Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 8 Articles
When deploying large antenna arrays in arctic environments, a local measurement system may be necessary in order to ensure\r\ncontrol over the position and phase of the individual antenna elements. In this paper, a method of estimating the position and\r\nphase of each individual antenna element in the presence of mutual coupling is presented. It uses both measurements of the\r\nscattering matrix in the array and measurements of the electric field using a minimum of four probes located in the near field\r\nof the array. Simulations show that the method gives accurate results even in the presence of noise in the measurements. The\r\ngeometry of the probe-array system affects the performance significantly....
Efficient and accurate forward modeling of logging tool responses is essential for data inversion in the log data interpretation\r\nin both real time and postprocessing. With the aggressive advancement of various high-performance computing techniques and\r\ncomputer hardware technology, it is possible to significantly improve the efficiency of the forward modeling. In this paper, we\r\napply OpenMP to parallelize the simulation of triaxial induction logging tools in 1D multilayered anisotropic formation. The\r\nparallel process is explained in detail and numerical examples are presented to demonstrate the effect of the parallel programming.\r\nComparison of the original code and the parallel code shows that the latter is much faster without loss of accuracy, which is very\r\npromising for future real-time inversion....
As part of the typical usage mode, interaction between a handheld receiver antenna and the operator�s RF absorbing body and\r\nnearby objects is known to generate variability in antenna radiation characteristics through blocking and pattern changes. It\r\nis counterintuitive that random variations in blocking can result in diversity gain of practical applicability. This diversity gain\r\nis quantified from a theoretical and experimental perspective. Measurements carried out at 1947.5MHz verify the theoretical\r\npredictions, and a diversity gain of 3.1 dB was measured through antenna blocking and based on the utilized measurement setup.\r\nThe diversity gain can be exploited to enhance signal detectability of handheld receivers based on a single antenna in indoor\r\nmultipath environments....
Aircraft seems to be the last isolated island where the wireless access is still not available. In this paper, we consider the distributed\r\nmultiple-input multiple-output (D-MIMO) system application based on measurements in aircraft cabin. The channel response\r\nmatrices of in-cabin D-MIMO system are collected by using a wideband channel sounder. Channel capacities with optimum\r\ntransmit antenna selections (TASs) are calculated from the measured data at different receiver positions. Then the optimum\r\ncapacity results are compared to those without selection in different transmit SNR. It is shown that the TAS can lead obvious\r\ncapacity gain, especially in the front and back of cabin. The capacity gain represents a decreasing trend with the transmit SNR\r\nincreasing. The optimal transmit antenna subset is closely related to the transmit SNR. With the SNR increasing, more transmit\r\nantennas will be chosen for higher performance. The subset of those transmit antennas near the receiver is a reasonable choice in\r\npractical application of D-MIMO system....
A novel compact MIMO antenna for personal digital assistant (PDA) and pad computer is proposed. The proposed antenna is\r\ncomposed by twomultipatch monopole antennas which are placed 90? apart for orthogonal radiation. To strengthen the isolation,\r\na T-shaped ground branch with proper dimension is used to generate an additional coupling path to lower the mutual coupling\r\n(below -15 dB), especially at GSM850/900 band. The proposed MIMO antenna is fabricated and tested, both the simulated and\r\nthe measured results are presented, and some parametric studies are also demonstrated. In addition, there are some advantages\r\nabout the proposed antenna such as simple structure, easy fabrication, and low cost....
In this paper software based design and analysis has been carried out for a circular patch antenna using different substrate materials. A coaxial probe fed circular microstrip patch antenna operating at C-band (4 to 8 GHz) is analyzed on different substrate materials like Rogers RT/duroid 5880, Rogers RT/duroid 5870, Neltec NX9240, Arlon DiClad 522, Rogers RO4003 and FR4_epoxy. The designs are analyzed by Finite Element Method (FEM) based HFSS™ EM simulator software....
This study proposes a novel 2 Ã?â?? 2 array antenna design with broadband and circularly-polarized (CP) operation. The proposed\r\ndesign uses a simple series-fed network to increase the CP bandwidth without requiring one-by-one adjustment of each array\r\nelement or a complex feed network. Selecting the appropriate spacing between each array element allows the proposed array\r\nantenna to generate CP radiation with a low axial ratio. Experimental results based on a prototype show that this 2 Ã?â?? 2 microstrip\r\narray antenna achieves a wide 3 dB axial ratio bandwidth of more than 10%. Simulated data are also provided to confirm the\r\nmeasured results....
Parallel FDTD method is applied to analyze the electromagnetic problems of the electrically large targets on super computer. It\r\nis well known that the more the number of processors the less computing time consumed. Nevertheless, with the same number\r\nof processors, computing efficiency is affected by the scheme of the MPI virtual topology. Then, the influence of different virtual\r\ntopology schemes on parallel performance of parallel FDTD is studied in detail. The general rules are presented on how to obtain\r\nthe highest efficiency of parallel FDTD algorithm by optimizing MPI virtual topology. To show the validity of the presented\r\nmethod, several numerical results are given in the later part. Various comparisons are made and some useful conclusions are\r\nsummarized....
Loading....