International Journal of Microwave Science and Technology http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. High Power Combline Filter for Deep Space Applications Sun, 14 Sep 2014 08:54:33 +0000 http://www.hindawi.com/journals/ijmst/2014/396494/ An S-band, compact, high power filter, for use in the Mars Orbiter Mission (MOM) of Indian Space Research Organization (ISRO), has been designed and tested for multipaction. The telemetry, tracking, and commanding (TT&C) transponder of MOM is required to handle continuous RF power of 200 W in the telemetry path besides simultaneously maintaining an isolation of greater than 145 dBc to its sensitive telecommand path. This is accomplished with the help of a complex diplexer, requiring high power, high rejection transmit path filter, and a low power receive path filter. To reduce the complexity in the multipaction-free design and testing, the transmit path filter of the diplexer is split into a low rejection filter integral to the diplexer and an external high rejection filter. This paper highlights the design and space qualification phases of this high rejection filter. Multipaction test results with 6 dB margin are also presented. Major concerns of this filter design are isolation, insertion loss, and multipaction. Mission performance of the on-board filter is normal. A. V. G. Subramanyam, D. Siva Reddy, V. K. Hariharan, V. V. Srinivasan, and Ajay Chakrabarty Copyright © 2014 A. V. G. Subramanyam et al. All rights reserved. Prediction of Rain Attenuation and Impact of Rain in Wave Propagation at Microwave Frequency for Tropical Region (Uttarakhand, India) Wed, 11 Jun 2014 09:33:08 +0000 http://www.hindawi.com/journals/ijmst/2014/958498/ The most classical approach of determining rain attenuation for radio-wave frequency has been to theoretically determine the specific attenuation. At frequency over 10 GHz, rain and precipitation can influence the attenuation a lot; the effect of atmospheric attenuation between the source and destination over wireless communication is of major concern and a proper site visit and proper method are required to control the attenuation level so that the performance can be increased. In this paper exponential model has been used to determine the attenuation level for k-region (India) which can be used for region having similar condition. The analyzed predicted attenuation data have been compared with ITU-R measured rain attenuation, and the results will provide useful estimation of rainfall attenuation on microwave links in tropical regions that have similar conditions as (Almora) Uttarakhand region. Mukesh Chandra Kestwal, Sumit Joshi, and Lalit Singh Garia Copyright © 2014 Mukesh Chandra Kestwal et al. All rights reserved. Ultrawide Bandwidth -Hybrid-Coupler in Planar Technology Mon, 02 Jun 2014 11:38:46 +0000 http://www.hindawi.com/journals/ijmst/2014/486051/ A new concept of an ultrawide bandwidth 180°-hybrid-coupler is presented. The ultrawideband design approach is based on the excitation of a coplanar waveguide (CPW) mode and a coupled slot line (CSL) mode in the same double slotted planar waveguide. The coupler is suitable for realization in planar printed circuit board technology. For verification of the new concept a prototype was designed for the frequency range from 3 GHz to 11 GHz, built, and measured. The measurement results presented in this paper show a good agreement between simulation and measurement and demonstrate the very broadband performance of the new device. The demonstrated coupler with a size of 40 mm × 55 mm exhibits a fractional bandwidth of 114% centered at 7 GHz with a maximum amplitude imbalance of 0.8 dB and a maximum phase imbalance of 5°. Steffen Scherr, Serdal Ayhan, Grzegorz Adamiuk, Philipp Pahl, and Thomas Zwick Copyright © 2014 Steffen Scherr et al. All rights reserved. A Simple Method to Stabilize Radiation Pattern over a Large Bandwidth Wed, 14 May 2014 09:43:15 +0000 http://www.hindawi.com/journals/ijmst/2014/712735/ An alternative radiation stabilization method has been presented for patch antenna. With this