Current Issue : July - September Volume : 2018 Issue Number : 3 Articles : 6 Articles
Based on the equivalent resonant cavity model, an effective analysis methodology of probe-fed hybrid microstrip antennas is carried\nout in this paper, resulting in a better understanding of the parameter interrelations affecting their behavior. With that, a new design\ncriterion focused on establishing uniform radiation patterns with balanced 3 dB angles is proposed and implemented. Results\nobtained with the proposed model closely matched HFSS simulations. Measurements made on a prototype antenna,\nmanufactured with substrate integrated waveguide (SIW) technology, also showed excellent agreement, thus validating the use\nof the cavity model for predesigning hybrid microstrip antennas in a simple, visible, and time- and cost-effective way....
The proposed MIMO (multiple input multiple output) antenna consist of compact four channel MIMO microstrip\nantennas whose incremental distance of 0.5�» was kept between adjacent patch elements, the four antenna elements were placed\northogonally from each other. The proposed MIMO antenna was operating at 2.6 GHz and 5.1 GHz with -15.2 dB and -20.1 dB\nisolations respectively for S and C radio band applications. The introduction of complimentary octagon split ring slot defected\nground structure (COSRSDGS) integrated with MIMO antenna leads to limits the surface wave between them and reduction of\nmutual coupling by -25 dB and -20 dB with respect to resonating frequencies 2.6 GHz and 5.1 GHz respectively. The system can\ncover a 75.2 MHz and 290 MHz operating bandwidth with total size of 40 x 40 x 1.6 mm3. The simulated and measurement\nresults such as return loss, impedance bandwidth, VSWR (Voltage Standing Wave Ratio), gain, mutual coupling coefficients and\nradiation pattern, envelope correlation coefficient (ECC), diversity gain were identified as having good performance of the MIMO\nantenna....
This work discusses an alternative geometrical optics (GO) technique to synthesize omnidirectional dual-reflector antennas with\nuniform aperture phase distribution together with an arbitrary main-beam direction for the antenna radiation pattern. Sub- and\nmain reflectors are bodies of revolution generated by shaped curves defined by local conic sections consecutively concatenated.\nThe shaping formulation is derived for configurations like ADC (axis-displaced Cassegrain) and ADE (axis-displaced ellipse)\nomnidirectional antennas. As case studies, two configurations fed by a TEM coaxial horn are designed and analyzed by a hybrid\ntechnique based on mode matching and method of moments in order to validate the GO shaping procedure....
E-shaped multiple-input-multiple-output (MIMO) microstrip antenna systems operating in WLAN and WiMAX bands (between\n5 and 7.5 GHz) are proposed with enhanced isolation features. The systems are comprised of two antennas that are placed parallel\nand orthogonal to each other, respectively. According to the simulation results, the operating frequency of the MIMO antenna\nsystem is 6.3 GHz, and mutual coupling is below âË?â??18 dB in a parallel arrangement, whereas they are 6.4 GHz and âË?â??25 dB,\nrespectively, in the orthogonal arrangement. The 2 Ã?â?? 3 matrix of C-shaped resonator (CSR) is proposed and placed between the\nantenna elements over the substrate, to reduce the mutual coupling and enhance the isolation between the antennas. More than\n30 dB isolation between the array elements is achieved at the resonant frequency for both of the configurations. The essential\nparameters of the MIMO array such as mutual coupling, surface current distribution, envelop correlation coefficient (ECC),\ndiversity gain (DG), and the total efficiency have been simulated to verify the reliability and the validity of the MIMO system in\nboth parallel and orthogonal configurations. The experimental results are also provided and compared for the mutual coupling\nwith simulated results. An adequate match between the measured and simulated results is achieved....
An investigation on the improvement of the resolution of a radar target identification system is presented in this paper. Degradation\nof resolution is mainly due to influence factors associated with antennas, including the strong coupling between transmitting and\nreceiving antennas and the variation in the antenna response. A filtering technique was therefore introduced to mitigate the\nunderlying problem. In the technique, the antenna effects were filtered out of the total response backscattered from the objects\nin the radar target identification system. The short-time matrix pencil method (STMPM) was then employed to extract the poles\nfrom the backscattered response in order to identify the object. Simulation and experimentation examples are illustrated to\nconfirm the improvement of the resolution by filtering the antenna effects. The simulation and experimentation were divided\ninto several categories, that is, different antennas and differently shaped objects, in order to validate the advantage of filtering\nthe antenna effects. They were setup in order to demonstrate that the poles obtained from performing the STMPM without the\nfiltering technique were mainly because of the antenna rather than the object�s characteristic. The results showed that the\nresolution of the identification was significantly increased when performing pole extraction and filtering the antenna effects....
Radio and clutter that cover a certain number of range-Doppler-angle cells have a major impact on the detection performance of a\nhigh-frequency surface wave radar (HFSWR) system. Especially for a small-aperture array, the angle spectrums of radio and clutter\nsuffer from severe broadening, so the targets that are more easily submerged in the broadened radio and clutter can be hardly\ndetected. To tackle this issue, this paper proposes an algorithm for radio decontamination and clutter suppression to enable\ndetection of the submerged targets. First, the spatial correlation of the array is derived, and the characteristics of radio and\nclutter are analyzed based on angle-Doppler joint eigenvector. Then owing to the analysis, the information of radio and clutter\nin the main beam can be accurately estimated from that in the auxiliary beams and eliminated by subtracting it. The results of\nsimulations and measured data indicate that the proposed method offers a significant performance improvement and has a\nstrong robustness against the array amplitude-phase errors....
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