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2012-02-13 PIER Vol. 124, 511-525, 2012. doi:10.2528/PIER11121903

Frequency-Selective Nanostructured Plasmonic Absorber by Highly Lossy Interface Mode

Yongkang Gong, Kang Li, Jungang Huang, N. J. Copner, Antony Davies, Leiran Wang, and Tao Duan

We report on an existence of a highly lossy interface mode (HLIM) in a designed plasmonic nanostructure for perfect absorption of the incident optical waves. Interactions between the single thin-metallic-layer ($TML$) and slits arrays for excitation of the HLIM in the proposed plasmonic absorber are investigated, and eigenfrequency formula for the HLIM is derived. Analytical and numerical results show that the HLIM is frequency-selective, opens a narrow and steep absorption band in photonic stopband of the slits arrays. Due to the HLIM lossy characteristic, surface plasmon polaritons are significantly trapped at the TML interface with absorption close to 100%.

2012-02-12 PIER Vol. 124, 487-510, 2012. doi:10.2528/PIER11091204

Dosimetry and Temperature Evaluations of a 1800 MHz TEM Cell for in Vitro Exposure with Standing Waves

Jian Zhao, Hongmin Lu, and Jun Deng

A 1800 MHz transverse electromagnetic wave (TEM) cell is introduced for experiments investigating effects on biological samples caused by the exposure from mobile communications. To characterize and quantify the exposure environment in the setup for standardized in vitro experiments, we evaluate the dosimetry and the exposure-induced temperature rise in cultured cells. The study is numerically based on the finite-difference time-domain (FDTD) formulation of the Maxwell equations and the finite-difference formulation of the bioheat transfer equation, with all algorithms and models strictly validated for accuracy. Two sample formations of cells are considered including the cell layer and the cell suspension cultured in the 35 mm Petri dish. The TEM cell is designed to establish standing waves with the maximum E field and the maximum H field, respectively, at the position of the Petri dish. The Petri dish is oriented to E, -E, H, k, and -k directions of the incident field, respectively, to receive the exposure. The specific absorption rate (SAR) is calculated in cells for 10 exposure arrangements combined from the maximum fields and Petri dish orientations. A comparison determines the best arrangement with the highest exposure efficiency and the lowest exposure heterogeneity. The dosimetry and the exposure-induced temperature rise in cells are evaluated for the selected arrangement. To avoid thermal reactions caused by overheating, the maximum temperature rises in cells are recorded during the exposure. Based on the records, the temperature control is performed by setting limits to the exposure duration. We introduce a method to further reduce the exposure heterogeneity and evaluate the influence of the Petri dish holder on the dosimetry and temperature rise. The study compares the TEM cell to the waveguide, as well as the standing wave exposure to the propagating wave exposure. The TEM cell and the selected arrangement of the standing wave exposure improve the exposure quality over the traditional methods, with increased efficiency and decreased heterogeneity of the exposure.

2012-02-08 PIER Vol. 124, 473-486, 2012. doi:10.2528/PIER12011103

Improvement of Iterative Physical Optics Using Previous Information to Guide Initial Guess

Huicheol Chin, Jae-Hyun Yeom, Hyo-Tae Kim, and Kyung-Tae Kim

We propose an improved method of iterative physical optics (IPO) to analyze electromagnetic scattering by open-ended cavities. The traditional IPO method uses a fixed number of iterations; if this number is too small, the accuracy of the estimated monostatic radar cross section (RCS) of open-ended cavities degrades as the incident angle of the incident field increases. The recently-introduced adaptive iterative physical optics-change rate (AIPO-CR) method uses a variable number of iterations; compared to the IPO method, it predicts monostatic RCS more accurately, but requires more computation time. In this paper, a new algorithm is devised to improve both the monostatic RCS prediction accuracy of the IPO method, and the computational efficiency of the AIPO-CR method. The proposed method, iterative physical optics-retained previous solution (IPO-RPS), calculates the currents at one incident angle, then reuses them as the initial currents of iterations for the next incident angle. In simulations of the monostatic RCS for various open-ended cavities, the IPO-RPS method was more accurate than the traditional IPO method, and computationally more efficient than both the IPO and AIPO-CR methods.