method, side radiation could be suppressed when a conductor ring and a circular slot both with the width of a quarter-wavelength are placed on the same layer and around patch antenna. An experimental structure has been simulated and the distance from antenna part to conductor ring is optimized using parametric function of HFSS software. Measured results given in this paper obviously indicate that not only the side radiation from the boundary of substrate could be suppressed effectively, but also the antenna directivity could be adjusted and enhanced after this method has been carried out. Both simulation and measurement indicate that when the distance is set to one guided wavelength (), side radiation could be suppressed the most effectively and the return loss of patch antenna is only slightly affected. Haiyang Zhang, Yann Mahe, Tchanguiz Razban, and Serge Toutain Copyright © 2014 Haiyang Zhang et al. All rights reserved. Application of Response Surface Methodology to Enhance Phenol Removal from Refinery Wastewater by Microwave Process Mon, 28 Apr 2014 09:57:01 +0000 http://www.hindawi.com/journals/ijmst/2014/639457/ Phenol contaminated petroleum refinery wastewater presents a great threat on water resources safety. This study investigates the effect of microwave irradiation on removal of different concentrations of phenol in an attempt for petroleum refinery wastewater treatment. The obtained results show that the MW output power and irradiation time have a significant positive effect on the removal efficiency of phenol. The kinetic reaction is significantly affected by initial MW output power and initial phenol concentrations. Response surface methodology (RSM) was employed to optimize and study the interaction effects of process parameters: MW output power, irradiation time, salinity, pH, and H2O2 concentration using central composite design (CCD). From the CCD design matrix, a quadratic model was considered as an ultimate model (2 = 0.75) and its adequacy was justified through analysis of variance (ANOVA). The overall reaction rates were significantly enhanced in the combined MW/H2O2 system as proved by RSM. The optimum values for the design parameters of the MW/H2O2 process were evaluated giving predicted phenol removal percentage of 72.90% through RSM by differential approximation and were confirmed by experimental phenol removal of 75.70% in a batch experiment at optimum conditions of 439 W MW power, irradiation time of 24.22 min, salinity of 574 mg/L, pH 5.10, and initial H2O2 concentration of 10% (v/v). Sherif A. Younis, Waleed I. El-Azab, Nour Sh. El-Gendy, Shuokr Qarani Aziz, Yasser M. Moustafa, Hamidi Abdul Aziz, and Salem S. Abu Amr Copyright © 2014 Sherif A. Younis et al. All rights reserved. A Multifrequency Radar System for Detecting Humans and Characterizing Human Activities for Short-Range Through-Wall and Long-Range Foliage Penetration Applications Wed, 16 Apr 2014 17:25:41 +0000 http://www.hindawi.com/journals/ijmst/2014/958905/ A multifrequency radar system for detecting humans and classifying their activities at short and long ranges is described. The short-range radar system operates within the S-Band frequency range for through-wall applications at distances of up to 3 m. It utilizes two separate waveforms which are selected via switching: a wide-band noise waveform or a continuous single tone. The long-range radar system operating in the W-Band millimeter-wave frequency range performs at distances of up to about 100 m in free space and up to about 30 m through light foliage. It employs a composite multimodal signal consisting of two waveforms, a wide-band noise waveform and an embedded single tone, which are summed and transmitted simultaneously. Matched filtering of the received and transmitted noise signals is performed to detect targets with high-range resolution, whereas the received single tone signal is used for the Doppler analysis. Doppler measurements are used to distinguish between different human movements and gestures using the characteristic micro-Doppler signals. Our measurements establish the