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2012-11-12
PIER
Vol. 133, 591-605, 2013
download: 131
Nonlocal Effects on Surface Enhanced Raman Scattering from Bimetallic Coated Nanoparticles
Yang Huang Lei Gao
We study the surface enhanced Raman scattering (SERS) from bimetallic core-shell nanoparticles by taking into account the nonlocal effect. The Gersten-Nitzan model is applied to investigate SERS from a molecule adsorbed on the nonlocal bimetallic nanoparticle. Numerical results show that there are two enhanced SERS peaks for bimetallic coated nanoparticles, and nonlocal effects will lead to less enhancement and blue-shift of SERS peaks. In addition, unusual resonant electric-field patterns are found in the nonlocal gold core in comparison with those in the local case. Our investigation is helpful for understanding some details of SERS schemes in nano-optics and plasmonics when nonlocal effects are considered.
NONLOCAL EFFECTS ON SURFACE ENHANCED RAMAN SCATTERING FROM BIMETALLIC COATED NANOPARTICLES
2012-11-09
PIER
Vol. 133, 571-590, 2013
download: 144
Hermetic Implantable Antenna Inside Vitreous Humor Simulating Fluid
Hans Permana Qiang Fang Wayne Rowe
Retinal prosthesis system is currently being developed in various places around the world. This system involved data transfer between an implanted antenna inside an eyeball and an external camera that is located just in front of the eyeball. While there are plenty of publications about the stimulating electrodes or the processing unit of the system itself, very limited amount has been published regarding the wireless communication link between the two antennas despite the fact that the electromagnetic wave will propagate through a complex medium in the form of Vitreous Humor. This paper will discuss about the constraints associated with implanting an antenna into an eyeball. An antenna design and simulation was performed with the aid of High Frequency Structure Simulator (HFSS) and its Finite Element Method (FEM) mathematical solver in the operating frequency of 402-405 MHz. The antenna, which was a 4 layer microstrip antenna, was positioned at the centre of a spherical model filled with homogeneous Vitreous Humor material. Antenna performances that include return loss, bandwidth, gain, radiation pattern, and SAR value are analysed and compared against those of other implantable antennas operating in Medical Implant Communication Service (MICS) band. Free space and simulating fluid measurements were also conducted on the fabricated antenna to validate the simulation results. It was concluded that the fabricated antenna was able to produce the similar performance to the simulation results and hence at the same level as the other antennas operating in material with lower dielectric constants and conductivities.
HERMETIC IMPLANTABLE ANTENNA INSIDE VITREOUS HUMOR SIMULATING FLUID
2012-11-08
PIER
Vol. 133, 555-570, 2013
download: 145
Compact and High Isolation Microstrip Diplexer for Broadband and WLAN Application
Hong-Wei Deng Yong-Jiu Zhao Yong Fu Ji Ding Xiao-Jun Zhou
In this paper, a compact and high isolation microstrip diplexer is designed for broadband and wireless local area network (WLAN) application, simultaneously. The bandpass filter (BPF) for broadband channel is formed by three-coupled-line structure and two short stubs with different size loaded in 50 feed lines, and the BPF for WLAN channel consists of two coupling quarter-wavelength resonators (QWR) and one open stub loaded in short parallel-coupling feed structure. Multiple transmission zeros can be generated due to their intrinsic characteristics, so the broadband BPF with sharp skirt and wide upper-stopband performance and the WLAN BPF with sharp roll-off and lower-stopband characteristic can be realized. The tapped stub not only can generate transmission zeros to deepen the stopband, but also can connect other BPF as an its part without deterioration of in-band performance. Hence, a compact microstrip diplexer combines of two BPFs without the extra junction matching network. The mutual loading effect approximately equivalent to a coupled short QWR can also generate new transmission zero at the passband edge to improve the isolation. A microstrip diplexer with the 3 dB fractional bandwidth (FBW) of 80% for broadband channel and 5% for WLAN channel is designed and fabricated. Good agreement between the simulated and measured results is observed.
