http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2012, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/ijmst/2012/628237/We present the results of the measurement of complex dielectric permittivity, in the microwave frequency region, on glass reinforced polybutylene terephthalate (PBT) with blue inorganic pigments. The cavity resonant method had been used in order to measure the shift in the resonant frequency of the cavity, caused by the insertion of a sample, which can be related to the real part of the complex permittivity. Also, the quality factor of the cavity decreases with the insertion of a sample. The changes in the inverse of this quality factor give the imaginary part. In order to predict the dielectric behavior of this composite, we had developed a program of numerical simulation to calculate the complex permittivity of the inclusion. By using some of dielectric mixture laws (Maxwell-Wagner-Sillars, Hanai, Looyenga, inverse and direct Wiener, and Bruggemann), we can predict the dielectric behavior of the composite in a large range of volume fraction of inclusions.L. C. Costa and F. HenryCopyright © 2012 L. C. Costa and F. Henry. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/387137/A complete design flow starting from the technological process development up to the fabrication of digital circuits is presented. The aim of this work is to demonstrate the GaAs Enhancement/Depletion (E/D) double stop-etch technology implementation feasibility for digital applications, aimed at mixed signal circuit integration. On the basis of the characterization of small E/D devices with different Gate peripheries, developed by the SELEX-SI foundry, and the analysis of several GaAs-based logical families, the most suitable logic for the available technology has been selected. Then, simple test vehicles (level shifters, NOR logic gates and D Flip-Flops) have been designed, realized, and measured to validate the design strategy applied to the GaAs E/D process. These logical circuits are preliminary to the design of a more complex serial-to-parallel converter, to be implemented onto the same chip together with RF analog blocks, such as stepped attenuators and phase shifters.Andrea Bentini, Benedetto Pasciuto, Walter Ciccognani, Ernesto Limiti, Antonio Nanni, and Paolo RomaniniCopyright © 2011 Andrea Bentini et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/160129/Dielectric constant and dielectric loss (ε′ and ε″) of different soil samples with bulk densities varying from 1.3 to 2.0 gm/cm3 are determined at a single microwave frequency 9.78 GHz and at temperature 37.0°C. Different bulk densities of same soil are achieved by filling the wave guide cell with an equal volume but a different mass of soil. Further, ε′ and ε″ of these soil samples are also estimated by semiempirical model and compared with the experimental results. The values of ε′ and ε″ increase as bulk density of the soil increases. In view of microwave remote sensing, the Fresnel reflectivity of soil is computed from the knowledge of the complex dielectric constant and the surface boundary condition. Using Kirchhoff’s reciprocity theorem the microwave emissivity is estimated from Fresnel reflectivity of the surface. It is observed that the microwave emission from the soil surface inhibits as bulk density of soil increases. Further, the roughness of soil surface has been taken into consideration in the emissivity computation and observed that the emissivity increases with increasing roughness of the soil surface.V. K. Gupta and R. A. JangidCopyright © 2011 V. K. Gupta and R. A. Jangid. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/945189/This study presents the temperature dependence of small signal parameters of GaN/SiC HEMTs across the 0–150°C range. The changes with temperature for transconductance (gm), output impedance (Cds and Rds), feedback capacitance (Cdg), input capacitance (Cgs), and gate resistance (Rg) are measured. The variations with temperature are established for gm, Cds, Rds, Cdg, Cgs, and Rg in the GaN technology. This information is useful for MMIC designs.Ali M. Darwish, Amr A. Ibrahim, and H. Alfred HungCopyright © 2011 Ali M. Darwish et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/452348/This paper presents the formation of the parasitic components that exist in the RF MOSFET structure during its high-frequency operation. The parasitic components are extracted from the transistor's S-parameter measurement, and its geometry dependence is studied with respect to its layout structure. Physical geometry equations are proposed to represent these parasitic components, and