New technology development has consistently outpaced EMC test standards from Bluetooth to 802.11 to changes as simple as extended frequency ranges. Whether it’s in the form of updates to a current standard or an entirely new standard yet to be written, a balance must be provided between test lab capability and real-world threat scenarios. The rapid development of cellular technology leading to advanced 5G topologies has emphasized the need to examine new immunity testing methods. This also applies to 5G’s effect on other technologies, such as radar altimeters on aircraft.
5G, the term applied to the 5th generation mobile network, enables a new kind of communication network designed to connect virtually everyone and everything. This new communication includes machines, objects, and devices, otherwise known as the Internet of Things or IoT. In order to get 5G radios incorporated into IoT devices, technological advances must be developed. These technological advances will present potential EMI issues not present in earlier wireless systems, and interference potential, just such as in aircraft, military equipment, and commercial devices, remains unknown. The networks utilizing 5G technology will inherently become more crowded with IoT users as more devices become available, while increased throughput and minimized latency are the key attributes of this advancement.
Three fundamental aspects of any new technology should be considered in new or updated EMC test methods: frequency range, modulation format, and expected field levels. 5G devices and their end products are no exception to this. Regarding frequency range, current wireless frequency bands cover 450 MHz – 6 GHz, but 5G extends this up as high as 52.6 GHz. Modulation formats are also increasing in bandwidth from 100 MHz up to 400 MHz. The modulation spectrum, seen in Figure 1, exhibits very high peak excursions and is dominantly time-gated or pulsed. Field levels in 5G will be impacted by the very high gain antenna arrays, shown in Figure 2.
It is important for a test laboratory to continuously prepare for new test approaches from a testing perspective. Equipment typically needs to be procured in some way, including signal generators, amplifiers, cabling, waveguides, directional couplers, power meters, spectrum analyzers, and so on. Additionally, test personnel, including both the engineers and the technicians, will need to be trained on how to perform new testing and justify different approaches.
When it comes to 5G testing, there exists a likelihood that an independent commercial test laboratory may not be properly equipped to perform testing for new test standards or approaches due to an evolution of technology. This will further limit the ability for manufacturers to be able to make sure they are compliant with new standards that may be introduced.
New EMC susceptibility testing should include the capability to achieve the aforementioned frequency band requirements, modulation, and field strength. This achievement may require a significant upgrade to standard equipment used in most EMC test labs. Signal generators will need to extend to 7.5 GHz to cover the low-frequency bands of the 5G spectrum and potentially past 50 GHz to cover the high-frequency bands. Amplitude Modulation (AM) or pulsed modulation (PM) alone will not sufficiently replicate the wide spectral signature of 5G.
Also, field levels will also be higher than previously tested. This measurement is due to 5G’s use of high gain antenna arrays. Gain for one of these antennas may exceed 30 dBi. Assuming an applied power of 6 W, a single beam’s expected field level at 3 m is 141 V/m. This field level far exceeds the current IEC 61000-4-3 maximum test levels of 30 V/m. It even approaches the higher levels of RTCA/DO-160 (150 V/m for Category R) and MIL-STD-461 (200 V/m)
A simple change or evolution in technology does not eliminate the fundamental approach of applying what standards are already in place. The same approaches can always be utilized when implementing a radio module into a larger device, such as a smart household appliance. Applying the product family standard (when testing for CE compliance) and the Radio Equipment Directive to meet each compliance goal starts developing a true compliance program. If testing for the FCC, it’s essential to pay attention to the highest internally generated frequency of both the module and the device installed within. At that point, decisions will be made on how to proceed. When in question, rely on an ISO 17025 fully accredited test laboratory to guide you through the process.
Unfortunately, directly testing the radio module, as opposed to the large appliance, is not as straightforward. If a wireless device or module is 3G, 4G, and 5G compatible, you will still need to test each of the scenarios that the radio can operate. However, some of the standards do not fully address all aspects of a radio device. For example, EN 301 908 series of standards for Europe give direction on testing cellular devices but haven’t been updated since 2016, and we all know that major advancements have been implemented into cellular radios since then. Further, additional testing is required once the wireless device is installed into an appliance or other digital apparatus. When this scenario occurs, the EN 301 489 series of standards covers wireless technology EMC while not directly testing 5G or wireless module.
Although 5G is here, cellular technology evolution will continue to progress, and the standards of testing these new evolutions will inevitably lag the technology development. While these standards may lag, old test approaches can still be utilized to enact compliance programs until test standard committees update or write new standards to handle evolving technology. Test laboratories must train their people on how to test products with 5G installed to ensure compliance with all essential requirements of each directive and economy where requirements exist. All of this will result in a spectrum devoid of issues and – as expected – keep radio modules from interfering with each other or minimizing the chance of an upset due to the necessary compliance testing.