2012-02-08 PIER Vol. 124, 457-471, 2012. doi:10.2528/PIER11120707

Coupling Issues Associated with Electromagnetic Vulnerability (Emv) Testing of Vehicles Over Ground

Thomas H. Shumpert, Marsellas L. Waller, Steven H. Wong, and Robert W. Scharstein

Electromagnetic Vulnerability (EMV) testing of ground vehicles and helicopters is (by necessity) performed in the immediate presence of ground surfaces (natural earth, asphalt, concrete, ship decks, and other finitely conducting grounds). The impact of the nature of these grounds on the EM coupling to the various vehicles being tested is the focus of this work. As one approach to addressing these issues quantitatively, personnel at Redstone Test Center Electromagnetic Environmental Effects (RTC/E3) Division have combined measurements on a semi-canonical physical structure along with EM modeling. In particular, a hollow 25 foot long, 4 foot diameter aluminum cylinder with a finite slot (~8 in wide) running along its entire length is positioned over (and near to) a finite conducting ground plane. Measurements of the electric fields produced both in the slot aperture and inside the hollow cylinder by an external log period dipole antenna (LPDA) positioned (broadside to the horizontal cylinder) approximately 5\,m away radiating both vertical and horizontal polarizations, respectively, are presented and discussed. The entire experimental setup (aluminum cylinder, finite aluminum ground plane, and radiating LPDA) are enclosed inside an RF anechoic chamber (inside dimensions between the respective tips of the anechoic pyramids of approximately 19 m х 9.0 m х 5.0 m). A moment method model (CARLOS) is also developed and the fields in the aperture and inside the cylinder are compared to the measured fields.

2012-02-08 PIER Vol. 124, 441-455, 2012. doi:10.2528/PIER12011108

Synthesis of Microwave Resonator Diplexers Using Linear Frequency Transformation and Optimization

Rui Wang, Jun Xu, Mao-Yan Wang, and Yu-Liang Dong

This paper presents a method for synthesizing coupled resonator diplexers composed of TX and RX filters (two types of junctions connecting the TX and RX filters are considered). For the first junction type, the common port is directly coupled to the first resonator of the TX and RX filters, respectively. For the second junction type, common node is realized by adding an extra resonator besides those of the TX and RX filters. The method is based on the evaluation of the characteristic polynomials of the diplexer using the proposed linear frequency transformation and well-established method, and then the "N + 3" coupling matrix of overall diplexer can be obtained using hybrid optimization methods. Two diplexers have been designed and fabricated to validate the proposed method.

2012-02-06 PIER Vol. 124, 425-440, 2012. doi:10.2528/PIER11120517

Design of an Ultra-Wideband Power Divider via the Coarse-Grained Parallel Micro-Genetic Algorithm

Lei Chang, Cheng Liao, Ling-Lu Chen, Wenbin Lin, Xuan Zheng, and Yan-Liang Wu

An ultra-wideband (UWB) power divider is designed in this paper. The UWB performance of this power divider is obtained by using a tapered microstrip line that consists of exponential and elliptic sections. The coarse grained parallel micro-genetic algorithm (PMGA) and CST Microwave Studio are combined to achieve an automated parallel design process. The method is applied to optimize the UWB power divider. The optimized power divider is fabricated and measured. The measured results show relatively low insertion loss, good return loss, and high isolation between the output ports across the whole UWB (3.1-10.6 GHz).

2012-02-04 PIER Vol. 124, 405-423, 2012. doi:10.2528/PIER11112210

Optimal Synthesis of Phase-Only Reconfigurable Linear Sparse Arrays Having Uniform-Amplitude Excitations

Andrea Francesco Morabito, Tommaso Isernia, and Loreto Di Donato

In a large number of applications, including communications from satellites, an optimal exploitation of the available power is of the outmost importance. As a consequence, isophoric array architectures, i.e., arrays using the same power in all the different entry points and achieving the amplifiers' maximum efficiency, are of great interest. At the same time, the easy reconfigurability of the power patterns results fundamental in order to get a full exploitation of the payload. In this paper, an innovative and deterministic approach is proposed for the optimal synthesis of linear phase-only reconfigurable isophoric sparse arrays able to commute their pattern amongst an arbitrary number of radiation modalities. The introduced perspective leads to an effective solution procedure for the fast design of antennas with high performance, and does not recur to computationally expensive global-optimization techniques. Numerical results concerning applications of actual interest and employing realistic element patterns are provided in support of the given theory.

