In this work, the package influence on a feedback low-noise amplifier has been studied.The electromagnetic simulator of ADS was used to obtain the QFN16 package model and the bonding model. The influence of the package and the pad on the supply node was negligible when it was studied separately. However, the circuit performance is reduced when the inductance introduced by the bonding of the supply node is combined with the parasitic capacities associated to the pad with electrostatic discharge protection. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1435–1440, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27601

We propose a compact planar dual-mode resonator based on a Hilbert fractal curve that operates at two arbitrary frequencies. The resonator is used to design two types of dual-band bandpass filters for WLAN applications, which exhibit a good trade-off between compact size and high performances, with the overall sizes ranging from 0.22 × 0.21 to 0.44 × 0.1 guided wavelengths and measured insertion losses from 0.38 to 2.5 dB. At the same time, the fabrication of filters is quite simple and requires no modifications in the ground plane or use of vias. In addition, the proposed resonator is used to design single-band filters as well. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1440–1443, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27667

In this article, we present a TRx stacked microstrip patch antenna with improved isolation using double spur-line band rejection filters (DSL-BRFs).The typical TRx stacked microstrip patch antenna designed to operate at Ku-band with downlink frequency band of 12.25–12.75 GHz and uplink frequency band of 14.0–14.5 GHz had inherent isolation of 16 dB within TRx-band. The isolation performance of the antenna was improved by at least 23.45 dB in Rx-band and 17.82 dB in Tx-band after introducing the DSL-BRFs into Tx- and Rx-feed networks, respectively. Because the DSL-BRFs are compatible to be embedded in 50-Ω transmission lines, the TRx antenna with the filters are remained in as same size as the antenna without filters. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1444–1448, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27632

In this article, a compact ultra-wideband (UWB) slot antenna with band-notched performance is presented. To increase the impedance bandwidth of an ordinary slot antenna, we use a pair of S-shaped slots in the ground plane that with this structure a new resonance at the higher frequencies can be achieved, and a wide usable fractional bandwidth of more than 130% is provided. Additionally, by cutting a rectangular slot with a rotated E-shaped strip protruded inside the slot in the square radiating stub, a frequency-notched band performance has been obtained. The designed antenna has a small size of 20 × 20 mm² while showing the radiation performance in the frequency band of 3.13 to over 14.3 GHz with a band rejection performance in the frequency band of 5–6 GHz. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB-frequency range. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1448–1451, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27631

This article presents a bandpass filter with second harmonic suppression using nonuniform open stubs.The proposed bandpass filter uses the nonuniform open stub instead of the uniform open stub to suppress the second spurious harmonic frequency. The nonuniform open stub consists of two serial combined stepped impedance resonators with different characteristic impedances and different electrical lengths. The use of nonuniform open stubs improves the second harmonic suppression. The proposed bandpass filter using nonuniform open stub provides the broad bandwidth outside the passband without external circuits. The proposed bandpass filter has a return loss below 10 dB from 2.42 to 2.54 GHz and improved second harmonic suppression of 48 dB at 4.54 GHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1451–1453, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27640

We propose a new splicing technique by precisely aligning and directly connecting coated fibers with a capillary. The assembled splice for 1.3-μm single-mode fibers with an 80 μm cladding and a 125 μm coating can provide a low insertion loss of 0.2 dB and a high return loss of over 46 dB. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1453–1456, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27636

This article proposes the design of a 2 (2 array electromagnetic band gap superstrate antenna capable to fulfill the specific radiofrequency (RF) requirements of a C-band (3.7 GHz) TT&C telecommunication system from geostationary orbits. Design efforts are focused on overall volume reduction while complying with RF performances over the required frequency bandwidth, trying to provide an advantageous alternative to the bulky horn antennas usually used for TT&C operations in current satellites. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1457–1461, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27616

In this study, an ultrawideband antenna with variable frequency notch band characteristics is presented. Using only one pin diode, which is mounted to the back side of the antenna, WLAN signals (5.15 and 5.875 GHz) are easily suppressed. The designed antenna bandwidth is 2–11 GHz covering the entire band assigned for the UWB application, which is more than 135%. The detailed design considerations are described in the article. The proposed antenna is implemented, and the experimental results are carried out to validate simulation results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1461–1466, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27602

A compact asymmetric coplanar strip-fed staircase ultrawideband (UWB) antenna with notch band reconfigurable characteristic is proposed and investigated numerically and experimentally.The reconfigurable notch bands are realized by using a spur-slot and an ideal switch. By controlling the switch at OFF and ON states, the notch bands of the proposed UWB antenna can work at 3.5 and 8.2 GHz, respectively. Numerical and experimental results show that the proposed antenna is capable of working for entire UWB application and providing the reconfigurable notch bands. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1467–1470, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27634

An integrated antenna array comprising two decoupled multiband WWAN/LTE antennas having an isolation ring strip embedded therebetween and all disposed on a same FR4 substrate of small size 10 × 70 mm² is presented. The two decoupled antennas cover the 824–960/1710–2690 MHz bands for the GSM850/900 and GSM1800/1900/UMTS/LTE2300/2500 operations and are promising to be mounted at the bottom edge of a smartphone for dual wireless wide area network (WWAN) operation for dual-talk function or for long term evolution (LTE) multiple-input multiple-output operation. The measured transmission coefficient S₂₁ between the two antennas is less than −15 dB over both the 824–960 and 1710–2690 MHz bands, and the envelop correlation coefficient is less than about 0.03 over both bands. Port-decoupling of the two antennas is obtained because the excited surface currents on the system ground plane of the smartphone between the two antennas are decreased owing to the isolation ring strip attracting some of the same. In addition to good isolation obtained, the antenna efficiencies are better than about 40 and 50% over the lower and upper bands, respectively. Details of the decoupled WWAN/LTE antennas are described. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1470–1476, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27654