by implementing them into the RF model, a scalable RFCMOS model, that is, valid up to 49.85 GHz is demonstrated. A new verification technique is proposed to verify the quality of the developed scalable RFCMOS model. The proposed technique can shorten the verification time of the scalable RFCMOS model and ensure that the coded scalable model file is error-free and thus more reliable to use.Ah Fatt Tong, Wei Meng Lim, Choon Beng Sia, Xiaopeng Yu, Wanlan Yang, and Kiat Seng YeoCopyright © 2011 Ah Fatt Tong et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/264249/A domestic microwave oven (1000 W) was modified to permit the continuous flow of liquids run through a helical coil centrally located inside the oven cavity. Heating characteristics were evaluated by measuring inlet and outlet temperatures of coil as a function of system variables. The influence of number of turns, coil diameter, tube diameter, pitch and initial temperature were evaluated at different flow rates. The average residence time of water was computed by dividing the coil volume by the volumetric flow rate. The influence of Dean number was evaluated. Results from this study showed that (1) higher number of turns resulted in lower heating rate, lower temperature fluctuations, higher exit temperature and longer time to achieve temperature equilibrium; (2) larger tube or coil diameter gave larger coil volume causing the heating rate to decrease; (3) faster flow rates resulted in lower exit temperatures, lower temperature fluctuation, higher Dean number and slightly higher heating rate; (4) higher initial temperatures resulted in higher exit temperatures; (5) higher Dean number resulted in more uniform heating and slightly higher heating rate. Overall, the coil volume was the more dominant factor affecting heating rate as compared with flow rate and Dean number.Hosahalli S. Ramaswamy and Manguang LinCopyright © 2011 Hosahalli S. Ramaswamy and Manguang Lin. All rights reserved.http://www.hindawi.com/journals/ijmst/2012/842489/Physical principles for designing a multipurpose set of high Q-factor quasioptical and corrugated resonators with automatic frequency tuning (Q>6×104, VSWR<1.6) that can operate in the frequency band from 37.5 to 400 GHz are presented. The electrodynamical calculation methods of resonators, the constructive particularities of resonators, the methods and results of the experimental researches are considered. This set of resonators can be used as a universal measuring resonator for measuring radio-signal fluctuations and parameters of different media, in particular, nanotube composites and high-temperature superconductors.Tatiana Gaevskaya, Victor Karpovich, and Valentina RodionovaCopyright © 2012 Tatiana Gaevskaya et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/468074/This paper presents simulation and measurement results of fully distributed tunable coplanar bandpass filters (BPFs) with center frequencies around 6 GHz that make use of ferroelectric Barium Strontium Titanate (BaxSr1−xTiO3 or BST-x) thin film as tunable material. The two experimental bandpass filters tested are based on a novel frequency-agile structure composed of cascaded half wavelength slow-wave resonators (2 poles) and three coupled interdigital capacitors (IDCs) optimized for bias voltage application. Devices with gap dimensions of 10 and 3 μm are designed and fabricated with a two-step process on polycrystalline Ba0.5Sr0.5TiO3 thin films deposited on alumina substrate. A frequency tunability of 9% is obtained for the 10 μm gap structure at ±30 V with 7 dB insertion loss (the BST dielectric tunability being 26% with 0.04 loss tangent for this gap size). When the structure gap is reduced to 3 μm the center frequency shifts with a constant 9 dB insertion loss from 6.95 GHz at 0 V to 9.05 GHz at ±30 V, thus yielding a filter tunability of 30% (the BST dielectric tunability being 60% with 0.04 loss tangent for this gap size), a performance comparable to some extent to localized or lumped element BPFs operating at microwave frequency (>2 GHz).Sébastien L. Delprat, JaeHo Oh, Feng Xu, Lin Li, Erick E. Djoumessi, Marwa Ismail, Mohamed Chaker, and Ke WuCopyright © 2011 Sébastien L. Delprat et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/425710/Time reversal is a physical concept that can focus waves both spatially and temporally regardless of the complexity of the propagation medium. Time reversal mirrors have been demonstrated first in acoustics, then with electromagnetic waves, and are being intensively studied in many fields ranging from underwater communications to sensing. In this paper, we will review