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Abstract: A wide band flexible substrate based metamaterial is presented. The metamaterial is fabricated on photo paper using conductive nanoparticle ink targeting flexibility applications. The metamaterial structure shows a wide double negative region of 1.848 GHz (8.298–10.146 GHz). The transmission coefficient of the proposed metamaterial has been measured and verified with simulated one. The perceptible novelties of the proposed work are its simplicity, cost effectiveness, and flexibility with covering wide X‐band microwave spectra. [ABSTRACT FROM AUTHOR]

In this paper, a circularly polarized metasurface antenna for microwave energy harvesting (MEH) is proposed. First, a 4 × 4 metasurface is analyzed and integrated with the microstrip slot based on characteristic mode analysis for broadband, low profile, and high gain metasurface antenna. The measured results show that the impedance bandwidth of the metasurface antenna is 1.82 GHz, the 3 dB axial ratio bandwidth is 0.96 GHz. Subsequently, a wideband rectifier for C‐band is fabricated and measured according complex impedance compression theory. The frequency of efficiency >50% is from 5.1 to 6.3 GHz with 17 dBm input power. Finally, the novel antenna and rectifier are connected as rectenna for MEH, which shows great potential due to the tunability of the polarization mode (right‐handed CP [RHCP]/left‐handed CP [LHCP]) and the flexibility of the structure. [ABSTRACT FROM AUTHOR]

As a representative technique in electronics, the Smith Chart provides a fast, less‐computation, and graphical approach to solve the problems related to impedance matching. In this paper, we transplanted the Smith Chart into the design and analysis of a microwave metamaterial absorber (meta‐absorber) to develop an analytical and graphical approach for impedance matching of electromagnetic wave absorption. Before the structural design, four traces on the Smith Chart plane from the load to arrive at the impedance matching point (the center of the Smith Chart) can be graphically found to obtain perfect absorption. Then, we have designed four impedance matching circuit networks made of resistance, inductance, and capacitive elements and transmission lines to fit the four traces. Then, the matching circuits are mapped into the meta‐absorber structure by using three types of proposed layers. The full simulation method based on the finite element method is used to verify the proposed concept. Furthermore, an external dielectric loading strategy has been developed to achieve good angular stability up to 60° for the radar cross section reduction under transverse electric and transverse mangetic polarization incidence. The proposed method may provide a convenient way for various microwave devices, such as antennas. [ABSTRACT FROM AUTHOR]

Significant research and development in the areas of microwave photonics in Brazil are presented in this paper. These include direct microwave modulation of semiconductor laser diodes, optical control of MESFETs and HEMTs as well as high speed fiber optic components. Future directions for research in this area are discussed. [ABSTRACT FROM AUTHOR]

The GaAs MESFET is a light-sensitive device. For normal microwave applications this is considered an undesirable property, and device manufacturers attempt to minimize it. In the last decade researchers discovered ways of utilizing this effect. In this article we present briefly the optical detection properties of the MESFET and describe some typical applications. [ABSTRACT FROM AUTHOR]

This paper presents a new wideband waveguide substrate integrated waveguide (SIW) coupler with maximum deviation of ±0.5 dB in a 7.5–12.25 GHz bandwidth (48% fractional bandwidth). Proposed coupler consists of the standard WR90 waveguide and single layer/double clad SIW printed circuit board (PCB) which is placed crosswise on the waveguide. Proposed three port coupler (isolated port was ended with match load) has a two coupling level (average of coupling in 8–12 GHz frequency range) of 43.2 and 58.3 dB, which is correspond with the hole diameter of 3.5 and 3 mm, respectively. The main contribution of this work is based on the hybrid techniques of SIW and RWG for coupler design in the high power microwave application. Validation of the simulation results with measurement one proves that the proposed X‐band waveguide to SIW coupler is a good candidate for use in high power industrial/commercial applications. [ABSTRACT FROM AUTHOR]