A multistage optimization procedure is provided to maximize the operating bandwidth of a very high frequency circulator. We show through hardware validation that bandwidths on the order of 52.3–80.9 MHz are achievable using a 15 dB isolation specification. Simulation studies indicate that bandwidths on the order of 100% are possible, but such wideband performance has not been achieved in hardware to date. The optimization procedure uses both genetic algorithms and orthogonal sweep methods to find the best crossover geometry and ferrite properties, but the outcome of both methods is roughly the same. Matching networks are used to tune the response and to widen the operating frequency band. These networks are optimized using Pareto tradeoff charts in the context of power metrics like return loss, isolation, and insertion loss. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1476–1481, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27654

A passive UHF band radio frequency identification tag antenna design is presented in this article. To allow compact size and circular polarization (CP) radiation, a radiating square patch is loaded with two pairs of unequal slits, while a quarter-wave microstrip line connected to a tag chip and terminated by a short-circuited stub line is used to excite the radiating patch. The 10-dB impedance bandwidth of the tag antenna is measured to be 31 MHz (896–927 MHz), whereas its 3-dB CP bandwidth is 6 MHz (911–917 MHz). Further experiment has demonstrated that the proposed tag antenna can provide better reading distance when mounted on a metallic surface as compared with the free-space condition. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1481–1485, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27607

A design of a broadband six-port reflectometer has been presented.Broad bandwidth has been achieved with the use of coupled-line directional couplers. An appropriate modification of a standard six-port which ensures uniform circle centers' distribution against frequency has been proposed. The influence of power detectors' uncertainty on the calibration procedure and measurement results is discussed, and the estimated measurement accuracy is given. The performance of the presented six-port reflectometer has been experimentally verified by measurements of the reflection coefficient in a frequency range 2–3.5 GHz. The obtained results are in good agreement with measurements performed with a commercial vector network analyzer. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1485–1490, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27607

A fully integrated, 5.6 GHz low-phase noise Colpitts quadrature voltage-controlled oscillator (VCO/QVCO) is presented. This QVCO is a complementary cross-coupled voltage-controlled Colpitts oscillator with a three-bit switched capacitor array parallel to the inductor to form LC-resonant tank and was implemented in TSMC 0.18 μm CMOS technology with 1.8 V supply voltage. Without buffer circuits, measured results achieve a tunable frequency range from 4.81 to 5.75 GHz, corresponding to 17.8%, a phase noise of −121 dBc/Hz at 1 MHz offset frequency from 5.64 GHz, while the QVCO draws 3.8 mA current and 6.84 mW consumption, respectively. Including pads, the chip area is 1.046 mm² (1.35 × 0.775 mm²). The output power is −10.04 dBm with 50-Ω termination at the frequency of 5.64 GHz, and the calculated figure of merit is −187.7 dBc/Hz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1490–1493, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27629

A dual-resonance complementary Colpitts voltage-controlled oscillator (VCO) is proposed to serve as a dual-band oscillator operated at 4.3 and 11.7 GHz.The VCO consists of two single-ended dual-resonance LC-tank complementary Colpitts oscillators sharing a common varactor-switching LC resonator. The proposed VCO has been implemented with the TSMC 0.18 μm 1P6M CMOS technology and the core power consumption is 3.60/3.96 mW at the supply voltage of 1.2 V. The VCO has figure of merit −192.7/−189.4 dBc/Hz at high/low band, respectively. The die area of the dual-band VCO is 0.822 × 0.628 mm². © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1494–1497, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27626

In this article, in order to enhance the linearity of power amplifier modules (PAM), we have suppressed the harmonics at the output port of a high-power amplifier (HPA) and cancelled the third-order intermodulation distortion (third IMD) by a predistortion scheme. The matching network to suppress the harmonics consists of metamaterial like the composite right/left-handed structure. Both the second and third harmonics are suppressed over 27 dBc. A phase of generated third IMD at the output of the drive amplifier has changed in order to offset the third IMD of HPA. The harmonics of the proposed PAM suppresses over 6 dB more than a single HPA and over 20 dB more than a reference power amplifier. The PAM has 37 dBm of output power and 21.6 dB of power gain. The second harmonic and third IMD are −53 and −42.5 dBc about PAM, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1497–1500, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27625

A methodology to design high-power amplifiers composed of several amplifier blocks and passive combiners/dividers is proposed.The optimum matching condition between amplifiers and combiners has been found using the mixed-mode S-parameters approach. Measurements and computer-aided design simulations have been successfully used to validate the proposed approach. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1500–1504, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27600

A chaotic ultra-wideband (UWB) over fiber link based on optical feedback laser diode which generates the chaotic laser signals is proposed and demonstrated. Flexible generation of up to 1.44 Gb/s on-off keying chaotic-UWB signals is successfully achieved. Without utilizing any dispersion compensation module, the signals with bit rate of 1.44 Gb/s were detected using a digital signal processing receiver after 20-km optical fiber and 0.6-m wireless channel transmission. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1504–1507, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27615