COMPACT AND HIGH ISOLATION MICROSTRIP DIPLEXER FOR BROADBAND AND WLAN APPLICATION
2012-11-07
PIER
Vol. 133, 535-554, 2013
download: 165
A New Method for Non-Line-of-Sight Vital Sign Monitoring Based on Developed Adaptive Line Enhancer Using Low Centre Frequency UWB Radar
Wen Zhe Li Zhao Li Hao Lv Guohua Lu Yang Zhang Xijing Jing Sheng Li Jianqi Wang
The physiological parameters monitoring of human target are considered to be a meaningful and challenging task in non-line-of-sight (NLOS) scenes such as rescue of trapped survivors in post-disaster. In this paper, a new method based on developed adaptive line enhancer (DALE) is proposed to monitor vital signs via ultra-wideband (UWB) radar with centre frequency of 400 MHz. The validity of this new method is proved by means of two experiments with different positions of human target. The good results demonstrate that this new method can be used for vital sign monitoring including respiration and heartbeat through the obstacle. Furthermore, the motion responses due to respiration and heartbeat in different body positions are also discussed.
A NEW METHOD FOR NON-LINE-OF-SIGHT VITAL SIGN MONITORING BASED ON DEVELOPED ADAPTIVE LINE ENHANCER USING LOW CENTRE FREQUENCY UWB RADAR
2012-11-07
PIER
Vol. 133, 515-534, 2013
download: 278
Critical Review of the Modified Winding Function Theory
Luis Serrano-Iribarnegaray Pedro Cruz-Romero Antonio Gomez-Exposito
The Modified Winding Function Theory (MWFTh), regarded as a very powerful and general theory, has been extensively used for the last 15 years. This paper performs an in-depth review of the mathematical and physical framework on which the MWFTh is based, showing that it is indeed very well suited to analyse machines with small air gaps of arbitrary shape. However, contrary to what is usually stated in the literature, it is also proved that its general formulae fail when applied to large air gaps. This major finding is deduced from two different approaches, both of which are later reinforced by numerical examples. In spite of that, there is an important industrial field (diagnosis techniques of salient-pole synchronous machines eccentricities) in which very good theoretical results are reported by applying the MWFTh to these large air-gap machines. This issue is addressed and clarified in the paper.
CRITICAL REVIEW OF THE MODIFIED WINDING FUNCTION THEORY
2012-11-06
PIER
Vol. 133, 495-513, 2013
download: 201
The Use of a Human Body Model to Determine the Variation of Path Losses in the Human Body Channel in Wireless Capsule Endoscopy
Md. Rubel Basar Mohd Fareq Bin Abd Malek Khairudi Mohd Juni Mohd Iskandar Mohd Saleh Mohd Shaharom Idris Latifah Mohamed Norshafinash Saudin Nur Adyani Mohd Affendi Azuwa Ali
Presently, wireless capsule endoscopy (WCE) is the sole technology for inspecting the human gastrointestinal (GI) tract for diseases painlessly and in a non-invasive way. For the further development of WCE, the main concern is the development of a high-speed telemetry system that is capable of transmitting high-resolution images at a higher frame rate, which is also a concern in the use of conventional endoscopy. A vital task for such a high-speed telemetry system is to be able to determine the path loss and how it varies in a radio channel in order to calculate the proper link budget. The hostile nature of the human body's channel and the complex anatomical structure of the GI tract cause remarkable variations in path loss at different frequencies of the system as well as at capsule locations that have high impacts on the calculation of the link budget. This paper presents the path loss and its variation in terms of system frequency and location of the capsule. Along with the guideline about the optimum system frequency for WCE, we present the difference between the maximum and minimum path loss at different anatomical regions, which is the most important information in the link-margin setup for highly efficient telemetry systems in next-generation capsules. In order to investigate the path loss in the body's channel, a heterogeneous human body model was used, which is more comparable to the human body than a homogenous model. The finite integration technique (FIT) in Computer Simulation Technology's (CST's) Microwave Studio was used in the simulation. The path loss was analyzed in the frequency range of 100 MHz to 2450 MHz. The path loss was found to be saliently lower at frequencies below 900 MHz. The smallest loss was found around the frequency of 450 MHz, where the variation of path loss throughout the GI tract was 29 dB, with a minimum of -9 dB and a maximum of -38 dB. However, at 900 MHz, this variation was observed to be 38 dB, with a minimum of -10 dB and a maximum of -48 dB. For most positions of the capsule, the path loss increased rapidly after 900 MHz, reaching its peak at frequencies in the range of 1800 MHz to 2100 MHz. During examination of the lower esophageal region, the maximum peak observed was -84 dB at a frequency of 1760 MHz. The path loss was comparatively higher during examination of anatomically-complex regions, such as the upper intestine and the lower esophagus as compared to the less complex stomach and upper esophagus areas.
