PIER | PIER Journals

2013-02-04

PIER

Vol. 136, 765-773, 2013

download: 149

Novel Nested Split-Ring-Resonator (SRR) for Compact Filter Application

Yong Liu Xiaohong Tang Zhong Xun Zhang Xiao Long Huang

In this paper, a novel miniaturized nested split-ring resonator (SRR) structure is proposed. The nested SRR structure incorporates multiple split-ring resonators in a compact nested structure, and has more split gaps than the conventional SRR structure. Compared with conventional SRR, this nested SRR has better performance on miniaturization and high-Q value. To verify good characteristics of the proposed resonator structure, a novel resonator-embedded band-pass filter (BPF), which is constructed by four nested resonators, is designed. This novel BPF is very compact and has good in- and out-band performances. The proposed nested SRR unit cell has size of 0.04λ_g x 0.04λ_g(λ_g is the signal wavelength at the 2.4 GHz central frequency of the pass-band). Its stop-bands are extended 0.5~2 GHz at lower band and 2.7~5.4 GHz at upper band with a rejection level of higher than 20 dB, and its 1-dB pass-band is 2.2~2.55 GHz with 1.8 dB optimized insertion loss. The measured and simulated results are well complied with each other.

NOVEL NESTED SPLIT-RING-RESONATOR (SRR) FOR COMPACT FILTER APPLICATION

2013-02-04

PIER

Vol. 136, 753-764, 2013

doi:10.2528/PIER12122203

download: 122

Coherent Phase Compensation Method Based on Direct IF Sampling in Wideband Radar

Qianqiang Lin Zeng Ping Chen Yue Zhang Jianzhi Lin

In order to eliminate the negative influence of the rotational phase component (RPC) of target prominent scattering centres on the performance of Doppler centroid tracking (DCT) method, a coherent phase compensation method is proposed. The coherence of echo pulses sampled directly in intermediate frequency (IF) is firstly analyzed and proved. Based on the coherence property, the proposed approach improves the translational phase component (TPC) estimation accuracy of DCT. Compared to the modified Doppler centroid tracking (MDCT) algorithm, the proposed method achieves better phase compensation performance with simpler operations. Both the theoretical analysis and experimental results based on the real ISAR data prove the effectiveness and efficiency of the presented strategy.

COHERENT PHASE COMPENSATION METHOD BASED ON DIRECT IF SAMPLING IN WIDEBAND RADAR

2013-02-04

PIER

Vol. 136, 739-751, 2013

doi:10.2528/PIER12122811

download: 129

A New Method for Broadening Bandwidths of Circular Polarized Microstrip Antennas by Using DGS & Parasitic Split-Ring Resonators

Zhao-Bin Deng Wen Jiang Shu-Xi Gong Yun-Xue Xu Yang Zhang

A new method for broadening the impedance and the axial-ratio (AR) bandwidths of circular polarized microstrip antennas (CPMAs) is proposed. It has improved the bandwidths of a reference antenna greatly without enlarging the antenna size or deteriorating circular polarized radiation characteristics by placing four sequentially rotated parasitic split-ring resonators (SRRs) around the patch of the reference antenna and embedding four defeated ground structure (DGS) elements on the ground plane. Improvements of 51.3% and 49.8% in the impedance and the axial-ratio bandwidths of the antenna are achieved in simulation, respectively. The simulated -10dB impedance and 3dB axial-ratio bandwidths of the antenna have been improved from 101.1 MHz (4.12%) to 153.0 MHz (6.26%) and from 25.1 MHz (1.02%) to 37.6 MHz (1.54%).

A NEW METHOD FOR BROADENING BANDWIDTHS OF CIRCULAR POLARIZED MICROSTRIP ANTENNAS BY USING DGS & PARASITIC SPLIT-RING RESONATORS

2013-02-01

PIER

Vol. 136, 725-737, 2013

doi:10.2528/PIER12112013

download: 126

Printed Antenna for Penta-Band WWAN Tablet Computer Application Using Embedded Parallel Resonant Structure

Zhi Chen Yong-Ling Ban Si-Cheng Sun Joshua Le-Wei Li

A compact printed antenna for WWAN tablet computer application is proposed in this article. The designed antenna occupies a small area of 35×12 mm², which is small enough to be incorporated in a tablet computer, and is placed close to the edge of the shielding wall with a distance of 10 mm. The antenna has a simple structure of comprising a long coupling strip and a feeding strip to capacitively excite the long coupling strip. In this scheme, a chip inductor (L = 25 nH) is loaded on one branch of the feeding strip, which can form a parallel resonant structure to enhance the bandwidth of the lower band. As a result, two wide operating bands to cover GSM850/900 and GSM1800/1900/UMTS2100 operation are obtained with desired 3:1 VSWR. The proposed antenna is an all-printing structure with low production cost, which is especially suited for the thin-profile tablet computers.

