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The Team RF "μWaveRiders" blog series is a showcase for Cadence AWR RF products. Monthly topics will vary between Cadence AWR Design Environment release highlights, feature videos, Cadence Academic Network news (including the former AWR University Program), as well as software tips, tricks, customization, and feature spotlights.
A significant challenge for RF designers is the optimization of an RF chain for noise and distortion performance. An example of an RF chain is represented here, although in practice, an entire RF link can have many more components than shown in this simple example.
Determining the noise and distortion as a progression through the RF chain is known as cascade analysis. Fortunately, Visual System Simulator (VSS) software in the AWR Design Environment platform has many measurements that assist in cascade analysis. One of the key attributes of cascade analysis is to show noise and distortion performance at each stage of the RF chain. RF Budget measurements within VSS allow for the display of cascade performance metrics as a function of stage, as shown in this graph.
A visual representation of the stages in the RF chain is presented on the x-axis, allowing for quick identification of key elements that contribute most to either noise or distortion.
Analyzing the cascade is useful for completed designs, however the challenge is to optimize the cascade. Optimization may take the form of choosing components that favor noise and/or distortion performance, choosing proper gain distribution throughout the system, and setting fixed attenuation values between gain stages. This process is complicated at a single frequency and power condition, but even more complex optimizing over a swept frequency and power range.
"Cascade Analysis: Optimizing RF Systems for Dynamic Range" addresses the use of VSS in the cascade analysis and optimization. The optimization problem can be summarized by quickly identifying the high contributing elements in an RF chain that lead to noise and/or distortion degradation. This article covers a theoretical development in how noise figure and third-order intermodulation distortion plays into the overall system performance. With this knowledge, using VSS measurements for the rapid identification of high noise and distortion contributors becomes more apparent.
Like any engineering problem, analyzing data in a different manner can lead to new insights that aid in the solution. With scripting, the VSS measurements can be used for further processing and presented. The article demonstrates examples of VSS measurement manipulation that help with quick identification of the high noise and distortion contributors in the cascade.
By: Brian AvenellSr. Principal Product EngineerCadence AWR R&D - U.S.
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