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AXIEM Insitu Antenna Measurements
The antenna in this example is a stacked circular patch antenna that is simulated for antenna characteristics using AXIEM. In previous versions of the AWRDE, you could visualize antenna patterns in 3D, super-imposed over the EM layout or take cuts of the pattern to display on 2D graphs. When measuring such quantities, you must configure the ports in the EM layout with the proper settings such as power and phase. The insitu feature allows the circuit simulators to determine these quantities for you as a result of circuit simulation.
The “Single_Element” EM structure contains the AXIEM setup for the antenna. Shape modifiers control the size of each circular patch with the size of the circles controlled from variables in the global definitions.
The schematic “Driven_Antenna” uses the EM structure as a subcircuit and then drives the antenna with several components. An attenuator and phase shifter are added in the path driving port 1 of the antenna. This is a simple example, but the circuit could be a power amplifier design or other circuitry. Note: the schematic must have a nonlinear source since power levels are needed to generate the patterns.
There are two groups of graphs in the project. Graphs in the first group have names that start with “Single Element”, and are results directly on the EM structure. Graphs in the second group have names that start with “Driven Circuit”, and are results from the circuit simulation. The “Driven Circuit 30 Deg Conic” measurements are unique in that these are the antenna patterns under the circuit drive. From these measurements you define both the EM structure for the antenna and the circuit schematic that is driving it.
The attenuation and phase blocks are setup for tuning. Bring up the tuner and change these values to see the 3D antenna pattern and the 2D antenna cuts that reference the schematic update in real time (hold down the ctrl key to get updates at every tuner point). Notice no new EM simulation is required.
Separate from the insitu measurements of this antenna, the antenna geometry has been setup to optimize the circuit patch sizes and the dielectric heights of the boards used to make the antenna. Variables H1, D1, and RTB are setup to optimize the geometry. The D1 and D2 variables control the size of each circular patch using the shape modifiers in the EM layout. H1 is used for layer 5 in the Enclosure of the EM structure on the “Dielectric Layers” tab. The return loss of port 1 is setup as the optimization goal on the “Optimize S11” graph. The antenna is already meeting the optimization specs so you will need to change the variables listed above or change the frequency range to run the optimization. We highly recommend using the “Discrete Local Search” optimizer.