the principles of time reversal and in particular its ability to focus waves in complex media. We will show that this focusing effect depends on the complexity of the propagation medium rather than on the time reversal mirror itself. A modal approach will be utilized to explain the physical mechanism underlying the concept. A particular focus will be given on the possibility to break the diffraction barrier from the far field using time reversal. We will show that finite size media made out of coupled subwavelength resonators support modes which can radiate efficiently in the far field spatial information of the near field of a source. We will show through various examples that such a process, due to reversibility, permits to beat the diffraction limit using far field time reversal, and especially that this result occurs owing to the broadband inherent nature of time reversal.Fabrice Lemoult, Abdelwaheb Ourir, Julien de Rosny, Arnaud Tourin, Mathias Fink, and Geoffroy LeroseyCopyright © 2011 Fabrice Lemoult et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/468497/We propose a two-step identification approach for twin-box model (Wiener or Hammerstein) of RF power amplifier. The linear filter block and the static nonlinearity block are extracted, respectively, based on least-squares method, by iterative calculation. Simulations show that the method can get quite accurate parameters to model different nonlinear models with memory such as Wiener, Hammerstein, Wiener-Hammerstein (W-H), and memory polynomial models, hence, demonstrating its robustness. Furthermore, experimental results show excellent agreement between measured output and modeled output, where one carrier WCDMA signal is used as the excitation for a wideband RF amplifier.You-Jiang Liu, Bang-Hua Zhou, Jie Zhou, and Yi-Nong LiuCopyright © 2011 You-Jiang Liu et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/278070/The design of a two-element antenna array using the substrate integrated waveguide (SIW) technique and operating at 10 GHz is presented. The proposed antenna array consists of two SIW phase shifter sections with two SIW slot antennas. The phase shifting is achieved by changing the position of two inductive posts inserted inside each element of the array. Numerical simulations and experimental measurements have been carried out for three differential phases between the two antenna array elements, namely, 0°, 22.5°, and 67.5°. A prototype for each differential phase has been fabricated and measured. Results have shown a fairly good agreement between theory and experiments. In fact, a reflection coefficient of better than 20 dB has been achieved around 10 GHZ. The E-plane radiation pattern has shown a beam scan between 5° and 18° and demonstrated the feasibility of designing an SIW antenna phased array.Kheireddine Sellal and Larbi TalbiCopyright © 2011 Kheireddine Sellal and Larbi Talbi. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/980982/The effects of substrate materials on the design of microstrip power divider are investigated theoretically and experimentally. Three dielectric substrate materials, Duroid 3003, G10/FR4 epoxy Glass, and Duroid 3010, are chosen to be studied. A three-way two-stage power divider is designed at S-band frequency of 2.25 GHz and etched on each studied substrate separately. The substrate effects on the characteristics and performance of the microsrip circuits are studied taking into consideration the large difference in dielectric constant and the dissipation factor. The circuit designs presented here are analyzed using the Genesys CAD program and implemented and tested experimentally. The simulated and measured results are compared and discussed, and they indicate that significant changes in the characteristics of the microstrip power divider are observed.Suhair Mansoor Mahmood and Asaad M. Jassim Al-HindawiCopyright © 2011 Suhair Mansoor Mahmood and Asaad M. Jassim Al-Hindawi. