Current Issue : October - December Volume : 2013 Issue Number : 4 Articles : 7 Articles
A planar-spiral antenna to be used in an ultrawideband (UWB) radar system for heart activity monitoring is presented. ?e antenna,\r\nnamed ââ?¬Å?twin,ââ?¬Â is constituted by two spiral dipoles in a compact structure. ?e re??ection coefficient at the feed point of the dipoles is\r\nlower than -8 dB over the 3ââ?¬â??12 GHz band, while the two-dipoles coupling is about -20 dB. ?e radiated beam is perpendicular to\r\nthe plane of the spiral, so the antenna is wearable and it may be an optimal radiator for a medical UWB radar for heart rate detection.\r\n?e designed antenna has been also used to check some hypotheses about the UWB radar heart activity detection mechanism. ?e\r\nradiation impedance variation, caused by the thorax vibrations associated with heart activity, seems to be the most likely explanation\r\nof the UWB radar operation....
A design method of an ultra-wideband transition from double-sided parallel stripline (DSPSL) to coplanar waveguide (CPW) is\r\nproposed based on analytical expressions of characteristic impedance. ?e conformal mapping is used to obtain the characteristic\r\nimpedance for each section of the transition within 3.7% accuracy as compared with the EM simulation results. An efficient and\r\nclear guideline for the design of the transition is proposed. ?e implemented transition performs less than 0.6 dB insertion loss per\r\ntransition for frequencies from 40 MHz to 12 GHz and less than 1.2 dB insertion loss to 27 GHz, which well exceeds the previous\r\nresults in the literature...
This paper had been comparing the performance of the normal patch antenna with single complimentary SRR patch antenna. Four different shapes of single complimentary.This simulation works had been done with HFSS simulation software .The operating frequency of this antenna is 11.0 GHz for WiMax application. The parameters that considered in works as return loss, input impedance, resonant frequency, gain, radiation pattern and bandwidth. The focusing parameter is to achieve the best gain performance that obtained from the complimentary split ring resonator patch antenna. The addition of square type split ring resonator onto patch antenna will improve the gain from 2.0dB to 2.25 dB....
?e interaction between human head model and electromagnetic ??eld sources is studied. ?e head models are composed of one\r\nand six layers. ?e six layers are skin, fat, bone, dura (the outer membrane of brain and spinal cord), CSF (colony stimulating factor),\r\nand brain. An antenna as a source of exposure is simulated too. ?e E-??eld strength distribution in both one- and six-layer human\r\nmodels is shown to estimate the intensity of E-??eld penetration in human head. Like standard models, the antenna is situated near\r\nthe head model at a distance of 5 mm. ?e local and average SARs (speci??c absorption rates) are simulated at ??00 MHz in both\r\nhuman head models. ?e results are then compared between the two models. ?e HFSS so?ware is used for all the simulations. ?e\r\npaper wants to show that the initial model (one layer) is not a good model, because the real human head tissue is not equivalently\r\nmodeled. It seems that the values of one-layer model are not reliable, so the paper considers the better and more similar human\r\nhead model and compares these two models....
This paper provides an overview of ongoing research in over-the-air (OTA) testing for next-generation communication and data\r\ntransmission devices with special consideration of cognitive radio (CR). Existing state-of-the-art techniques and their merits and\r\nlimitations are discussed. We identify the requirements and issues for the OTA test in a virtual electromagnetic environment\r\n(OTAinVEE) which needs to address the more complex scenario of future networks, where interference emulation becomes a\r\nhighly challenging task. A complex interference scenario arises due to the attempt to simultaneously utilize several opportunity\r\ndimensions such as frequency, time, direction (space), and polarization, in a dynamic manner in a multiuser scenario. Although\r\nMIMO-OTA testing addresses many limitations of single antenna-conducted test systems, more dimensions and parameters to be\r\naddressed in the new scenarios imply further increase in cost and complexity. Closed-loop OTA test setups for CR evaluation are\r\ndiscussed along with an overview of other test scenarios....
This paper presents the design of a novel, small coplanar antenna using microelectromechanical systems (MEMS) and metamaterial (MTM) properties. The antenna is designed using coplanar waveguide (CPW) technology, presenting lower dielectric losses and higher signal integrity. The design method for this MEMS-MTM antenna, herein presented, is based on a composite right/left hand (CRLH) transmission Line (TL) using a mixed approach; considering the circuit model and full-wave simulations. The fabrication process is based on high-resistivity silicon wafers. The radiator has dimensions of 0.017?gÃ?â??0.033?g and a thickness of 0.0116 ?g, whereas the complete circuit, of 5?mm Ã?â?? 11?mm, is equivalent to 0.14?g Ã?â??0.31?g . The antenna is designed using MEMS parallel-plate capacitors as the radiator, which also allows for the reconfiguration of the central frequency by electrostatically varying the capacitance. The results presented here correspond to a central frequency of 8.4?GHz. Due to its small size, this antenna has a wide variety of applications in wireless circuits for different fields....
A novel planar low-profile cavity-backed slot antenna for circularly polarized applications is presented in this paper. The lowprofile\r\nsubstrate integrated waveguide (SIW) cavity is constructed on a single PCB substrate with two metal layers on the top and\r\nthe bottom surfaces and metallized via array through the substrate. The SIW cavity is fed by a SIW transmission line. The two\r\northogonal degenerate cavities resonance TM110 mode are successfully stimulated and separated.The circularly polarized radiation\r\nhas been generated fromthe crossed-slot structure whose two arms� lengths have slight difference Its gain is higher than 5.4 dBi, the\r\npeak cross-polarization level is lower than -22 dB, and themaximum axial ratio (AR) is about -1.5 dB. Compared with the previous\r\npresented low-profile cavity-backed slot antenna work, the spurious radiation from the proposed antenna�s feeding element is very\r\nlow and it has less interference on the following circuits....
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