PRINTED ANTENNA FOR PENTA-BAND WWAN TABLET COMPUTER APPLICATION USING EMBEDDED PARALLEL RESONANT STRUCTURE

2013-02-01

PIER

Vol. 136, 703-724, 2013

doi:10.2528/PIER12122104

download: 130

A Multi-GPU Sources Reconstruction Method for Imaging Applications

Miguel Lopez-Portugues Yuri Alvarez-Lopez Jesus A. Lopez-Fernandez Cebrian Garcia-Gonzalez Rafael Ayestaran Fernando Las Heras Andres

A profile reconstruction method using a surface inverse currents technique implemented on GPU is presented. The method makes use of the internal fields radiated by an equivalent currents distribution retrieved from scattered field information that is collected from multiple incident fields. Its main advantage over other inverse source-based techniques is the use of surface formulation for the inverse problem, which reduces the problem dimensionality thus decreasing the computational cost. In addition, the GPU implementation drastically reduces the calculation time, enabling the development of real time and accurate geometry reconstruction at a low cost.

A MULTI-GPU SOURCES RECONSTRUCTION METHOD FOR IMAGING APPLICATIONS

2013-02-01

PIER

Vol. 136, 681-702, 2013

doi:10.2528/PIER12110808

download: 195

Reflection and Transmission from Biaxially Anisotropic-Isotropic Interfaces

Jennifer W. Graham Jay Kyoon Lee

In this paper we explore electromagnetic behavior of arbitrarily oriented biaxially anisotropic media; specifically with respect to reflection and transmission. The reflection and transmission of electromagnetic waves incident upon half-space and two-layer interfaces are investigated. The waves may be incident from either the isotropic region or the biaxial region. The biaxial medium considered may be aligned with the principal coordinate system or may be arbitrarily oriented. Critical angle and Brewster angle effects are also analyzed.

REFLECTION AND TRANSMISSION FROM BIAXIALLY ANISOTROPIC-ISOTROPIC INTERFACES

2013-02-01

PIER

Vol. 136, 665-679, 2013

doi:10.2528/PIER12122301

download: 225

Robust Superdirective Beamforming for HF Circular Receive Antenna Arrays

Qing-Chen Zhou Huotao Gao Huajun Zhang Fan Wang

Superdirective beamforming can highly reduce the aperture size of high-frequency receive array. At the same time, the closely spaced elements of a small aperture array can make it low efficiency and sensitivity to the array uncertainty, which limit its application in practice. Using a parameter called sensitivity factor, we found that array efficiency and robustness against array error could be considered simultaneously. On that basis, we derive a novel superdirective beamforming criterion based on a constrained sensitivity factor for the HF circular receive array. New method is analytical and computationally inexpensive. Through making the directive gain with a given sensitivity factor maximum, we calculate the optimal weights of the array elements. To illustrate the proposed method can increase the acceptance of HF superdirective receive arrays in practice, several numerical results are provided.

ROBUST SUPERDIRECTIVE BEAMFORMING FOR HF CIRCULAR RECEIVE ANTENNA ARRAYS

2013-01-30

PIER

Vol. 136, 647-664, 2013

doi:10.2528/PIER12121805

download: 285

Magnetic Field Shielding by Metamaterials

Mustafa Boyvat Christian V. Hafner

Magnetic field shielding at low frequencies is a problem of high importance that is known for a long time. Metamaterials, which are known from fancy applications such as the so-called perfect lens and cloaking, also offer a new way to create efficient magnetic shielding by means of anisotropic metamaterials with low permeability in one direction. Such metamaterials can be constructed by assembling arrays of relatively simple LC circuits. In this paper, we analyze different metamaterials and show how they may be designed. We show that typical resistive losses in the coils and capacitors of the LC circuits reduce the shielding quality. Then, we consider the possibility of active electronic loss compensation and discuss the drawbacks of this concept. After this, we propose a purely passive way that benefits from the inhomogeneity of the magnetic field to be shielded. Finally, we present experimental results, which show the performance of metamaterial shields.