This article proposed a new high loaded quality factor (Q_L) hairpin resonator with a combination of a stepped impedance resonator and single split ring resonator and its application to low phase noise oscillator for X-band applications.A new resonator has a good characteristic of S-parameter responses. The microwave oscillator is designed at 10 GHz that exhibited a low phase noise characteristic due to the high loaded Q_L of the new resonator. A series feedback network is used to generate the negative resistance to make oscillation. Experimental results of the microwave oscillator show the phase noise characteristic of −103.69 dBc/Hz at 100 kHz offset with output power of 15.56 dBm. The second harmonic suppression is −32.25 dBc, which is very important in wireless communication system. The figure of merit of the fabricated oscillator is −180 dBc/Hz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1508–1511, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27608

This article presents a linearly polarized slot-array antenna that consists of a slot series-fed by a microstrip line for radio frequency identification (RFID) shelf applications in the ultra-high frequency band in which the end of the microstrip line is shorted to the ground plane by a via-hole. The radiating element is a U-shaped slot etched in the ground plane on one side of a substrate and the microstrip line for feeding is etched on the other. The designed 6 × 3 array antenna has the near-field distribution of electric field intensity from 0.5 to 3.36 V/m for RFID shelf applications. The fractional bandwidth for a reflection coefficient of less than −10 dB is approximately 5.5% at 920 MHz, ranging from 892 to 943 MHz. The antenna installed in the RFID shelf stably reads pharmaceutical products with various package options on the shelf. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1511–1515, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27653

Oblique TM^z polarized plane wave scattering from a perfectly electrically conducting cylinder of circular cross-section is modeled using a finite-element time-domain formulation in terms of the scattered electric field using a modal nonreflecting boundary condition and both nonperiodic and periodic formulations.© 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1516–1520, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27614

This article presents a solution to bypass the cost and flatness problems for low-cost electronic devices which is the inkjet printing. This process allows the use of flexible substrate materials, such as paper or plastics, suitable for a real-to-real process. More precisely, the procedure to design an electromagnetic band gap antenna using frequency selective surfaces and coplanar wire-patch antenna for 2.5-GHz applications is detailed. This kind of antenna has been designed before, but the used substrate is expensive and thin. These antennas were fabricated using inkjet printing technology on a flexible, low-cost paper substrate using a simple, fast, and cheap process compared to the photolithography technology. The design characteristics of the antennas were verified and the experimental measurements were successfully compared to the simulated ones. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1520–1526, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27613

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

Based on theoretical analysis and experiments, the low-pass filter effects of the μ-negative materials/double positive materials/μ-negative materials (MNG-DPS-MNG) surface plasmon polaritons waveguide are studied by using L-C loaded transmission line structures in microwave band. It is shown that the pass-band width of the waveguide is not determined by its size but the effective permeability in MNG materials. So it can be used to realize the small size and tunable low-pass filter. The experimental results are in good agreement with results of simulations. These properties will have potential application values in the miniature and tunable low-pass filters. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1531–1533, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27627

Structurally simple and miniaturized ultra wideband (UWB) printed rectangular antenna fed by a coplanar waveguide (CPW) is proposed.Overall dimension of the antenna is as compact as 12 (0.13λ) × 12 (0.13λ) × 1.6 mm³, where λ is the wavelength of the first resonance of the antenna. The main feature of the proposed antenna is its compact size and controllable structure which lead to four different antenna designs. By adjusting the dimensions of the elements of the antenna, notch frequency in different ranges of the UWB can be obtained. The resulting VSWR < 1.5 impedance bandwidth is as large as 11.6 GHz. The antenna presents a stable gain and omnidirectional radiation pattern in its operational frequencies. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1533–1537, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27624

In this article, a narrow-bandwidth duplexer with a triple-split ring resonator (T-SRR) using mu-negative metamaterial is presented. The T-SRR not only has negative permeability at the operating frequency band but also flexibility in size adjustment. The experimental results for insertion and return losses are 1.33 and 16.1 dB with a bandwidth of 10% at a RX center frequency of 8 GHz, and they are 1.27 and 16.8 dB at the same bandwidth at a TX center frequency of 10 GHz, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1537–1540, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27656

This article describes the design of a four-channel parallel 40 Gb/s laser diode voltage driver (LDVD) circuit using 0.18-μm CMOS technology.The LDVD circuit consists of input buffer stage, preamplifier stage, and output driver stage. The LDVD uses dual power supplies, including the 1.8-V supply in the preamplifier stage and the 3.5-V supply in the output driver stage. To increase the bandwidth, the preamplifier stage is made up of two-stage cascaded differential amplifiers. The output driver circuit uses the RC negative feedback and capacitively coupled current amplifier (C³A) structure to speed up the operation of laser diode. The isolation has been carefully taken to avoid the cross-talk issues among channels. Experimental results show that each channel of the LDVD can work at 10 Gb/s rate, and the output current swing is over 10 mA. The total power dissipation is 450 mW, and the chip area is 460 × 1230 μm². © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1540–1543, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27635