2012-02-04 PIER Vol. 124, 383-404, 2012. doi:10.2528/PIER11122501

Improvement to Performance of Solid-Rotor-Ringed Line-Start Axial-Flux Permanent-Magnet Motor

Amin Mahmoudi, Solmaz Kahourzade, Nasrudin Abd Rahim, and Hew Wooi Ping

This paper presents two design-and-analysis cases of a line-start axial-flux permanent-magnet motor: with solid rotor and with composite rotor. For a novel structure of the motor, two concentric unilevel spaced raised rings are added to the inner and outer radii of its rotors to enable auto-start capability. The composite rotor was coated by a thin (0.05 mm) layer of copper. The basic equations for the solid rotor ring were extracted. The motor's lack of symmetry necessitated 3D time-stepping finite element analysis, conducted via Vector Field Opera 14.0, which evaluated the design parameters and predicted the motor's transient performance. Results of the FEA show the composite rotor significantly improving both starting torque and synchronization capability over solid rotor.

2012-02-04 PIER Vol. 124, 365-381, 2012. doi:10.2528/PIER11122010

A New Tri-Band Bandpass Filter for GSM, WiMAX and Ultra-Wideband Responses by Using Asymmetric Stepped Impedance Resonators

Wei-Yu Chen, Min-Hang Weng, Shoou-Jinn Chang, Hon Kuan, and Yi-Hsin Su

In this paper, a design of new tri-band bandpass filter for the application of GSM (1.8 GHz), WiMAX (2.7 GHz) and UWB (3.3-4.8 GHz) is proposed. The first two narrow passbands are created, and the bandwidth of the third passband can be tuned by properly selecting the impedance ratio (R) and physical length ratio (u) of the asymmetric stepped-impedance resonator. To improve passband performance and form the UWB passband, a U-shape defected ground structure and extra extended coupling lines are integrated with the asymmetric SIR. Due to the three transmission zeros appearing near the passband edges, the band selectivity of the proposed filter is much improved. The filter was fabricated, and the measured results have a good agreement with the full-wave simulated ones.

2012-02-02 PIER Vol. 124, 347-364, 2012. doi:10.2528/PIER11112501

Analysis of Electromagnetic Behavior in Switched Reluctance Motor for the Application of Integrated Air Conditioner on-Board Charger System

Jianing Liang, Linni Jian, Guo Xu, and Ziyun Shao

In order to achieve low cost and compact design, it becomes more and more popular to integrate the circuit of the on-board charger into other power electronic circuits existing in EVs. In this paper an integrated air conditioner on-board charger system based on switched reluctance motor (SRM) was proposed, and the electromagnetic behavior occurring in the SRM when working in the charging mode was investigated. Three charging patterns, viz. single-phase charging, double-phase charging and triple-phase charging were analyzed. The specific rotor positions for which the rotor can be kept still when injecting charging currents to the armature windings were identified. The optimal design for maximizing the keeping-still capability was conducted. The power losses occurring in the SRM when working in charging mode were estimated.

2012-01-30 PIER Vol. 124, 331-345, 2012. doi:10.2528/PIER11112312

Characteristics of Guided Modes in Uniaxial Chiral Circular Waveguides

Jian-Feng Dong and Jie Li

The characteristics of guided modes in the circular waveguide consist of uniaxial chiral medium have been investigated. The characteristic equation of guided modes is derived. The dispersion curves and energy flux of guided modes for three kinds of uniaxial chiral media are presented. Unusual dispersion characteristics and negative energy flux are found, i.e., backward wave is supported in the uniaxial chiral waveguide.

