bluuebunny/crossref_metadata_2025 huggingface dataset:
A low‐power, high‐gain, and low‐noise 5–6 GHz CMOS low‐noise amplifier with excellent reverse isolation for IEEE 802.11 n/ac WLAN applications
Authors: Lin Yo‐Sheng , Liu Run‐Chi
Published: December 2014

A low power, high gain, and low‐noise figure (NF) 5–6 GHz low‐noise amplifier (LNA) with excellent reverse isolation in a cost effective 0.18 μm CMOS technology is reported. To achieve sufficient power gain (S21) and reverse isolation (S12), the LNA comprises an inductive source‐degeneration cascode stage followed by a cascode stage. The LNA consumes 7.99 mW, achieving high S21 of 19 ± 1.5 dB for frequencies of 5.1–6.2 GHz and excellent S12 of −67.9 to −73.3 dB for frequencies of 5–6 GHz. In addition, the LNA achieves minimum NF of 2.8 dB at 5.5 GHz and NF of 2.91 ± 0.11 dB for frequencies of 5–6 GHz, one of the best NF results ever reported for a 5‐GHz‐band CMOS LNA. To verify the 5‐GHz LNA, a test IEEE 802.11 wireless local area network (WLAN) transceiver based on the LNA is also designed and implemented. The measured results show that for the 24 channels in 5‐GHz band, the average sensitivity is −77 and 3 dBm better than that (−74 dBm) of the conventional one. A conventional one means the 802.11 WLAN controller in this work is replaced by a commercial RTL8812AR‐VN WLAN controller. In addition, the average error vector magnitude of received IQ data is −32 dB (or 2.5%), 2.5 dB (or 0.8%) better than that (−29.5 dB [or 3.3%]) of the conventional one. The impressive results from this work indicate the high potential of the proposed LNA in 5‐GHz WLAN applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:296–304, 2015
EIT in hollow‐core fibers for optical communications devices
Authors: Tiburcio Bruno D. , Fernandes Gil M. , Monteiro Jorge , Rodrigues Silvia , Ferreira Mario , Facão Margarida , Carvalho M. Inês , Pinto Armando N.
Published: December 2014

We developed an experimental setup for electromagnetically induced transparency able to manufacture microcells, suitable for optical fiber communications technology. A hollow‐core photonic crystal fiber (HC‐PCF) is filled with acetylene, to work in the 1500 nm telecommunications window. We used a HC‐PCF with the mode‐field diameter compatible with standard single‐mode fibers, with the purpose of achieving low‐loss splicing and enabling us to work at low pumping powers. This allows to induce a narrow transparency window, which can be spectrally adjusted and dynamically controlled. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:348–352, 2015
Small size tripleband monopole antenna with a parasitic element
Authors: Sim Chow‐Yen‐Desmond , Chen Horng‐Dean , Yeh Chih‐Husan , Lin Hen‐Lun
Published: December 2014

A small size (20 × 38.5 × 0.8 mm3) coplanar waveguide (CPW)‐fed monopole antenna for wireless local area network and worldwide interoperability for microwave access applications is proposed. To achieve tripleband operation, the proposed monopole antenna is designed with a modified symmetrical U‐shaped printed structure attached with a parasitic element behind it. Good impedance matching is also attained by loading two dissimilar notches separately into the two CPW ground planes. The measured 10‐dB impedance bandwidths of the three operating bands (fL, fM, and fH) are 16.96% (2.105–2.495 GHz), 28.72% (3.22–4.30 GHz), and 23.32% (4.895–6.125 GHz), respectively, and all bands of interest have yielded peak gain and radiation efficiency of more than 2.7 dBi and 65%. Detail process of designing the proposed antenna is explicitly shown, and vital parametric studies were also conducted by simulation. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:342–348, 2015
Estimation of resonant frequency and bandwidth of compact unilateral coplanar waveguide‐fed flag shaped monopole antennas using artificial neural network
Authors: Gunavathi N. , Sriramkumar D.
Published: December 2014

Neural network based estimation of resonant frequency and bandwidth of compact unilateral coplanar waveguide (CPW)‐fed flag shaped printed monopole antennas is presented. The proposed antennas are similar to CPW‐fed antenna; however, by replacing unilateral CPW feed instead of CPW feed, compactness of about 48.615 percent is achieved. These are designed on an inexpensive FR4‐epoxy substrate with dielectric constant of 4.4 and thickness of 1.6 mm. Resonant frequencies and bandwidths of the flag shaped antennas with different dimensions are computed using method of moment electromagnetic solver IE3D 15.10 and they have been given as training and test data for the proposed multilayered perceptron feed forward neural network with Levenberg–Marquardt training algorithm to estimate the resonant frequency and bandwidth of the proposed antennas. The estimated values of resonant frequency and bandwidth with average percentage of error are 1.275 and 0.325, respectively. For verification, the proposed antenna is fabricated and measured with resonant frequency 5.78 GHz and bandwidth of 1.0 GHz for HiperLAN/2 and IEEE802.11a applications. It has impedance bandwidth from 5.0 to 6.0 GHz for return loss lower than −10 dB and good omnidirectional radiation performance over entire frequency range, with a compact size of 11.07 × 27.5 × 1.6 mm3. Various features such as compactness, simple geometry, and low cost, uniplanar structure make the antennas suitable for modern wireless communication systems. This approach replaces the use of very complicated analysis. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:337–342, 2015
Coupled microstrip line Wilkinson power divider with compensating capacitor
Authors: Wang Xiaolong , Ma Zhewang , Yoshikawa Masayuki
Published: December 2014

