Borrowing a line from Contributing Editor Bob Pease of our sister publication, Electronic Design, many have been asking about MIMO. What is it, and just as importantly, why is it? An acronym for multiple-input, multiple-output, MIMO refers to a wireless system architecture that is simple in conceptuse multiple antennas to improve signal qualitybut not always simple to implement. And it is not the place of this short column to even try to explain it. But Microwaves & RF will feature numerous tutorials and more advanced articles on the basics and theory of MIMO communications in upcoming issues.

Interest in MIMO is high most likely because it is the modus operandi of the latest "fourth-generation" (4G) wireless systems, such as WiMAX, as well as the Third-Generation Partnership Program's (3GPP's) Long Term Evolution (LTE). Most of the major test-equipment companies have devoted numerous application notes and white papers to explaining MIMO and, in particular, in how to test it (with their equipment, of course). Although there is a nice variety of literature available from such companies as Aeroflex, Azimuth Systems, ETS-Lindgren, LitePoint, National Instruments, Rohde & Schwarz, Spirent, and Tektronix, it is Agilent Technologies with an easy-to-follow poster, "Ten things you should know about MIMO," that provides an excellent five-minute education. The company is currently offering the poster (with registration required) for free in its "What's New" section on the main page, at www.agilent.com/find/MIMO.