Rob Campling, Manager for Global Market Access at TÜV SÜD explains the latest iterations of European regulations on wideband testing
EN 300 328 covers wideband data transmission equipment which operates in the unlicensed 2.4 GHz ISM band. This includes WiFi, Bluetooth and Zigbee devices, as well as other technologies such as proprietary wideband transmission systems and frequency-hopping spread spectrum (FHSS) devices, and covers both transmitters & receivers.
After 6 August 2021, the latest version (V2.2.2) must be followed to provide a ‘presumption of conformity’ to the EU’s Radio Equipment Directive or UK’s Radio Equipment Regulations. As EN 300 328 is one of the most frequently used standards for approval tests for products with radio technologies, these changes affect millions of devices.
Radio testing updates
The minimum performance criteria for receiver blocking has been updated to allow for a Frame Error Rate (FER) of less than or equal to 10%. This will result in a more consistent and quantifiable means of test, but it does mean less flexibility for manufacturers. For devices that do not facilitate a Packet Error Rate (PER) or FER, the standard mandates that there must be no loss of transmission for the intended use of equipment.
A change in the test requirement mandates that all Receiver Categories should now feature a blocking signal power of -34 dBm at the receiver of the equipment, after having compensated for in-band antenna assembly gain in conducted measurements or power flux density (PFD) in radiated measurements. This is a much more stringent requirement than previously.
All Receiver Categories feature a wanted signal mean power from companion device (WSMPCD) that is derived from a calculation based on the occupied bandwidth (OCBW) of the device. The WSMPCD no longer uses calculations based on the level of the wanted signal at the input of the equipment (Pmin), unless in a radiated test where the wanted signal from the companion device cannot be determined. This will result in a more consistent approach to testing and ensure the minimum receiver sensitivity for all devices.
All Receiver Categories must also be tested to new blocking signals defined in V2.2.2 that were not required in V2.1.1. This means that all equipment will need to be re-assessed to the revised Receiver Blocking requirements of V2.2.2 and manufacturers cannot self-declare against the previous version of the standard.
FHSS equipment capable of employing both adaptive and non-adaptive modes must comply with the requirements for non-adaptive FHSS equipment. Equipment must also meet the requirements for Accumulated Transmit Time, Frequency Occupation and Hopping Sequence.
Emissions
The updated standard also relaxes the transmitter unwanted emissions in the spurious domain requirement. Previously equipment had to meet -54 dBm from 470 MHz to 862 MHz and -36 dBm from 862 MHz to 1 GHz (when measured with a Resolution Bandwidth (RBW) of 100 kHz). Therefore, a device which complies with the more stringent limits in V2.1.1 also complies with the limits in V2.2.2.
The measurement procedure for determining the number of operating channels in the hopping sequence previously used an RMS detector. It is now specified that a peak detector must be used. However, as the change of detector type is unlikely to impact the number of channels detected, a device previously deemed compliant against V2.1.1 can therefore be considered compliant with V2.2.2.
Updates to standards can often cause designers and manufacturers problems, as they may be confused as to what applies to their products and how tests should be applied. In the case of V2.2.2, if a product was compliant with the old version (V2.1.1) there is no presumption of conformity and new tests must be undertaken regardless. The Technical Construction File and Declaration of Conformity must also be updated to V2.2.2 accordingly.