In this article, π/4 coupled microstrip line is used in the design of two‐way Wilkinson power divider for compact circuit size. A capacitor is shunted to compensate the phase velocities between even and odd mode in coupled microstrip line and its position can be placed arbitrary in the coupled microstrip line. The capacitance value is determined by effective dielectric constants of substrate, coupling strength, and its position in the coupled microstrip line. Design charts, frequency responses, calculated bandwidths, and several design examples are presented. In experiment, one circuit was fabricated, the measurement results showed good agreement with theoretical results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:328–332, 2015
Design of a compact CPW‐feed asymmetric elliptical slot ultrawideband antenna for high gain
Authors: Kushwaha Nagendra , Kumar Raj
Published: December 2014

A compact, CPW‐feed slot antenna for ultrawideband applications is proposed. The antenna uses an elliptical patch as radiating element and an asymmetric slotted ground plane to provide a measured usable bandwidth of 120% (2.81–11.2 GHz). The asymmetric slot in the ground plane creates an extra inductive reactance which neutralizes the capacitive effect of the open ended elliptical patch and results into wider impedance matching. To improve the gain of the proposed antenna, a three metallic layer frequency selective surfaces (FSSs) of overall thickness 3.5 mm and with a stop band (transmission < −20 dB) of 8.3 GHz (2.6–10.9 GHz) is proposed. With the FSS, there is a 4–5 dBi improvement in the antenna peak gain and the back lobes are reduced by around 10 dBi. The measured and simulated results are in good agreement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:314–319, 2015
A modified unequal power divider with a complex isolation component for enhanced isolation
Authors: Kim Young , Yoon Young‐Chul
Published: December 2014

This article presents a modified unequal power divider with a complex isolation component for enhanced physical and electrical isolation between output ports. In the proposed power divider, the complex isolation component is positioned at an arbitrary phase angle inside a quarter‐wave transmission line. A theoretical analysis is performed to derive the design equations for the proposed unequal power divider. For validating the performance of the proposed unequal power divider, samples of the device operating at the center frequency of 2 GHz were fabricated and tested. The test results are in good agreement with the simulation results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:322–324, 2015
An investigation on transient effects in EDFA with variable duty cycle and wavelength multiplexed signals
Authors: Dasan Meena , Thodiyil Sarath , Francis Fredy , Elambilayi Dipin , Talabattula Srinivas
Published: December 2014

The advent of erbium doped fiber amplifiers (EDFA) has revolutionized optical communication in the past few decades. Traditionally, it was being used with relatively high bitrates system for amplification in the optical domain. The slow gain response of EDFA is inherently resistant to transient effects from bit rate and duty cycle variations in high bit rate optical systems. We investigate the transient effects of EDFA on low bitrate systems with variable duty cycle and pump power configurations. Also, the effect of transients in WDM multirate systems has been investigated. The work is supported with both simulation and experimental results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:352–356, 2015
Design of compact patch antenna based on metamaterial for WiMAX applications with circular polarization
Authors: Kuhestani Hamed , Rahimi Maryam , Mansouri Zahra , Zarrabi Ferdows B. , Ahmadian Rahele
Published: December 2014

In this article, compact antenna with high gain and circular polarization (CP) for WiMAX applications is noticed. Using metamaterials with negative permittivity and permeability improves the antenna parameters; thus, the prototype antenna is designed based on metamaterial composite right‐/left‐handed to achieve CP and compact size. The final antenna has directional pattern and high gain with CP at 3450 MHz. The antenna gain is 8.28 dBi. The size of prototype patch antenna is 30
30 mm2. It is designed and fabricated on Taconic TLY‐5, Laminate substrate with εr = 2.2 and thickness of 1.6 mm. It is simulated by CST microwave studio and HFSS. Also, equivalent circuit and experimental results are presented and compared here. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:357–360, 2015
Experimental radiation characteristics of micromachined terahertz low‐profile corrugated horn antenna
Authors: Lu Hong‐da , Lv Xin , Gao Zi‐jian , Liu Yong
Published: December 2014

A terahertz (THz) low‐profile corrugated horn antenna is proposed. This antenna consists of WR2.2 feeding waveguide, pyramidal horn, and four V‐grooves, integrated fabricated by silicon micromachining. The grooves significantly enhance the gain and maintain the low profile of original horn antenna. The measured results from 480 to 500 GHz show the gain above 15.6 dB and the narrow beamwidths without sidelobe, agreeing well with simulated results and indicating the potential to be applied in compact array of THz imaging and detection systems. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:364–367, 2015
Biased gates CMOS resistive ring mixer
Authors: Amiri Parviz , Tabatabaei Babak Shojaei
Published: December 2014

