Test & measurement
have been maintained after integration of the radio module into the host device. As a minimum, EMC requirements need to be tested on the host device along with a representative re-test of radiated spurious emissions (RSE). For both, intended use and worst-case operating conditions are within scope of the regulatory requirements. Both test disciplines require that the radio module is configured to use a radio channel with well- defined physical layer characteristics. The most important of these are transmit power, frequency band, test channel number, channel bandwidth, waveform, modulation, and channel utilisation. For radios that are less complex, like Wi-Fi and Bluetooth, these parameters can usually be set by regulatory test modes. However, for complex cellular radio technologies, such as, WCDMA, eMTC, NB-IoT, LTE ,5G NR & REDCAP, regulatory test modes are not available.
TEST EQUIPMENT
Manufacturers that have integrated pre-certified radio modules need access to specialist testing equipment and expertise. This includes base
30
station simulators covering all above-mentioned cellular radio technologies. These need to be flexibly configured to control all of the above physical layer parameters via over-the-air (OTA) signalling sent to the radio module. Tests include stimulating the radio module receiver and transmitter to establish the intended worst- case operation mode for EMC and RSE testing. As already mentioned, the wireless host device manufacturer’s main interest is to enable a wireless connection to the internet by integrating a radio module. That brings another practical challenge as many host devices require a live connection to the internet to allow the embedded radio module to remain in transmit (TX) mode for extended periods, as needed during EMC or RSE testing in an anechoic chamber.
This means getting the internet connection to the equipment under test (EUT) within the anechoic chamber. As this is a room designed to eliminate echoes and reflections of sound or electromagnetic waves, this causes issues during testing. One solution is to connect the internet via LAN cable to a base station simulator, thereby enabling the internet traffic to be sent
two-way on the IP layer using the active radio connection which is already established for EMC or RSE testing.
GLOBAL COMPLEXITY
A key reason for non-compliance of final host products containing wireless modules is that while these modules are complaint as an independent unit, once they are integrated into another product that changes the regulatory requirements. Best practice advice would be to follow some basic guidelines when integrating wireless modules into products. For European compliance, ensure that the wireless module you are integrating is fully compliant with the latest Harmonised Standards. For USA and Canada, host product manufacturers should check the conditions of the module grant and ensure that the product is not breaking those conditions. Always ensure that the module is integrated in accordance with the manufacturer’s supplied instructions.
TÜV SÜD
www.tuvsud.com/uk May 2025 Instrumentation Monthly
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