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5.2.5.3. Examples

  1. An antenna can be loaded with lumped RLC circuit elements. An example of a loaded coplanar monopole antenna is shown.

    Unlike when implementing a matching network with lumped RLC elements, the location of the lumped RLC circuit element when loading an antenna is not as prone to model error. For this example, locating the lumped RLC element at the top middle of the cylinder gives very similar results as locating it at the top outer edges.

  2. Modeling frequency dependent circuit components embedded within antenna (e.g. PIN diodes in a frequency reconfigurable antenna). PIN diodes and other circuitry in a reconfigurable antenna can be modeled using lumped RLC circuit elements. An example of a frequency reconfigurable ring planar monopole antenna is shown below.

    In this antenna, lumped RLC circuit elements are used to model DC blocking capacitors, the PIN diode switch ON state, and the PIN diode switch OFF state. The ON and OFF state models are shown in the two images below. The gaps in the metal where the lumped RLC elements are placed represent the actual gaps that will be present upon fabrication.

  3. Lumped RLC circuit elements can be used to construct a matching network for testing with an antenna. Note that simulating a matching network with an antenna in Analyst is not the preferred method, as it is prone to model error. The preferred method is to use a Circuit Schematic with the Analyst Arbitrary 3D EM Structure in AWRDE. Also, AWRDE has a Network Synthesis Wizard that automatically creating a matching network to use with an antenna. Some recommendations for setting up the matching network with an antenna model in Analyst are: (1) keep the matching network out of antenna fields as much as possible (e.g. under the ground plane for a coaxial fed patch antenna) and (2) attach the lumped RLC circuit elements in locations of maximum surface current (e.g. edges of planar metal and on the outside or inside cylindrical edges of a cylinder). A good way to verify the model is correct is to simulate the antenna with the same matching network in AWRDE as described above. The two images below show an example of a good location for placing a matching network with a coaxial fed patch antenna. The location is close to the bottom of the inner pin of the bottom of the coaxial line, and the inner pin has been slightly extended.

    For reference, this is the matching network being implemented.

    An illustration of the entire antenna with matching network is shown in the two images below.

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