A biased gates passive resistive ring mixer with integrated baluns in 0.18‐μm CMOS Taiwan Semiconductor Manufacture Company (TSMC) process is reported. The mixer shows 10% improvement compared with the mixer without biased gates. This is the first circuit report of biased gates resistive ring mixer with integrated baluns. The circuit has been designed and optimized for 2.4 GHz RF frequency and for applying in the contactless heart rate extraction system using microwave Doppler radar. The circuit has the conversion loss of 8.36 dB for 2.4 GHz frequency and indicates 17% improvement compared to the similar types without gate biasing have been reported so far. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:388–391, 2015
A compact dual‐polarized cavity‐backed annular slot antenna for indoor mimo systems
Authors: Li Wei‐Wen , Wang Chen , Lai Yun‐Qing , Zhou Jian‐Hua
Published: December 2014

A unidirectional, dual‐polarized multi‐input multi‐output (MIMO) antenna is designed for indoor 2.4‐GHz WLAN application. The proposed antenna consists of a cavity‐backed annular slot and two inverted microstrip fed lines which are mutually orthogonal. To further suppress the cross polarization levels and enhance the ports isolation, two grounded strips, being opposite to the microstrip lines of the same size, are introduced above the annular slot. Meanwhile, a conductor pillar is loaded into the back cavity. The experimental results show that this antenna has the ports isolation of more than 28 dB and the cross‐polarized levels of less 30 dB than the copolarization over the working band. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:384–388, 2015
Broadband circularly polarized antenna with high gain and wide axial ratio beamwidth
Authors: Wang Hao , Wang Xiang , Liu Shu Fang , Li Ping , Shi Xiao Wei
Published: December 2014

A broadband circularly polarized (CP) antenna with simple structure and wide angular coverage is proposed. The interlaced coplanar dipole is excited by a coaxial cable to achieve the CP wave. To obtain a high gain and low backward radiation, a rectangular cavity‐backed reflector is used. An initial design at around 6.0 GHz is presented to show the performance of this configuration. An impedance bandwidth and axial ratio bandwidth of about 35.6 and 33.5% can be achieved at this frequency. Also, a stable gain of about 10 ± 0.5 dBi and a wide axial ratio beamwidth of about 200° over the frequency of interest are obtained. Then, a parametric analysis is conducted to estimate the significance of the design parameters that affect the antenna's performance. Finally, a prototype at 11.0 GHz is fabricated to validate the design. The measured results are in good agreement with the simulated ones, which shows that the design can be easily applied to other frequency and that the design may be a good candidate for the CP antenna family. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:377–381, 2015
Compact lowpass filter with wide stopband bandwidth
Authors: Chen Xianhong , Zhang Lijun , Peng Yatao , Leng Yongqing , Lu Hui , Zheng Zhanqi
Published: December 2014

A compact microstrip lowpass filter (LPF) which consists of a meander line, a coupled line and two open stubs is proposed. The mechanism for reallocating filter transmission zeros and the design procedure are explained. The simulated and measured results demonstrate that this LPF provides compact size, low insertion loss, and wide stopband. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:367–371, 2015
Doherty power amplifier with enhanced in‐band load modulation for 100 MHz LTE‐advanced application
Authors: Xia Jing , Zhu Xiaowei
Published: December 2014

This article presents a modified GaN Doherty power amplifier (PA) for 100 MHz long‐term evolution (LTE)‐advanced application at 2.5 GHz. To improve load modulation and consistency of the output power and efficiency in the operation bandwidth, a method was proposed by choosing optimal load impedances in Class C mode, properly increased gate bias voltage and optimized input matching network for the design of the peaking amplifier. When driven with 100 MHz LTE‐advanced signals, the designed PA achieves adjacent channel leakage ratio of −49 dBc after digital predistortion at 9 dB back‐off output power of about 40.5 dBm with efficiency of 42%. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:391–395, 2015
Multiwavelength tunable ring fiber laser operating at 1.9 μm
Authors: Aihui Gong , Wanzhuo Ma , Tianshu Wang , Qingsong Jia , Peng Zhang , Chunming Wan
Published: December 2014

A multiwavelength tunable fiber laser operating at 1.9 µm is demonstrated. A 4 m long Tm‐doped single‐mode fiber is pumped by a 1.57 µm fiber laser. A Sagnac fiber loop is used in the fiber laser cavity as a tunable filter, and the fiber loop consists of a 3‐dB coupler, a polarization controller (PC), and a segment of polarization‐maintaining fiber. Adjusting the PC state and pump power, multiwavelength laser with wavelength spacing of 2.5 nm 1895–1915 nm is observed. The number of output wavelength can be tuned precisely from one to four by adjusting the PC state. The 3‐dB linewidth and side‐mode suppression ratio are 0.045 nm and 45 dB, respectively. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:401–403, 2015
Uniform magnetic field by changing the current distribution on the planar coil for displacement‐insensitive wireless power transfer/near field communication
Authors: Shen Laiwei , Tang Wanchun , Xiang Huiling , Zhuang Wei
Published: December 2014