In this article, a novel compact dual-band bandpass filter with controllable bandwidths is presented. A set of central-loaded resonators are employed to generate dual band responses. Three coupled-capacitors, loaded at the corresponding voltage-zero points of the resonators, are utilized to control the coupling coefficients of two bands separately. Besides, two extra series capacitors, between feed lines and resonators, are adopted to simultaneously achieve the desired external quality factors of dual passbands. Thus, the bandwidths of the dual bands can be independently controlled. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1543–1546, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27665

A novel annular monopole antenna with a dual-band rejection characteristic for ultra-wideband (UWB) applications is proposed.This antenna comprises an annular-shape radiating element with a tuning stub and a backside elliptical radiating element that is connected to it by a shorting pin, to create dual-notched bands at 3.2–4.4 GHz and 4.8–5.9 GHz across the UWB frequency band from 2.5 to 14.5 GHz, to filter the WIMAX and WLAN signals. Measurements demonstrate that the proposed antenna provides a very large bandwidth from 2.5 to 14.5 GHz (141%, voltage standing wave ratio 2). A good monopole-like radiation pattern except the notched bands is obtained. Details of the proposed antenna design and the simulated results are presented and discussed. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1546–1549, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27609

Double diffraction and double reflection in NURBS-UTD method are studied in this article. Algorithms being used to trace double reflected rays and double edge diffracted rays are presented. The ray fields carried by these kinds of rays are investigated to discuss the contribution of the double effected ray fields to the total ray fields. Numerical measures are used throughout the whole process and the ray fields are calculated based on single effected ray fields. Two examples are presented and it can be seen from data achieved that double effected ray fields can improve the computational precision according to the relationship between surfaces. Numerical results show the validation and the improvement. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1549–1553, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27652

In the framework of the multitask Bayesian compressive sensing (BCS) paradigm, two innovative approaches for the solution of coherent imaging problems are proposed within the first-order Born approximation and the Rytov approximation.Selected numerical results are reported to compare the proposed techniques with state-of-the-art BCS approaches as well as global optimization-based methods. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1553–1558, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27612

In this article, a conical antenna fed by coaxial line fed for the excitation of the radial transmission line (RTL) chamber is designed and fabricated. This antenna is analyzed by the finite-difference time-domain (FDTD) method and the input impedance is simulated. An RTL chamber was used by the device for in vitro experiments. The designed antenna has advantages, such as ultra-broadband characteristic and omnidirectional radiation. The bandwidth of fabricated antenna has 630–2590 MHz at voltage standing wave ratio ≤ 2. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1558–1560, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27646

This article presents a novel bandpass-response power divider with high frequency selectivity. The centrally stub-loaded resonators are applied to this power divider in order to provide bandpass-filtering frequency response. In addition, the presented power divider has three transmission zeros, which can be used to improve the frequency selectivity. The measured results demonstrate the good performance of the fabricated bandpass-response power divider with high selectivity. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1560–1562, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27644

This letter proposes novel design for a compact LTCC bandpass filter with high rejection over a wide stopband operating in the 3.4–3.6-GHz worldwide interoperability for microwave access band. The presented bandpass filter has feedback paths for the grounding inductor and the coupled capacitor to provide controllable multiple transmission zeros at 2.4/5-GHz wireless local area network band, which enhances the desired stopband rejection. The presented design derives simple formulas for synthesizing a bandpass filter to meet the specification requirement in the passband insertion loss and passband return loss as well as the stopband attenuation. The bandpass filter is designed and implemented using LTCC process and has an area of 2.0 × 1.25 mm². Experiments results are very agreement with the full-wave simulation results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1563–1565, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27643

We present an analytical formula to calculate the resultant effective permittivity of a metamaterial medium composed of unit cells with complementary structures. Complementary metamaterial can be considered to be the complementary screen of artificial magnetic materials. Based on Babinet's principle and duality, complementary metamaterial provides a negative effective permittivity in the vicinity of its resonance frequency. The developed formula is general and predicts the effective permittivity for a specific topology. The derived model validated by comparison to results obtained using full-wave simulation. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1565–1569, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27655

A multi-input multi-output (MIMO) antenna with improved isolation using radio frequency choke (RFC) is proposed.The proposed MIMO antenna consists of two radiating elements and an RFC that is located in between the two radiating elements. To improve the isolation between the two radiating elements of the MIMO antenna, the RF signal is suppressed at the desired frequency band by utilizing an RFC. The isolation is improved by ∼20 dB at the center frequency. The fabricated antenna satisfies the 6 dB return loss in long-term evolution band 13 from 746 to 787 MHz. The measured average efficiency and gain of the MIMO antenna are about 30.5% and −1.5 dBi, respectively. The measured envelope correlation coefficient is less than 0.4 over the frequency band of interest. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1569–1574, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27623

We have demonstrated a widely wavelength tunable Brillouin-erbium fiber laser (BEFL) with multiwavelength lasing in the L-band region. The Brillouin pump (BP) is injected from the external cavity and preamplified by an intracavity bismuth-based erbium-doped fiber amplifier (Bi-EDFA) before entering the single-mode fiber. By combining the broadband gain of Bi-EDFA and BP preamplification technique within the linear cavity, our BEFL exhibits a broad tuning range of 65 nm from 1555 to 1620 nm, which is the widest one achieved in L-band BEFLs to the best of our knowledge. The maximum number of wavelengths obtained within this wavelength range is 12 channels with a spacing of approximately 0.088 nm. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1574–1577, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27664

