MIMO testbed with an insight into signal strength distribution around transmitter/receiver sites

This paper presents a high precision test-bed to obtain an insight into the operation of a multiple element antenna (MEA) communication system in an indoor environment. In this system, transmitter and receiver are equipped with 180deg or 90deg 3 dB hybrids whose two output ports are terminated with co-polar monopole antennas. By feeding the signal to one of the remaining two ports of the hybrids various radiation patterns are established. These in turn create various communication channels formed by MEA and a surrounding scattering environment. The testbed allows for the signal strength measurements around the receiver/transmitter sides for various radiation pattern modes generated by transmitting and receiving array antennas operating in conjuncture with the hybrids. Details concerning mechanical, electrical and electronics hardware and associated measurement software are described. Initial measurement results in the ISM 2.4 GHz band for a 2times2 MIMO system that includes Bluetooth modules equipped with planar monopoles and 180deg/90deg hybrids are given