ability of this system to detect and range humans and distinguish between different human movements at different ranges. Ram M. Narayanan, Sonny Smith, and Kyle A. Gallagher Copyright © 2014 Ram M. Narayanan et al. All rights reserved. Wideband Microstrip 90° Hybrid Coupler Using High Pass Network Mon, 07 Apr 2014 13:20:18 +0000 http://www.hindawi.com/journals/ijmst/2014/854346/ A wideband 90° hybrid coupler has been presented and implemented in planar microstrip circuit. With similar structure of conversional 2-section branch-line coupler, the proposed coupler consists of a lumped high-pass network but not the quarter wavelength transmission at the center. The values of all lumped elements were optimized to replace a quarter-wavelength transmission line with a phase inverter. To demonstrate the proposed concept, a 1-GHz prototype was fabricated and tested. It achieves 90% impedance bandwidth with magnitude of S11 less than −10 dB. Within this bandwidth, more than 13 dB port-to-port isolation, less than 5.0 degree phase imbalance, and less than 4.5 dB magnitude imbalance are achieved, simultaneously. The proposed coupler not only achieves much wider bandwidth but also occupies less circuit area than that of the conversional 2-section branch-line coupler. Leung Chiu Copyright © 2014 Leung Chiu. All rights reserved. Dominant Mode Wave Impedance of Regular Polygonal Waveguides Thu, 06 Feb 2014 09:08:07 +0000 http://www.hindawi.com/journals/ijmst/2014/485794/ Polygonal metal waveguides are analyzed analytically and numerically. Classical equation for the wave impedance of arbitrary shaped waveguides is completed with approximate expression for the cutoff wavelength of the dominant mode. Proposed approach is tested with the help of 3D finite difference time domain models of microwave waveguides junctions. Obtained data are used for computer-aided design of microwave transition from coaxial line to cylindrical waveguide. Vyacheslav V. Komarov Copyright © 2014 Vyacheslav V. Komarov. All rights reserved. Compact and Wideband Parallel-Strip 180° Hybrid Coupler with Arbitrary Power Division Ratios Thu, 26 Dec 2013 09:34:40 +0000 http://www.hindawi.com/journals/ijmst/2013/567342/ This paper presents a class of wideband 180° hybrid (rat race) couplers implemented by parallel-strip line. By replacing the 270° arm of a conventional 180° hybrid coupler by a 90° arm with phase inverter, the bandwidth of the coupler is greatly enhanced and the total circuit size is reduced by almost half. Simple design formulas relating the characteristic impedance of the arms and power division ration are derived. To demonstrate the concept, four couplers with different power division ratios of 1, 2, 4, and 8 were designed, fabricated, and tested. -parameters of the coupler are simulated and measured with good agreement. All working prototypes operate more than 112% impedance bandwidth with more than 25 dB port-to-port isolation and less than 5° absolute phase imbalance. The proposed 180° hybrid couplers can be employed as a wideband in-phase/differential power divider/combiner, which are essential for many RF and microwave subsystem designs. Leung Chiu and Quan Xue Copyright © 2013 Leung Chiu and Quan Xue. All rights reserved. Design and Performance Evaluation of a Time Domain Microwave Imaging System Tue, 24 Dec 2013 09:16:49 +0000 http://www.hindawi.com/journals/ijmst/2013/735692/ We design a time domain microwave system dedicated to medical imaging. The measurement accuracy of the system, that is, signal-to-noise ratio, due to voltage noise and timing noise, is evaluated. Particularly, the effect of coupling media on the measurement accuracy is investigated both numerically and experimentally. The results suggest that the use of suitable coupling media betters the measurement accuracy in the frequency range of interest. A signal-to-noise ratio higher than 30 dB is achievable in the range of 500 MHz to 3 GHz when the effective sampling rate is 50 Gsa/s. It is also indicated that the effect of the timing jitter on the strongest received signal is comparable to