AWR eBooks

RF Electronics Chapter 2: Computer Simulation Page 10 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. Select Simulate Analyse to give the required frequency response as shown in figure 2.6. The scales, line thickness and other parameters of the graph can be set from inside the Graph Property toolbar, (the left element of the right toolbar shown in the blue top area in figure 2.6), or the properties can be accessed by right clicking inside the Low Pass graph and selecting Properties. In figure 2.6, the blue graph is the transfer function S 21 and the magenta one is the input reflection coefficient S 11 . Equations in AWR DE It is possible to use variables and equations either as global variables for the whole project or as part of an individual circuit diagram. This allows greater control over the filter parameters and avoids having to use a spreadsheet to calculate the filter element values. For instance, by making the cut off frequency a variable, the filter can easily be tuned to achieve a required cut off frequency. The cut off frequency can be tuned or optimised to meet required specifications. The resulting circuit diagram is shown in figure 2.7. The variables can be placed in any order, but any variable specification must be above the use of that variable. The resistance R and frequency variable F c must thus be on top, since those are used by C1, L2, C3 and L4. The equations are added to the circuit diagram using: Draw Add Equation, and then placing the equation location on the circuit diagram. Variables, which AWR DE cannot find, either globally or in the current schematic, are shown in red. Any corrective action may simply be the moving around of a variable to satisfy this top to bottom flow requirements. The full list of built in functions is shown in section 8.5.3 of the 2010 AWR DE users-guide, available by selecting Help on the pull down menu. Variables can be tuned manually or be changed automatically as part of optimisation by selecting Properties and then enabling the Tune and/or Optimize check boxes. If needed the range of values can be constrained to specified upper and lower values. It is desirable to constrain R, L and C from becoming negative. Figure 2.7. Tuneable filter. Any variables or equations whose variables can be tuned are displayed in a blue font as shown in figure 2.7. Circuit values can either be shown as base values, such as H, F or RF Electronics: Design and Simulation 10 www.cadence.com/go/awr

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