Monday, February 17, 2014

Multiport matching in Optenni Lab, part 2

Guest post by Jussi Rahola, Managing Director, Optenni Ltd.
As discussed in the previous blog entry, when we at Optenni were designing the multiport features in the Optenni Lab matching circuit optimization software, one of the key questions was the choice of an appropriate cost function in the matching circuit optimization. We identified two distinct cases for the multiport matching, each with its own optimization goals. The radiating antenna case was discussed before, and this time I’ll be focusing on multiport matching of non-antenna devices.

In radiating antenna applications, coupling between the antennas is undesirable as it reduces the antenna efficiency. However, in many other matching applications (for example, amplifier and filter matching, matching of coil-type antennas for maximal power transfer in wireless charging, and near-field communication), coupling between the external ports is actually desired. The picture below describes the various loss mechanisms affecting the transfer of power between the ports.

In this matching application, the main optimization goal is to maximize some of the S-parameters of the system describing the transmission (e.g. S21), but at the same time stop bands for the same S parameters can also be specified. Optenni Lab designs matching circuits that obtain an optimal balance between the different loss terms. Note that it is not enough to minimize the reflected power alone (i.e. S11); losses in the matching network may reduce the transferred power dramatically.

Losses in general multiport matching

The design flow for multiport matching using CST STUDIO SUITE® and Optenni Lab is very simple. First, simulate the multiport structure in CST MICROWAVE STUDIO®. With a macro command, the simulated impedance data can be transferred straight to Optenni Lab. Next, depending on the application, start either the multiantenna matching or the general multiport matching procedure, enter the relevant frequency bands that the efficiencies or S-parameters should be optimized over, along with the number of matching components and component series to be used from the component library. Optenni Lab will quickly calculate multiple suitable optimized matching circuit configurations. The sensitivity of the results to component tolerances can be analyzed, allowing you to quickly optimize and analyze different multiport matching configurations.  The matching circuits can then be transferred back into CST DESIGN STUDIO™ with a single command for further analysis and inclusion in the full 3D model.

If you’re interested in matching circuit optimization and the link between Optenni Lab and CST STUDIO SUITE, more information is available at the Optenni Ltd website and in the CST-Optenni whitepaper.

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