In this paper, a novel compact dual‐band dual‐polarized microstrip stacked patch antenna suitable for base stations is presented. The first and second frequency bands cover the GSM and DCS bands respectively. The antenna layout consists of a single circular patch with four symmetrical slots along its periphery mainly responsible for the upper frequency band and one cross‐shaped slot at the center, mainly responsible for the lower one. The stacked configuration is considered for bandwidth enhancement. The antenna utilizes a simple orthogonal feed network for the two polarizations, which feeds the patch through a relatively wide cross‐shaped slot at the antenna's ground plane, placed centrally with respect to the patch. The antenna bandwidth completely covers the two desired bands with relatively good return loss and also exhibits polarization isolation of greater than 33 dB and 40 dB in the lower and upper frequency bands respectively. In addition, the antenna has good radiation characteristics in terms of cross‐polarization in both bands of interest. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2557–2559, 2016
This paper presents an efficient method to redesign a horn-fed, double-curvature reflector antenna. It helps reconstruct or repair the reflector according to a correct reference or analyze its radiation characteristics through full-wave electromagnetic simulations. The proposed method mainly consists of five stages. At first, it is necessary to obtain initial data in the form of three-dimensional coordinates of a sufficient number of points sampled from the reflector's different surface areas, especially from its central section curve and its peripheral contour. Then, the best-fitting surface to the sampled points is found using geometrical-optics (GO)-based formulations in an invasive weed optimization (IWO) algorithm. The GO relations extend the reflector laterally using elevation angle, horizontal, or focal point strips. As these are intrinsic formulations for designing doubly-curved reflectors, the fitted surface can resolve the possible defects in the reference reflector's geometry or inaccuracies in the sampled information partly. For this purpose, the reflector's central section curve is estimated by fitting a fifth-degree polynomial curve to the data sampled from it. Also, two kinds of errors, which are based on Euclidean distances, define the optimization algorithm cost function for more reliable surface fitting. In the third stage, the fitted surface's peripheral contour is adjusted to match the outline of the reference reflector using the points sampled from this section. In stage four, the redesigned reflector in the form of a point cloud is converted to a .stl file format for further simulation in a fullwave electromagnetic software. Finally, the similarity between the redesigned and reference reflectors' radiation patterns is examined using a radiation-based cost function in an iterative process, and the previously devised four stages repeat until appropriate results are obtained. In particular, an already designed and fabricated UHF band, doubly-curved reflector antenna, capable of generating a cosecantsquared radiation pattern in the elevation plane and narrow in the azimuth, is redesigned using 99 points sampled from it. It is found that horizontal strips can best fit the reflector with the small normalized error about 3 mm at the end of the IWO algorithm, indicating a nearly perfect geometrical similarity between the redesigned and reference reflectors. For further verification of the suggested method, the redesigned reflector's radiation pattern is simulated in CST simulation software, and the results are compared with the measured radiation pattern of the fabricated reflector and the simulated radiation pattern of the antenna's initial CAD model in the azimuth and elevation planes. Specifically for the redesigned antenna, the amounts of HPBW and sidelobe level in the azimuth plane are about 2.6 • and 29.85 dB, respectively. Also, the amounts of gain, HPBW, and predefined parameters of α and β in the elevation plane are 28.25 dB, 13.5 • , 5.07 dB, and 11.7 • , respectively. All of the measured ...
<p>A series-fed traveling-wave uniform circular array of sequentially rotated slot antennas producing two orbital angular momentum (OAM) modes is presented. The antenna operates at 10190 MHz, is built using a single layer of substrate integrated waveguide technology, and can be readily expanded to create additional modes from a shared aperture. A unique simulation-based step-by-step design procedure is presented, taking practically all functional features of a series-fed array into account. A novel formulation for computing the radiation pattern of an array with variable-polarization elements is also offered. The antenna’s performance is evaluated using simulated, calculated, and measured data, with a significant correlation between the three sets. The first mode is a left-hand circularly polarized (LHCP) antenna, with measured impedance, gain, and axial ratio bandwidth of around 8.2, 5.9, and 3.9 percent, respectively. The second mode, which has a measured impedance bandwidth of roughly 7.9 percent, also features an LHCP radiation pattern around the broadside null. The simulated radiation efficiency for the first and second modes is around 48% and 30%, respectively. Furthermore, the orthogonality bandwidth for two identical antennas placed 28 cm apart in front of each other is around 4.5 percent. The antenna's near-field radiation patterns are also studied.</p>
<p>A series-fed traveling-wave uniform circular array of sequentially rotated slot antennas producing two orbital angular momentum (OAM) modes is presented. The antenna operates at 10190 MHz, is built using a single layer of substrate integrated waveguide technology, and can be readily expanded to create additional modes from a shared aperture. A unique simulation-based step-by-step design procedure is presented, taking practically all functional features of a series-fed array into account. A novel formulation for computing the radiation pattern of an array with variable-polarization elements is also offered. The antenna’s performance is evaluated using simulated, calculated, and measured data, with a significant correlation between the three sets. The first mode is a left-hand circularly polarized (LHCP) antenna, with measured impedance, gain, and axial ratio bandwidth of around 8.2, 5.9, and 3.9 percent, respectively. The second mode, which has a measured impedance bandwidth of roughly 7.9 percent, also features an LHCP radiation pattern around the broadside null. The simulated radiation efficiency for the first and second modes is around 48% and 30%, respectively. Furthermore, the orthogonality bandwidth for two identical antennas placed 28 cm apart in front of each other is around 4.5 percent. The antenna's near-field radiation patterns are also studied.</p>
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