As an important index of industrial oil, moisture content affects the performance of oil. With the increase of requirement to the oil quality, the measurement of ultra‐low moisture content is gradually concerned. To achieve nondestructive measurement of the moisture content in oil, this paper analyzes the principle of dielectric loss of oil‐water mixture and proposes a measurement system based on the microwave transmission method. The hardware of the system, horn antenna, and experimental device were designed and built. The system uses a subtracter circuit together with a high‐performance microwave chip and high‐precision analog‐to‐digital converter to detect 1dB microwave attenuation. The results showed that the system can measure the moisture content of 0.01%–0.8% in quenching oil and the single detection absolute error is less than ±0.05%, and the average detection absolute error of 10 detections is less than ±0.02%. This study is useful for nondestructive detection of the moisture content in oil and provides a reference for related product development. [ABSTRACT FROM AUTHOR]

By periodically patterning the conductor surface, the so‐called spoof surface plasmon polaritons (SSPPs) in microwave band can be transmitted and SSPP mode devices with the cutoff frequency at high frequency end can be constructed. In this paper, the spiral slots are loaded in the edge and the feed port of a printed monopole antenna element and two rejection bands are achieved. The results indicate that in the intuitive physical sense, the slot‐typed band‐stop resonator in antenna structure actually works according to the SSPP mode mechanism. Furthermore, it is proposed that its structure size should be determined according to the principle that the slot resonant frequency is a bit lower than the asymptotic frequency of SSPP modes. [ABSTRACT FROM AUTHOR]

An all‐metal beam scanning metamaterial antenna with polarization transform based on the concept of Risley prism is presented in this paper. The antenna is composed of a feed source and three different all‐metal metamaterial lenses. Each lens consists of numerous cross‐slot metamaterial elements. A full transmission phase range of 360° can be achieved for a transmission efficiency over 99% at 14.25 GHz by rotating the cross‐slot on the element. Mechanically rotating the three lenses along the same axis can steer the radiation beam in both azimuth and elevation planes. The simulation results agree well with the theoretical analysis which indicates that the metamaterial antenna can realize a beam scanning range of 120° revolving cone angle with the side lobe better than −13 dB. During the scanning, the directivity of the antenna varies from 34.82 dBi to 37.84 dBi, with the aperture efficiency in the range of 38%‐76%. For the radiated circular polarized (CP) plane wave beam, the beam width remains below 4° and the axial ratio is basically better than −5 dB. Furthermore, the power handling capacity of the metamaterial antenna in this paper is gigawatt (GW) class, which can be applied in the field of high‐power microwave (HPM). [ABSTRACT FROM AUTHOR]

A three‐dimensional lightweight metamaterial (MM) with ultra‐wideband microwave absorption is proposed in this paper. Based on the concept of MMs, periodically arranged resistive films are introduced into the standing frame to form a standing lossy structure, which can introduce electric resonances in the gap between adjacent sub‐wavelength unit cells at lower frequencies. Several standing wave modes are also excited in the standing lossy structure at higher frequencies, resulting in an ultra‐wideband absorption for electromagnetic waves. The full‐wave simulation demonstrates that the MM can absorb over 90% of the incident wave energy in the range 1.46–40 GHz, with a relative bandwidth of 185.9%. The experimentally measured results correspond to the simulated results across the entire frequency range. In addition, the proposed MM is lightweight, easy to fabricate. [ABSTRACT FROM AUTHOR]

Conventional microwave oven suffers nonuniform electric field distribution due to standing wave inside the cavity, requiring improved heating uniformity. Multimode ovens, which are regarded as the most popular method, suffer from relatively limited accuracy and dependency on experimental validations. In this paper, a new class of microwave heating methodology is proposed to achieve heating uniformity improvements through the suppression of undesired standing waves. Microwave absorbers and focusing of electromagnetic waves using reconfigurable diffractive surface are devised, validated, and discussed. Numerical and experimental studies ascertain that the heat uniformity is improved by more than three factors compared to conventional microwave applicators, indicating its potential application and feasibilities. [ABSTRACT FROM AUTHOR]

