octoBox.jpgOctoScope’s new refrigerator-sized anechoic chamber, called the octoBox, reminds me of past projects involving RF and EMI testing.  When I was at Jabil Circuit, they had a nice 100 sq ft walk-in chamber. The DUT and antennas could be placed in the chamber with the “master” and the test equipment outside.  In practice, we often moved the test equipment into the chamber so we could make changes to the DUT and get immediate feedback by looking over at the test equipment.  The chamber had white lights illuminating the equipment and non-reflective black tiles on all sides of the room.  Even the most cheerful person would experience some sense of sensory deprivation after spending most of the day working in the room.

I have never worked with a small chamber like octoBox, but I imagine the time spent opening and closing the doors would be less than the time gained by not having to leave the room to look at the test equipment.  OctoBox is divided into two chambers: one for the master and a larger one for the DUT and antennas.  The isolation between the two chambers is 80dB at 6GHz, 90dB and 2.4GHz, and around 100dB at VHF and UHF frequencies.   Isolation between the chambers and the outside world is around 80dB.  The walls reflect -20dB of incident waves.

MIMO_Testing.jpgOne application of a small chamber is testing MIMO devices with various channel emulations.  In MIMO, antennas are an important part of the channel model, so you cannot simply put the DUT in an RF shielded enclosure and connect the channel emulator to the DUT through coax and attenuators. 

Wireless devices increasingly have integrated antennas.  Lab testing with the devices’ actual antennas, even when the radios are not MIMO, is better than soldering coax to the antenna connections.  For functional test in production, an over-the-air test is the only option.  Automated test equipment can be configured to test multiple devices at once in the chamber. 

Even without expensive equipment like a channel emulator, it would be nice to have a large anechoic box to pre-test products to get an idea of whether they will pass EMI emissions testings and to be able to test transceivers with real antennas in a repeatable way in the lab.