that of the voltage noise. Xuezhi Zeng, Andreas Fhager, Peter Linner, Mikael Persson, and Herbert Zirath Copyright © 2013 Xuezhi Zeng et al. All rights reserved. A Parallel-Strip Balun for Wideband Frequency Doubler Wed, 04 Dec 2013 15:04:14 +0000 http://www.hindawi.com/journals/ijmst/2013/892590/ A parallel-strip phase inverter with a pair of simple impedance matching networks is designed. The phase inverter introduces the almost frequency independent 180° phase shift and was employed in the wideband parallel-strip balun. The balun was designed and measured with the maximum magnitude imbalance of 0.5 dB and the maximum phase imbalance of 6.0°. The proposed balun is used as input network for the wideband balanced frequency doubler. The proposed frequency doubler achieves significant conversion gain from 0.1 GHz to 1.7 GHz. The frequency doubler achieves 7.4 dB conversion gain and 23 dB fundamental signal suppression at 1 GHz. Leung Chiu and Quan Xue Copyright © 2013 Leung Chiu and Quan Xue. All rights reserved. Advanced RF and Analog Integrated Circuits for Fourth Generation Wireless Communications and Beyond Thu, 16 May 2013 09:28:47 +0000 http://www.hindawi.com/journals/ijmst/2013/272070/ Ramesh Pokharel, Leonid Belostotski, Akira Tsuchiya, Ahmed Allam, and Mohammad S. Hashmi Copyright © 2013 Ramesh Pokharel et al. All rights reserved. Rainfall Rate Duration Study for Performance Assessment of Satellite Communication Links Thu, 09 May 2013 11:31:16 +0000 http://www.hindawi.com/journals/ijmst/2013/209067/ The duration of rainfall events as a function of precipitation rate is investigated in this paper. The experimental data used in this study were measured along a rain gauge network with 8 pluviographs located in the Amazon region. The most important point to be highlighted in this study is the evidence of a correlation between rain and fade events durations observed in a 12 GHz satellite link. This result is quite important under the engineering point of view, once it can be used in the design of improvement techniques for low availability satellite systems. Jorge L. Cerqueira and Mauro S. Assis Copyright © 2013 Jorge L. Cerqueira and Mauro S. Assis. All rights reserved. CMOS Ultra-Wideband Low Noise Amplifier Design Tue, 30 Apr 2013 08:49:43 +0000 http://www.hindawi.com/journals/ijmst/2013/328406/ This paper presents the design of ultra-wideband low noise amplifier (UWB LNA). The proposed UWB LNA whose bandwidth extends from 2.5 GHz to 16 GHz is designed using a symmetric 3D RF integrated inductor. This UWB LNA has a gain of 11 ± 1.0 dB and a NF less than 3.3 dB. Good input and output impedance matching and good isolation are achieved over the operating frequency band. The proposed UWB LNA is driven from a 1.8 V supply. The UWB LNA is designed and simulated in standard TSMC 0.18 µm CMOS technology process. K. Yousef, H. Jia, R. Pokharel, A. Allam, M. Ragab, H. Kanaya, and K. Yoshida Copyright © 2013 K. Yousef et al. All rights reserved. Downconverting Module Architectures for High Performance Multipixel Cameras Mon, 15 Apr 2013 15:06:28 +0000 http://www.hindawi.com/journals/ijmst/2013/586158/ Multipixel cameras represent an emerging topology for arrays receivers, improving speed and accuracy of both security scanning systems and radioastronomical sky surveys by means of a matrix of phased elements. Difficulties in the generation and proper distribution to each pixel of the local oscillator signal still limit their use to frequency ranges below a few GHz or at least seriously affect the complexity of the implementable cameras. This work presents a full comparison between two possible system architectures, alternatively based on LO frequency multiplication or subharmonic mixing strategies, aiming to overcome the aforesaid limitations: design and performance of two compact test vehicles in MMIC technology, both operating in the Q-band frequency range with ultrabroadband IF section, are reported. Diego Palombini, Maciej Jankowski, and Ernesto Limiti Copyright © 2013 Diego Palombini et al. All rights reserved. Performance and Trends