An ultra-wideband (UWB) bandpass filter (BPF) using the hybrid microstrip and coplanar waveguide (CPW) structure is proposed in this article.The BPF composes of CPW feed lines and H-shaped microstrip resonator. By a CPW/microstrip back-to-back coupling structure, the UWB BPF was realized with the passband covering the entire UWB band (3.1–10.6 GHz). A narrow notched band achieved by etching slots on the lower impedance part of the H-shaped resonator to form an open circuit stub. At last, three U-slot DGSs are used to achieve a good upper-stopband rejection. The measured results are in good agreement with the simulated results. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1577–1581, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27663

A design technique to increase the output amplitude and hence the output power of push-push LC-based voltage-controlled oscillators (LC VCOs) is presented that relies on LC resonance boosting of the second harmonic. Measurement results are in good agreement with the results predicted from the analysis. Using the proposed technique, a low-power push-push LC VCO is designed and implemented in 90-nm CMOS. Based on the measurement results, the VCO has a frequency tuning range of 23%, from 20.1 to 24.8 GHz. It exhibits up to 8 dB improvement in its output power at the middle of the frequency band compared to a traditional push-push VCO. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1581–1584, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27599

A novel CPW-fed compact inverted L-strip ultra wideband (UWB) microstrip antenna is proposed for ultra wide band applications. The proposed antenna possesses a method to minimize the monopole antenna by loading of inverted L-strip over the conventional monopole patch antenna to lower the height of the antenna. The ground was vertically extended toward two sides of the single radiator. Therefore, the large space around the radiator that is usually wasted can be effectively saved. The antenna is practically fabricated and simulated. Measured results show a good agreement with simulated results. The prototype with overall size of 25 × 25× 1.6 mm³ achieves good impedance matching, constant gain, stable radiation patterns, and constant group delay over an operating bandwidth of 2.6–13.04 GHz (10.44 GHz). © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1584–1589, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27651

A highly compact 2 × 2 (four element) and 2 × 4 (eight element) multiple-input-multiple-output (MIMO) antenna systems are designed for the IEEE 802.11ac standard. The antennas operate in the 5-GHz band with a minimum effective bandwidth of 80 MHz. The elements of the MIMO antenna system are patch antennas loaded with complementary split-ring resonators. A minimum isolation of 10.5 dB and maximum gain of −0.8 dBi are measured. Total size of the MIMO antenna systems is 50 × 100 × 0.8 mm³. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1589–1594, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27611

We demonstrate the feasibility of bulk illumination technique for low-power photonic control of RF resonance.Using this technique, the transmitted RF power through a microstripline-ring filter on a junction-less silicon substrate is changed by 11 dB with less than 2 mW of interacting optical power. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1594–1599, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27606

A miniaturized circularly polarized (CP) patch antenna with wide impedance matching and axial ratio bandwidths and a good efficiency using an electromagnetic band gap (EBG) ground plane is presented. CP is obtained with the truncated corners technique applied on a square patch and size reduction of this radiating element is based on the slow wave phenomenon created in the EBG structure. This antenna is fabricated on a 117 × 117 × 4 mm³ FR-4 substrate (ε_T = 4.4 and tan δ = 0.22) and dedicated to the European UHF radio frequency identification band (865–868 MHz). The measured bandwidth, realized gain, and total efficiency are 14.4%, 3.7 dBi, and 79%, respectively. Experimental and theorical results are presented and discussed. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1599–1602, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27642

A novel compact half-mode substrate integrated waveguide (HMSIW) filter with capacitively loaded complementary single split ring resonators (CSSRRs) is presented in this article.The proposed structure demonstrates lower resonant frequency and enhanced miniaturization compared to the HMSIW with conventional CSSRRs due to the additional capacitance generated by an additional conductor connected to the inner metal disk and overlaid across the ground plane of the CSSRR. Even lower resonant frequency and greater miniaturization can be achieved conveniently by increasing the area of the overlap or using thin dielectric substrate and the technique can readily be realized in a range of multilayer technologies. The equivalent circuit model for the proposed structure of the HMSIW with the capacitively loaded CSSRR is derived and a second-order bandpass filter with the proposed structure, operating at 4.92 GHz, is designed and fabricated. Excellent agreement is achieved between the simulation and the measurement. The proposed HMSIW filter with capacitively loaded CSSRRs shows good selectivity, low loss, and compact size, with the total size being only 9.8 × 7 mm² (0.17 λ₀ × 0.115 λ₀) without the feed lines. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1602–1606, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27604

In this research, a dual-band ultrathin metamaterial absorber with wide-angle and polarization-insensitive characteristic is presented. The metamaterial absorbers consist of a periodic arrangement of two scales of Jerusalem resonators and a metallic background plane, separated by only 0.8 mm dielectric spacer. By changing the direction of polarization, we achieve that the structure is polarization insensitive. Simulations demonstrate two good absorption rates in the designed frequency bands over wide angles of incident waves for both transverse electric and magnetic polarizations. Waveguide experiments are conducted to verify that the proposed designs can achieve two good absorptivity peaks. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1606–1609, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27622

