In January 2003 I started working as a temp at Square D in Knightdale. Following are some pictures from the lab.
Below is a shot of the radiated immunity/emissions chamber. The equipment in the foreground is used for both emissions as well as immunity testing. Inside the chamber a bi-log antenna can be seen. This antenna is used for testing at a 15v/m field strength from 20 to 2000 MHz, and up to a 30v/m field strength from 150 to 1000 MHz.
The main factor limiting the field strength from this antenna (and any wide-band bi-log antenna, for that matter) is the performance below 80 MHz. To allow testing up to 30v/m, we recently purchased a high-power biconical antenna with extended elements. This will cover the frequency range from 20 to 200 MHz only, the bi-log antenna will cover the rest of the frequency range.
As the result of my investigation into the feasibility of 30v/m testing, I discovered the cable from the amp to the antenna was very lossy, almost 9dB at 2GHz. As a result, we acquired some low-loss heliax cable.
Below is a shot of the conducted immunity test area. It is a raised ground-plane to make testing and setup easier. Two amplifiers allow testing from 150 kHz to 1000 MHz. Much of the early work that I did was to calibrate multiple setups and configuring the software. Also, a new AR amp was purchased, as well as additional CDNs and attenuators, to improve the range of testing possible in the lab.
The Tile! software is used to perform test sweeps, but my Radcon software is used for calibrations since it is more accurate, reliable and fast. Tile! might take three hours to run a single calibration, while Radcon takes less than 30 minutes to perform a calibration from 150 kHz to 230 MHz.
Below is a shot of the ESD and EFT test areas. EFT testing is performed in the shield room in the background, while ESD is performed on the table in the foreground.
The lab where I previously worked.
Above is a 10 meter semi-anechoic chamber. The walls are covered with materials that absorb radio-frequency energy, reducing unwanted reflected signals. The floor is metallic, to reflect signals on purpose. Both emission and immunity tests can be done in this chamber, although some ferrite tiles must be placed on the floor for immunity testing.
Most radiated emissions standards were developed before anechoic materials were practical. The standards were written with the idea of testing on an open-area test site (OATS) which have reflective ground planes. Now that anechoic materials are practical, and the ambient signals outside are great, testing in a shielded, anechoic chamber makes testing quicker and easier. The down side is that the cost for building a facility like this can cost a few million dollars. Also, the site attenuation is not as good as an OATS.
(click on pictures for larger images)
Above is a tri-plate, used for RF immunity testing of small devices. It is shown inside a compact anechoic chamber. The tri-plate is used primarily for testing automotive components. This picture was taken during calibration. The field probe can be seen under the septum (middle plate) with the fiber-optic cable running from the probe to the computer outside the chamber. During an actual test, the device-under-test (DUT) is placed under the septum along with part of the wiring harness associated with the device. A camera is used to monitor the device during the test to observe it for proper operation. There might also be equipment outside the chamber to exercise/monitor the device. A computer is used to operate the amps, signal generator, and power meters needed to control the test. A large RF field is generated between the septum and the outer plates, covering the frequency range from 10 kHz to 1000 MHz.
Originally, software that I wrote was used to drive this setup. The Ford test standard changed a couple of times and required changes to the software as a result. The final version that I wrote performed the test using mid-point power, which was calculated from the forward and reverse power levels on the input side of the triplate (net power) averaged with the power measured at the output of the triplate.
Above is another shot inside the 10 meter chamber. In this picture, the chamber is configured for a radiated immunity test. The antenna on the left, a dual-ridge horn antenna, is used for the frequency range from 1 to 10 GHz. This picture was taken after a calibration was performed to IEC 1000-4-3 specs. The white PVC rack on the right is for holding the field probe at the 16 positions needed for calibration purposes. The combination of ferrite tiles on the floor and the cones on top of the tile help to reduce reflections of the signals off of the floor. This helps to insure a uniform field strength at the various probe positions. During an actual test, the probe and probe rack will be replaced by the equipment-under-test (EUT). As with the triplate test, the product will be observed/monitored during the test for proper operation.