RF and Wireless Testing

RF and wireless testing shows that a device containing a radio uses the spectrum correctly and operates within the limits the relevant legislation allows. This family is a separate body of work from EMC: EMC addresses unwanted interference, whereas here INTENTIONAL emission is assessed.

Spectrum is a public and limited resource, and this determines the legal character of the field. A device spilling outside its permitted band or emitting excess power is not merely a technical defect but a violation that disrupts someone else's service. Radio conformity is therefore policed more strictly than other test fields and markets maintain their own national regimes.

Measurements run separately on the transmitter and receiver sides. On the transmitter side, output power, occupied bandwidth, frequency error, unwanted emissions, adjacent channel power and the power envelope are measured. On the receiver side, sensitivity, selectivity, blocking and spurious response rejection are assessed. The receiver side is often neglected, but in some bands it is a regulatory requirement.

Access protocol specific behaviours are a third axis: listen before talk (LBT), duty cycle, dynamic frequency selection (DFS) and transmit power control (TPC). These mechanisms enable spectrum sharing and it must be shown that they work correctly.

HUMAN EXPOSURE is the fourth axis and one of the most commercially critical. For devices used close to the body, SAR (specific absorption rate) is measured; for devices used at a distance, a field strength assessment is made. Limits and measurement methods vary by market; the same device is assessed separately for Europe and the United States.

Market regimes are decisive in this family and do not substitute for one another: the Radio Equipment Directive and ETSI harmonised standards in Europe, FCC authorisation in the United States (through a TCB for intentional radiators), ISED in Canada, MIC in Japan, KC in South Korea and SRRC in China each carry their own set of requirements. The same device requires a separate file for each market, and some markets impose a local representative or local testing requirement.

Module integration is the subject that raises the most questions in the field. Using a certified radio module does not automatically make the device compliant. A module certificate is valid for a defined antenna, a defined supply and defined conditions of use; if the antenna changes, the layout changes or the module is operated at a different power level, reassessment is required.

The presence of several radios in the same device (Wi-Fi + Bluetooth + cellular + NFC) gives rise to a simultaneous transmission assessment: SAR and unwanted emission measurements are made for the worst case in which the radios operate together.