In this article, a compact multielement antenna system composing of microstrip patch antennas is designed by using electromagnetic bandgap (EBG) structures. Two distinct EBG structures are designed to achieve the two objectives of miniaturization and suppression of interelement coupling due to surface waves in a multiantenna system. By embedding an EBG array operating in the slow-wave region, the area of the microstrip patch antenna is reduced by 67.48%. To alleviate the resulting increased back radiation, a second EBG structure is designed to surround the miniaturized patch antenna and close to 8 dB improvement in the front-to-back lobe ratio is achieved. As well, the second EBG design is included in a 2 × 2 multiantenna system to suppress interelement coupling. It is found that the coupling is reduced significantly when utilizing the proposed EBG rings. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1609–1612, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27621

An electrodynamic analysis of an optical resonator comprising a half-wavelength dielectric layer that is covered from both sides by quarter-wavelength layers with higher and lower refractive indices (RIs) is carried out.For such a resonator, the dependences of the external quality factor on number and RIs of the layers are obtained first. That allows one to determine minimum number of the layers in the structure to achieve the required quality factor at practically any contrast of the RIs. The results of this study provide an easy way to optimize the structures of 1D photonic crystal devices, particularly high-selectivity bandpass filters. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1613–1616, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27662

We report a process to integrate microfluidic channels on standard radio-frequency (RF) printed circuit board (PCB) substrate. A 10.56-GHz RF microstrip interferometer was fabricated using the proposed technique and used to compare electrical responses for liquids with various dielectric properties and thereby demonstrate the capability of RF PCB-integrated microfluidic devices for biological sensing. Microchannels were milled into a substrate and prepreg outlines for microchannels were cut using a laser system. Substrates were adhered and bonded by clamping and baking. The RF interferometer responded to changes in liquid permittivity with high sensitivity relative to many other types of dielectric sensors. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1616–1618, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.2766

It is observed that some antennas can transmit a signal conforming to the applied voltage to the far field without any distortion in the time domain, whereas other antennas can receive a signal from the far field which will induce a current on the antenna conforming to the shape of the incident field.With a pair of transmit/receive antennas chosen from this class, one can construct a communication system that will transmit a time-domain wideband signal and receive it without any distortion of the pulse shape. In this article, we study the effects of the presence of obstacles along the path between the transmit and receive antennas, and we demonstrate that in some cases even when the signal is scattered by the obstacles, the shape of the received scattered pulse may not get distorted. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1618–1622, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27650

We propose in this article, a novel compact reconfigurable patch antenna with frequency diversity. This antenna can be tuned by changing the switching mode of two PIN diodes from the ON–ON state to OFF–OFF state to switch it over two different mobile communication technologies, namely 3G and 4G. The antenna has a simple geometry and a small structure, its dimensions are 45 × 38 × 1.5 mm³ and it is printed on an FR4 substrate with a thickness of 1.5 mm. The prototype of this antenna has been fabricated and tested. The measurement results confirmed the simulation predictions in terms of frequency diversity performances. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1622–1626, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27649

This article presents a UHF radio frequency identification tag antenna used in proximity to the chest of a human body for student ID card identification.The proposed tag antenna is a rectangular slot-type patch structure printed on a PVC card. For near-body applications, stratified square plates with physical parameters are used as a human model. The radiation properties of the slotted tag antenna placed near the model and the absorption effects due to human body are investigated. The research used the HFSS simulator to optimally design the antenna and employed the FEKO simulator to verify the simulated results. The designed tag was constructed for testing the reading range. The measured reading range achieved is around 4.2 m as the tag is put close to the chest. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1626–1631, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27610

This article presents a hybrid digital and RF front-end module (FEM) of a 24-GHz pulse-Doppler radar system for intelligent transport system applications. The conventional pulse generators use analog components such as step recovery diode. It is difficult to control the parameters of the pulse. In addition, the heterodyne architecture based transceivers show good performance, but they are very expensive. To overcome these limitations, a digital pulse generator was developed based on field-programmable gate array platform to obtain high degree of freedom in a waveform design. Instead of the heterodyne architecture, a transceiver based on the homodyne architecture was developed. For the first time, hybrid digital FEM based 24-GHz pulse-Doppler radar was developed by combining a digital pulse generator and a homodyne-based transceiver. Experimental results showed the feasibility of using a hybrid digital FEM for a 24-GHz pulse-Doppler radar. The developed hybrid digital FEM contributes to the advancement of the digital radar field. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1631–1638, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27666

A compact two-way equal power divider with improved out-of-band rejection based on substrate-integrated waveguide technology is presented in this letter.The proposed power divider with 4.3-GHz center frequency and 38% fractional bandwidth has been designed, fabricated, and measured. The measured results show that the insertion losses are about 3.7 ± 0.5 dB, and the input return loss is greater than 10.6 dB in the pass band, which are in good agreement with the simulated data. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1638–1640, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27641

A novel broadband bandpass filter with multiple resonant modes based on parallel-coupled microstrip line is proposed. The required cutoff frequency and out-of-band performance are achieved by placing L-shaped capacitive cross-coupling open stubs at the middle resonator with appropriate dimensions. A compact broadband bandpass filter of dimensions 18 × 29 mm² is fabricated and tested for performance confirmation. The proposed filter demonstrates a wide bandwidth (from 3 to 7 GHz), as well as excellent out-of-band performance with more than 25-dB rejection up to more than 12 GHz and sharp upper cutoff frequency due to the proper location of two transmission zeros. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1640–1644, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27637

