Search

In this work, an ultra‐wideband double slot Vivaldi antenna (DSVA) loaded with a novel wideband nonresonant metasurface is proposed to enhance the gain. The semi‐elliptical slots are etched on both sides of the ground plane of the DSVA to improve the current distribution. In addition, the nonresonant metasurface composed of WiFi‐shaped unit cells could maintain a stable high refractive index in the operating bandwidth of 1−18 GHz, which could bend the outgoing wave to the end‐fire direction. Both the original antenna and the proposed antenna are simulated, fabricated, and characterized. The measured results are in good accordance with the simulated ones. The return losses of both antennas are less than −10 dB in the frequency range of 2−13.4 GHz, while the gain of the proposed antenna is improved from 13.6 to 16.3 dBi with a maximum gain enhancement of 3.1 dB. [ABSTRACT FROM AUTHOR]

A novel design of circularly polarized broadband slot antenna with high gain, low profile, and low radar cross‐section (RCS) is proposed by employing polarization conversion metasurface (MS). By introducing sawtooth corner‐truncated square MS with diagonal gaps, a compact circularly polarized antenna composed of 4 × 4 unit cells is presented. It is found that a smaller MS slot antenna can achieve an impedance bandwidth of 42.9% (3.7–5.72 GHz) and a 3‐dB axial ratio (AR) bandwidth of 22.8% (4.55–5.72 GHz). Simultaneously, the MS can realize polarization conversion. The MS and its orthogonal units were arranged in a chessboard‐type pattern and applied as the radiator of a larger MS slot antenna, which was fed by a sequentially rotated feeding network. In addition, owing to the anti‐phase cancellation and scattering, the 5‐dB average RCS reduction can be obtained within the frequency range from 3.8 to 6.9 GHz. For verification, the proposed larger circularly polarized antenna was fabricated and tested. The operating bandwidth was measured as 44% (3.78–5.91 GHz) with a 3‐dB AR bandwidth of 39.6% and a high gain of 10.3 dBic. Furthermore, the larger antenna produces a useful RCS reduction from 3.7 to 6.7 GHz. The simulated and measured results are in good agreement. [ABSTRACT FROM AUTHOR]

In this letter, a triple‐mode bandpass filter based on isosceles right‐angled triangular (RAT) resonator with three magnetic walls is proposed. To realize the triple‐mode filter, the RAT resonator is perturbed by two metalized via‐holes around the center. These via‐holes form an LC resonant unit with the patch. Also, the via‐holes make mode shifting of the TM010Z mode while not affecting the TM110Z mode in order to form the passband. The proposed filter is fabricated and measured. The center frequency is 5.51 GHz and the fractional bandwidth is 20%. The minimum in‐band insertion loss and return loss are measured to be 1.26 dB and 20.5 dB. The measurement results show that the filter has featured both compact size and excellent in‐band responses. [ABSTRACT FROM AUTHOR]

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 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]

