dual-frequency application can provide flexible frequency ratio between the two working frequencies. Moreover, analytical design equations are derived using the even–odd-mode method. The final explicit design equations are concise. To verify the design concepts, both a single-band crossover working at 1 GHz and a dual-frequency crossover working at 1/2.3 GHz are fabricated and tested. The measurement results agree well with the design theory. [ABSTRACT FROM AUTHOR]

A low-profile, compact and easily integrated antenna for RF/microwave applications is presented in this article. The designed antenna works around 430 MHz and can be easily scaled to other frequencies. Metamaterial-inspired slot loop antennas are used as the radiating elements. To shrink the total size of the antenna, periodical structures are loaded to the original slot loop. It is found that with this modification, the total size of the antenna is reduced and the impedance matching of the antenna is improved. To further improve the performance of the proposed antenna, a floating ground plane and a parasitic slot were added, made possible by the multilayered structure of the antenna. As a result, the bandwidth and gain of proposed antenna are increased. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:219-223, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25654 [ABSTRACT FROM AUTHOR]

In this article, a novel balanced wideband filter based on microstrip coupled lines is proposed. It features characteristics such as wide bandwidth, compact size, and good common-mode suppression. The proposed balanced filter was calculated analytically, simulated by full-wave electromagnetic simulator and validated by the measurements. The calculated, simulated, and measured results are in good agreement with each other. The experimental results show that it can allow the differential-mode signal to be transmitted with low insertion loss across a wide frequency band, whereas the common-mode signal will be well suppressed. The fractional bandwidth of the designed filter is 88%. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1139-1141, 2014 [ABSTRACT FROM AUTHOR]