This article presents performance evaluation of the use of one or two edge filter(s) based on singlemode-multimode-singlemode (SMS) fiber structure on an all-fiber ratiometric wavelength monitor system.Several aspects of noise, polarization-dependent loss (PDL), and temperature-dependent loss (TDL) that can influence the system's performance were investigated. It was demonstrated that the use of two SMS edge filters can improve the system's resolution and wavelength error when compared with the use of one edge filter. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1645–1649, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27619

In this article, we describe a frequency-tunability procedure for a waveguide single-pole bandpass filter adopting a split-ring resonator (SRR). The tuning procedure is, in this article, achieved by inserting a metal or ferrite tuning screw, depending on the desired tuning direction. The screw plays a role in the adjustment of the magnetic field passing through the center of the SRR. The discrepancy between the proposed waveguide filter and the evanescent-mode filter has been included. The aperture size of the waveguide filter is decreased by about 70% in comparison with conventional waveguides. The wide tuning bandwidths and lower insertion losses obtained by both simulation and measurement confirm the validity of the proposed technique. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1649–1653, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27618

A four-element microstrip antenna array excited with a tunable feeding network is described.The feeding network is composed of three quasi-lumped couplers and a 90° phase delay line. By controlling one dc bias, the network can provide the same amplitude and two different phase combinations, including (0°, 0°, 180°, 180°) and (0°, 90°, 180, 270°), for the four array elements. With the tunable feeding network, the excitation method of the array can be switched between sequentially rotated feed mechanism and differential-feed mechanism. A reconfigurable array prototype is constructed. Experimental results show that the array has a broadside radiation and it can provide good linear and circular polarization performances at one frequency. Simulated results are also provided to validate the designs of the microstrip antenna array with switchable polarization. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1653–1657, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27660

Antenna beam tilting or steering requires multiple antenna elements to be phase shifted and arranged in the form of an array. This article presents a novel method to tilt the main beam of a microstrip patch by partially covering it with a high dielectric-constant superstrate. The beam tilting is possible because of the dual-slot radiation mechanism of the microstrip antenna. In effect, the electromagnetic radiation from the covered radiating slot reaches the far-field with an additional phase with respect to the uncovered slot, resulting in an inclined beam whose angle depends on the superstrate's refractive index. Experimentally and numerically, a beam deflection of 25° is achieved when a microstrip patch is partially covered with a superstrate having a dielectric constant of 10. Moreover, the proposed structure provides gain enhancement of about 3 dB. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1657–1661, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27659

This article first presents a frequency-selectable branch-line hybrid coupler.To provide a frequency-selection function, a dual-band band-pass transmission-line transformer (TLT) with a frequency selective function is used. This is achieved by replacing a dual-band TLT with a variable capacitively loaded spur-line filter. The technique is demonstrated with a design at 0.8 and 1.75 GHz. Measured S-parameter results confirm the validity of the technique. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1661–1663, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27648

An original architecture based on composite configurations of printed-circuit hybrid rings is developed for flexible signal-processing functionalities in advanced monopulse radar applications. The modularity of the proposed topology, together with proper design choices, strongly simplifies the structure of the beam forming network, reducing the relevant ohmic losses, and consequently improving the antenna gain. The circuit also allows us to manage only two radio frequency channels (instead of the conventional three), combining the delta- and omnidirectional channel functions. The principles of the structure are presented, and a specific layout is designed. Stripline prototypes are fabricated and tested for L-band applications. The compared results of simulations and measurements fully confirm the interesting performance of this device. The versatility of the architecture is illustrated further considering alternative circuit implementations. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1663–1670, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27647

Fourth mobile generation requiring of multistandard operating handsets of small physical size as well as increasing demand for higher data rates.Compact multiband printed inverted-F antennas (IFA) for available wireless communications are proposed in this article. New design of printed IFA based on uniplanar compact electromagnetic band gap (EBG) concept is proposed. A printed-IFA with L-loaded shaped over artificial ground plane is designed as the main antenna to cover the GSM, LTE, UMTS, Bluetooth, and WLAN. The multiband is created by means of an EBG structure that is used as a ground plane. Different shapes of uniplanar EBG as ring, split ring resonator, and spiral rather than mushroom-like structure are investigated. The proposed antenna is built on the uniplanar EBG ground plane with size of 35 × 45 mm², which is suitable for most of the mobile devices. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1670–1676, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27633

We propose and experimentally demonstrate an optical millimeter-wave and sub-terahertz signal generation method based on frequency 18-tupling using a power amplifier, an optical modulator, and a semiconductor optical amplifier (SOA). The power amplifier is operated in the nonlinear region and generates a third-order harmonic frequency. Next, frequency doubling by optical carrier suppression using the optical modulator is performed. Four-wave mixing of the SOA and optical filtering produce two-tone waves whose frequency spacing corresponds to 18-tupling of the input RF frequency. The experimental results show that two idlers could be obtained at 1549.98 and 1550.85 nm in the wavelength domain corresponding to the beat frequency of 108 GHz from the 6 GHz RF signal. Because of the bandwidth limitations of our available photodetectors, the phase noise of the beat signal is measured at a lower frequency of 60 GHz for the input of 3.3 GHz and is −74.60 dBc/Hz at an offset of 100 kHz. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1677–1680, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27605

