Direction finding by exploiting the directional radiation patterns of an Switched Parasitic Antenna (SPA) is considered. By employing passive elements (parasites), which can be shorted to ground using pin diodes, directional radiation patterns can be obtained. The direction finding performance of the SPA is examined by calculating a lower bound on the direction finding accuracy, the Cramér-Rao lower Bound (CRB). It is found that the SPA offers a compact implementation with high-resolution direction finding performance using only a single radio receiver. Thus, exploiting SPAs for direction finding is an interesting alternative to traditional antenna arrays offering compact and low-cost antenna implementations.

We investigate the switched parasitic antenna (SPA), which is a novel technique for electronically directing the radiation pattern, in a MIMO system. The correlation between the received signal modes are shown to be sufficiently low to yield a diversity gain. The capacity limit using the SPA is investigated for different SPA configurations and it is found that the capacity is comparable with an array antenna configuration in certain situations. Finally, a space time block coding scheme is used to evaluate the bit error rate of a MIMO-SPA system. It is found that the SPA requires a 5 dB higher SNR than an antenna array solution to achieve a BER= ¢ ¡ ¤ £ ¦ ¥ . However, the array antenna requires a radio transceiver for every antenna, as opposed to the SPA which uses only one transceiver.

The issue of channel state information at the transmitter is investigated using MIMO channel measurements and by deriving expressions for ergodic and outage capacity in a Rayleigh fading channel. Expressions for bit error rates in Rayleigh fading channels are also presented for orthogonal space time block codes and for beamforming where the bit error rates in the beamforming case follow from the distribution of the largest eigenvalue to Wishart matrices. We demonstrate by measurements that Rayleigh fading is a valid assumption in non line of sight channels, although a Nakagami-m distribution showed to be a more appropriate distribution model in both line of sight and NLOS environments. It was also demonstrated that channel state information at the transmitter is less useful in high-SNR scenarios but is more useful in line of sight channels compared to non line of sight environments.

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