2012-01-30 PIER Vol. 124, 315-329, 2012. doi:10.2528/PIER11122307

Hydrostatic Pressure Sensor Based on a Gold-Coated Fiber Modal Interferometer Using Lateral Offset Splicing of Single Mode Fiber

Daru Chen and Xin Cheng

A novel hydrostatic pressure sensor based on a gold-coated fiber modal interferometer (FMI) is proposed and demonstrated. Two single mode fibers (SMFs) are spliced with a lateral offset which forms a single-end FMI. The single-end FMI is gold-coated to enhance the reflectivity and to avoid the influence of any unwanted light from getting into the sensor. Relative reflection spectra of the proposed FMIs with different sensing SMF lengths or different lateral offsets are experimentally investigated. A high hydrostatic pressure sensor test system is proposed for the testing of the proposed FMI pressure sensor. The performance of a gold-coated FMI pressure sensor based on a 12-mm sensing SMF has been experimentally investigated. The proposed pressure sensor has a sensing range from 0 to 42 MPa and a sensitivity of 53 pm/MPa.

2012-01-27 PIER Vol. 124, 301-314, 2012. doi:10.2528/PIER11112605

Design of a Terahertz Polarization Rotator Based on a Periodic Sequence of Chiral-Metamaterial and Dielectric Slabs

Cumali Sabah and Hartmut G. Roskos

The lack of wave-plates for the terahertz region opens the way for novel components/devices enabling polarization control at these frequencies. With the aid of chiral metamaterials - a new class of metamaterials - novel possibilities for the fabrication of multilayer structures for the realization of polarization rotators emerge. In this study, we present design and analysis of a polarization rotator for the terahertz frequency regime based on a multilayer structure consisting of an alternating sequence of chiral-metamaterial- and dielectric-plates. The combination of chiral constituents with dielectrics permits optimization of the spectral-filter and polarization-rotation features. We can generate either polarization-rotation combs or narrow rotation bands with very good and broad sideband suppression, of interest for example for data transmission or sensing purposes.

2012-01-25 PIER Vol. 124, 285-299, 2012. doi:10.2528/PIER11110805

A Multi-Beam and Multi-Range Radar with FMCW and Digital Beam Forming for Automotive Applications

Seong-Hee Jeong, Han-Yeol Yu, Jae-Eun Lee, Jun-Nam Oh, and Kwae-Hi Lee

In this paper, we propose a multi-beam and multi-range (MBMR) radar with frequency modulated continuous wave (FMCW) waveform and digital beam forming (DBF) algorithm to cover a detection area of long range and narrow angle (150 m, ±10°) as well as short range and wide angle (60 m, ±30°) as a single 24 GHz sensor. The developed radar is highly integrated with multiple phased-array antennas, a two-channel transmitter and a four-channel receiver using K-band GaAs RF ICs, and back-end processing board with subspace-based DBF algorithm. The proposed 24 GHz MBMR radar can be used for an adaptive cruise control (ACC) stop-and-go system which typically consists of three radars, such as two 24 GHz short-range radars for object detection in an adjacent lane and one 77 GHz long-range radar for object detection in the center lane.

2012-01-22 PIER Vol. 124, 265-283, 2012. doi:10.2528/PIER11120515

Detuning Study of Implantable Antennas Inside the Human Body

Neus Vidal, Sergio Curto, José Mª Lopez-Villegas, Javier Sieiro, and Francisco Manuel Ramos

This study quantifies the detuning and impedance mismatch of antennas implanted inside the human body. Maximum frequency shifts caused by variations in the electrical properties of body tissues and different anatomical distributions were derived. The results are relevant to the design of implantable antennas. They indicate the bandwidth enhancement and initial tuning necessary for correct functioning. The study was carried out using electromagnetic modeling based on the finite-difference time-domain method and high-resolution anatomical models. Four anatomical computer models of two adults and two children were used. The implanted antennas operated in the Medical Implant Communication Service band. The most important detuning and impedance mismatch was found for subcutaneous locations and in areas where a layer of fat tissue was present. The maximum frequency shift towards higher frequencies was 70 MHz. The frequency shift did not occur symmetrically around 403 MHz, but was shifted towards higher frequencies.