THE USE OF A HUMAN BODY MODEL TO DETERMINE THE VARIATION OF PATH LOSSES IN THE HUMAN BODY CHANNEL IN WIRELESS CAPSULE ENDOSCOPY
2012-11-05
PIER
Vol. 133, 477-493, 2013
download: 190
Wideband Millimeter-Wave Cavity-Backed Bowtie Antenna
Shi-Wei Qu Kung Bo Ng
Although many directive antennas operating in a narrow band of millimeter (mm) waves were reported, e.g., antennas for 60-GHz wireless local area network (WLAN), their wideband counterparts are still unpopular. Cavity-backed antennas (CBAs) are widely developed and reported in microwave frequency bands, but few literatures can be found about mm-wave CBAs in spite that their many properties are quite suitable for mm-wave applications. This paper presents a wideband unidirectional CBA with a bowtie exciter, operating in a frequency band of 40 ~ over 75 GHz, and it is carefully analyzed in terms of influences of all antenna components on radiation patterns, broadside gains, and reflection coefficients. Then, the antenna prototype is built by generic printed circuit board (PCB) technologies, and measurements prove the validity of simulations.
WIDEBAND MILLIMETER-WAVE CAVITY-BACKED BOWTIE ANTENNA
2012-11-03
PIER
Vol. 133, 459-475, 2013
download: 108
Sparse Time-Frequency Representation Based Feature Extraction Method for Landmine Discrimination
Yuming Wang Qian Song Tian Jin Yunfei Shi Xiao-Tao Huang
Low-frequency ultra-wideband synthetic aperture radar is a promising technology for landmine detection. According to the scattering characteristics of body-of-revolution (BOR) along with azimuth angles, a discriminator based on Bayesian decision rule is proposed, which uses sequential features, i.e. double-hump distance. First, the algorithm estimates the target scatterings in all azimuth angles based on regions of interest. Second, sequential aspect features are extracted by sparse time-frequency representation. Third, the distributions of features are obtained by training samples, and then the posterior probability of landmine class is computed as an input to the classifier adopting Mahalanobis distance. The experimental results indicate that the proposed algorithm is effective in BOR target discrimination.
SPARSE TIME-FREQUENCY REPRESENTATION BASED FEATURE EXTRACTION METHOD FOR LANDMINE DISCRIMINATION
2012-11-01
PIER
Vol. 133, 443-458, 2013
download: 236
Design and 3-D Particle-in-Cell Simulation of a 140 GHz Spatial-Harmonic Magnetron
Nasrin Nasr Esfahani Majid Tayarani Klaus Schunemann
Design and 3-D numerical simulation of a 140 GHz spatialharmonic magnetron (SHM) are presented. The effect of geometrical parameters of the side resonators of the anode block on the output power are considered using the results of a theory based on a single harmonic approximation approach. This theory enables the determination of the optimum geometrical parameters of the side resonators. SHM design evaluation is carried out via numerical simulations performed with a 3-D particle-in-cell (PIC) code embedded in CST-Particle Studio. Simulations of the SHM are performed without artificial RF priming and without assuming restrictive assumptions on the mode of operation or on the number of harmonics to be considered. Thus in our simulations the electromagnetic oscillations grow naturally from noise. The results of time evolved electron flow simulations and gradual formation of a single frequency RF oscillation are presented. The presented SHM shows stable operation in the π /2-1-mode at 140 GHz over a range of DC anode voltages extending from 11.3 kV to 11.5 kV and for an axial magnetic flux density equal to 0.79 T. RF Output power of the SHM varies from 2 kW to 11 kW over these voltages with a maximum efficiency of around 6.8%.
DESIGN AND 3-D PARTICLE-IN-CELL SIMULATION OF A 140 GHz SPATIAL-HARMONIC MAGNETRON
2012-11-01
PIER
Vol. 133, 425-441, 2013
download: 131
Investigation on the Scattering from One-Dimensional Nonlinear Fractal Sea Surface by Second-Order Small-Slope Approximation
Gen Luo Min Zhang
In this paper, a one-dimensional nonlinear fractal sea surface model has been established based on the narrow-band Lagrange model, which takes into account the vertical and horizontal skewnesses for the sea surface. By using the method of second-order small-slope approximation (SSA-II), the normalized radar cross section (NRCS) and Doppler spectrum of linear and nonlinear fractal sea surface are calculated. The calculated NRCS of the nonlinear fractal sea surface is larger than the linear surface for backscattering, especially for large incidence angles, which indicates the nonlinear surface has stronger scattering echoes. And the result of nonlinear fractal sea surface is also larger than the linear fractal sea surface for bistatic case, which is characterized as the discrepancies being small near specular direction, while the discrepancies becoming larger as the scattering angles departing from the specular direction. For the Doppler spectrum of sea surface, the nonlinearity of sea surface effects greatly enhances the Doppler shift and the Doppler spectrum bandwidth at large incidence angles, which are attributed the fact that the nonlinear-wave components propagate faster than the linear-wave components and the nonlinear fractal sea surface corrects the phase velocities by adding the horizontal and vertical skewness. And also, all the results can indicate the validity of this nonlinear model.