MAGNETIC FIELD SHIELDING BY METAMATERIALS

2013-01-28

PIER

Vol. 136, 635-646, 2013

doi:10.2528/PIER12112612

download: 123

The Serial Resonant Antenna for the Large Field of View Magnetic Resonance Imaging

Bo O. Zhu Ed Xuekui Wu Patrick Peng Gao Peng Cao Li Jun Jiang

A serial resonant antenna for the large field of view (FOV) magnetic resonance imaging (MRI) is presented. It consists of metallic patches cascaded through lumped capacitors in serial on the top layer of a grounded dielectric substrate. The theoretical analysis show that at the resonant frequency, uniformly distributed current with zero phase delay is produced independent of the antenna length, hence a uniform magnetic field for large FOV MRI can be achieved. Integrated with the L-shaped tunable matching network, the antenna can be tuned easily to operate rigorously at the working frequency of the MRI system. The numerical modeling, physical fabrication and measurement, as well as the phantom imaging are carried out to design, characterize and verify the performance of the proposed antenna for MRI.

THE SERIAL RESONANT ANTENNA FOR THE LARGE FIELD OF VIEW MAGNETIC RESONANCE IMAGING

2013-01-27

PIER

Vol. 136, 623-634, 2013

doi:10.2528/PIER12122507

download: 144

A CPW-Fed Dual Band-Notched UWB Antenna with a Pair of Bended Dual-L-Shape Parasitic Branches

Xiang Long Liu Ying-Zeng Yin Ping An Liu Jun Hui Wang Bin Xu

In this paper, a novel coplanar waveguide (CPW) fed dual band-notched ultra-wideband (UWB) antenna with circular slotted ground is proposed. In order to achieve two notched bands at 3.3-3.7 GHz for worldwide interoperability for microwave access (WiMAX) and 5.15-5.825 GHz for wireless local area network (WLAN) respectively, a pair of bended dual- L-shape branches are attached to the slotted ground. By optimizing the lengths and positions of the branches, the desired notch-bands of WLAN and WiMAX can be achieved. The prototype of the proposed antenna was fabricated and tested. The simulated and measured results show good agreement over the ultra-wideband. Besides these mechanical features, such as compact in size, easy in fabrication, the proposed antenna also shows good characteristics in its radiation patterns and time-domain behaviors. So it is a nice candidate for modern UWB communication systems.

A CPW-FED DUAL BAND-NOTCHED UWB ANTENNA WITH A PAIR OF BENDED DUAL-L-SHAPE PARASITIC BRANCHES

2013-01-24

PIER

Vol. 136, 607-622, 2013

doi:10.2528/PIER12120313

download: 127

Structure Analysis of Single- and 2 Multi-Frequency Subspace Migrations in 3 Inverse Scattering Problems

Young-Deuk Joh Young Mi Kwon Joo Young Huh Won-Kwang Park

We carefully investigate the structure of single- and multi frequency imaging functions, that are usually employed in inverse scattering problems. Based on patterns of the singular vectors of the Multi-Static Response (MSR) matrix, we establish a relationship between imaging functions and the Bessel function. This relationship indicates certain properties of imaging functions and the reason behind enhancement in the imaging performance by multiple frequencies. Several numerical simulations with a large amount of noisy data are performed in order to support our investigation.

STRUCTURE ANALYSIS OF SINGLE- AND 2 MULTI-FREQUENCY SUBSPACE MIGRATIONS IN 3 INVERSE SCATTERING PROBLEMS

2013-01-23

PIER

Vol. 136, 595-606, 2013

doi:10.2528/PIER12121505

download: 163

A Novel Dual Mode Substrate Integrated Waveguide Filter with Mixed Source-Load Coupling (Mslc)

Ziqiang Xu Yu Shi Congyu Xu Peng Wang

A novel single-cavity dual mode substrate integrated waveguide (SIW) filter with mixed source-load coupling (MSLC) is presented. By using an interdigital slot-line (ISL) to introduce mixed coupling between source and load, the proposed filter with only one cavity could have three transmission zeros which can be controlled flexibly. Under the circumstances, the filter exhibits better frequency selectivity in comparison with conventional dual mode SIW filters. An experimental filter with a center frequency of 10 GHz and a 3 dB fractional bandwidth of 6.0% is designed, fabricated, and measured to validate the proposed structure. Measured results are provided to show good performance and in agreement with the simulated ones.

