Standards & Regulations
Overview of radio compliance testing
By Phil Evans, business development director - connectivity (Northern Europe) at TÜV SÜD, a global product testing and certification organisation
T
he purpose of radio compliance testing is to demonstrate that your radio equipment meets with legislative requirements. These often differ from region to region and whilst all regions require transmitter parameters to be assessed, some also require an evaluation of receiver performance. For efficient testing that optimises time to market for products, preparation is key.
Typical transmitter tests include: Radio frequency (RF) output power
-Measurement of the amplitude of the fundamental signal being emitted from the device under test (DUT). Frequency error – Determining the difference between the actual and nominal frequency the transmitter is intended to use.
Power spectral density – The amount of power in a given bandwidth which is often specified in terms of dBm/MHz.
Occupied bandwidth – The bandwidth of the frequency spectrum the fundamental signal occupies.
Spurious emissions – Outside the operating frequency band of the DUT, does the DUT emit above a specified amplitude at unintentional frequencies?
Band edge – At the edges of the operating band, does the device comply with the out- of-band domain requirement? The growth of wireless technologies has seen the frequency spectrum being more carefully managed by regulatory authorities. This is especially so with the unlicenced frequency spectrum, which has become subject to new tests whereby radio frequency spectrum congestion is assessed before assignment of resource channels. This includes adaptivity, where ETSI EN 300 328 / EN 301 893 / EN 303 687 require devices to implement a channel access mechanism. Both the Federal Communications Commission in the USA and FCC and ISED (Industry Canada) require the use of a contention- based protocol, also known as “listen
38 June 2025
before talk,” to prevent interference with incumbent (licensed) services. Users of the 5250-5350 and 5470-5725 MHz bands must also implement dynamic frequency selection whereby the presence of radar signals must be assessed.
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 receiver tests such as: Receiver selectivity – The measurement of the minimum level of signal received by a device that still results in effective communication.
Receiver blocking – The ability to receive a wanted signal in the presence of an out-of- band interference signal.
Adjacent channel selectivity – The ability to receive a wanted signal in the presence of a similar signal using the adjacent channel. It should be noted that in the UK, the
Components in Electronics
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.
Before testing begins
Whilst the test laboratory will have an in-depth knowledge of the test standards, they may be less familiar with your products. Therefore, they will need two crucial pieces of information to aid with the timely completion of testing. Firstly, application forms contain critical data specific to the DUT, such as voltages, operating temperature ranges, antenna gain, and nominal channels/ bandwidths. For devices with multiple technologies, the test laboratory may require multiple forms to be completed, and they should help you complete these forms. Secondly, detailed step-by-step test sample instructions are required to show how to put the DUT into the required modes
of operation. As the laboratory may be unfamiliar with your product, and often multiple engineers on different shifts work on projects, easy-to-follow, detailed guides are a must, and screenshots and photographs are fantastic aids.
Hardware requirements Most radio compliance testing requires the manufacturer to provide specially configured samples for assessment; it is rare that a normal ‘off-the-shelf’ product is suitable for compliance testing. For example, equipment with integral or permanently attached antennas may require a modified sample which provides a temporary antenna connector in order to facilitate the test to be performed by direct connection via a coaxial cable to measuring instrumentation. As test samples can be subject to stresses and strains, as the connections to the test equipment are made and removed, temporary antenna connectors need to be robust. A top tip is to glue the antenna
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