INVESTIGATION ON THE SCATTERING FROM ONE-DIMENSIONAL NONLINEAR FRACTAL SEA SURFACE BY SECOND-ORDER SMALL-SLOPE APPROXIMATION
2012-11-01
PIER
Vol. 133, 407-424, 2013
download: 131
Discrete Optimization Problems of Linear Array Synthesis by Using Real Number Particle Swarm Optimization
Dong Liu Quanyuan Feng Wei-Bo Wang
It is generally believed genetic algorithm (GA) is superior to particle swarm optimization (PSO) while dealing with the discrete optimization problems. In this paper, a suitable mapping method is adopted and the modified PSO can effectively deal with the discrete optimization problems of line array pattern synthesis. This strategy has been applied in thinned linear array pattern synthesis with minimum sidelobe level, 4-bit digital phase shifter linear array pattern synthesis and unequally spaced thinned array pattern synthesis with minimum sidelobe level. The obtained results are all superior to those in existing literatures with GA, iterative FFT and different versions of binary PSO, that show the effectiveness of this strategy and its potential application to other discrete electromagnetic optimization problems.
DISCRETE OPTIMIZATION PROBLEMS OF LINEAR ARRAY SYNTHESIS BY USING REAL NUMBER PARTICLE SWARM OPTIMIZATION
2012-11-01
PIER
Vol. 133, 391-406, 2013
download: 140
Compact Planar UWB Antenna with Band Notch Characteristics for WLAN and DSRC
Rezaul Azim Mohammad Tariqul Islam
In this paper, a compact ultra-wideband microstrip-fed annular ring antenna with band notch characteristics for wireless local area network (WLAN) and dedicated short-range communication (DSRC) is proposed. The proposed antenna comprises an annular ring patch and a partial ground plane with a rectangular slot. The notched frequency band is achieved by etching a partial annular slot in the lower portion of the ring radiator. The centre frequency and bandwidth of the notched band can be controlled by adjusting the width and position of the annular slot. Measured results show that the proposed antenna achieved an impedance bandwidth of 3-10.6 GHz with a notched frequency band cantered at 5.5 GHz. Compared to the recently reported band-notched UWB antennas, the proposed antenna has a simple configuration to realize the band notch characteristics to mitigate the possible interference between UWB and existing WLAN & DSRC systems. Furthermore, a symmetric radiation patterns, satisfactory gain and good time domain behaviour, except at the notched frequency band, makes the proposed antenna a suitable candidate for practical UWB applications.
COMPACT PLANAR UWB ANTENNA WITH BAND NOTCH CHARACTERISTICS FOR WLAN AND DSRC
2012-10-30
PIER
Vol. 133, 367-390, 2013
download: 119
Effect of Beamforming on Multi-Antenna Two Hop Asymmetric Fading Channels with Fixed Gain Relays
Min Lin Kang An Jian Ouyang Yongming Huang Min Li
In this paper, we investigate the impact of beamforming (BF) on a multi-antenna two hop amplify-and-forward (AF) fixed gain relay network over Rician-Rayleigh and Rayleigh-Rician asymmetric fading channels, respectively. The network consists of a relay with single antenna used to assist the signal transmission from the source to the destination, both of which are equipped with multiple antennas. By using the channel state information (CSI), the maximal output signal-to-noise ratio (SNR) with optimal beamforming is first obtained. Then, the novel analytical expressions for the outage probability (OP), probability density function (PDF) and generalized moments of the maximal output SNR are derived. Moreover, the theoretical formulas of the Ergodic capacity and average symbol error rates (ASERs) with various modulation formats are also developed. To gain further insights, the asymptotic ASERs at high SNR are presented to reveal the diversity order and array gain of the multi-antenna relay network. Finally, computer simulations confirm the validity of the theoretical analysis and indicate the influence of antenna number and Rican factor on the system performance.