A NOVEL DUAL MODE SUBSTRATE INTEGRATED WAVEGUIDE FILTER WITH MIXED SOURCE-LOAD COUPLING (MSLC)

2013-01-23

PIER

Vol. 136, 579-594, 2013

doi:10.2528/PIER12123106

download: 164

A Family of Ultra-Thin, Polarization-Insensitive, Multi-Band, Highly Absorbing Metamaterial Structures

Theofano M. Kollatou Alexandros I. Dimitriadis Stylianos Assimonis Nikolaos V. Kantartzis Christos S. Antonopoulos

The systematic design of size-confined, polarization-independent metamaterial absorbers that operate in the microwave regime is presented in this paper. The novel unit cell is additionally implemented to create efficient multi-band and broadband structures by exploiting the scalability property of metamaterials. Numerical simulations along with experimental results from fabricated prototypes verify the highly absorptive performance of the devices, so developed. Moreover, a detailed qualitative and quantitative analysis is provided in order to attain a more intuitive and sound physical interpretation of the underlying absorption mechanism. The assets of the proposed concept, applied to the design of different patterns, appear to be potentially instructive for various EMI/EMC configurations.

A FAMILY OF ULTRA-THIN, POLARIZATION-INSENSITIVE, MULTI-BAND, HIGHLY ABSORBING METAMATERIAL STRUCTURES

2013-01-23

PIER

Vol. 136, 561-578, 2013

doi:10.2528/PIER12122202

download: 129

Design and Analysis of Multichannel Transmission Filter Based on the Single-Negative Photonic Crystal

Chien-Jang Wu Min-Hung Lee Jun-Zhe Jian

In this work, the multiple filtering phenomenon in a photonic crystal made of single-negative (SNG) materials is investigated. We consider a finite photonic crystal (AB)^N immersed in air, in which A, B are epsilon-negative (ENG) and mu-negative (MNG) materials, respectively, and N is the stack number. It is found that such a photonic crystal can function as a multichannel transmission filter with a channel number equal to N-1. The required condition is that the thickness of MNG layer must be larger than that of ENG layer when magnetic plasma frequency is greater than electric plasma frequency. The channel frequencies can be red-shifted as the thickness of MNG layer decreases. The channel positions can be tuned by the incidence angle for both TE and TM polarizations. That is, the peak frequency is blue-shifted when the angle of incidence increases. Additionally, the influence of the static permeability of ENG medium and permittivity of MNG medium is also illustrated. The proposed structure can thus be used to design as a tunable multichannel filter which is of technical use in signal processing.

DESIGN AND ANALYSIS OF MULTICHANNEL TRANSMISSION FILTER BASED ON THE SINGLE-NEGATIVE PHOTONIC CRYSTAL

2013-01-23

PIER

Vol. 136, 543-559, 2013

doi:10.2528/PIER12121104

download: 123

Analysis of Transient Electromagnetic Scattering Using Time Domain Fast Dipole Method

Ji Ding Chang Qing Gu Zhuo Li Zhenyi Niu

In this paper, a new time domain fast dipole method (TDFDM) is proposed for solving time-domain magnetic field integral equations. The proposed scheme is the extension of the frequency domain fast dipole method (FDM) to the time domain. The principle is based on the Taylor series expansion of far fields. The computational complexity of TD-FDM scales as O(N_s^3/2N_t) as opposed to O(N_s²N_t ) for marching-on in-time (MOT) method. Here, N_s is the number of spatial basis functions and N_t is the number of the time steps. Numerical results about the electromagnetic scattering from perfect electric conductor (PEC) objects are given to demonstrate the validity and efficiency of the proposed scheme.

ANALYSIS OF TRANSIENT ELECTROMAGNETIC SCATTERING USING TIME DOMAIN FAST DIPOLE METHOD

2013-01-23

PIER

Vol. 136, 523-542, 2013

doi:10.2528/PIER12110809

download: 191

Range Alignment and Motion Compensation for Missile-Borne Frequency Stepped Chirp Radar

Bo Liu Wenge Chang

One of the difficulties for frequency stepped chirp radar (FSCR) is to resolve the range-Doppler coupling due to relative motion between the radar and the target. Motion compensation is usually adopted to solve the problem in realizing synthetic high range resolution profile (HRRP) for a moving target. For missile-borne FSCR, the range migration of target echo during a coherent processing interval, which is resulted from the high speed motion of missile, is serious and will affect target detection and synthetic high range resolution profile. Therefore, range migration correction and motion compensation are very important for missile-borne FSCR signal processing. In the paper, with the background of terminal guidance anti-ship FSCR seeker, the range alignment is accomplished in frequency domain during the process of real-time digital pulse compression. Then an effective velocity estimation algorithm based on the waveform entropy of the Doppler amplitude spectrum of target echoes is addressed and the velocity estimation accuracy is derived. Finally, the simulation indicates that the new method can estimate the radial velocity accurately and reconstruct the distorted HRRP successfully. In addition, the method has good anti-noise performance and works in the scenario of multi-target with different velocities as well.

