How is a thermal power measurement made?
Thermal power is a broadband, unfiltered measurement that measures all power present at the test set's RF IN/OUT connector using a thermal detector. Because of its high accuracy when measuring power up to +28 dBm, this is the preferred measurement to use for higher power measurements, such as the Maximum Output Power test (3GPP TS 34.121, section 5.2, v3.2.0).
The 3GPP standard specifies that this measurement be made over at least 1 timeslot (667 µs). The implementation of this measurement in the test set measures over 10 ms with the UE in power control algorithm 2.
The thermal power measurement automatically zeroes itself for each measurement; no other calibration is required. To meet specified performance, the test set must be operated in the temperature range of 20° C to 55° C.
The thermal power measurement is not as fast as the channel power measurement, and is not intended to measure signal levels below -10 dBm. Use the channel power measurement to measure power levels from -11 dBm to -61 dBm, or when maximum measurement speed is required. See
Channel Power Measurement Description
.
Trigger Source
No synchronization between the test set and the mobile station (UE) is needed, so immediate triggering is always used for this measurement. No trigger delay is available.
Differences in Thermal Power and Channel Power Measurement Results
Because the thermal power measurement is an unfiltered measurement, its results are typically about 0.25 dB higher than the filtered channel power measurement results.
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