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/687548/Prepared apple (Red Gala) cylinders were subjected to microwave-osmotic dehydration treatment under continuous flow medium spray (MWODS) conditions and then air-dried to a final 20% moisture content. The dried samples were evaluated for color and textural properties, and rehydration capacity. The MWODS pretreatments were based on a central composite rotatable design and a response surface methodology using five levels of sucrose concentration, temperature, and contact time at a constant flow rate of 2800 mL/min. The air-drying was carried out at 60°C, 15±1% relative humidity, and 0.64±0.02 m/s air velocity. The results were compared to untreated air-dried (AD) (worst-case scenario) and freeze-dried (FD) (best-case scenario) apples without the MWODS treatment. Color properties were affected regardless of the type of treatment. Conventional AD apples were darker in color, whereas MWODS-treated samples were lighter with higher L∗ and b∗ values, higher Hue and Chroma values but lower a∗ value and ΔE. Further the color parameters of MWODS-treated samples were closer or equal to the FD apples. The texture properties were also affected by the osmotic variables with MWODS treatment resulting in softer and chewier products. The AD samples were hard, and FD apples were brittle.Elham Azarpazhooh and Hosahalli S. RamaswamyCopyright © 2011 Elham Azarpazhooh and Hosahalli S. Ramaswamy. All rights reserved.http://www.hindawi.com/journals/ijmst/2012/418264/The fully Cu-metalized GaAs pHEMT using developed Cu/Ge-based ohmic contacts and T-gate Ti/Mo/Cu with length of the 150 nm has been successfully fabricated for the high-frequency applications. The fabricated Cu-metalized pHEMT has a maximum drain current of 360 mA/mm, an off-state gate-drain breakdown of 7 V, and a transconductance peak of 320 mS/mm at Vds=3 V. The maximum stable gain value was about 15 dB at frequency 10 GHz. The current gain cutoff frequency of the copper-metalized device is about 60 GHz at Vds=3 V, and maximum frequency of oscillations is beyond 100 GHz. This work investigated in detail the formation of Cu/Ge ohmic contacts to n-GaAs with an atomic hydrogen preannealing step. It was shown that after the first preliminary annealing is carried out in a flow of atomic hydrogen with a flow density of atoms of 1013/1016 at. cm2 s−1 a reduction in specific contact resistance by 2/2.5 times is observed. The reduction in specific contact resistance is apparently caused by the action of the hydrogen atoms which minimise the rate of the oxidizing reactions and activate solid phase reactions forming the ohmic contact during the thermal treatment process.E. V. Anichenko, V. S. Arykov, E. V. Erofeev, and V. A. KagadeiCopyright © 2012 E. V. Anichenko et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/368080/We present a theoretical study of reflection and transmission characteristics of a microwave planar array on a thin dielectric substrate with unit cell made of two concentric rings. This array possesses high quality factor transmission resonance with polarization insensitivity for normally incident plane wave. This resonance is defined by the trapped-mode regime. We show that for oblique incidence, there are some differences in characteristics of the array and a small change in quality factor of the trapped-mode resonance.M. N. Kawakatsu and V. A. DmitrievCopyright © 2011 M. N. Kawakatsu and V. A. Dmitriev. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/812078/This paper presents a dual-band band-pass filter using modified cross-coupled step-impedance and capacitively loaded hairpin resonators for WLAN systems. The proposed filter has been designed to operate at a fundamental frequency of 2.4 GHz and the first harmonics frequency of 5.2 GHz. The techniques of step impedance and load capacitor are combined in the design of the proposed filter. In particular, the techniques of modified cross-coupling and overlap resonators are applied to improve the response of insertion losses S21 at the first harmonic frequency of 5.2 GHz. The simulated and experimental results of insertion losses and return losses are better than 3 dB and 20 dB, respectively, at the operating frequencies.P. Chomtong, C. Mahatthanajatuphat, and P. AkkaraekthalinCopyright © 2011 P. Chomtong et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/249647/Decoupling networks can alleviate the effects of mutual coupling in antenna arrays. Conventional decoupling networks can provide decoupled and matched ports at a single frequency. This paper describes dual-frequency decoupling which is achieved by using a network of series or parallel resonant circuits instead of single reactive elements.Jacob Carl CoetzeeCopyright © 2011 Jacob Carl Coetzee. All rights reserved.http://www.hindawi.com/journals/ijmst/2011/714927/The microwave attenuation due to rainfall in tropical regions has not been very widely studied yet. In Pakistan's tropical environment, line-of-sight microwave communication links were set up and have been operated for several years to study the microwave attenuation characteristics due to tropical rainfall. In this paper the experimental results are presented, including the cumulative distributions of microwave attenuation and the relationship between specific attenuation