This article presents a power amplifiers (PA) driver IC which has a parallel combined structure with a dual bias network.Each PA cell for parallel combination has an optimized bias to achieve both lower current consumption and IM3 cancellation at the same time, so that the overall PA driver IC has an improved linearity with a low current consumption. An incomplete Wilkinson divider including an input matching capability was proposed. This was adopted to prevent a stability degradation which can be caused by a parallel combination. The proposed PA driver IC was designed. This was implemented using a 2-μm InGaP/GaAs heterojunction bipolar transistor (HBT) to have an output power of 1 Watt. The quiescent currents for the upper and lower PA cells were optimized to have the best compromised performances with quiescent current levels of 100 and 150 mA, respectively. By the implemented PA driver IC, a gain of 17.25 dB and a high power-added efficiency of 54.15% at a P1dB of 31 dBm were achieved at a center frequency of 900 MHz. For a two-tone signal having a tone-spacing of 1 MHz, it also exhibited a high output IP3 of 54.28 dBm at an output power level of 20 dBm. The average output power was 22.36 dBm to which the IMD3 level should be lower than −60 dBc. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1680–1683, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27639

In this article, a novel variable power divider based on varactor diodes is introduced and described in detail.Its main components are 3-dB couplers, varactor diodes, and lumped elements. The proposed power divider is initially studied using the even- and odd-mode techniques. Then, based on the derived equations and as an experimental verification, the proposed varactor-based power divider operating at the center frequency of 2.5 GHz is fabricated and its performance is measured. It is shown that the power divider offers a maximum insertion loss of about 1.8 dB with a minimum dynamic range of over 6 dB in the frequency range from 2.3 to 2.7 GHz. The results are discussed. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1684–1686, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27603

A high directional beam antenna for wireless interoperability microwave access (WiMAX) and wireless fidelity (WiFi) is proposed. With a single circular radiator and a full ground plane, the antenna has successfully achieved a high directional gain of 6.7 dBi. Moreover, the proposed antenna is compact with a square substrate dimension of 50 × 50 mm². The implementation of the slot with a dimension of 0.8 × 10 mm² at the center of the radiator has resulted the circular current distribution that leads to the antenna efficiency of up to 87%. The patch antenna performed under tolerable S₁₁ of −10 dB covering operating frequencies of 2.36 GHz up to 2.40 GHz. Parametric study of the narrow slot size, coaxial port position, and the substrate size have been conducted in order to achieve the best antenna dimension with an optimum performance. The measured radiation patterns of the proposed single antenna show a top main beam of 0° and a peak side-lobe level of −17.6 dB, exhibiting a good agreement with the simulated results. Both simulation and measurement results prove that this optimized circular antenna is reliable for IEEE 802.16d fixed WiMAX, IEEE 802.16e mobile WiMAX, and WiFi application. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1686–1692, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27638

This article develops an optical fiber sensor using a fiber Bragg grating (FBG) and a piezo-electrical transducer (PZT) to measure reactive power. By mounting an FBG on a PZT bar, a dynamic strain simulator was constructed. The equivalent voltage produced by reactive power applied to the PZT was converted to the dynamic variation of the FBG Bragg wavelength. The reactive power was attained by measuring the changing value of the wavelength. Thus, the sensor can be used to measure reactive power without the use of a traditional power meter. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1692–1696, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27617

This article proposes a novel millimeter-wave microstrip (MSL) to WR 12 standard rectangular waveguide transitions. These dissimilar structures are interconnected via a substrate integrated waveguide (SIW). The MSL and the SIW are integrated on the same ceramic substrate of 9.9 relative permittivity and 125 μm thickness. The MSL was first transformed into an air-filled rectangular waveguide, and then a stepped impedance or horn transformer was used to match the WR12 standard rectangular waveguide. The central frequency of operation is 61 GHz as required in V-band wireless communications applications. Commercial Finite Element Method Software and High Frequency Structure Simulator (HFSS) was used to perform the design and the optimization. The S parameter measurements of the back-to-back connected transitions show an insertion loss less than 1.5 dB and a return loss better than −10 dB over a 4 GHz band from 60 to 64 GHz. The high performance, the compact size, and the simple fabrication, enable similar transitions to be employed in a number of other millimeter-wave applications. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1696–1700, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27658

We propose and demonstrate a novel all-fiber temperature sensor that is a single-end fiber modal interferometer (FMI) based on a segment of a few mode fiber (FMF) and a segment of a single-mode fiber (SMF).The FMF spliced to a lead-in SMF is used to expend the optical beam in the fiber and the sensing SMF with a well-cleaved end is spliced to the FMF. Owing to the core mismatch between the FMF and the sensing SMF, part of the guided light propagates in the cladding of the sensing SMF and part of the guided light propagates in the core of the sensing SMF, which finally forms the FMI when the reflective light comes back to the FMF. Temperature sensing is achieved by measuring the wavelength shift of the FMI. A temperature sensor with an average sensitivity of 0.1 nm/°C in a temperature range from 33 to 833°C is presented. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1700–1703, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27657

Originally published Microwave Opt Technol Lett 55:926–929, 2013. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1703, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27668 (Original article DOI 10.1002/mop.27408)

Originally published Microwave Opt Technol Lett 55:730–734, 2013. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1703, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27669 (Original article DOI 10.1002/mop.27449)