AWR Application Notes

Addressing 5G and MIMO Design with Circuit/ Antenna In-Situ Simulations

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APPLICATION NOTE Addressing 5G and MIMO Design with Circuit/ Antenna In-Situ Simulations with AWR Software Electromagnetic (EM) simulation software is commonly used to simulate antennas with multiple-feed, including phased arrays, stacked radiators with different polarizations, and single apertures with multiple feed points. These types of antennas are popular for communication systems where multiple-in-multiple-out (MIMO) and polarization diversity antenna configurations are being used. Their use is likely to explode with the rollout of 5G wireless systems over the next several years. The beam of multiple-feed antennas is controlled by changing the phase and amplitude of the signals going into the various feeds. An accurate simulation of such a system must account for the interaction that occurs between the antenna elements and the driving feed network. The problem for simulation software is that the antenna and the driving feed network influence each other. The antenna's pattern is changed by setting the input power and relative phasing at its various ports. At the same time, the input impedances at the ports change with the antenna pattern. Since input impedance affects the performance of the nonlinear driving circuit, the changing antenna pattern affects the overall system performance. Design Overview Until now, engineers have been forced to manually simulate the coupled circuit/antenna effects using an iterative process. For example, first the antenna is driven with idealized sources with known phasing at the input ports. The impedance of the ports is then used as the load impedance for the driving circuit. The process is then iterated until convergence is reached. This procedure is awkward and time consuming. Fortunately, there is a faster, more accurate way to attain the final result. The in-situ measurement feature in Cadence ® AWR Design Environment ® software, specifically AWR ® Microwave Office ® circuit design software, enables communication between the circuit and antenna, thus automatically accounting for the coupling between the circuit and the antenna in an easy-to-use framework. The designer identifies the antenna data source, the circuit schematic driving the antenna, and the measurement under consideration; for example, the power radiated over scan angle. This concept is illustrated in this application note using two phased array examples in which the antennas are simulated in AWR AXIEM ® 3D planar and AWR Analyst™ 3D finite-element method (FEM) EM simulators respec- tively.

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