and rainfall rate. In addition, a rain outage prediction model is proposed which not only predicts microwave radio link performance but will also be useful in calculating the link degradations due to interference issues. The main focus of this research work has been done keeping in mind the wireless networks of Pakistan. The results show that the rainfall rate, the microwave propagation characteristics, and outage predictions in Pakistan differ from the International Radio Consultative Committee predictions and ITU recommendation P530.7/8, respectively.Uzma Siddique, Laeeq Ahmad, and Gulistan RajaCopyright © 2011 Uzma Siddique et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/535307/Three patch antennas suitable for integration and operation in a compact 24 GHz wireless sensor node with radar and communication functions are designed, characterized, and compared. The antennas are manufactured on a low loss glass wafer using thin film (BCB/Cu) wafer level processing (WLP) technologies. This process is well suited for 3D stacking. The antennas are fed through a microstrip line underneath a ground plane coupling into the patch resonator through a slot aperture. Linear polarization (LP), dual mode (DM) operation, and circular polarization (CP) are achieved through the layout of the slot aperture and rectangular patch dimensions. Antenna gain values of ∼5.5 dBi are obtained in addition to the 10 dB impedance bandwidths of 900 MHz and 1.3 GHz as well as 500 MHz CP bandwidth with a 3 dB axial ratio for the LP, DM, and CP patch antennas, respectively.Florian Ohnimus, Uwe Maaß, Gerhard Fotheringham, Brian Curran, Ivan Ndip, Thomas Fritzsch, Jürgen Wolf, Stephan Guttowski, and Klaus-Dieter LangCopyright © 2010 Florian Ohnimus et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/297519/An effective solution to reduce both the mutual coupling and return loss of a microstrip array antenna consisting of rectangular patches is proposed. The patch is made concave in both horizontal and vertical sides. Applying the proposed structure to a microstrip array antenna having two elements, the effects of patch concavity on the mutual coupling and return loss are simulated and studied. To obtain a concave rectangular patch array antenna having low amounts of mutual coupling and return loss, the patch length and width as well as the amounts of concavities are optimized using an enhanced genetic algorithm. To verify the simulation results, then, the optimal array antenna is fabricated. The simulation and experimental results confirm that the optimal concave rectangular array antenna has low amounts of mutual coupling and return loss.Shahram Mohanna, Ali Farahbakhsh, Saeed Tavakoli, and Nasser GhassemiCopyright © 2010 Shahram Mohanna et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/624846/This paper reports a wide bandwidth planar bandstop filter with improved RF characteristics. The proposed filter on alumina is realized incorporating tapped open stub along with spurline topology. Further, stepped impedance resonator (SIR) approach has been introduced in the tapped stubs to achieve wider band performance with improved selectivity. The proposed topology effectively controls the transmission poles. Fabrication of this BSF has been carried out on glass substrate showing minimal effect of permittivity variation on bandwidth performance. This validates the applied approach with achievable bandwidth of more than 100% ranging from S- to Ku-band. Close agreement with simulation and practical results have been demonstrated with measured insertion loss of less than 1 dB and attenuation loss better than 30 dB at C-band.Kamaljeet Singh and K. NagachenchaiahCopyright © 2010 Kamaljeet Singh and K. Nagachenchaiah. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/517187/A novel technological method to improve the quality factor (Q) of RF-integrated inductors for wireless applications is presented in this paper. A serious reduction of substrate losses caused by capacitive coupling is provided. This is realised by removing the oxide layers below the coils with optimized underetching techniques. This special etching procedure is used to establish an environment in the inductor substructure with very low permittivity. A set of solid oxide-metal-columns placed below the metal windings stabilize the coil and prevent the hollowed out structure from mechanical collapse. The oxide capacitance is lowered significantly by the reduction of the permittivity εr from values around 4 to nearly 1. Capacitive coupling losses into substrate are decreasing in the same ratio. The resulting maximum Q-factors of the new