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International Journal of Antennas and Propagation
Volume 2014, Article ID 879127, 10 pages
http://dx.doi.org/10.1155/2014/879127
Research Article

A Single RF MIMO Loading Network for High-Order Modulation Schemes

1Athens Information Technology (AIT), Peania, 19002 Athens, Greece
2Center for TeleInFrastructur (CTIF), Aalborg University (AAU), 9220 Aalborg, Denmark
3SignalGeneriX, 59627 Limassol, Cyprus
4Department of Digital Systems, University of Piraeus, 18534 Piraeus, Greece

Received 20 July 2013; Accepted 12 October 2013; Published 22 July 2014

Academic Editor: Demosthenes Vouyioukas

Copyright © 2014 Bo Han et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Recently, a novel MIMO transmitter architecture has been introduced that requires only a single radio-frequency (RF) chain and is built on parasitic antenna arrays. MIMO transmission in this case is achieved by shaping directly the radiation pattern with the aid of analog tunable loads attached to the parasitics. As it has been shown, such a single RF MIMO system can support all PSK modulation formats with purely imaginary loading values. This paper extends its capabilities and proposes a novel architecture for parasitic antennas that is able to provide complex loading values, even with a negative real part. Definitely, this will extend the flexibility of parasitic antennas to multiplex successfully over the air more complex signaling formats, for example, QAM signals. The bit error rate evaluation shows that the proposed architecture could be very promising in emerging devices and also illustrates its robustness under possible loading perturbations that might have been raised due to nonidealities in the design.