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 coupler using Pi-shaped coupled lines for dual-band operations. In this design, two open circuited stubs are tapped at both ends of a coupled line structure to realize the 90° phase changes at two frequencies. The designed structure is used in place of a conventional quarter wavelength transmission line for dual-band application. For verification, a 3-dB branch line coupler with operating frequencies of 0.95 and 1.52 GHz is designed. The simulated and measured results are in good agreement with each other. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:501-504, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, a novel multiband branch-line coupler employing multiband transmission lines is designed to operate at three different frequencies. To realize multiband operations, a Pi-type-based multiband transmission line network with open- and short-ended stubs is employed. Specifically, the Pi-type line is applied to realize the dual-band operation at the first two working frequencies. For the third operating frequency, the open- and short-ended stubs are tapped at the center of the Pi-type line. ABCD-matrix is employed to derive the design formulas for the proposed triband transmission line. To verify the design concept, a planar coupler operating at 1/2.5/4.5GHz is designed and fabricated. The simulation and measurement results show good agreement with the design theory. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2841-2845, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT An eye-opening measurement circuit provides information about the signal quality of the high-speed data through the band-limited channel. Thus this information can be used to evaluate the channel performance, especially when the communication environments are changing constantly. By implementing this as a system-on-a chip, it is possible to realize the reconfigurable system such as an adaptable feed-forward equalizer, which will adapt itself through the changes of the communication channel. Moreover, the highly integrated single-chip eye-opening monitoring block can achieve more efficient and cost-effective communication chip test. In this article, we propose a new eye-opening measurement circuit, which can work up to 10 GHz. Using the fall time and rise time of the signal, which are affected by intersymbol interference, the corresponding characteristic is converted to DC values to assess the channel performance. The proposed eye-opening measurement circuit and tunable delay line are fabricated in 0.18-µm CMOS technology. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2136-2141, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT In this letter, utilizing multimetal layers in the CMOS process, an ultra-slow-wave on-chip coplanar waveguide (CPW) transmission line with interdigital loaded stubs and floating strips is proposed. From the full-wave 3D EM simulation and measurement results, it is found that the proposed on-chip transmission line features smaller size and lower loss comparing to traditional on-chip CPW transmission lines. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:604-606, 2017 [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]

ABSTRACT In this article, a transversal filter with winner-take-all variable gain amplifiers is investigated to improve the performance of a feed-forward equalizer. The proposed equalizer structure with nine gain cells has wide bandwidth and improved voltage headroom, at the same time achieving the low power consumption per gain cell. The proposed equalizer is fabricated in a 0.18 μm CMOS process and shows the successful compensation with 30 and 60 in backplanes with 3 Gbps signal. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2666-2670, 2013 [ABSTRACT FROM AUTHOR]

This article presents the design of a microwave bandpass filter with tunable center frequencies and reconfigurable transmission zeros. The tuning of the center frequencies is realized by loading varactors at the ends of the λ/2 resonator. The reconfiguration of transmission zero is implemented through varactors in combination with tapped λ/4 stubs. The equivalent circuit models of the tunable filters are provided. The transmission zeros can be set to be at the lower side, the upper side, or both sides of the passband. The design concept is demonstrated by measurement results for both one transmission zero case and two transmission zeros case. The tuning frequency ranges are 680-890 MHz and 680-1020 MHz for one zero case and two zeros case, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1526-1531, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27628 [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]

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]

This article presents the design of Fermi antenna array with improved gain for radar respiration measurement. A six-element Fermi antenna array working at 5.8 GHz is optimally designed and integrated with the respiration radar system. Specifically, to easily feed the antenna array as well as reduce the total size of the array system, a feeding network based on 0-degree phase shifters is used along with suitable impedance transformers. The whole system is proposed to function as a radar sensor for respiration rate measurement, which is known as a promising noncontact and noninvasive approach for lung cancer radiotherapy. The measurement results verify the improved performance of the proposed system for radar respiration measurement in motion-adaptive lung cancer radiotherapy. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1649-1654, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26871 [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]

ABSTRACT A tunable sequential power amplifier (SPA) is presented in this article. The proposed SPA, including a tunable coupler, a carrier amplifier, a peaking amplifier, and a combining coupler is fabricated on Isola I-TeraMTRF boards with 3.45 dielectric constant and 0.508 mm substrate thickness. A conventional SPA (nontunable) is also designed for reference and performance comparison. Measurement results show that the tunable SPA provides about 2 dB higher gain and 1 dB higher power output comparing with the reference design. The measurement results match well with the analysis. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2899-2901, 2015 [ABSTRACT FROM AUTHOR]

A narrow beam monopole antenna is realized by embedding the antenna within a periodic metallic wire array. The 2D wire array is designed to have an effective index of refraction smaller than unity (neff < 1) at the X-band frequencies (8–12 GHz), within which the antenna operates. The narrow beam effect due to the low refractive index of the wire medium is demonstrated in both simulation and experiment. Measured antenna properties including return loss and radiation pattern are in good agreement with simulation results. This simple and straightforward antenna design methodology can be applied at any microwave frequency. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2341–2345, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23653 [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]