In either inductive or strongly coupled magnetic resonance type wireless power transfer, the uniformity of magnetic field distribution near the transmitting coil is urgent needed as it would affect the stability of transfer efficiency when the receiving coil is moving. In this article, we proposed a new coil structure to achieve uniform magnetic field based on the relationship between the magnetic field distribution and current distribution of a coil structure. The coil is constructed of three or more spiral coils in series, where each spiral coil has a different current through a novel winding structure. The design procedure is presented, and the improved performance is verified by experiment. Compared with previous literatures, this proposed coil can generate a better uniform magnetic field distribution. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:424–427, 2015
A reconfigurable mobile antenna for multiband operation using PIN‐diode
Authors: Hwang Sun‐Gook , Yoon Cheol , Yoon In Seop , Chares Ludovic , Park Chan Seop , Kim Woo‐Su , Lee Hwa‐Choon , Park Hyo‐Dal
Published: December 2014

This article proposes a mobile embedded antenna having tunable capacitance, and the validity of the proposed solution has been proven through its design, fabrication, and measurement. The antenna can be applied to long‐term evolution (LTE) and DCS/PCS/wideband code division multiple access bands that are currently being used. The 4G mobile service requires antennas to expand its bandwidth so that it can include the LTE band and other service bands. However, it is difficult to obtain the low‐band frequency due to the limited space for antennas in terminals. The proposed antenna with a PIN‐diode was added to a basic planar inverted‐F antenna structure to satisfy the intended bandwidth through the ON/OFF characteristics of the PIN‐diode. To meet this requirement, a PIN‐diode (MA4P274–1279T) manufactured by MACOM, was used to make the operation frequency of the low‐band tunable. The antenna was fabricated and then measured using the optimized parameters, and the results have been compared with the simulated results. The antenna satisfied the requirements for operation frequency and performance for both low‐band and high‐band frequencies. The measured performance of the antenna fabricated with the optimized parameters was analyzed and compared with the simulation results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:406–409, 2015
A W‐band power detector RFIC design in 0.13 μm SiGe BiCMOS process
Authors: Jonsson Rolf , Reyaz Shakila Bint , Malmqvist Robert , Kaynak Mehmet
Published: December 2014

This article presents the results of a wideband power detector radio frequency integrated circuit design intended for W‐band passive imaging sensors. The power detector was fabricated in a 0.13 µm SiGe BiCMOS process technology with 300 GHz/500 GHz fT/fmax. The experimental results show broadband RF properties such as a responsivity of 40–60 kV/W and a noise equivalent power (NEP) of 0.3–0.4 pW/Hz1/2 at 70–95 GHz, respectively (the DC power consumption is 225 µW). To the authors' best knowledge, the SiGe detector design reports the widest s11 −10 dB bandwidth (s11 ≤ −10 dB at 79–102 GHz) among silicon based W‐band power detectors and is competitive with InP‐based W‐band detectors in terms of a higher responsivity and similar NEP. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:414–417, 2015
Beam steering patch antenna using reactive loading and Yagi‐antenna concept
Authors: Nguyen Duy‐Thong , Siragusa Romain , Tedjini Smail
Published: December 2014

This letter reports a technique to create beam‐steering antennas using reactive loading and passive patches. In this antenna configuration, the center patch is fed by a microstrip line and the two neighbor patches are excited through the mutual coupling from the active antenna. These two patches are loaded with a varactor diode and present a phase shift that depends on varactor capacitance. The impact of the mutual coupling on the impedance matching is investigated through a numerical calculation that combines 3D full‐wave simulation and network analysis formulas. The steering capability is enhanced by adding “director” passive patches as in the Yagi antenna principle. A prototype is designed, fabricated, and measured at UHF frequency (865–868 MHz) and shows a good agreement with the simulation. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:417–421, 2015
A compact ultra‐wideband quadrature hybrid based on coupled‐line phase shifter and power divider
Authors: Liu Qiang , Liu Yuanan
Published: December 2014

A compact ultra‐wideband three‐port quadrature hybrid based on a coupled‐line 90° phase shifter and a Wilkinson power divider is proposed. The circuit configuration and theoretical calculation are presented. Using a short‐circuited stub and coupled lines, the design not only exhibits considerably large bandwidths but also provides compact structure. A microstrip prototype at 1.68 GHz is simulated, implemented, and measured for verification. The measured performance is consistent with the simulated result. The prototype achieves measured bandwidths of 118% for output power imbalance less than ±0.5 dB, and the return loss of input port and isolation between output ports are better than 11 dB in the band. What is more, the bandwidth for output ports phase deviation of 90° ± 4.5° is large than 137%. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:432–434, 2015
Self‐phasing of quadrifilar helix antenna by relative axial displacement of bifilars
Authors: Masoud Qureshi Adil , Amin Muhammad , Ali Shah Waqar
Published: December 2014

Self‐phasing can be achieved in a quadrifilar helix antenna (QHA) by displacing one of the bifilars along the axis of the helix, yielding a circularly polarized cardioid shaped pattern. Impedance bandwidth of 10% (2105–2345 MHz) has been achieved with Front to back ratio greater than 10 dB. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:430–432, 2015
Analysis and design of implantable Z‐monopole antennas at 2.45 Ghz ISM band for biomedical applications
Authors: Ashok Kumar Srinivasan , Shanmuganantham T.
Published: December 2014

