For the last couple of decades, reverberation technology was solely used as a tool for engineers specializing in electromagnetic compliance (EMC) testing. Bluetest innovations have transformed this technology into a powerful solution tuned to the needs of current wireless developers. They are the next generation of over-the-air (OTA) test systems that bridge the testing gap between conducted and drive test methods.
Reverberation Chamber Technology
A reverberation chamber is essentially a large reflective enclosure, or cavity, that will resonate when signals are introduced into it. These resonances makes microwave signals reverberate, similar to how sound reverberate in an enclosure.
As signals bounce off the walls and objects in the chamber they interfere. This constructive and destructive interference of multiple signal reflections form cavity modes. A reverberation chamber adds special stirring functions to move the points of constructive and destructive interference around in the chamber. By proper stirring, multipath fading effects can be distributed in a statistically well defined and repeatable way inside the chamber. This multipath fading environment is particularly appropriate to today's small, multi-purpose and high data rate wireless devices.
Multipath fading has for many years been a problem for mobile communication engineers, to be overcome by designing systems that have sufficient signal-to-noise ratio (SNR) or signal-to-interference ratio (SIR) margins. The fading is caused by multiple reflections in walls and ceilings (indoors) or cars and buildings (outdoors) that add constructively or destructively at the location of the terminal or base station antennas.
Base stations and/or terminals with multi-antenna configurations are expected to significantly contribute to much higher bit rates in mobile broadband systems. Higher bit rates using multi-antenna systems can, when there is rich scattering in the communication channel, be achieved 1) by increasing the modulation rate and/or reducing the coding rate as the Signal to Noise Ratio (SNR) is increased through the use of diversity combining, or 2) through the use of simultaneous partially uncorrelated communication channels (Multiple Input Multiple Output, MIMO).
A reverberation chamber is ideally suited for testing antennas for multi-antenna technologies such as diversity and MIMO. Bluetest Flow for diversity and MIMO measurements are well-proven and will give you instant feedback of the performance of the antenna array after the measurement is finished - no waiting time needed! In combination with the extreme measurement speed, the user will have the antenna performance in a single minute only.
Antenna efficiency goes under the category of Bluetest passive measurements in the reverberation chamber. An important parameter for all different types of antennas is radiation efficiency and is a basic parameter for all antenna designs. In fact, it is the dominating factor for antenna performance in multipath environments.
Total Radiated Power (TRP) and Total Isotropic Sensitivity (TIS) goes under the category of Bluetest's active measurements. Active measurements means that the transmitter/receiver in the DUT is active and powered up. Active measurements will give you a complete overview of how the whole system in your device is performing. These are parameters directly related to the antenna radiation efficiency, and are well proven measurements in Bluetest's reverberation chambers. The TRP and TIS measurements in a reverberation chamber are standardized and included in the 3GPP Test Specification TS 34.114.
The current trend in active device over-the-air (OTA) testing is to characterize the system performance via data throughput. With Bluetest measurement software the throughput can be measured at either IP or MAC layer in a fast, repeatable, and convenient way.