RANGE ALIGNMENT AND MOTION COMPENSATION FOR MISSILE-BORNE FREQUENCY STEPPED CHIRP RADAR

2013-01-22

PIER

Vol. 136, 509-521, 2013

doi:10.2528/PIER12112508

download: 147

Second-Order Formulation for the Quasi-Static Field from a Vertical Electric Dipole on a Lossy Half-Space

Mauro Parise

Improved quasi-static expressions are derived for the time-harmonic electromagnetic (EM) field components excited by a vertical electric dipole (VED) lying on the surface of a flat and homogeneous lossy half-space. An analytical procedure is developed that allows to evaluate the complete integral representations for the fields, once the non-oscillating part of the integrand in the expression of the magnetic vector potential is replaced with its quadratic approximation for small values of the free-space wavenumber. The advantage of the proposed second-order quasi-static approximations resides in the possibility of relaxing the assumption of highly conducting half-space. This makes it possible to overcome the limitations implied by the previously published zeroth-order formulation, whose validity is restricted to extremely low frequencies for poorly conducting media. Numerical results are presented to illustrate the reduction of relative percent error arising from using the improved quasi-static field expressions.

SECOND-ORDER FORMULATION FOR THE QUASI-STATIC FIELD FROM A VERTICAL ELECTRIC DIPOLE ON A LOSSY HALF-SPACE

2013-01-22

PIER

Vol. 136, 495-508, 2013

doi:10.2528/PIER12111502

download: 119

Two Dimension Digital Beamforming Preprocessing in Multibeam Scansar

Pingping Huang Wei Xu Weikong Qi

The novel multibeam ScanSAR takes advantage of the displaced phase center multiple azimuth beam (DPCMAB) imaging scheme and intra-pulse beam steering in elevation in ScanSAR to achieve the high-resolution ultra-wide-swath imaging capacity. This letter proposes an innovative two-dimensional (2D) digital beamforming (DBF) space-time preprocessing approach for multibeam ScanSAR. According to echo proprieties of such imaging scheme, both azimuth ambiguity and range ambiguity problems should be resolve before a conventional ScanSAR imaging processor. After range compressing in each receive channel, a 2D DBF processor is carried out in the range-Doppler domain. The azimuth DBF operation is adopted to resolve the azimuth nonuniform sampling problem in multichannel SAR systems, while the DBF preprocessing in elevation is carried out to separate echoes from different subswaths corresponding to different sub-pulses. Imaging results on simulated distributed targets validate the proposed 2D DBF preprocessing approach.

TWO DIMENSION DIGITAL BEAMFORMING PREPROCESSING IN MULTIBEAM SCANSAR

2013-01-21

PIER

Vol. 136, 479-494, 2013

doi:10.2528/PIER12110504

download: 194

On the Efficiency and Gain of Antennas

Anders Karlsson

The fundamental limits of the gain and efficiency of an antenna are explored. These are very important quantities for e.g., superdirective arrays. The antenna is in this paper confined in a sphere and all of the currents are assumed to run in a material with a given conductivity. It is shown that one can find the current distribution in the sphere that optimizes the gain, given the frequency and the radius of the sphere. The results indicate the distribution of antenna elements in an antenna array in order to maximize gain, or efficiency. The analysis is based on the expansion of the electromagnetic fields in terms of vector spherical harmonics. Explicit expressions for the limits of gain and efficiency, and the corresponding current densities, are derived for different types of antennas.

2013-01-21

PIER

Vol. 136, 457-478, 2013

doi:10.2528/PIER12121402

download: 138

Reconstruction of Faulty Cable Network Using Time-Domain Reflectometry

Xiaolong Zhang Minming Zhang Deming Liu

Based on Time-Domain Reflectometry (TDR) technique, a novel method which could locate faults on the coaxial cable distribution network by using Support Vector Machine (SVM) is proposed in this paper. This approach allows the faulty network to be reconstructed by estimating the lengths of branches. A State-transition Matrix model is employed to simulate the TDR response at any port and evaluate the transfer function between two points. SVM is used to solve the inversion problem through training datasets created by the State-transition matrix model. Compared to the existing reflectometry methods, our proposed method can tackle multiple faults in the complex cable networks. Numerical and experimental results pointing out the performance of the SVM model in locating faults are reported.