in Millimetre-Wave CMOS Oscillators for Emerging Wireless Applications Thu, 28 Mar 2013 08:51:28 +0000 http://www.hindawi.com/journals/ijmst/2013/312618/ This paper reports the latest advances on millimeter-wave CMOS voltage-controlled oscillators (VCOs). Current state-of-the-art implementations are reviewed, and their performances are compared in terms of phase noise and figure of merit. Low power and low phase noise LC-VCO and ring oscillator designs are analyzed and discussed. Design and performance trends over the last decade are provided and discussed. The paper shows how for the higher range of millimeter-waves (>60 GHz) the performances of ring oscillators become comparable with those of LC-VCOs. Marius Voicu, Domenico Pepe, and Domenico Zito Copyright © 2013 Marius Voicu et al. All rights reserved. A Novel Reconfigurable MB-OFDM UWB LNA Using Programmable Current Reuse Mon, 25 Mar 2013 11:08:13 +0000 http://www.hindawi.com/journals/ijmst/2013/924161/ This paper presents a design of a reconfigurable low noise amplifier (LNA) for multiband orthogonal frequency division multiplexing (MB-OFDM) ultra wideband (UWB) receivers. The proposed design is divided into three stages; the first one is a common gate (CG) topology to provide the input matching over a wideband. The second stage is a programmable circuit to control the mode of operation. The third stage is a current reuse topology to improve the gain, flatness and consume lower power. The proposed LNA is designed using 0.18 μm CMOS technology. This LNA has been designed to operate in two subbands of MB-OFDM UWB, UWB mode-1 and mode-3, as a single or concurrent mode. The simulation results exhibit the power gain up to 17.35, 18, and 11 dB for mode-1, mode-3, and concurrent mode, respectively. The NF is 3.5, 3.9, and 6.5 and the input return loss is better than −12, −13.57, and −11 dB over mode-1, mode-3, and concurrent mode, respectively. This design consumes 4 mW supplied from 1.2 V. Ahmed Ragheb, Ghazal Fahmy, Iman Ashour, and Abdel Hady Ammar Copyright © 2013 Ahmed Ragheb et al. All rights reserved. Systematic Design Methodology of a Wideband Multibit Continuous-Time Delta-Sigma Modulator Thu, 07 Mar 2013 09:29:19 +0000 http://www.hindawi.com/journals/ijmst/2013/275289/ Systematic design of a low power, wideband and multi-bit continuous-time delta-sigma modulator (CTDSM) is presented. The design methodology is illustrated with a 640 MS/s, 20 MHz signal bandwidth 4th order 2-bit CTDMS implemented in 0.18 µm CMOS technology. The implemented design achieves a peak SNDR of 65.7 dB and a high dynamic range of 70 dB while consuming only 19.7 mW from 1.8 V supply. The design achieves a FoM of 0.31 pJ/conv. Direct path compensation is employed for one clock excess loop delay compensation. In the feedforward topology, capacitive summation using the last opamp eliminates extra summation opamp. Awinash Anand, Nischal Koirala, Ramesh K. Pokharel, Haruichi Kanaya, and Keiji Yoshida Copyright © 2013 Awinash Anand et al. All rights reserved. An Inductorless Cascaded Phase-Locked Loop with Pulse Injection Locking Technique in 90 nm CMOS Mon, 04 Mar 2013 10:57:02 +0000 http://www.hindawi.com/journals/ijmst/2013/584341/ An inductorless phase-locked loop with subharmonic pulse injection locking was realized (PLL area: 0.11 mm2) by adopting 90 nm Si CMOS technology. The proposed circuit is configured with two cascaded PLLs; one of them is a reference PLL that generates reference signals to the other one from low-frequency external reference signals. The other is a main PLL that generates high-frequency output signals. A high-frequency half-integral subharmonic locking technique was used to decrease the phase noise characteristics. For a 50 MHz input reference signal, without injection locking, the 1 MHz offset phase noise was −88 dBc/Hz at a PLL output frequency of 7.2 GHz (= 144 × 50 MHz); with injection locking, the noise was −101 dBc/Hz (spur level: −31 dBc; power consumption from a 1.0 V power supply: 25 mW). Sang-yeop Lee, Hiroyuki Ito, Shuhei Amakawa, Noboru Ishihara, and Kazuya Masu