EFFECT OF BEAMFORMING ON MULTI-ANTENNA TWO HOP ASYMMETRIC FADING CHANNELS WITH FIXED GAIN RELAYS
2012-10-26
PIER
Vol. 133, 347-366, 2013
download: 135
Optical Fiber Extrinsic Micro-Cavity Scanning Microscopy
Andrea Di Donato Antonio Morini Marco Farina
An extrinsic Fabry-Perot cavity in optical fiber is used to achieve surface imaging at infrared wavelengths. The micro-cavity is realized by approaching a single mode fiber optic with a numerical aperture NA to a sample and it is fed by a low-coherence source. The measurement of the reflected optical intensity provides a map of the sample reflectivity, whereas from the analysis of the reflected spectrum in the time/spatial domain, we disentangle the topography and contrast phase information, in the limit of nearly homogeneous sample with complex permittivity having Im(ε) << Real(ε). The transverse resolution is not defined by the numerical aperture NA of the fiber and consequently by the conventional Rayleigh limit (about 0.6λ/NA), but it is a function of the transverse field behavior of the electromagnetic field inside the micro-cavity. Differently, the resolution in the normal direction is limited mainly by the source bandwidth and demodulation algorithm. The system shows a compact and simple architecture. An analytical model for data interpretation is also introduced.
OPTICAL FIBER EXTRINSIC MICRO-CAVITY SCANNING MICROSCOPY
2012-10-25
PIER
Vol. 133, 331-346, 2013
download: 98
Theoretical Analysis of Sub-Wavelength Light Propagation through the Double-Chain Silver Nanorings
Yuan-Fong Chau Wayne Yang
Surface plasmon resonance effects on a system consisting of the double-chain silver nanorings are numerically investigated by means of the finite element method with three-dimensional calculations. The numerical results for resonant wavelengths corresponding to different light polarizations, pair numbers, illumination wavelengths, charge distribution and the permittivities filled inside the dielectric holes are reported as well. Results show that the double-chain silver nanorings exhibit tunable plasmon resonances in the near field zone that are not observed for the silver nanodisks of the same volume. The resonance wavelength is redshifted as the filling medium in dielectric holes increases, which is attributed to a longer effective optical path. It can be verified that the proposed structure (e.g., twelve pairs or more pairs) is pertinent to the functionality of long range of wave guiding and also show promise for applications in nanooptical devices, sensing, and surface-enhanced spectroscopy, due to their strong and tunable plasmon resonance.
THEORETICAL ANALYSIS OF SUB-WAVELENGTH LIGHT PROPAGATION THROUGH THE DOUBLE-CHAIN SILVER NANORINGS
2012-10-22
PIER
Vol. 133, 309-329, 2013
download: 119
Experimental Demonstration of Pulse Shaping for Time-Domain Microwave Breast Imaging
Adam Santorelli Magdalena Chudzik Evgeny Kirshin Emily Porter Aintzane Lujambio Israel Arnedo Milica Popovic Joshua D. Schwartz
We experimentally demonstrate a low-cost hardware technique for synthesizing a specific electromagnetic pulse shape to improve a time-domain microwave breast imaging system. A synthesized broadband reflector (SBR) filter structure is used to reshape a generic impulse to create an ad-hoc pulse with a specifically chosen frequency spectrum that improves the detection and imaging capabilities of our experimental system. The tailored pulse shape benefits the system by improving the level of signal detection after transmission through the breast and thus permits higher-resolution images. We report on our ability to use this technique to detect the presence of tumours in realistic breast phantoms composed of varying quantities of glandular tissue. Additionally, we provide a set of images based on this experimental data that demonstrates the increased effectiveness of the system using the SBR-shaped pulse in the localisation and identification of the embedded tumour.
EXPERIMENTAL DEMONSTRATION OF PULSE SHAPING FOR TIME-DOMAIN MICROWAVE BREAST IMAGING
2012-10-22
PIER
Vol. 133, 285-307, 2013
download: 117
Three-Dimensional SAR with Fixed Transmitter and Its Scattering Explanation
Jun Shi Ke-Fei Liao Xiao-Ling Zhang
During the experimental data processing, we find that corner reflectors cannot be focused properly using 3-D SAR with a moving transmitter due to the phase reversal phenomenon based on the phase history analysis, i.e. the phases at different observation angles might shift rad, and the echoes cancel, rather than accumulate, to each other. To overcome this defect, 3-D SAR with fixed transmitter is designed. Since the geometry of the transmitter and targets remains unchanged during the observation session, the coherence of echoes is well preserved. The mechanism of 3-D SAR with fixed transmitter can accurately be explained using the Stratton-Chu equation. For perfect conductor, the 3-D image is related to the electric current density. For general dielectric medium, the 3-D image is related to the electric current density, magnetic current density and directional vector of scatterer. Experimental results show that one can focus corner reflectors and cavity-shaped objects by fixing the transmitter, which might fail for the traditional 3-D SAR because of the phase reversal phenomenon.
