HFSS15: Tune a Coax Fed Patch Antenna

Description - A coax fed quarter wave patch antenna will be tuned using the Adjoint Derivatives. The antenna is shorted on one end. The design variable, feed_pos, controls the location of the coax feed along the x direction. Derivatives of the S parameter w.r.t. this variable will be computed.

Model - The patch, shoulder, and ground plate are united into a single PEC object. The air filled coax has an internal port that is capped by the PEC ground plate. The variable feed_pos controls the value of X for the coax location in millimeters. The surrounding air box with radiation boundary is not shown.

Setup - Adapt at 1.8 GHz., and do an interpolating sweep from 1.5 to 2 GHz. The derivative of the S parameter data w.r.t. feed_pos about the default value of 10.8 mm is computed. This feature is enabled in the Derivatives tab of the Setup1 window.

Post processing for tuning a Coax Fed Patch Antenna

After solving, you can view solution data by right-clicking on Setup1 and selecting Profile to display the Solution dialog. You also view the Solution tabs for Convergence, Matrix Data, and Mesh Statistics.

To view the derivatives you can create a new plot by right clicking on Results and choosing Create Modal Solution Data Report>Rectangular Plot. In the New Report Setup window, select feed_pos in the derivative box and select the desired quantities to plot.

To tune the design, double-click on XY Plot 2 under Results to open the plot shown. In a separate project, the response for feed_pos = 10.5 and 11 mm was computed and the results from each was imported into this plot. By right clicking on Results and choosing Tune Reports you can open the Report Tuning dialog shown. As you adjust the slider, the plot is recomputed using the derivatives. Adjust the Offset to -0.3 and +0.2 to compare to the imported feed_pos = 10.5 and 11mm results.