Copyright © 2013 Sang-yeop Lee et al. All rights reserved. Wideband Lithium Niobate FBAR Filters Tue, 26 Feb 2013 09:57:49 +0000 http://www.hindawi.com/journals/ijmst/2013/459767/ Filters based on film bulk acoustic resonators (FBARs) are widely used for mobile phone applications, but they can also address wideband aerospace requirements. These devices need high electromechanical coupling coefficients to achieve large band pass filters. The piezoelectric material LiNbO3 complies with such specifications and is compatible with standard fabrication processes. In this work, simple metal—LiNbO3—metal structures have been developed to fabricate single FBAR elements directly connected to each other on a single chip. A fabrication process based on LiNbO3/silicon Au-Au bonding and LiNbO3 lapping/polishing has been developed and is proposed in this paper. Electrical measurements of these FBAR filters are proposed and commented exhibiting filters with 8% of fractional bandwidth and 3.3 dB of insertion losses. Electrical measurements show possibilities to obtain 14% of fractional bandwidth. These devices have been packaged, allowing for power handling, thermal, and ferroelectric tests, corresponding to spatial conditions. Thomas Baron, Eric Lebrasseur, Florent Bassignot, Haixia Wang, Sylvain Ballandras, Ji Fan, Lise Catherinot, Matthieu Chatras, Philippe Monfraix, and Laetitia Estagerie Copyright © 2013 Thomas Baron et al. All rights reserved. A Quasi-Yagi Antenna Backed by a Jerusalem Cross Frequency Selective Surface Thu, 21 Feb 2013 18:39:02 +0000 http://www.hindawi.com/journals/ijmst/2013/354789/ A quasi-Yagi antenna is developed to operate at 2.4 GHz (ISM band) presenting a low profile and off-axis radiation when packaged over a metal ground plane. The off-axis radiation is realized by incorporating a Jerusalem cross frequency selective surface (JC-FSS) as the ground plane for the antenna. A JC-FSS is preferred because of its frequency stability in the operating band for a large angular spectrum (≈70°) of TE- and TM-polarized incident waves. In this research, the substrate of the antenna flush-mounted on top of the FSS is added to the JC-FSS model and allows for a smaller cell grid. The prepared quasi-Yagi antenna over the JC-FSS offered 260 MHz of functional bandwidth and 54° of beam tilt towards the end-fire direction. To the best of the authors’ knowledge this is the first instance that these two structures are combined for off-axis radiation. Additionally, to support the preferred use of the JC-FSS, the quasi-Yagi is backed by a square patch (SP) FSS for comparison purposes. Sergio E. Melais, David Cure, and Thomas M. Weller Copyright © 2013 Sergio E. Melais et al. All rights reserved. Compact Multiband Printed IFA on Electromagnetic Band-Gap Structures Ground Plane for Wireless Applications Tue, 12 Feb 2013 17:50:19 +0000 http://www.hindawi.com/journals/ijmst/2013/248501/ The fourth mobile generation requires of multistandard operating handsets of small physical size as well as has an increasing demand for higher data rates. Compact multiband printed inverted-F antennas (IFAs) for available wireless communications are proposed in this paper. A new design of a printed IFA based on a uniplanar compact EBG concept is proposed. An L-loaded printed IFA shaped over an artificial ground plane is designed as the main antenna to cover the GSM, LTE, UMTS, bluetooth, and WLAN. The multi-band is created by means of an electromagnetic band-gap (EBG) structure that is used as a ground plane. Different shapes of uniplanar EBG as ring, split ring resonator, and a spiral rather than mushroom-like structure are investigated. The proposed antenna is built on the uniplanar EBG ground plane with a size of  mm2, which is suitable for most of the mobile devices. Dalia Elsheakh and Esmat Abdallah Copyright © 2013 Dalia Elsheakh and Esmat Abdallah. All rights reserved. Microwave-Osmotic Dehydration of Cranberries under Continuous Flow Medium Spray Conditions Wed, 30 Jan 2013 09:34:17 +0000 http://www.hindawi.com/journals/ijmst/2013/207308/ Microwave-osmotic