A novel coplanar waveguide fed z‐monopole implantable antenna has proposed for ISM band biomedical applications. The antenna operates at the resonant frequency of 2450 MHz, wideband communication for high‐data rate implantable biomedical application. The size of the antenna is 38.675 mm3 (7, 8.5, and 0.65 mm). To make the designed antenna suitable for implantation, it is printed on biocompatible Al2O3 ceramic substrate. The proposed antenna was simulated and measured by a phantom liquid and imitating the electrical properties of the human muscle tissue. A study of the understanding of the antenna performance as a function of its dielectric parameters of the environment in which it is immersed was performed. Simulations in various slot widths state demonstrate that the antenna covers the complete ISM band. The specific absorption rate distribution induced by the implantable antenna inside a tissue‐mimicking solution is evaluated. The proposed antenna shows the lower return loss, good impedance matching, and high gain compared to other implantable antennas. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:468–473, 2015
A low profile tri‐band diversity antenna for WLAN/WiMAX/HIPERLAN applications with high isolation
Authors: Singh Hari S. , Pandey Gaurav K. , Bharti Pradutt K. , Meshram Manoj K.
Published: December 2014

A low profile tri‐band compact multiple input multiple output (MIMO) antenna operating at 2.4 GHz band (2.4−2.485 GHz), 3.4 GHz band (3.25−3.5 GHz), and 5.5 GHz band (5.15−5.85 GHz) for WLAN, WiMAX, and HIPERLAN band is presented, respectively. The proposed MIMO antenna consists of two planar inverted‐F antenna elements located at the top two corners of PCB. Each element dimension is reduced substantially by using a meandered line and folded patch structure with two vertical parasitic strips so that it takes a small volume of 9 × 8.8 × 5.4 mm3. Two nonradiating folded shorting strips are connected between each antenna element and ground plane of PCB to enhance the port isolation. The S‐parameters, mean effective gain, envelope correlation coefficient, effective diversity gain, total efficiency, and peak realized gain are studied. The optimized structure is fabricated and measured. Good agreement is obtained between the simulated and measured results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:452–457, 2015
A semicircular shaped super wideband patch antenna with high bandwidth dimension ratio
Authors: Samsuzzaman M. , Islam M. T.
Published: December 2014

In this article, a novel semicircular shaped mono pole antenna has been investigated for super wideband (SWB) applications with high bandwidth dimension ratio (BDR). The proposed antenna consists of semicircular shape patches and partial trapezoid ground plane. A tapered feed line is precisely connected to semicircle shaped patch, which provides extremely wide impedance bandwidth greater than ultra‐wideband (UWB). The gap between the trapezoid ground plane and semicircular patch also plays a vital role to achieve wide impedance bandwidth. Studies of the antenna are performed using computer simulation tool HFSS. Prototype of the antenna is used for validation and verification for simulation results. Measurements to determine that the proposed printed antenna has an extremely wide impedance bandwidth (VSWR 2:1) from 1.30 to 20 GHz (175.58%) with a ratio bandwidth of 15.38:1 and BDR of 4261. 007 which is the highest among literature review. Furthermore, the proposed antenna also demonstrated a wide 14‐dB bandwidth from 4.90 to 10.95 GHz, which is suitable for UWB outdoor propagation. The simple construction, much impedance bandwidth, average peak gain (4.18 dBi), and stable omnidirectional radiation pattern are a good deal sounder than the recently reported SWB antennas which make it appropriate for many wireless communication systems such as L band, WCDMA, ISM, Wi‐Fi, LTE 2600, Bluetooth, WLAN, WiMAX, UWB, and MVDDS. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:445–452, 2015
The impact of different light sources on the optical correlator based on fiber dispersion
Authors: Zhongwei Tan , Ka Li , Fengjie Qin
Published: December 2014

We investigate the impact of different light sources on the optical correlator based on fiber dispersion that can implement a time‐spectrum convolution. Simulation and experiment show that the performance of optical correlator degenerates with the increase of optical source's bandwidth. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:441–445, 2015
Three‐dimensional RF SoP technologies: LTCC versus LCP
Authors: Arabi Eyad , Shamim Atif
Published: December 2014

The system on package (SoP) is an emerging platform, introduced to provide enhanced functionality, and immense miniaturization through vertically integrated passive components in a multilayer process. This way the package is not a mere holder or cover but is a functional part of the system. The leading multilayer packaging technologies for SoP designs: low temperature co‐fired ceramic (LTCC) and liquid crystal polymer (LCP) are compared in this work for the first time. Passive components and filters have been implemented in both technologies to show the advantages of the three‐dimensional nature of these technologies. The comparison results show that parallel plate capacitors implemented in the ultra‐thin LCP provides the highest capacitance density. For spiral inductors, conversely, LTCC inductors have the highest inductances while LCP inductors offer the highest self‐resonant frequencies and the highest quality factors (Q). In a circuit level, simulated and measured results of a bandpass filter at 1.5 GHz show that both LCP and LTCC can provide similar performances with an incredible size reduction for the case of ultra‐thin LCP. Also, the thin LCP filter exhibits a large degree of mechanical flexibility which makes this technology suitable for future flexible modules. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:434–441, 2015
Small‐size two‐branch monopole antenna with integrated wideband matching network for LTE tablet computer
Authors: Wong Kin‐Lu , Hsu Shan‐Ni
Published: December 2014

