• • • TEST & MEASUREMENT • • •
Overview of radio compliance testing
The growth of wireless technologies has seen the frequency spectrum being more carefully managed by regulatory authorities
By Phil Evans, Business Development Director - Connectivity (Northern Europe), TÜV SÜD
he purpose of radio compliance testing is to demonstrate that your radio equipment meets with legislative requirements, which differ from region to region. For efficient testing that optimises time to market for products, preparation is key.
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A communications system is made up of two parts - the transmitter and the receiver. As the performance of the receiver can impact on the required transmitter power, receiver performance must be assessed. In Europe, the Radio Equipment Directive contains such receiver tests. It should be noted that in the UK, the requirements of the Radio Equipment Regulations 2017 are presently very close to the RED. The current UK government will keep UK regulation closely aligned with the EU to allow easier market access for manufacturers. There are two crucial pieces of information to ensure the timely completion of testing. Firstly, application forms contain critical data specific to the device under test (DUT). Secondly, detailed step-by-step test sample instructions are required to show how to put the DUT into the required modes of operation.
Most radio compliance testing requires the manufacturer to provide specially configured samples for assessment. As test samples can be subject to stresses, temporary antenna connectors need to be robust. A top tip is to glue the antenna connector to the PCB with hot melt
adhesive or to use a small tie wrap connector to provide added protection.
The special test modes that radio compliance requires can be power intensive. If your DUT is a battery-powered device, it is important to provide a suitable number of spare batteries and/or a means to charge them. Alternatively, should the standard permit, a battery eliminator may be provided, which allows the DUT to be powered by a bench power supply. Test laboratories use a range of wireless communications test sets that can be used to emulate a mobile network for test purposes, so the equipment must not be locked to a particular mobile operator.
Many IoT devices now use an embedded UICC, a MFF2 form factor that is soldered directly onto the circuit boards during manufacturer. The laboratory will need the MFF2 UICC to be replaced with a test SIM as mobile network operators will not share the security algorithms required by the test set to connect to the DUT. To enable a test SIM profile, a remote SIM provisioning tool is required. Many internet-enabled devices may be looking to connect to a specific server (or IP address). The test sets are not normally connected to provide an end-to-end connection to the internet, and so a DUT firmware may need to be changed so that the DUT remains connected to the test network if a specific IP address or server cannot be reached.
Efficient testing normally requires the DUT to be configured to perform differently to how it would in normal use, also special test modes enable the radio to be controlled by the RF engineer so that they can take the measurements required by the standard. The ability to vary the output power can also be useful, should a device need to be modified.
Most RF chipset manufacturers build the necessary test modes into their devices and provide support tools to enable them. Some products have a convenient interface to enable the test modes to be activated. Other equipment will not have such a convenient interface, so a different means of triggering the test mode must be established.
Some standards require evaluation of the
receiver’s performance, so the test laboratory must be provided with the means for this to be achieved. A support device, such as a laptop, is usually used to configure the sample and control the test modes. If your product features a display, then this can be used to configure the test mode. However, this is not recommended for products undergoing climatic testing, as opening the chamber door to configure the device between tests will alter the internal temperature and may cause condensation to form.
Effective preparation ensures efficient and timely testing in the laboratory. It is, therefore, paramount that the supplied application form is completed, samples can be easily configured to facilitate testing, and instructions are provided with the samples.
40 ELECTRICAL ENGINEERING • JULY/AUGUST 2025
electricalengineeringmagazine.co.uk
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