dehydration of cranberries was evaluated under continuous flow medium spray (MWODS) conditions after some pretreatments. A central composite rotatable design was used with three input variables at five levels (temperature, 33°C–67°C; sucrose concentration, 33°B–67°B; and contact time, 5–55 min). Responses were moisture loss (ML), solids gain (SG), and weight reduction (WR) as well as color and texture parameters. The responses were related to process variables using response surface methodology and statistical analysis: each model was tested for lack of fit to assure nonsignificance and each process variable was tested for significance . Temperature was found to have the most prominent effect as it was significant with all drying (ML, SG, and WR) and quality (hardness and chewiness) parameters, while contact time was found to be significant with ML and WR. Concentration wasn’t found to be significant for any response. Increasing skin pretreatment severity generally promoted SG but had little effect on ML. The exception was chemical peeling, which favored ML but had no effect on SG. Overall, MWODS enables food dehydration in a much faster period of time than conventional osmotic dehydration (COD), while specifically promoting moisture loss over solids gain. Derek Wray and Hosahalli S. Ramaswamy Copyright © 2013 Derek Wray and Hosahalli S. Ramaswamy. All rights reserved. Permittivity and Backscattering Coefficient of Diesel Oil-Contaminated Soil at C Band (5.3 GHz) Mon, 28 Jan 2013 13:17:27 +0000 http://www.hindawi.com/journals/ijmst/2013/950862/ Studying the behavior of soil contaminated by diesel requires the measurement and calculation of electrical parameters such as permittivity and backscattering coefficient. It is also necessary to study the physical parameters such as surface roughness. The intent of this paper is to present a broad and updated overview of the diesel oil contaminated soil, emphasizing permittivity and scattering coefficient that are involved in determining and detecting the rate at which and extent to which hydrocarbons contaminate the soil and environment. The measurement of permittivity and the calculations of backscattering coefficient values were made with different amounts of diesel oil contamination and different incident angles in 5° intervals ranging from 10° to 80° for both horizontal and vertical polarization at C band. The values of scattering coefficient for different look angles (25°, 30°, 35°, 40°, 45°, 50°, and 55°) were calculated and are suitable for comparison with data generated from other remote sensing platforms. Accurate electrical parameter measurements of soil contamination and recognition of their dependence on physical and chemical composition are interesting and can support using microwave remote sensing instruments to observe the earth. Nima Ahmadian, Sayeh Hasan, and Om Prakash Narayan Calla Copyright © 2013 Nima Ahmadian et al. All rights reserved. A Systemic Approach to the Compensation of Rain Attenuation in Ka-Band Communication Satellites Tue, 04 Dec 2012 14:59:25 +0000 http://www.hindawi.com/journals/ijmst/2012/791635/ Rain attenuation at Ka-band is a severe phenomenon that drastically impairs satellite communications at these frequencies. Several adaptive compensation techniques have been elaborated to counteract its effects and most often applied one at a time. The present paper proposes the contemporary exploitation of different techniques in a combined approach. Such an integrated approach is thoroughly analyzed in a simplified scenario and will be shown to achieve a very effective solution, making the Ka-band spectrum fully available for broadband satellite applications and network-centric systems. Piero Angeletti and Marco Lisi Copyright © 2012 Piero Angeletti and Marco Lisi. All rights reserved. Microwave and Millimeter-Wave Sensors, Systems, and Techniques for Electromagnetic Imaging and Materials Characterization Tue, 20 Nov 2012 14:36:59 +0000 http://www.hindawi.com/journals/ijmst/2012/132136/ Andrea Randazzo, Kristen M. Donnell, and Yeou Song (Brian) Lee Copyright © 2012 Andrea Randazzo et al. All rights reserved. Swarm Optimization Methods in Microwave Imaging Wed, 24 Oct 2012 15:08:59 +0000 http://www.hindawi.com/journals/ijmst/2012/491713/ Swarm intelligence denotes a class of new stochastic algorithms inspired by the collective social behavior of natural entities (e.g., birds, ants, etc.). Such approaches have been proven to be quite effective in several applicative fields, ranging from intelligent routing to image processing. In the last years, they have also been successfully applied in electromagnetics, especially for antenna synthesis, component design, and microwave imaging. In this paper, the application of swarm optimization methods to microwave imaging is discussed, and some recent imaging approaches based on such methods are critically reviewed. Andrea Randazzo Copyright © 2012 Andrea Randazzo. All rights reserved. A Dual-Band SiGe HBT Frequency-Tunable and Phase-Shifting Differential Amplifier Employing Varactor-Loaded, Stacked LC Resonators Sun, 21 Oct 2012 16:20:26 +0000 http://www.hindawi.com/journals/ijmst/2012/157971/ A dual-band SiGe HBT frequency-tunable and phase-shifting differential amplifier has been developed for the future active phased array antennas with a multiband, multibeam, and multitarget tracking operation. The amplifier uses varactor-loaded, stacked LC resonators in the design of the output circuit in order to provide frequency-tunable and phase-shifting capabilities for dual frequencies. By utilizing the varactor-loaded LC resonator, which has a variable resonant frequency and a large insertion phase variation, frequency-tunable and phase-shifting performances become available. Moreover, by using the stacked configuration, the frequency and insertion phase can be varied independently for dual frequencies. A dual-band SiGe HBT differential amplifier has achieved a lower-frequency tuning range of 0.56 to 0.7 GHz for a higher fixed frequency of 0.97 GHz as well as a higher-frequency tuning range of 0.92 to 1.01 GHz for a lower fixed frequency of 0.63 GHz. A lower-frequency phase variation of 99° and a higher-frequency phase variation of 90.3° have been accomplished at 0.63 and 0.97 GHz, respectively. This is the first report on the dual-band differential amplifier with frequency-tunable and phase-shifting capabilities. Kazuyoshi Sakamoto and Yasushi Itoh Copyright © 2012 Kazuyoshi Sakamoto and Yasushi Itoh. All rights reserved. Performance Comparison of UWB Pulse Modulation Schemes under White Gaussian Noise Channels Tue, 02 Oct 2012 09:03:26 +0000 http://www.hindawi.com/journals/ijmst/2012/590153/ In this paper, and for the first time, the performance of various ultra wideband pulse modulation schemes are discussed and compared in terms of narrowband interference robustness, symbol error rate, system complexity, data rate, and maximum transmit power with respect to transceiver distance and channel capacity. The channel model is the UWB IEEE 802.15.3a multipath indoor channel model under additive white Gaussian noise. The transmit power was evaluated by integrating the fifth derivative of the power spectrum density of the Gaussian pulse over the whole bandwidth. O. Abedi and M. C. E. Yagoub Copyright © 2012 O. Abedi and M. C. E. Yagoub. All rights reserved. A Second Harmonic Self-Oscillating Mixer Incorporating Resonant Cell Structure Sat, 29 Sep 2012 09:30:14 +0000 http://www.hindawi.com/journals/ijmst/2012/565906/ A downconverting second harmonic self-oscillating mixer (SOM) is developed for low-cost wireless communications applications. Incorporating resonant cell in the SOM, we can provide suitable oscillation for generating LO and terminations to all major unwanted mixing products, leading to high conversion gain design. The proposed SOM was measured with 8.5 dB downconversion gain at the RF frequency of 8.2 GHz RF, LO frequency of 4.0 GHz, and IF frequency of 0.2 GHz. The proposed design achieves higher conversion gain than that of the SOM without resonant cell. Leung Chiu and Quan Xue Copyright © 2012 Leung Chiu and Quan Xue. All rights reserved.