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Accelerating MIMO over-the-air device testing

Posted: 09 Jul 2015     Print Version  Bookmark and Share

Keywords:MIMO  antenna  Over-the-Air  polarisation  LTE 

CTIA recommends a ring of at least eight antennas in an anechoic chamber, which is ideal for testing mobile phones and small tablets. MIMO OTA testing also includes the testing of larger devices such as tablets and laptops, which require a ring of 16 antennas. Since each antenna requires signals from two channel emulator ports, the channel emulator will, in such cases, need to support up to 32 channels. Test set-up is much simpler and quicker with a 32 port channel emulator compared to a 2 x 16 port channel emulator.

We have partnered with several test laboratories, including China Academy of Information and Communications Technology (CAICT), China Telecommunication Technology Labs Terminals (CTTL-Terminals), SGS in Taiwan, and AT4 Wireless to provide our Propsim F32 channel emulators for MIMO OTA testing. The following includes test set up specifics.

These test houses provide OTA testing with an anechoic or a reverberation chamber and incorporate a channel emulator to create a realistic radio channel propagation environment.

In an anechoic chamber, multiple antennas are deployed at various angles to simulate the reflections. The anechoic chamber is a non-reflecting chamber (with no external interferences) that systematically eliminates multi-path reflections and is therefore widely used in testing the performance of wireless devices. Anechoic chambers provide vector information as a function of the orientation of the antenna under test so that the antenna pattern can be determined under different set-up conditions in full compliance with CTIA OTA measurements. Anechoic chambers also have the ability to accurately reproduce spatial channel models (e.g. SCME channel models), which is important for MIMO transmission and, therefore, MIMO OTA testing. This is why CTIA has recommended the use of anechoic chambers for MIMO OTA testing.

A reverberation chamber is a highly reflective environment where multi-path signals fill the chamber with standing waves, which are mechanically stirred to expose the DUT to a highly variable propagation environment. Multiple samples enable the test engineer to characterise a statistical response of the DUT to this reflective environment. Reverberation chambers are compliant to CTIA recommendations as they are suitable for Transmit-Diversity testing. They also offer a simple and quick method for pre-compliance OTA performance testing and a first order assessment of the device performance.

MIMO OTA testing in an anechoic or reverberation chamber enables test houses, manufacturers, and mobile operators to verify the performance of a mobile device that is equipped with multiple antennas. MIMO OTA testing is important in order to ensure end-users have access to a truly mobile broadband experience with higher data rates.

About the author
James joined Anite in 2000 as Project Manager of the GPRS conformance product line. After managing the development of many of Anites products through the technology progression from 2G to 3G, he joined the companys product management team in 2007. He has now director of product management, responsible for the portfolio management of Anites Handset Testing products. James is a Chartered Engineer and holds a PhD and MEng in Electrical and Electronic Engineering.


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