2012-01-21 PIER Vol. 124, 249-263, 2012. doi:10.2528/PIER11112303

Improved CRLH-TL with Arbitrary Characteristic Impedance and its Application in Hybrid Ring Design

Xianqi Lin, Peng Su, Yong Fan, and Zhong Bo Zhu

An improved designable composite right/left-handed transmission line (CRLH-TL) is presented in this paper, whose operating frequency-band and transmission characteristics can be tuned, respectively, by three structure variables. The equivalent characteristic impedance is studied carefully, and CRLH-TLs with arbitrary characteristic impedances are obtained. Some useful empirical formulae are derived for engineering application. Then, a sample of 50-Ω CRLH-TL, which can be used directly as a wide-band filter, is fabricated with the center frequency of 2.8 GHz. The measured results show that a relative 3-dB bandwidth of 74.6% is achieved, in good agreement with the simulated results. Moreover, the phase-frequency responses of our proposed CRLH-TLs are discussed in detail. A novel hybrid ring is then proposed, where 70-Ω CRLH-TL is used. At the center frequency of 5.8 GHz, equal power dividing is achieved with return loss and isolation more than 20 dB and 30 dB, respectively. The sample is finally fabricated and good agreements among theoretical analysis, simulated results, and measured results are obtained.

2012-01-20 PIER Vol. 124, 233-247, 2012. doi:10.2528/PIER11121808

Coupling Effect of Split Ring Resonator and its Mirror Image

Fuli Zhang, Qian Zhao, Jingbo Sun, Ji Zhou, and Didier Lippens

We report on experimental and numerical studies on the coupling effect of a single split ring resonator (SRR) and its mirror image inside an X-band hollow waveguide. It is shown that, for single SRR with gap bearing side perpendicular to $E$ field, the magnetic resonance exhibits red/blue shift as SRR moves to the gap facing/backing waveguide edge, due to the capacitance and magnetic dipoles coupling effect between original SRR and its mirror image, respectively. Furthermore, electric dipole interplay dominates the coupling effect between SRR and its image when SRR has the gap bearing side parallel to the E field, although SRR is excited by E and H field simultaneously.

2012-01-19 PIER Vol. 124, 211-231, 2012. doi:10.2528/PIER11120511

HF-Band Wireless Power Transfer System: Concept, Issues, and Design

Byung-Jun Jang, Seongjoo Lee, and Hyungoo Yoon

High-frequency (HF) band wireless power transfer systems offer the promise of cutting the last cord, allowing users to seamlessly recharge mobile devices as easily as wireless communication. Yet there are still many technical issues that need to be overcome. Among them, one of the most difficult problems is maintaining impedance match over a short range, where the distance between a transmitter and receiver could vary. In this paper, the effect of impedance mismatch of a HF-band wireless power transfer system is carefully investigated and two compensation methods are suggested to overcome this within a short range, where frequent impedance mismatch can occur. Each method has pros and cons. In order to verify the feasibility of the proposed methods, HF-band wireless power transfer systems, with a pair of rectangular loop resonators, were designed. The efficiency and input impedance variation were simulated and measured. From these results, proposed methods show enhanced efficiency performance than a typical wireless power transfer system without any compensation circuits.

2012-01-19 PIER Vol. 124, 187-210, 2012. doi:10.2528/PIER11112105

On Body Concealed Weapon Detection Using a Phased Antenna Array

Stuart William Harmer, Shawn Edward Cole, Nicholas John Bowring, Nacer Ddine Rezgui, and David Andrews

The detection and identification of metal items and, in particular weapons, of linear size ≥10 cm, concealed upon the human body, is demonstrated as being entirely feasible by using a phased array of suitably ultra wide band transceivers. The complex natural resonances and especially the fundamental resonance, are excited by ultra wide band, stepped frequency continuous wave illumination of the target, using a phased array of antennae to focus the radiation. Broadband illumination of the target with microwave radiation of suitable frequency range (Typically 0.3-3 GHz for handgun sized objects) excites low order complex natural resonances and the late time response of the concealed item can be spatially located using phased array imaging techniques. Further processing of the late time response enables classification of the concealed object, based on the complex natural resonant frequencies of the object, so that threat items such as handguns and knives can be differentiated from benign items such as mobile phone handsets and cameras.