A simple two‐branch monopole antenna with an integrated wideband matching network to achieve the LTE dual‐wideband operation (698–960/1710–2690 MHz) with a small occupied volume (10 × 30 × 3 mm3) in the tablet computer is presented. The two‐branch monopole contributes to one resonant mode in the LTE low band and one resonant mode in the LTE high band. With the aid of the wideband matching network, the bandwidths of the two resonant modes can both be widened to cover the LTE dual‐wideband operation. In addition, the matching network requires no additional board space on the system circuit board of the tablet computer and is disposed inside the ground clearance region occupied by the antenna. This makes it attractive for practical applications. Working principle of the wideband matching network on achieving the antenna's dual‐wideband operation is described in this study. The antenna is also fabricated and tested. Experimental results are presented and discussed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:507–513, 2015
Large printed loop antenna dimension reduction through layered substrates
Authors: Souza Jorge A. M. , Mosso Marbey M. , Magri Vanessa P. R.
Published: December 2014

This article presents a new way to use multilayered substrates configurations aiming to, instead to optimize the gain of a printed loop antenna, to obtain a significant reduction of the antenna dimension. A circular loop antenna transformed in an octagonal shaped loop antenna is conceived, simulated, realized, and measured. A new antenna inside a multilayer configuration presenting a dimension reduction of 61% is obtained. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:504–507, 2015
A dual‐band branch line coupler based on Pi‐shaped coupled lines
Authors: Katakam Sri , Ren Han , Shao Jin , Zhou Mi , Arigong Bayaner , Ding Jun , Zhang Hualiang
Published: December 2014

This article presents a coupler using Pi‐shaped coupled lines for dual‐band operations. In this design, two open circuited stubs are tapped at both ends of a coupled line structure to realize the 90° phase changes at two frequencies. The designed structure is used in place of a conventional quarter wavelength transmission line for dual‐band application. For verification, a 3‐dB branch line coupler with operating frequencies of 0.95 and 1.52 GHz is designed. The simulated and measured results are in good agreement with each other. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:501–504, 2015
Reconfigurable notched wideband antenna using EBG structure
Authors: Majid Huda A. , Kamal Mohamad , Rahim A. , Hamid Mohamad R. , Murad Norasniza A. , Asmawati Samsuri Nor , Fairus Mohd Yusof Mohd , Ayop Osman
Published: December 2014

In this article, a wideband monopole antenna with band notched reconfigurability is proposed. The antenna consists of a wideband monopole antenna, incorporated with reconfigurable electromagnetic bandgap (EBG) structures. Six EBG structures with different band notched frequency are used to achieve six band notched reconfigurations. The EBG structures are placed underneath the feed line of the antenna. A switch is placed at each EBG structure, and by controlling the state of the switch, the band notched operation of the EBG can be activated or deactivated. The proposed antenna is capable to provide useful features for the notched band UWB communication system. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:497–501, 2015
Broadband high‐efficiency power amplifier with harmonic suppression based on load‐pull technique
Authors: Wang Zhenyang , Liu Falin , Wang Haoyu
Published: December 2014

In this letter, a novel design method for broadband and efficient power amplifier (PA) is proposed and a broadband PA with a compact matching topology is designed and fabricated to verify the validity of the method. In the method, specific attention has been paid to harmonic suppression to enhance efficiency and an appropriate design space of the fundamental and harmonic impedances, based on load‐pull technique which actually takes into account of the influences of the parasitics, is found to alleviate the difficulty of designing broadband matching network. Then a compact matching network topology is proposed to lead the fundamental and second harmonic impedances to the design space on the Smith chart over a wide bandwidth, simultaneously. The fabricated PA exhibits greater than 63% power added efficiency from 1.5 to 2.5 GHz (50% relative bandwidth), and 40.5–42 dBm saturated output powers. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:481–485, 2015
Wide‐field circular SAR imaging: An empirical assessment of layover effects
Authors: Demirci Sevket , Yigit Enes , Ozdemir Caner
Published: December 2014

In circular synthetic aperture radar (CSAR), targets are usually scanned over the complete azimuthal aperture of 360°. A major challenge inhibiting successful CSAR image production is encountered in two‐dimensional imaging of relatively large scenes (i.e. wide‐field scenarios). For such cases, the spatially variant radar signature gives rises to image degradations known as layover effects. In this paper, the imaging results for hypothetical and real complex targets using their CSAR data at C band are demonstrated to characterize these effects. In real experiments, a ground‐based, outdoor CSAR system is exploited thanks to the circular balcony of a building that provides 270° view of targets. A spherical back‐projection algorithm is used to focus near‐field data and the reconstructed images are also cleaned out from clutter to more easily visualize the layover artifacts. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:489–497, 2015
Compact and high‐selectivity microstrip bandpass filter using quad‐mode resonator
Authors: Chen Jianzhong , Sheng Jie , Gao Ni , Zhang Anxue
Published: December 2014