In this paper, a near field focusing transmission metasurface (MS) based on polarization sensitivity is developed at microwave frequency. The MS unit cell has only three metal layers, which is less than the published dual‐polarized transmission structure. And the phase shifting range can cover 320° for x‐ and y‐polarized waves. The biggest bright spot of the focusing MS made of the proposed units is its changeable focus point by rotating the horn 0°–90° round its central axis: focusing switching between one and two focusing points. In addition, the developed MS has the following advantages: multifunctional, low sidelobe, high focusing efficiency, small size, wideband, and less layer number. The focusing relative bandwidth is 9.7%, and the maximum focusing efficiency is 30% at center frequency 15.5 GHz. The efficiency is higher than that of published results in transmission orthogonal polarization mode. The proposed MS has potential applications in medical treatment, noncontact sensing system. [ABSTRACT FROM AUTHOR]

In this paper, a new type of microwave microfluidic sensor is presented, using three separate half wave microstrip resonators with a common junction. The sensor comprises three parallel resonators with resonant frequencies of 2.5, 3.5, and 4.5 GHz. This sensor exhibits all the usual advantages of microwave resonant methods for dielectric liquid characterization, such as high precision, accuracy, and sensitivity, but here also over a wideband of frequencies. The resonators have common input and output ports. The sensor was tested using several types of liquids, including water, methanol, ethanol, and chloroform, and experimental results are in excellent agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Presents a call for papers about microwave and millimeter-wave photonics to be published in a special issue of "IEEE Transactions on Microwave Theory and Techniques."

Solicits papers for a special issue of the "IEEE Transactions on Microwave Theory and Techniques on Microwave and Millimeter-Wave Photonics," to be published in October 2001.

Presents a call for articles on the use of photonics technology in microwave and millimeter-wave applications.

In the microwave and millimeter‐wave transmission regions, substrate‐integrated waveguide (SIW) is a very promising candidate for the development of circuits and components. The channel of the SIW is a bandpass or high pass filter. This characteristic impedes the conventional baseband transmission using nonreturn‐to‐zero pulse shaping scheme. As an alternative to using mixers to facilitate a passband transmission, this paper proposes a spectrum shaping scheme of low complexity for the channel of SIW, namely spread reshaping code. It aims at matching the spectrum of the transmit signal to the channel frequency response. It facilitates the transmission through the SIW channel while it avoids using carrier modulation and equalization. Simulations reveal a good performance of this scheme, such that, as a result, eye opening is achieved without any equalization or modulation for the respective transmission channels. [ABSTRACT FROM AUTHOR]

Abstract: Microwaves have proven their efficiency in the thickness measurement field. However, in certain environments, the full accessibility to the measured samples is one big challenge; an illustration of these challenging environments is the ceramic thickness monitoring in aerospace industry. Since ceramic materials are known for their ability to support high pressure and high temperature, the control of their geometries and structures is of an utmost stature. In literature, several methods have been proposed to allow a non‐contact thickness measurement. One of the well‐known methods is based on waveguide open‐end radiation. Given the need of new accurate structures, a new model that takes into account the air gap between the sensor and the material under test is proposed. Accordingly, the study of multilayered dielectric composite is unavoidable. In this paper, a new multilayer thickness measurement structure using a coaxial waveguide probe is proposed. Moreover, an artificial neural networks algorithm which estimates and corrects the reflection coefficient shift caused by the air gap effect is implemented. Experimental results show that the estimation error of the system is less than 3% for Plexiglas and less than 2% for FR4. More results, with calibration techniques, validate the proposed measurement system. [ABSTRACT FROM AUTHOR]

