RF Immunity test standards continue to evolve, how do you keep up?
EMC Test Manager, Bernie Papocchia, of Ametek CTS discusses key considerations for effectively managing your test equipment and setup.
How have the requirements for Radiated Immunity Testing changed over the years?
Radiated Immunity testing has been around for decades with MIL-STD-461 and DO-160 leading the way (these standards are already on revision G). With the advent and evolution of computer controlled and wireless devices, the need for standards of medical devices, consumer electronics, industrial devices, and automobiles, has become more critical.
Originally, with the exception of Military and Aerospace industries, many standards only covered 80MHz to 1GHz for small test levels (3v/m). The test setup was simpler and could be performed with one amplifier and one antenna. However, as the standards continue to evolve, the frequency ranges keep expanding (10kHz to 40GHz) and test levels continue to rise higher (1-600v/m). To meet these changing requirements and accommodate the increasing number of items to be tested, the number of amplifiers and antennas needed to successfully perform radiated immunity testing has also expanded.
Unfortunately, the amplifiers and antennas available 10 years ago do not meet the new requirements of linearity, harmonics and noise figure/ noise power. Multiple antennas and amplifiers at even higher wattages are now necessary in order to achieve current test specifications However, switching capabilities are not keeping up with the changing requirements, and with wireless technologies like 5G and 6G on the horizon, the frequency spectrum will soon be highly crowded and even more testing should be expected.
What are some of the key factors in determining how an existing setup can accommodate modern test requirements?
As communications and technology expand, a big concern is not only the frequency expanding but the power and modulation requirements can require higher field levels. Knowing the limitations of the equipment available to you can correlate directly to what is needed to meet the new requirements.
Cables loss and length over frequency should be calculated and maintained. Bulkhead connectors are notorious for not handling the power or frequency range and using adapters should be avoided, if possible. Plus, adapters are lossy over power and the inexpensive ones usually fail over time.
Knowing the antenna gain, loss of a cable and distance as specified by the test requirement will help you to easily calculate the power needed to generate the field.
Using the Field Strength Formula of: E= √(30xGx P) /R where is E = Volts/Meter(V/M), G = Linear Gain (dB), R = distance (Meters), P = Power (Watts) and 30 is derived from the impedance of free space (120p), will help determine the power needed from the amplifier to the antenna. Once this is determined, you can add the cable loss and the factor for modulation.
How would you recommend engineers manage their test setup to keep up with these ever-changing requirements?
Maintain detailed records and data for all the equipment in inventory so that the information is easily accessible. Profiling the lab’s equipment can and will save time and money. The more information available, the easier it will be to make the right decision about how to best proceed with the test setup.
As you develop test plans and evaluate existing equipment and future purchases, it is important to take into consideration how your current and future products being tested will interface with the products around it. Keeping up-to-date with developing standards and upcoming revisions will provide you with the additional foresight needed to prepare your setup for optimal, long-standing operation.
EMC Test Manager
Ametek CTS is a leader in RF Amplifiers, featuring the IFI, Teseq and Milmega brands.
The Ametek CTS IFI brand has been designing and manufacturing RF Amplifiers, Solid State Amplifiers and Traveling Wave Tube (TWT) Amplifiers (pulsed, CW and combination amps) since 1953.
Ametek CTS works with industry-leading experts to provide you with the best compliance test solutions.