In this letter, a compact high‐selectivity microstrip bandpass filter utilizing a novel quad‐mode resonator is presented. The proposed quad‐mode resonator can be treated as the combination of a short‐circuited stub loaded open‐ended resonator and a short‐circuited stub loaded short‐ended resonator. It results to generate four resonatant modes closely to each other, while each modal resonant frequency can be freely and easily controlled in a wide range as well. Due to the inherent transmission zero produced by the feed lines, the passband selectivity gets improved, which results good out‐of‐band rejection. Finally, a quad‐mode filter example with miniaturized size, wide fractional bandwidth, and high selectivity is designed and fabricated. Good agreement between experiment and simulation is observed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:478–481, 2015
Erratum for: Raman amplified access networks with pump signal recycling for electrical power conversion
Authors: Andre P.S. , Lima M. J. N. , Rocha A. M. , Fernandes N. , Granada M. , Almeida T. , Cang Jin , Lan Rao , Xiang‐Jun Xin
Published: December 2014

Nowadays, the structure of the passive optical networks is evolving, to keep the network survivability, the powering of some elements in this kind of networks is a key issue. In this work we propose the recycling of the Raman pump remaining optical power at the receiver to be converted to electrical power. With a 24 dBm optical pump signal a 8 dB on/off gain over 25 km of single mode optical fiber was achieved. Also, the recycling of the pump signal generated 18.1 mW of electrical power at the receiver. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:116–119, 2012
BUILDING ENFORCEMENT CAPACITY: EVIDENCE FROM THE MEXICAN CIVIL SERVICE REFORM
Authors: Nieto Morales Fernando , Heyse Liesbet , del Carmen Pardo María , Wittek Rafael
Published: December 2014

Building enforcement capacity, that is, attaining and sustaining control in order to implement changes, is crucial for the success of public management reforms. However, this aspect of public management reform does not receive much theoretical or empirical attention. This paper analyzes the process of building enforcement capacity for the case of the Mexican Professional Civil Service reform. Although this reform experienced several complications (e.g., limited support, resources, and credibility), important goals were attained and some control was achieved. We study how officials attained control over implementation through the adaptive management of combinations of different types of control strategies (regulatory, normative, and procedural). The case study, focused on the analysis of in‐depth interviews with the highest officials involved in the implementation of this reform, finds evidence for three combinations of strategies next to a general pattern characterized by a trade‐off between compliance and coordination. This trade‐off shows that the process of building enforcement capacity may affect the goals of the reform, deviating from lawmakers' original intentions Copyright © 2014 John Wiley & Sons, Ltd.
Mapping parameters across system boundaries: parameterized model reduction with low rank variability in dynamics
Authors: Baur Ulrike , Beattie Christopher , Benner Peter
Published: December 2014

Linear dynamical systems with an affine parameter dependence producing low‐rank variation in the state matrix can be recast as a nonparameterized system operating in parallel with a parameterized feed forward term operating under output constraints. This mapping permits the application of standard (nonparametric) model reduction strategies to solve parameterized problems. We demonstrate the approach on a parameterized vibration problem using
${\cal H}_2$
optimal tangential interpolation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Modeling and Force Control of a Redundant Robot for Polishing Applications
Authors: Parzer Herbert , Gattringer Hubert , Neubauer Matthias
Published: December 2014

For many robotic applications with tasks such as cutting, assembly or polishing, it is necessary to get in contact with the surrounding. In this paper a redundant robot with seven degrees of freedom in a metal polishing task is considered. For simulation as well as for the controller design a dynamic model of the robot and a contact model are required. The equations of motion of the robot are calculated with the Projection Equation in subsystem representation and the contact model contains linear tool elasticities and work piece elasticities. In the case of a polishing task, a constant contact force during the process is required even if the robot moves along a trajectory. Thus some degrees of freedom of the robot tool center point have to be position controlled while the other ones have to be force controlled. The redundant robot offers the possibility to avoid singular positions or to maximize the available end‐effector forces within the inverse kinematics and is therefore best suited for polishing large objects. The actual process forces are measured with a six axis force‐torque‐sensor mounted at the tool center point. These forces are used in a parallel force/position control law to achieve the desired behavior. Results from measurements of a test arrangement are presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydraulic effects of fracture in brittle porous materials
Authors: Nguyen Minh N. , Timothy Jithender J. , Beckhuis Sven , Meschke Günther
Published: December 2014

This paper presents a multi‐level model for the description of hydraulic effects of fracture within the context of Enhanced Geothermal Systems. The standard Biot's poroelastic formulation is used to model the physical processes in a geomechanical reservoir in terms of the material deformation and the fluid pressure. Crack propagation is modeled using the phase field method. The influence of a propagating fracture on permeability is taken into account by using a micromechanical homogenization technique. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microsopic Simulation of Thermally‐Induced 2nd Order Eigenstresses in AlSi‐Alloys
Authors: Staub Sarah , Kabel Matthias , Andrä Heiko , Hofmann Michael , Schöbel Michael
Published: December 2014