Abstract: The planar Gunn diode offers the potential of microwave, milli‐metric and THz‐based oscillators, which can be fabricated as part of a microwave monolithic integrated circuit (mmic). The paper develops an electrical representation of an aluminum gallium arsenide (AlGaAs) based planar Gunn diode with an active channel length of approximately 4 μm and width of 120 μm, embedded in an oscillator circuit. The work indicates a maximum simulated RF output power of +5 dBm compared with published experimental results of −19 dBm for similar diodes. [ABSTRACT FROM AUTHOR]

The most puzzling task faces by security agency is detection and identification of the targets like, blade, and knife inside the book and capability to differentiate with book mark. Millimeter wave (MMW) imaging system may have good potential for this because of its resolution and penetration capability. Therefore, in this paper a statistics based adaptive algorithm is proposed for detection and identification of targets like blade, knife and book mark inside the book for MMW imaging system. [ABSTRACT FROM AUTHOR]

In high-power microwave (HPM) area, increasing the cross-sectional dimension makes the device work in overmoded state, is an efficient way to improve the device's power handling capacity. However, the high order mixed modes may decrease the efficiency of the microwave output. Therefore, it is necessary to study the mixed modes in overmoded waveguides. Mixed modes analysis in circular waveguide system will be discussed in this paper, and the measurement results are agreed well with the theoretical and simulation results. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper describes a new design for a compact tri-band (TB) branch line coupler (BLC) using a modified double-Lorentz (DL) composite right/left handed (CRLH) transmission line (TL). For this design, the positive phase response is selected at the 2nd operating band so that the unit structure of DL CRLH TL yields phase responses of − π/4, π/4, and − π/4 at TB. This structure is employed to operate the TB BLC at 0.195, 0.67, and 1.465 GHz. The proposed TB BLC has a compact size that has been reduced by 85.8% relative to the previous TB BLC where both were designed using DL CRLH TLs for the same TB. The results obtained through a simulation and experimental measurements are in good agreement, and the operating frequencies for all TB are well attained. Thus, the proposed TB BLC is significantly compact and offers steady performances due to its reliable realization, which is very useful for practical applications. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:918-924, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT Wireless monitoring of human vital signs such as breathing rate is a nonintrusive alternative to contemporary solutions relying on physical contact. To ease the installment, fiber optical transmission is used to extend the reach from the transmitter and receiver circuitry to the antenna subsystem. In this paper, a frequency modulated carrier wave radar, operating at 25.7-26.6 GHz and utilizing optical fiber extension, was experimentally demonstrated to accurately recover the breathing rate of a human placed 1 m away from the radar antennas. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:353-356, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, a technique has been proposed to design microstrip antenna arrays at terahertz (THz) frequencies with improved gain and fabrication tolerance. The antenna is designed at 100GHz frequency and fabricated with simple laboratory based PCB etching process. The gain is improved to 13.4dBi with the help of only three patch elements. The measured −10dB return loss bandwidth (BW) is 5.55% of the central frequency. The measured and the simulation results are all in good agreement. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1819-1824, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper is intended to introduce a two-arm Archimedean spiral antenna fed by a novel feed structure based on DSPSL (Double Sided Parallel Strip Line). A DSPSL provides an ease perpendicular matching network and an impedance transition between input impedance of a spiral antenna and system's impedance of 50 Ω in broadband frequency range. Measured and simulated VSWR and radiation pattern results show a good performance over ultra-wide band from 2 to 20 GHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1879-1883, 2016 [ABSTRACT FROM AUTHOR]