2012-01-19 PIER Vol. 124, 163-186, 2012. doi:10.2528/PIER11111102

Nonlinear Modeling of Trapping and Thermal Effects on GaAs and GaN Mesfet/HEMT Devices

Mohamed Chaibi, Tomas Fernandez, Asmae Mimouni, José Rodriguez-Tellez, Antonio Tazón, and Angel Mediavilla Sanchez

A novel nonlinear model for MESFET/HEMT devices is presented. The model can be applied to low power (GaAs) and high power (GaN) devices with equal success. The model provides accurate simulation of the static (DC) and dynamic (Pulsed) I-V characteristics of the device over a wide bias and ambient temperature range (from -70ºC to +70ºC) without the need of an additional electro-thermal sub-circuit. This is an important issue in high power GaN HEMT devices where self-heating and current collapse due to traps is a more serious problem. The parameter extraction strategy of the new model is simple to implement. The robustness of the model when performing harmonic balance simulation makes it suitable for RF and microwave designers. Experimental results presented demonstrate the accuracy of the model when simulating both the small-signal and large-signal behavior of the device over a wide range of frequency, bias and ambient temperature operating points. The model described has been implemented in the Advanced Design System (ADS) simulator to validate the proposed approach without convergence problems.

2012-01-18 PIER Vol. 124, 151-162, 2012. doi:10.2528/PIER11121402

Proposal of Cylindrical Rolled-Up Metamaterial Lenses for Magnetic Resonance Imaging Application and Preliminary Experimental Demonstration

Yihong Xie, Jianfeng Jiang, and Sailing He

In this paper, we propose a cylindrical rolled-up negative permeability metamaterial (MM) lens for magnetic resonance imaging (MRI), and some analyses are given. The proposed cylindrical MM lens is fabricated by rolling a MM slab (constituted with capacitive-loaded copper split rings) into a tube that resembles a hollow ring. It can focus the field of a magnetic line source, which can increase the penetration depth and improve the sensitivity of a surface coil. The proposed cylindrical MM lens can also improve the discrimination of the signals coming from two independent sources. A clinical experiment is carried out in a General Electric Signa 1.5 T MRI system in order to verify the focusing ability of the proposed device.

2012-01-17 PIER Vol. 124, 137-150, 2012. doi:10.2528/PIER11120202

Improved Antenna Array Adaptive Beamforming with Low Side Lobe Level Using a Novel Adaptive Invasive Weed Optimization Method

Zaharias D. Zaharis, Christos Skeberis, and Thomas Xenos

An improved adaptive beamforming technique of antenna arrays is introduced. The technique is implemented by using a novel Invasive Weed Optimization (IWO) variant called Adaptive Dispersion Invasive Weed Optimization (ADIWO) where the seeds produced by a weed are dispersed in the search space with standard deviation specified by the fitness value of the weed. The adaptive seed dispersion makes the ADIWO converge faster than the conventional IWO. This behavior is verified by applying both the ADIWO and the conventional IWO on well-known test functions. The ADIWO method is utilized here as an adaptive beamformer that makes a uniform linear antenna array steer the main lobe towards the direction of arrival (DoA) of a desired signal, form nulls towards the respective DoA of several interference signals and achieve low side lobe level (SLL). The proposed ADIWO based beamformer is compared to a Particle Swarm Optimization (PSO) based beamformer and a well known beamforming method called Minimum Variance Distortionless Response (MVDR). Several cases have been studied with different number of interference signals and different power level of additive zero-mean Gaussian noise. The results show that the ADIWO provides sufficient steering ability regarding the main lobe and the nulls, works faster than the PSO and achieves better SLL than the PSO and MVDR.

