MIMO TIS/TRP active testing with second-generation mode-stirred chambers

Resumo

With the first 4G trials scheduled for 2010 and the compulsory use of MIMO into both WiMAX and LTE standards, MIMO technology has finally exploded. Mobile Internet Peripherals and Devices are said to take a market share of 30% of all handsets and non-handsets wireless devices by 2013. In this complex scenario, antenna engineering has gained a tremendous importance. While the use of multiple antennas in the base station or access point (AP) is usually feasible, user terminals have size and weight restrictions that make the use of conventional antenna elements such as dipoles or patch antennas problematic. Thus, novel array topologies and antenna elements for multi-antenna systems are of great interest. But not only new geometries and designs are required, but also the antenna engineer is faced with a novel way to evaluate performance. While the parameters to characterize antennas in general are well defined and worldwide accepted, the way to evaluate the performance of an antenna array for MIMO is still an open issue, since multiple new concepts have to be considered, such as pattern diversity, corrrelation among elements, fading environment or polarization diversity, among others. Typical active parameters being currently tested for 2G and 3G systems are Total Radiated Power (TRP) and Total Isotropic Sensitivity (TIS). 4G systems are already envisioned to require more complex active testing due their inherently embedded MIMO technology. In this article, the way of using a second generation mode-stirred chamber (EMITE Ing E300 MIMO Analyzer) connected to a rradiocommunications tester (Rohde & Schwarz CMU200) to characterize wireless devices by measuring TRP and TIS is decribed. Measurements have been perormed for the UMTS system, but are simply extende to other systems. Since second-generation mode-stirred chambers can emulate a wide variety of Rayleigh, Rician, isotropic and non-isotropic scenarios, the procedure described in this paper opens the door for more advanced evaluation of active parameters for a variety of fading scenarios, which is unheard of in the wireless communications arena.