OTA TRP – RED / ETSI / FCC

What Is OTA TRP — RED?

TRP (Total Radiated Power) is a measure of the total power the device radiates from its antenna into the environment. The measurement is made by reading power at many points on a sphere around the device and summing them. Its difference from conducted measurement made via a cable is that it also includes antenna efficiency and the effect of the device housing.

Purpose of OTA TRP — RED

The purpose is to measure the device's radiated performance in actual use. A transmitter that looks good on the circuit board can perform poorly in the field with a badly designed antenna; TRP reveals this difference.

Which Products Is OTA TRP — RED Applied To?

Smartphones and tablets
IoT and LPWAN devices
Automotive telematics and antenna systems
Wearable devices
Wireless medical devices

In Which Sectors Is OTA TRP — RED Used?

TelecommunicationsElectronicsAutomotiveMedical Device

Standards Related to OTA TRP — RED

REDEU radio equipment directive test
ETSIEuropean telecommunications standards test
FCCUS radio and EMC regulations test

OTA TRP — RED Conditions

Environment: Anechoic chamber or verified reverberation chamber
Screening: Measurement in defined steps on a spherical angle grid
Polarizasyon: Two perpendicular polarizations are measured separately and summed
Cihaz konumu: With free space and head/hand phantom if necessary

Equipment for OTA TRP — RED

Anechoic chamber and positioner system
Measurement antennas and low-loss RF chain
Communication test set
Calibration reference antenna
Head and hand phantoms

Sample Requirements for OTA TRP — RED

The sample must be taken so as to represent the batch or production run.
Sample description, material type, and production direction if any, must be stated.
The standard to be applied and any customer specification must be provided together with the sample.
The test may be destructive; the required number of samples must be confirmed in advance.
Surfaces that will be tested must be protected during transport.

Duration of OTA TRP — RED

Depends on the number of spherical scan points and bands; a typical study takes days. Duration increases when phantom configurations are added.

OTA TRP — RED Procedure

1The device is placed on the positioner in a free-space position.
2A communication link is established and the device set to transmit at maximum power.
3The measurement chain is calibrated with a reference antenna.
4Power is measured on the spherical angular grid in two polarisations.
5Measurements are integrated over the sphere to calculate TRP.
6Repeated with head/hand phantoms if required.
7Results are reported per band and configuration.

OTA TRP — RED Acceptance Criteria

The method standard defines how the test is performed, not what the result must be. The acceptance limit comes from the material or product standard, the customer specification, or the relevant regulation; this page therefore does not give a numerical limit.

Evaluation of Results

The result is given as TRP values per band and channel. The acceptance threshold usually comes not from a regulator but from an operator acceptance specification or the device manufacturer's internal target; comparison must therefore be made with the same test plan.

OTA TRP — RED Report

Sample description, material/product information, and batch number if any
Sample preparation method and conditioning conditions
Standard and test conditions applied
Instrument used and calibration status
Measurement results and units
Measurement uncertainty (if requested)
A statement that the result applies only to the specimen submitted for testing

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Harmonised standards applied according to the product family
EU 765/2008 (market surveillance and accreditation framework)
Relevant product regulations and customer specifications

RF and Wireless Testing — What Does This Testing Field Cover?

The section below describes the field that the OTA TRP test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

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.

Method groups in this field

Transmitter measurements
Output power, occupied bandwidth, frequency error, unwanted emissions, adjacent channel power, power spectral density.
Receiver measurements
Sensitivity, selectivity, blocking, spurious response rejection.
Spectrum sharing mechanisms
Verification of listen before talk, duty cycle, dynamic frequency selection and transmit power control.
Human exposure
SAR measurement (handheld and body-worn devices), field strength assessment, multi-radio scenarios.
Protocol conformity
Cellular network conformity testing, Bluetooth and Wi-Fi certification testing, GNSS performance.
Antenna measurements
Gain, radiation pattern, efficiency and total radiated power (TRP) measurements.

Commonly confused in this field

Using a certified module does not automatically make the device compliant; if the antenna, layout or power level changes, reassessment is required.
An FCC file does not replace a CE file; each market operates its own regime.
Receiver side measurements are a regulatory requirement in some bands; measuring only the transmitter produces an incomplete file.
SAR limits and measurement methods differ by market; a result in one market does not carry over to another.
For devices carrying several radios the simultaneous transmission scenario must be assessed; measuring them individually is not sufficient.
Some markets impose local testing or a local representative requirement; technical conformity alone does not secure market access.

Which decisions these results support

Market access under radio equipment legislation
Verification of the antenna and RF front end design
SAR and RF exposure conformity
Verification of module integration and the scope of reassessment
Determining the worst case in multi-radio scenarios

Related Tests

Frequently Asked Questions About OTA TRP — RED

Isn't conducted power measurement enough?

No. Conducted measurement gives the power before the antenna; it does not include the antenna's efficiency, directivity, or housing effect. The performance the user experiences is closer to TRP.

Why is phantom-based measurement done?

The human body absorbs RF energy and alters antenna behaviour. Head and hand phantoms are used to get a realistic result for devices used close to the body, such as phones.