In this paper we discuss a number of UHF/RFID tag designs including the hybrid loop (Chen and Hsu, International Symposium on Antennas and Propagation, Korea, Vol. 3, 2005, 1045–1048), dual crossed-dipoles, the dual crossed-dipoles utilizing an inductively coupled feed (Choo and Ling, Electron Lett 39 (2003) 3080–3081). We have carried out extensive parametric studies in the process of analyzing the characteristics of the earlier-mentioned antennas, and have investigated several techniques (Choo and Ling, Electron Lett 39 (2003) 3080–3081), including meandering, for size-reduction of these antennas. A design methodology based on the Genetic Algorithm (GA) is presented for the optimization of conformal antennas with Electromagnetic Bandgap (EBG) surfaces (Mittra, Proceedings of International Symposium on Antennas and Propagation 2005 (ISAP2005) Seoul, Korea, 2005, 325–328; Sievenpiper et al., IEEE Trans Microwave Theory Tech 47 (1999), 2059–2074) to improve the antenna performance. The EBG characteristic is realized by utilizing a Frequency Selective Surface (FSS) placed above a thin dielectric substrate backed by a metallic ground plane to act as an Artificial Magnetic Conductor (AMC). The antenna is then placed above the EBG surface to create a conformal integrated EBG - antenna. The initial design of the AMC is carried out by synthesizing a surface whose reflectivity is “+1”, for a normally incident plane wave. However, since the antenna situated above it produces not just a single plane wave but a spectrum of these waves, it becomes necessary to refine the initial design to optimize the performance of the antenna/AMC composite, and techniques for doing this are discussed in the paper. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 858–867, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22265 [ABSTRACT FROM AUTHOR]

This paper presents an innovative methodology for designing three new Artificial Magnetic Conductors (AMC) with very little sensitivity to the angle of incidence and compact size. The AMC structures are composed of a Frequency Selective Surface (FSS) placed at the interface of a metal-backed dielectric slab. The FSSs used belong to the family of Skewed Crosses (SC). The paper begins by investigating the properties of a GA-designed AMC presented in a previous literature. After that, a basic SC-based AMC is extracted from this AMC and is modified step by step to improve the desired features. The modifications are performed not based on time-consuming optimization methods, but by utilizing the theoretical clues presented in another literature for similar structures. Taking these strategies, such AMCs are obtained that have very good angular stability, compact size, and acceptable bandwidth. Periodic Method of Moments (PMM) is used to analyze and study the proposed periodic structure. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 781–786, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22280 [ABSTRACT FROM AUTHOR]

In this paper, field patterns in V-shaped microshield transmission line are calculated by using the edge-based finite element method. The dependence of the field patterns upon the thickness of metallic signal strip and the dielectric constant of dielectric substrate is presented. The figures in this paper have important values in the design of microshield lines in microwave and millimeter-wave integrated circuits. [ABSTRACT FROM AUTHOR]

There are many engineering problems currently in practice in which the phase of reflection coefficient is unknown or varies. This paper presents a reflection coefficient theory for lossless broadband matching networks and describes its limitations and band inequalities. An example matching problem is given in the end of the paper. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 221–224, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11335 [ABSTRACT FROM AUTHOR]

This paper presents a simplified hybrid calculation method, which enables calculation of a field very close to the surface of a perfect conducting object as well as the surface field itself. This method is based on the series electric dipole modeling (SEDM) technique, used to quickly and efficiently calculate near fields of wire antennas or objects, and the Kemptner method, used to find the surface fields of patches. The present method combines advantages of both the SEDM and Kemptner method techniques, without their weak points. Several examples in this paper show the validity of the SEDM and the simplified hybrid calculation method. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 471–474, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10793 [ABSTRACT FROM AUTHOR]

In this paper, the model and implementation of an optical transmission system using a multi-longitudinal mode optical source and a dispersive optical channel are described. Such a system exhibits multi-bandpass transmission windows, as a result of a combination of the wideband optical spectrum and chromatic dispersion on the optical channel. As shown in this paper, the band-pass windows are centered at frequencies that depend on the spectral free range of the optical source and optical channel length. In the telecommunications domain, band-pass transmission windows can be used for multiplexing analog and/or digital signals, as an alternative way for transmitting baseband and modulated subcarriers, through optical-fiber links. To show such a potential application, the multiplexed transmission of two microwave signals, using two adjacent band-pass windows, is also described in this paper. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 202–206, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10720 [ABSTRACT FROM AUTHOR]

