MIMO Transmission Using a Single RF Source: Theory and Antenna Design

An approach for transmitting multiple signals using a single switched parasitic antenna (SPA) has been recently reported. The idea there is to map the signals to be transmitted onto a set of basis functions that serve as "virtual antennas" in the beamspace (i.e., wavevector) domain. In this paper, we generalize the derivation of the antenna pattern basis functions regarding a three-element SPA of arbitrary radiating elements, within a symmetric array topology, for multiplexing signals in the wavevector domain (using different beampatterns) rather than in the hardware antenna domain with multiple feeding ports. A fully operational antenna system example is modeled, optimized regarding its return loss and the power imbalance between the basis functions, and finally realized. The measurements of the SPA show good agreement with the simulated target values, revealing an accurate design approach to be adopted as a fast SPA prototyping methodology. The SPA has been successfully employed for multiplexing two binary phase-shift-keying (BPSK) datastreams over-the-air, thus paving the way for practically compact and highly efficient MIMO transceiver designs.