THREE-DIMENSIONAL SAR WITH FIXED TRANSMITTER AND ITS SCATTERING EXPLANATION
2012-10-22
PIER
Vol. 133, 259-283, 2013
download: 303
Fast GPU-Based Interpolation for SAR Backprojection
Amedeo Capozzoli Claudio Curcio Angelo Liseno
We introduce and discuss a parallel SAR backprojection algorithm using a Non-Uniform FFT (NUFFT) routine implemented on a GPU in CUDA language. The details of a convenient GPU implementation of the NUFFT-based SAR backprojection algorithm, amenable to further generalizations to a multi-GPU architecture, are also given. The performance of the approach is analyzed in terms of accuracy and computational speed by comparisons to a ``standard", parallel version of the backprojection algorithm exploiting FFT+interpolation instead of the NUFFT. Different interpolators have been considered for the latter processing scheme. The NUFFT-based backprojection has proven significantly more accurate than all the compared approach, with a computing time of the same order. An analysis of the computational burden of all the different steps involved in both the considered approaches (i.e., standard and NUFFT backprojections) has been also reported. Experimental results against the Air Force Research Laboratory (AFRL) airborne data delivered under the ``challenge problem for SAR-based Ground Moving Target Identification (GMTI) in urban environments" and collected over circular flight paths are also shown.
FAST GPU-BASED INTERPOLATION FOR SAR BACKPROJECTION
2012-10-19
PIER
Vol. 133, 235-258, 2013
download: 110
The Sparsity-Promoted Solution to the Undersampling Tof-PET Imaging: Numerical Simulations
Dapeng Lao Mark W. Lenox Gamal Akabani
Recently, the limited-angle TOF-PET system has become an active research topic due to the considerable reduction of hardware cost and potential applicability for performing needle biopsy on patients while in the scanner. This undersampling measurement configuration oftentimes suffers from the deteriorated reconstructed images. However, the established theory of Compressed Sampling (CS) provides a potential framework for undertaking this problem, given that the imaged object can be sparse in some transformed domain. In here, we studied using numerical simulations the application of sparsity-promoted framework to TOF-PET imaging for two undersampling configurations. From these simulations, a relationship was obtained between the number of detectors (or the range of angle) and TOF time resolution, which provided an empirical guide of designing a low-cost TOF-PET systems while ensuring good reconstruction quality. Another contribution is the exploration of p-TV regularization, which showed that RMSE (Root of Mean Square Error) and SSIM (Structural Similarity) were optimized when p = 0.5. Several sets of representative numerical experiments were executed to validate the proposed methodology, which demonstrates the promising applicability of undersampling TOF-PET imaging.
THE SPARSITY-PROMOTED SOLUTION TO THE UNDERSAMPLING TOF-PET IMAGING: NUMERICAL SIMULATIONS
2012-10-19
PIER
Vol. 133, 217-234, 2013
download: 142
Reverberation Chamber as a Multivariate Process: FDTD Evaluation of Correlation Matrix and Independent Positions
Gabriele Gradoni Valter Mariani Primiani Franco Moglie
This paper evaluates the mode-stirring efficiency in terms of uncorrelated positions of a mechanical stirrer operating inside a reverberation chamber (RC). The actual RC is simulated and viewed as a multivariate random process: the chamber field is sampled in a lattice of spatial points distributed uniformly over a volume of arbitrary dimensions. By adopting such a grid, the stirrer efficiency is then computed through the correlation matrix, accounting for the residual correlation between stirrer positions. The second-order statistics are calculated averaging over the sampling volume. Results are presented for two stirrers that move in both synchronous and interleaved mode. A comparison with the traditional circular correlation (CC) method, for the determination of the uncorrelated positions, is done showing how CC overestimates stirrer efficiency.
REVERBERATION CHAMBER AS A MULTIVARIATE PROCESS: FDTD EVALUATION OF CORRELATION MATRIX AND INDEPENDENT POSITIONS