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Design and Physical Realization of Phased Array Antennas for MIMO/Beam Steering Applications

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Design and Physical Realization of Phased Array Antennas for MIMO/Beam Steering Applications 5 Antenna Elements and Design Parameters Certain antenna properties, such as desired frequency, gain, bandwidth, impedance, and polarization, are used as perfor- mance goals in the design process. Without the support of computer-aided design, antenna designers previously had to rely on textbook recipes and previous projects as the starting point in determining the appropriate materials and structure geometries to achieve a desired behavior. This approach offered little assurance that the final design would provide the optimum electrical performance or minimal size and cost. Furthermore, with next-generation communication and radar appli- cations, performance requirements and antenna compactness/integration have become even more stringent, and therefore more difficult to achieve. With the introduction of AWR AntSyn software as part of the overall suite of AWR software products, engineers can directly specify these performance goals and leverage a powerful genetic optimizer working with fast EM simulation. The software produces antennas that have undergone a more rigorous investigation of design possibilities, resulting in better performing design candidates. AWR AntSyn software was designed by antenna engineers to be used by all levels of experience, from experts to those who are relatively new to the field. The self-guiding templates are intuitive and easy to use, supporting dozens of antenna types ranging from spirals to patch antennas to Yagi and Vivaldi styles. The straightforward design process starts with the creation of a new project and SpecSheet (Figure 4), which enables the user to provide antenna specifications such as frequency band, target impedance match (return loss), gain pattern, and physical constraints and materials (if required). The antenna specifications ultimately impact the attributes of the antenna's physical design. Figure 4: AntSyn SpecSheet for input of antenna requirements, showing popular pre-defined frequency bands for user specification Radiation (gain) patterns, which define the power variations radiating from an antenna as a function of the direction away from the antenna, is another AWR AntSyn antenna specification input. Isotropic patterns are the same in all directions: an isotropic antenna doesn't exist in practice, but the behavior is used in comparison with a real antenna, such as an omnidirec- tional antenna that is isotropic in a single plane. Dipole and slot antennas are examples of omnidirectional antennas. In contrast, directional antennas generally have a single peak direction, where most of the radiated power travels. With AWR AntSyn software, designers enter radiation pattern requirements using the elevation and azimuth angles. 3D radiation requirements are addressed by specifying the pattern requirements for the 2D cut to be optimized (either elevation or azimuth), followed by specification of the angles to which the pattern extends in the other direction. Alternatively, a designer can specify a single gain value at a particular angle or at multiple angles. The designer can also specify whether gain can be exceeded, should be matched exactly, or should not exceed the specified value. Gain and beam width can also be used to define the radiation pattern, where beam width is the total number of degrees that the beam spans with the maximum gain term setting the gain target at the user specified angle, and the gain dropping by a user-specified level (dB) at the edges of the beam. Prior to running a simulation, the specified pattern is plotted on the polar chart to the right of the input field.

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