A modified locally conformal finite-difference time-domain method (MLC-FDTD) is presented in this paper, which is used to analyze broadwall radiating slots in a finite wall thickness waveguide, including the longitudinal slot and the inclined slot. In this paper, we make a direct analysis of the bulletheaded slots using MLC-FDTD, and give the transformation errors of two kinds of equivalent methods frequently employed in the engineering design; the equal-area and the equal-perimeter transformations from the squareheaded slot to bulletheaded slot. The results show that the equal-area transformation is more accurate. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 198–201, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10556 [ABSTRACT FROM AUTHOR]

The wavelength-routing assignment (WRA) task for optical networks usually calls for massive computer resources. This paper shows that the economic disadvantages of WRA demands may be solved through the use of an ingenious modification of some complex algorithms and a widely available platform, such as Maple. This paper also shows that a conventional PC can solve, in a few minutes, the disadvantage of the need for powerful workstations, sometimes running in an overnight task. The routines described here can assign wavelengths to a DWDM optical network by using either a minimum route delay procedure or a minimum number of wavelengths per branch alternative. Case studies are presented where solving time and scalability issues are discussed. It is seen that the presented algorithm is an easily reproducible one, and uses widely available tools. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 28: 406–410, 2001. [ABSTRACT FROM AUTHOR]

It has been conjectured that the incorporation of singular edge current behavior may facilitate the numerical solution of scattering problems. This paper will show that special attention is needed to properly incorporate this condition. It is demonstrated that, contrary to common practice, the edge condition is not only a geometry-specific condition, but also is source specific, greatly depending on the amplitude and direction of the incident field. Both analytical and numerical techniques are used to explain the key observations of this paper. ©2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 24: 218–223, 2000. [ABSTRACT FROM AUTHOR]

ABSTRACT A systematic measurement procedure of high isolation single-pole-double-throw (SPDT) switch utilizing six metal contact switches using micro electromechanical systems (MEMS) is presented in this paper. A complete measurement procedure of a MEMS DC-contact is outlined here including profile analysis, mechanical, electrical, switching/release time, temperature stability, power handling, intermodulation, IIP3, S-parameter and reliability. Measured return loss of better than 20 dB with worst case insertion loss of 1.67 dB and isolation greater than 42 dB have been experimentally obtained from the SPDT switch up to 20 GHz within 1.25 mm2 area. Switch demonstrates temperature stability up to 70°C temperature and 0.1-1 W of RF power handling. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1154-1159, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper is reported an experimental and numerical investigation of the microwave dielectric properties of Na2Nb4O11 (NN), ceramic matrix added with (0, 2, 5, and 10 wt%) of Bi2O3, obtained through a new procedure based on the solid-state method. The experimental and theoretical characteristics of the resonator like return loss, bandwidth, input impedance are in good agreement. The simulations of radiation patterns are presented. For NN reference sample, frequency response bandwidth is of 43MHz (simulated) and 35MHz (experimental) for frequency operation around 2.28 GHz. The NN reference sample showed a dielectric permittivity around 58.4, with loss around 7.3 × 10− 3. The adding of bismuth oxide (2 and 5 wt%) reduced the value of the dielectric permittivity, otherwise the adding of 10 wt% increases its value. The temperature coefficient of resonant frequency (τf) was also measured for all dielectric samples. The values obtained were in the range of −3378 to −250ppm/°C. The results obtained confirm the necessity of producing composites of this material with others positive τf materials for obtaining dielectric resonator antennas with τf = 0. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1211-1217, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, an ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna for on-body application is proposed. The proposed MIMO antenna is composed of a UWB antenna above the ground plane and an additional meander line isolator located between the two antennas to improve the isolation characteristic. Simulation and measurement were performed to analyze the effect of the human body on the antenna performance when a body is located in the near field of the antenna. The proposed folded UWB MIMO antenna has dimensions of 40 × 32 × 0.8 mm3. The fabricated antenna has a 10-dB return loss bandwidth over the UWB lower band from 3.1 to 4.8 GHz and an isolation characteristic higher than 20 dB over the required band. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2351-2357, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT The Fiber Loop Ring-down Spectroscopy (FLRDS) technique has become popular in recent years. However, as the ring-down signal is a series of decaying pulses, very few pulses' peak intensities and their time delays could be found and fitted in an exponential equation. This paper analyzes the importance of splitting ratio of the couplers with respect to improving the accuracy of the fitted equation, makes mathematical models of the whole system, simulates the ring-down signal under different splitting ratio of the couplers and establishes FLRDS experimental system. The experimental results are in good agreement with theory, which indicated that both of the two coupler splitting ratios of 10:90 are found to be the optimal solution with a ring-down time of 24.5 µs in our system. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:99-103, 2014 [ABSTRACT FROM AUTHOR]

