AWR Application Notes

AWR Software for the Design of MIMO and Phased Array Antenna Systems 6 www.cadence.com/go/awr Modeling Complex Interactions The mutual coupling between antenna elements affects antenna parameters like terminal impedances and reflection coeffi- cients, and hence, the antenna-array performance in terms of radiation characteristics, output signal-to-interference noise ratio (SINR), and radar cross section (RCS). AWR VSS software includes new capabilities for more accurate simulation of these parameters, including enhanced modeling of element patterns and mutual coupling. The next section of this appli- cation note will examine these recent advances in advanced phased array modeling, including accurate representation of the feed structure. As mentioned, in AWR VSS software, designers can define gains or full radiation patterns for each antenna element in the phased array. This enables them to use different radiation patterns for internal, edge, and corner elements of the phased array (Figure 10). Figure 10: Supports the ability to assign different antenna patterns to individual elements The radiation pattern of each antenna element will likely be affected by its position in the phased array. These patterns may be measured in the lab or calculated in AWR AXIEM or Analyst software. A simple approach to characterizing the appropriate radiation pattern for a given element is to use a 3X3 phased array and excite one element, either the internal element, one of the edge elements, or one of the corner elements, while terminating all others. This will provide the internal, edge, and corner element radiation patterns, which can then be automatically stored in data files using the AWR software output data file measurements (the same technique used in the example above). This approach includes the effect of mutual coupling from first-order neighbors. An array with a larger number of elements may be used to extend mutual coupling to first- and second- order neighbors. It is also important to capture the mutual coupling between neighboring elements. The AWR VSS phased array model does this through a coupling table defined in the configuration file. Different coupling levels can be defined based on distance from each other. The coupling, which is specified in magnitude (dB) and phase (degrees), is defined for two different distances (adjacent side elements: radius c_1 and adjacent corner elements: radius c_2) (Figure 11). Figure 11: 64-element array showing mutual coupling table

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