Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 7 Articles
Development of MIMO over-the-air (OTA) test methodology is ongoing. Several test methods have been proposed. Anechoic\r\nchamber-based multiple-probe technique is one promising candidate for MIMO-OTA testing. The required number of probes for\r\nsynthesizing the desired fields inside the multiprobe system is an important issue as it has a large impact on the cost of the test\r\nsystem. In this paper, we review the existing investigations on this important topic and end up presenting rules for the required\r\nnumber of probes as a function of the test zone size in wavelengths for certain chosen uncertainty levels of the field synthesis....
A planar antenna for ultra-wideband (UWB) applications covering the 3.1ââ?¬â??10.6 GHz range has been designed as a test bed for\r\nefficiency measurements of antennas manufactured using polymer conductors. Two types of conductive polymers, PEDOT and\r\nPPy (polypyrrole), with very different thicknesses and conductivities have been selected as conductors for the radiating elements.\r\nA comparison between measured radiation patterns of the conductive polymers and a copper reference antenna allows to estimate\r\nthe conductor losses of the two types of conductive polymers. For a 158 Ã?µm thick PPy polymer, an efficiency of almost 80% can be\r\nobserved over the whole UWB spectrum. For a 7 Ã?µm thick PEDOT layer, an average efficiency of 26.6% demonstrates, considering\r\nthe room for improvement, the potential of this type of versatile materials as flexible printable alternative to conductive metallic\r\npaints. The paper demonstrates that, even though the PEDOT conductivity is an order of magnitude larger than that of PPy, the\r\nthicker PPy layer leads to much higher efficiency over the whole UWB frequency range. This result highlights that high efficiency\r\ncan be achieved not only through high conductivity, but also through a sufficiently thick layer of conductive polymers....
The mathematical absorber reflection suppression (MARS) technique has been used to identify and then suppress the effects\r\nof spurious scattering within spherical, cylindrical, and planar near-field antenna measurement systems, compact antenna test\r\nranges (CATRs), and far-field measurement facilities for some time now. The recent development of a general-purpose threedimensional\r\ncomputational electromagnetic model of a spherical antenna test system has enabled the MARS measurement and\r\npostprocessing technique to be further investigated. This paper provides an overview of the far-field MARS technique and presents\r\nan introduction to the computational electromagnetic range model. Preliminary results of computational electromagnetic range\r\nsimulations that replicate typical MARS measurement configurations are presented and discussed which, for the first time, confirm\r\nthrough simulation many of the observations that have previously been noted using purely empirical techniques....
Three multibranch switch-and-stay combining (MSSC) schemes are analyzed for Rayleigh fading channels, where different\r\ndecision statistics for antenna switching (i.e., switch statistic) are used. Let a and r denote the fading factor and the received\r\nbaseband signal of a diversity branch, respectively. In contrast to the traditional MSSC that uses the faded signal-to-noise ratio\r\n(SNR) of diversity branches as the corresponding switch statistic, to enhance the receiver performance, |r|, |ar|, and a new linear\r\ncombination of a and |r| are used as switch statistics of the three MSSC schemes, respectively. For performance evaluation, the\r\nbit error rate (BER) of BPSK is derived for the three MSSC schemes over both independent-and-identical distributed (i.i.d.) and\r\nindependent-and-nonidentical distributed (i.n.d.) Rayleigh fading channels. To pursue optimal performance, the locally optimal\r\nswitch threshold (ST) of each MSSC scheme is obtained for general i.n.d. fading channels. In addition, the locally optimal ST\r\nbecomes the globally optimal ST for i.i.d. channels. Numerical results based on the analysis and simulations are presented. In\r\ncontrast to the MSSC over i.i.d. fading channels, we will show that the performance of MSSC schemes can be improved by\r\nincreasing the number of branches, if i.n.d. channels are considered....
We analyze theoretical distributions of MIMO channel capacity for different antennas in 2D and 3D statistically isotropic\r\nenvironments, which may be generated by multiprobe anechoic and reverberation chambers, respectively.We observe that the two\r\nenvironments yield comparable capacity distributions provided that (1) the 2D statistically isotropic environment�s capacity data\r\nare taken at many different antenna orientations and (2) the radiation elements have a low directivity. When these conditions are\r\nmet, we find that the relative error between the 2D statistically isotropic environment�s orientation-combined capacity distribution\r\nand the 3D statistically isotropic environment�s capacity distribution is typically less than 10% for signal-to-noise ratios greater\r\nthan 5 dB....
This paper presents software based design and analysis for a ‘C’- shaped slot loaded square microstrip patch antenna for multi band applications. In square patch, ‘C’ shaped slot is etched to provide multi band operation. Another design is also presented which uses two substrates (RT/Duriod and air) to achieve wideband. The designs are analyzed by FEM based HFSS™ v11.1 EM simulator software. The antenna is designed to operate in multiple frequency bands covering ISM bands, L, S and C-Band. Results of proposed antenna structure shows good return loss and VSWR and gain as depicted in graphs. The far-field radiation patterns with E-field distribution have been studied and plotted....
We present the radio channel experiments conducted in indoor scenarios to test the performance of a dual orthogonal polarization\r\nscheme in the single-branch receiver end of a mobile system with a centre frequency of 41.4 GHz and 61.5 GHz. The diversity gain\r\nhas been obtained according to three main combination methods for an outage probability of 1%: signal selection, equal gain\r\ncombining, and maximal ratio combining. Diversity gain calculated ranges from 0.25 to 4.5 dB, depending on the combination\r\ntechnique used, the radiation pattern, the scenario, and the frequency band. The spatial variation of the cross-polar discrimination\r\nfactor (XPD) has been estimated. The XPD ranges from 31 dB to 34 dB at 41.4 GHz and between 26 dB and 29 dB for the 61.5 GHz\r\nband. From the gain and discrimination results, we evaluated the performance of this scheme to conclude its suitability as either\r\na diversity technique for reducing signal fading, as the 41.4 GHz, or as a method for increasing the link capacity in the 61.5 GHz\r\ncase....
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