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A new concept in single-port adaptive antennas using parasitic elements with switched terminating impedances is presented including results from a concept prototype. Each parasitic element can be effectively terminated in three impedance values. The antenna concept provides multiple radiation patterns with a single RF signal port without the need for RF switches or phase shifters in the direct RF signal path. Impedance variations in the active antenna element are minimized by use of only rotationally symmetric configurations. Measured patterns are used to demonstrate the performance improvement expected using switched diversity combining in a simulated uniform scattering scenario. The concept prototype having one active element and four parasitic elements, is shown to have equivalent diversity performance to between three and four uncorrelated branches.Index Terms-Adaptive, averaged uniform scattering scenario, diversity gain, single-port diversity antenna, switched parasitic antenna elements, wire monopole antenna.

The spatial cross‐correlation function for antenna signals in multipath environments depends on the mutual coupling between the antennas. In general, this function is different from the spatial autocorrelation coefficient function of the multipath, fading field. This difference influences the design criteria for the element spacing of compact (that is, closely spaced elements) antennas. The relationship between the spatial autocorrelation function and the cross‐correlation function is presented and used for practical, compact diversity antenna design.

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