AWR White Papers

Radar Systems

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MIMO/Phased-Array Antenna Systems Phased-array antennas are becoming popular for a variety of applications such as automotive driver assist systems, satellite communications, advanced radar, and more. The complexity and cost issues involved in developing communications systems based on phased-array antennas are being addressed through new functionalities in EDA software that support designers with the means to develop new system architectures and component specifications, as well as implement the physical design of individual components and verify performance prior to prototyping. This application note discusses these trends and presents recent advances in EDA tools for phased-array-based systems. Design Management and EDA Tools While actively-steered phased-array antennas have many advantages, they are extremely complex, and their production, especially non-recurring development costs, is significantly higher than for conventional antenna design. As the industry shifts toward highly-integrated phased-array systems, it is critical for in-house systems expertise to work closely with hardware developers, with both fully exploring the capabilities and tradeoffs among possible architectures and integration technologies. In addition, a start-to-finish design flow made possible with EDA software has become critical in moving beyond the initial system simulation, which is focused on early architecture definition, to the development of link budgets and component specifications. A preferred phased-array system design flow manages the start-to-finish front-end development, embedding RF/microwave circuit simulation and/or measured data of radio/signal-processing (behavioral) models within a phased-array system hierarchy. Such software enables the system designer to select the optimum solution, ranging from hybrid modules through fully-integrated silicon core RF integrated circuit (IC) devices, addressing the specific requirements of the targeted appli- cation. Perhaps more importantly, a system-aware approach, carried throughout the entire phased-array development cycle, enables the team to continually incorporate more detail into their predictive models, observe the interactions between array components, and make system adjustments as the overall performance inadvertently drifts from early idealized simulations. Design failure and the resulting high costs of development are often due in part to the inability of high-level system tools to accurately model the interactions between the large number of interconnected channels, which are typically specified and characterized individually. Since overall phased-array performance is neither driven purely by the antenna nor by the microwave electronics in the feed network, simulation must capture their combined interaction in order to accurately predict true system behavior. Circuit, system, and EM co-simulation enables verification throughout the design process. Phased-Array Design Flow A leading phased-array design flow is available with AWR VSS software, which provides full system performance as a function of steered-beam direction, inclusive of the antenna design, and the active and passive circuit elements used to implement the electronic beam steering. System components can be modeled in greater detail using AWR Microwave Office ® circuit simulation, inclusive of EM analysis for antenna design and passive device modeling using AWR AXIEM ® 3D planar and Analyst™ 3D FEM EM simulators. These tools are fully integrated into AWR Design Environment software, supporting seamless data sharing within the phased- array hierarchy. Furthermore, individual antenna designs can be generated from performance specifications using the AntSyn antenna synthesis and optimization module, with resulting geometries imported into AXIEM or Analyst software for further EM analysis and optimization. Highlights of phased-array analysis in AWR VSS software include: f Automate/manage the implementation of beamforming algorithms and determine phased-array antenna configuration from a single input/output block f Accomplish array performance for over a range of user-specified parameters such as power level and/or frequency. f Perform various link-budget analyses of the RF feed network, including measurements such as cascaded gain, noise figure (NF), output power (P1dB), gain-to-noise temperature (G/T), and more f Evaluate sensitivity to imperfections and hardware impairments via yield analysis f Perform end-to-end system simulations using a complete model of the phased array f Simulate changing array impedance as a function of beam angle to study the impact of impedance mismatch and gain compression on front-end amplifier performance Radar Systems 18

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