designs are up to 100% higher compared to the same devices including the oxide layers but shifted significantly to higher frequencies. Improvements of Q from 10 up to 15 have been obtained at a frequency of 3 GHz for a 2.2 nH inductor with an outer diameter of 213 μm. The resonance frequency (fres) and frequency at maximum Q (f(Qmax)) are shifted to higher frequencies, caused by the shrunk total capacitance of the structure. This enables the circuit designer to use the inductors for applications working at higher frequencies. Coils with different layouts and values for inductance (L) were verified and showed similar results.Kevni Büyüktas, Klaus Koller, Karl-Heinz Müller, and Angelika GeiselbrechtingerCopyright © 2010 Kevni Büyüktas et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/671515/The effects of adaptive genetic algorithms (AGAs) and defected ground structures (DGSs) on performance optimization of tapered microstrip filter are investigated. The proposed structure achieves an ultra wide stopband with high attenuation within a small surface area, as well as 45% smaller size, in comparison with conventional filters. The parameters of the filter are optimized using in-home AGA code. In the proposed AGA algorithm, the crossover and mutation probabilities are adaptively changed according to the value of individual fitness. Then by utilizing the proposed DGS, a compact S-band lowpass filter with ultra-wide spurious free window is obtained. The proposed filter achieves an insertion loss of 0.8 dB from DC up to 4 GHz and 21 dB rejection in the stopband from 4.3 up to 60 GHz. The fabricated and measured results exhibit good agreement with the simulated results. They demonstrate that combining AGA and DGS yields best possible response for this group of filters.Amir Reza Dastkhosh, Gholamreza Dadashzadeh, and Mohammad Hossein SedaaghiCopyright © 2010 Amir Reza Dastkhosh et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/871027/Radio Frequency (RF) modules have been miniaturized to meet the demand for smaller and more enhanced handsets for wireless applications such as cellular phones. However, area for passive devices used in RF modules has made further miniaturization difficult. Passives embedded in substrates are now being studied intensively. In addition, circuit simulation technology has been developed that enables efficient designing of RF module circuits. Circuit designers, however, have limited database of organic substrates and embedded passives. Further, optimized thermal designs are required to prevent thermal resistance increase due to miniaturization of substrates. In this paper, we describe the high-frequency properties of the capacitors embedded in the organic substrates and present the equivalent circuit models of the embedded capacitors. We also present the thermal design of organic substrates applicable to RF modules.Yusuke Kondo, Yasushi Shimada, Yoshitaka Hirata, Kazunori Yamamoto, Etsuo Watanabe, and Akira KuriyamaCopyright © 2010 Yusuke Kondo et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2009/758783/A novel technique to reduce die area on a discrete-time sinc2↓2 filter for charge sampling is proposed. An SNR comparison of the conventional and the proposed topology reveals that the new technique saves 25% die area occupied by the sampling capacitors of the filter. The idea is also extended to implement higher downsampling factors, and greater percentage of area is saved as the downsampling factor is increased. The proposed filter also has the topological advantage over previously reported works of allowing the designers to use active integration to charge the capacitance, which is critical in obtaining high linearity.Karthik Raviprakash, Mandar Kulkarni, Xi Chen, Sebastian Hoyos, and Brian M. SadlerCopyright © 2009 Karthik Raviprakash et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/980957/A CMOS active inductor with thermal noise cancelling is proposed. The noise of the transistor in the feed-forward stage of the proposed architecture is cancelled by using a feedback stage with a degeneration resistor to reduce the noise contribution to the input. Simulation results using 90 nm CMOS process show that noise reduction by 80% has been achieved. The maximum resonant frequency and the quality factor obtained are 3.8 GHz and 405, respectively. An RF band-pass filter has been designed based on the proposed noise cancelling active inductor. Tuned at 3.46 GHz, the filter features total power consumption of 1.4 mW, low noise figure of 5 dB, and IIP3 of −10.29 dBm.Santosh Vema Krishnamurthy, Kamal El-Sankary, and Ezz El-MasryCopyright © 2010 