Dielectric resonators with a high dielectric constant (70–90) are commonly applied in UHF cellular telephone and L-band communication systems. With the advantages of compact size and ruggedness, dielectric resonators can be constructed as high-performance bandpass filters through direct coupling. Coaxial-type direct-coupling microwave ceramic bandpass filters are investigated in this paper. The filters exhibit excellent features of low dissipation and relatively good temperature stability due to their high-Q dielectric material and low temperature coefficient of resonant frequency (τf). This paper describes the performance of a high-permittivity ceramic coaxial-type direct-coupling microwave bandpass filter and the effect of aperture location on its response. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 258–260, 2000. [ABSTRACT FROM AUTHOR]

This paper presents a simple design method for behavior of metamaterials of metallic rods. Numerial and experimental results are given. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:421-425, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27311 [ABSTRACT FROM AUTHOR]

The in situ characterization of membranes for fuel cell applications is a rather complex and time-consuming procedure. It is therefore interesting to develop simple, short, and reproducible characterization tests and to limit in situ measurement only to the most promising materials. In this paper, a new characterization method is proposed to extract the DC ionic conductivity of track-etched nanoporous polyimide membranes from microwave measurements. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26163 [ABSTRACT FROM AUTHOR]

This article presents an improved factor of merit for the comparison of center-frequency tunable bandpass filters. This study draws up a comparison between existing tunable filters for which different commonly used parameters demonstrating their performance are given. A first factor of merit that takes all the major characteristics of such tunable filters into account is introduced. A second factor of merit is proposed to evaluate the filter compactness. These new factors of merit are applied for the comparison of more than 30 recently published papers. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 985–988, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24220 [ABSTRACT FROM AUTHOR]

This paper reports on the investigations into new configurations of unit cells which offer an increased phasing range for a single-layer printed reflectarray. It is shown that the extended phasing range can be obtained by utilizing similar in shape but different in size resonant elements. Using this principle it is shown that two resonant elements forming a unit cell can double while three elements can almost triple the phasing range of a single resonant element unit cell. These investigations also show that the relative sizes and spacing between the elements in the cell can be adjusted to linearize the phasing curves as a function of the elements dimensions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1028–1032, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23285 [ABSTRACT FROM AUTHOR]

Recently, RFID system has become popular and has been growing rapidly. Due to using many readers in limited area, RFID reader collision problem occurs when the reader is interfered with the signals from neighbor readers or other devices. Even if 50 channels are available in North America, 15 channels in Europe and 25 channels in Korea are available. Moreover, in the future, if many mobile (cellular) RFID readers might be used in limited area simultaneously, the number of channels is not enough, and the collision problem might be more serious. Therefore, this paper proposes an advanced RFID system with a channel holder and dual reader sensitivities/reduced reader output power. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2643–2647, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22808 [ABSTRACT FROM AUTHOR]