2012-01-16 PIER Vol. 124, 119-135, 2012. doi:10.2528/PIER11112301

Design Analysis of New Metamaterial for EM Absorption Reduction

Mohammad Rashed Iqbal Faruque, Mohammad Tariqul Islam, and Norbahiah Misran

A new triangular metamaterials (TMMs) is designed for electromagnetic (EM) absorption reduction at microwave frequencies in this paper. The reduction of EM absorption with a new TMMs attachment is investigated in this research. The finite-difference time-domain method with lossy-Drude model is adopted in this investigation. The method of EM reduction is presented and the effects of position, distance, and size of metamaterials are analyzed. TMMs have achieved a 1.0923 W/kg for SAR 1 gm which is 45.44% reduction of the initial SAR value for the case of 1 gm SAR.

2012-01-12 PIER Vol. 124, 101-118, 2012. doi:10.2528/PIER11111601

The Interferometry Phase of InSAR Coherent Jamming with Arbitrary Waveform Modulation

Qingfu Liu, Shiqi Xing, Xuesong Wang, Jian Dong, Dahai Dai, and Yongzhen Li

This paper focuses on the interferometry phase of an active coherent jamming in InSAR (Interferometry Synthetic Aperture Radar) images. Based on the signal models of coherent jammer, the jamming's imaging results are derived by employing the Omega-K algorithm. By comparing the imaging results of InSAR's two channels, the jamming's interferometry phases for both working modes, the single-pass and repeat-pass modes, are proved to be constants. And the values of the interferometry phases are determined by the jammer's geometry position relative to InSAR baseline, but independent of the jamming's waveform modulation and its background terrain.

2012-01-12 PIER Vol. 124, 85-100, 2012. doi:10.2528/PIER11121203

Hybrid-Surrogate-Model-Based Efficient Global Optimization for High-Dimensional Antenna Design

Ling-Lu Chen, Cheng Liao, Wenbin Lin, Lei Chang, and Xuan-Ming Zhong

Efficient global optimization has been extensively used in problems with expensive cost functions. However, this method is not suitable for high-dimensional problems. In this paper, the radial basis function network is introduced into the efficient global optimization, to avoid local optima and achieve a fast convergence for high-dimensional optimization. Our algorithm is applied to a 12-dimensional optimization of a transmitting antenna. Compared to the genetic-algorithm-based efficient global optimization and the differential evolution strategy, our algorithm converges to the global optimal value more efficiently.

2012-01-12 PIER Vol. 124, 71-83, 2012. doi:10.2528/PIER11110904

Design Analysis of a Beam Splitter Based on the Frustrated Total Internal Reflection

Jia-Ren Chang Chien, Chi-Chung Liu, Chien-Jang Wu, Pei Yu Wu, and Chang Ching Li

In this work, a theoretical analysis on the design of the beam splitter (BS) based on the frustrated total internal reflection (FTIR) is made. We consider a model structure made of a low-index gap layer bounded by two high-index layers. In the design of a 50/50 BS, we find that there exists a critical gap thickness which is a decreasing function of the angle of incidence for both TE and TM waves. There also exists a critical wavelength for the incident wave, and it increases with increasing angle of incidence. Finally, at a fixed gap thickness and wavelength of incident wave, the critical angle in $TE$ wave is slightly larger than that of $TM$ wave. The analysis provides some fundamental information that is of particular use to the design of a BS within the framework of FTIR.

2012-01-11 PIER Vol. 124, 55-70, 2012. doi:10.2528/PIER11121312

A Novel Wideband Antenna Array with Tightly Coupled Octagonal Ring Elements

Yikai Chen, Shiwen Yang, and Zai-Ping Nie

A novel phased array antenna with wide bandwidth and wide scan angle is presented. The radiating aperture of the phased array consists of periodically and closely spaced octagonal ring elements. Tight capacitive coupling between adjacent elements is realized by interdigitating the end portions of the ring elements. To improve the impedance matching of the individual antenna elements over wide frequency band, a novel impedance matching layer consists of periodic octagonal ring element is subtly designed and placed over the radiating aperture. Both of the radiating elements and impedance matching layer are printed on a flexible membrane substrate with a thickness of 0.04 mm. Measured results of a 16-element linear array demonstrate that good impedance matching over a 4.4:1 bandwidth can be obtained for beam scan angles within ±45° from broadside. As compared to conventional wideband phased array such as tapered slot antenna array, the proposed phased array has the features such as low cost, low profile, light weight, and ease of fabrication.