Due to the different coefficients of thermal expansion of aluminium and silicon, high residual stresses of second order occur in Al‐Si alloys depending on the cooling rate during the molding process. In products as for example crank cases made of Al‐Si alloys these residual stresses may cause microcracks. In the work at hand measurements of the eigenstresses in the single phases (i.e. residual stresses of second kind) performed via neutron diffractometry are compared to numerical simulations for a specific cooling rate. To this end a three‐phase model is presented, which considers the α aluminium, the eutectic aluminium, and the silicon particles. The presented model is able to predict the residual stresses in the single phases within an elastoplastic framework. The simulation of tensile loadings of these structures are compared to experiments. The numerical computations are carried on stochastic geometry models by using a fast solver [1] for the Lippmann‐Schwinger integral equation, which is based on the fast Fourier transformation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling of non‐conforming NURBS patches with the weak substitution method
Authors: Klinkel Sven , Dornisch Wolfgang , Vitucci Gennaro
Published: December 2014

Isogeometric analysis unifies the data model for the description of the geometry for design and analysis. The analysis is altered towards compatibility with the geometry model used in the design work flow. The basis functions of the geometry descriptions are used to approximate all unknown quantities in the numerical simulation. The most common geometry model in design industry is NURBS surfaces. The properties of NURBS surfaces do not allow local refinement. Geometrical models in industrial applications generally consist of several NURBS patches, which usually neither have conforming knot vectors nor the same degree. Thus, the control points do not coincide and a connection by shared control points is not possible. Special methods to avoid mutual refinement are necessary. This works presents a new method for the coupling of non‐conforming patches. A relation between the deformations of control points having influence on shared edges is established. This relation allows expressing the deformations of a set of slave control points as a function of the deformations of the appropriate master control points. Thus, the slave control points, as well as the associated degrees of freedom can be removed from the global system of equation. The method can also be used for nonlinear computations without additional effort. The derivation of the proposed relation is shown. Numerical examples show the high accuracy of the presented method. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A dynamic friction model for the pre‐sliding behavior of a tangentially loaded single asperity contact
Authors: Krasmik Viktor , Schlattmann Josef
Published: December 2014

We introduce a dynamic friction model for the pre‐sliding behavior of a single asperity subjected to a constant normal and a varying tangential load based on Cattaneo‐Mindlin's theory. The geometry of an arbitrary, axisymmetric asperity is included in the formulation of the governing differential equation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Introducing parametric uncertainty into a nonlinear friction model
Authors: Seibel Arthur , Schlattmann Josef
Published: December 2014

We introduce parametric uncertainty into a nonlinear model for static and kinetic friction of solids. The uncertain parameters are modeled by possibility distributions and an analytical approach is used to propagate the uncertainties through the computations. As a result, we obtain a symbolic expression for the whole spectrum of possible calculation results. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Functional Fatigue in polycrystalline Shape Memory Alloys
Authors: Waimann Johanna , Junker Philipp , Hackl Klaus
Published: December 2014

Shape memory alloys show the well known effect of pseudo‐elasticity associated with the formation of two stress plateaus in the stress/strain diagram for tension tests. Due to cyclic loading, the stress plateaus decrease with every load cycle, particularly the upper one. This important effect of functional fatigue results from plastic deformations that are produced during solid‐solid phase transformations between the austenitic and martensitic state. Outgoing from a polycrystalline approach for shape memory alloys we develop a micromechanical material model that is based on the Principle of the Minimum of the Dissipation Potential and predicts the evolution of plastic strains. Therefore, only a small number of material parameters is necessary and additionally, only a few assumptions are sufficient to model the effect of functional fatigue. We present yield functions as well as evolution equations for the volume fractions of austenite and martensite, and the plastic strains. Furthermore, we show an exemplary calculation for Nickel Titanium and compare it with experimental measurements to demonstrate the ability of our model. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An experimental study towards micro‐mechanical modeling of fiber‐reinforced aerogels
Authors: Rege Ameya , Dargazany Roozbeh , Itskov Mikhail , Deo Akash
Published: December 2014

Fiber‐reinforced aerogels are a class of reinforced aerogels characterized by very low thermal conductivity, hydrophobicity and most importantly load bearing capability. In this work, an experimental study describing the damage in these fiber‐reinforced aerogels through various uniaxial compression tests is presented. While understanding the damage evolution at the micro‐scale, we come across three probable sources contributing towards the damage evolution. They are: (a) matrix cracks, (b) debonding of particles due to fiber sliding, and (c) breakage of fibers. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐dimensional elastic phase‐field simulation of fcc to bcc martensitic phase transformations in polycrystals
Authors: Kochmann Julian , Rezaeimianroodi Jaber , Reese Stefanie , Svendsen Bob
Published: December 2014

Numerical results of two‐dimensional elastic phase‐field simulations of martensitic phase transformations (fcc‐bcc) in polycystals are presented. The stresses and strains in the diffuse interface domain are described by following Khachaturyan's approach of microelasticity. A fixed‐point iteration algorithm in Fourier space is used to solve the mechanical equilibrium condition for the microscopic, inhomogeneous strain field and apply mechanical loadings to the system. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)