Santosh Vema Krishnamurthy et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2009/681252/We present the design and construction of Frequency Selective Surface arrays composed of two subarrays of different slot lengths. We investigated their response variations with the variation of slot length differences of the elementary sub-arrays. Such nonhomogeneous arrays cannot be simulated with Computer Aided Design (CAD) programs because the boundary conditions are not fulfilled by the simulator. In infinite array simulation, the periodic boundary conditions are prescribed on the walls of the unit cell, whereas in the case of sub-arrays of unequal slot length such boundary conditions are not applicable. The CAD simulation of such combined array gives incorrect values of amplitude and phase responses. In this work, we investigate the characteristics of such complex arrays by using heuristic experimental approach. The results of the experimental approach demonstrate that the resultant reflection amplitude and phase of such complex array depend on the difference of slot lengths (ΔL) of the two sub-arrays.S. Islam, J. Stiens, G. Poesen, I. Jaeger, W. De Raedt, and R. VounckxCopyright © 2009 S. Islam et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2010/380108/RFIC integration has seen dramatic progress since the early 1990s. For example, Si-based single-chip products for GSM, WLAN, Bluetooth, and DECT applications have become commercially available. However, RF power amplifiers (PAs) and switches tend to remain off-chip in the context of single-chip CMOS/BiCMOS transceiver ICs for handset applications. More recently, several WLAN/Bluetooth vendors have successfully integrated less demanding PAs onto the transceivers. This paper will focus on single-chip RF-system-on-a-chip (i.e., “RF-SoC”) implementations that include a high-power PA. An analysis of all tradeoffs inherent to integrating higher power PAs is provided. The analysis includes the development cost, time-to-market, power efficiency, yield, reliability, and performance issues. Recent design trends on highly integrated CMOS WiFi transceivers in the literature will be briefly reviewed with emphasis on the RF-SoC product design tradeoffs impacted by the choice between integrated versus external PAs.D. Y. C. LieCopyright © 2010 D. Y. C. Lie. All rights reserved.http://www.hindawi.com/journals/ijmst/2009/715641/This paper presents a compact down-conversion oscillator mixer fabricated with a 0.18-μm CMOS technology. The oscillator mixer consists of a conventional nMOS differential coupled oscillator, a switch stage, and a pMOS cross-coupled pair which is used to release the design constraint between the conversion gain and the start-up condition. Since the switch stage and the pMOS cross-coupled pair are stacked on the nMOS differential oscillator, the bias currents of the switch stage and the pMOS cross-coupled pair can be entirely reused, so as to reduce the power dissipation. The experimental results show a conversion gain of 6.5 dB at 2.1 GHz associated with a single-sideband (SSB) noise figure of below 13 dB. The oscillator mixer also exhibits a tuning range of 184 MHz and a phase noise of −116 dBc/Hz at 1-MHz offset from the LO frequency of 6.8 GHz, and it consumes 11 mA from 1.8 V bias voltage.Chin-Lung Yang, Chih-Hsiang Peng, and Yi-Chyun ChiangCopyright © 2009 Chin-Lung Yang et al. All rights reserved.http://www.hindawi.com/journals/ijmst/2009/597592/Analysis and compensation methodology of the AM-AM and AM-PM distortion of cascode class-E power amplifiers are presented. A physical-based model is proposed to illustrate that the nonlinear capacitance and transconductance cause the AM-AM and AM-PM distortion when modulating the supply voltage of the PA. A novel methodology that can reduce the distortion is also proposed. By degenerating common-gate transistor into a resistor, the constant equivalent impedance is obtained so that the AM-AM and AM-PM distortion is compensated. An experimental prototype of 2.6 GHz cascode class-E power amplifier with the AM-AM and AM-PM compensation has been integrated in a 0.18 μm CMOS technology, occupies a total die area of 1.6 mm2. It achieves a drain efficiency of 17.8% and a power-added efficiency of 16.6% while delivering 12 dBm of linear output power and drawing 31 mA from a 1.8 V supply. Finally, a co-simulation result demonstrated that, when the distortion of the PA has been compensated, the EVM is improved from −17 dB to −19 dB with an IEEE802.11a-like signal source.Wen An Tsou, Wen Shen Wuen, Tzu Yi Yang, and Kuei Ann WenCopyright © 2009 Wen An Tsou et al. All rights reserved.