2012-01-11 PIER Vol. 124, 35-53, 2012. doi:10.2528/PIER11112406

Modified Wavenumber Domain Algorithm for Three-Dimensional Millimeter-Wave Imaging

Shiyong Li, Bailing Ren, Hou-Jun Sun, Weidong Hu, and Xin Lv

Millimeter-wave (MMW) imaging techniques have been used for the detection of concealed weapons and contraband carried on personnel at airports and other secure locations. The combination of frequency-modulated continuous-wave (FMCW) technology and MMW imaging techniques should lead to compact, light-weight, and low-cost systems which are especially suitable for security and detection application. However, the long signal duration time leads to the failure of the conventional stop-and-go approximation of the pulsed system. Therefore, the motion within the signal duration time needs to be taken into account. Analytical three-dimensional(3-D) backscattered signal model, without using the stop-and-go approximation, is developed in this paper. Then, a wavenumber domain algorithm, with motion compensation, is presented. In addition, conventional wavenumber domain methods use Stolt interpolation to obtain uniform wavenumber samples and compute the fast Fourier transform (FFT). This paper uses the 3-D nonuniform fast Fourier transform (NUFFT) instead of the Stolt interpolation and FFT. The NUFFT-based method is much faster than the Stolt interpolation-based method. Finally, point target simulations are performed to verify the algorithm.

2012-01-10 PIER Vol. 124, 17-34, 2012. doi:10.2528/PIER11111407

Design of Dual-Band Bandpass Filters with Controllable Bandwidths Using New Mapping Function

Girdhari Chaudhary, Yongchae Jeong, Kwisoo Kim, and Dal Ahn

In this paper, a novel design method for a dual-band bandpass filter (BPF) with arbitrary controllable bandwidths based on a simple frequency mapping function is proposed and its analytical design equations are also derived. The circuit conversion techniques are employed for implementation with distributed transmission line. To validate the proposed dual-band BPF with controllable bandwidths, a low temperature co-fired ceramic (LTCC) transmission line as well as microstrip lines are used, respectively. The two types of design for the dual-band BPF have the same and significantly different fractional bandwidths (FBWs), respectively. The first type of dual-band BPF with same FBWs are implemented at 2.11-2.17 and 3.45-3.55 GHz. The second type of dual-band BPF with different FBWs are implemented at 3.40-3.60 and 5.15-5.25 GHz. The measured and theoretical results show good agreement, significantly validating the proposed frequency mapping function methodology.

2012-01-09 PIER Vol. 124, 1-15, 2012. doi:10.2528/PIER11120103

Dual-Wideband Bandpass Filters with Extended Stopband Based on Coupled-Line and Coupled Three-Line Resonators

Jen-Tsai Kuo, Chun-Yu Fan, and Shao-Chan Tang

Coupled-line and coupled three-line resonators are proposed to design dual-wideband bandpass filters. Compared with the shorted and open stubs shunt at the same locations of the main line, in addition to saving the circuit area, these resonators provide alternative ways to the design of dual-wideband filters, with larger possible bandwidths and different frequency ratio of the two center passbands. The geometric parameters of the coupled-line and the coupled three-line structures are determined by deriving their equivalent circuits to a shunt open stub in parallel connection with a shunt shorted stub. To extend the upper stopband, a cross-shaped admittance inverter is devised to play the role of the 90-degree transmission line section at the center frequency and to create transmission zeros at the spurious passbands, so that the upper stopband of the filter can be extended. It is a quarter-wave section with two open stubs of unequal lengths shunt at its center. For demonstration, two dual-wideband bandpass filters operating at 900/1575 MHz and 900/2000 MHz are fabricated and measured. Measured results of the experimental circuits show good agreement with simulated responses.