This paper presents a compact dual-band bandpass filter (BPF) that consists of a pair of L-shape half-wavelength (λ/2) stepped-impedance resonators (SIRs) and an inverted Z-shape resonator. The latter is actually a combined structure of two λ/4 SIRs along with a magnetic coupling in between and hence designed to reduce the circuit size. Cross-coupled SIR configuration and 0° tapped-feed structures are adopted to introduce attenuation poles around the passband edges for selectivity improvement. A wider -20-dB upper stopband is achieved by properly separating the third resonant frequencies of the SIRs of different types. The newly designed dual-band BPF was verified by circuit implementation, and a very good agreement between the simulated and measured results was observed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2703–2706, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22823 [ABSTRACT FROM AUTHOR]

This paper presents an accurate scaling approach for small-signal modeling of high-power multi-cell heterojunction bipolar transistors (HBTs). This approach is mainly based on the characterization of an elementary-cell device and a proper modeling of the metalwork structure surrounding the transistor intrinsic part. The determined elementary-cell small-signal model is then scaled up to generate the S-parameters of the multi-cell device. An experimental validation was performed on a single-cell and three-cells GaAsHBT devices and excellent agreement was obtained between measured and simulated S-parameters over frequency range 1–15 GHz. This modeling approach is particularly useful for on-wafer characterization and modeling of high power HBT devices. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2429–2434, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22765 [ABSTRACT FROM AUTHOR]

In this paper, by exploiting surrounding fractal UC-EBG ground plane, a 2 × 2 microstrip array capable of X-band operation is studied. Result of comparison shows that this microstrip array proposed has much lower RCS than that of 2 × 2 array with the standard ground at frequencies outside operating band within 2–18 GHz while its gain is improved in the operating band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1418–1422, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22440 [ABSTRACT FROM AUTHOR]

It can be shown that a hyperbolic frequency-modulated waveform is Doppler-invariant only when the Doppler factor is a constant number, i.e., the target has a constant velocity and along the direction from the radar to the target. If the target moves in an arbitrary direction, the degradation of the pulse compression caused by the mismatch between the reflected signal and the matched filter may still exist. In this paper, we demonstrate that the Doppler effect caused by the moving target in an arbitrary direction can be approximated by a target with an initial velocity and a constant acceleration along the direction from the radar to the target, which results in a frequency shift in the reflected waveform. Therefore, a bank of matched filters with preselected values of frequency shifts can be utilized to compensate for the Doppler effect. Numerical examples, with target moving in an arbitrary direction, are presented to illustrate this effect, which has been successfully compensated by shifting the frequency response of the matched filter. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1449–1453, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22454 [ABSTRACT FROM AUTHOR]

In this paper, we present an electromagnetic analysis for three-dimensional arbitrarily shaped large structures illuminated by a short pulse. The time domain electric field integral equation (EFIE) formulation is used to obtain the early time data with a central differencing scheme to evaluate the time derivatives of the potential functions. The solution method is based on the method of moments (MoM) and marching-on-in-time (MOT) technique. Low frequency data is generated using a frequency domain integral equation method. The hybrid method is based on the singular value decomposition (SVD) of the frequency and the time domain data for a direct extrapolation of a causal signal. The detailed mathematical procedures are included along with representative numerical results from an aircraft model. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 898–904, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22253 [ABSTRACT FROM AUTHOR]

In the spectral domain method of moments (MoM) solution of printed structures on planar grounded dielectric slabs, the infinite double integrals which appear in the asymptotic parts of the MoM impedance matrix and the MoM excitation vector elements, have been previously transformed to one-dimensional finite integrals, which have been numerically computed using the highly specialized “International Mathematics and Statistics Library” subroutines. In this paper, these one-dimensional integrals are evaluated in closed-form, resulting in an improved efficiency and accuracy for the rigorous investigation of printed antennas and complex millimeter and microwave integrated circuits. Numerical results in the form of mutual impedance between two expansion functions and input impedance of various microstrip antennas are presented to assess the accuracy of these closed-form expressions. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 882–886, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22274 [ABSTRACT FROM AUTHOR]