What is the maximum allowed power for ZigBee applications under ETSI EN 300 328?
Although ETSI EN 300 328 allows 20dBm RF output power, there is a limitation for PSD (Power Spectral Density) for wide band modulations other than FHSS. This PSD limit restricts the maximum allowed power for ZigBee applications.
Section 126.96.36.199 in EN 300 328 V2.1.1 details the test method for PSD. The ZigBee modulated signal measured according to Option 2, Step 3 (with sweep time set to 10s):
CW signal with the same power level and spectrum analyzer settings:
The peak power difference between the ZigBee and CW signal measured with RMS detector is ~2.3dB. In order to meet the PSD limit of 10dBm per MHz, the maximum allowed power is 12.3dBm (EIRP).
Note: The 12.3dBm power limit is radiated (EIRP), which means that in case of an antenna with 0dBi, the maximum conducted power allowed is 12.3dBm. For antennas with lower gain than 0dBi, conducted power can be increased, while for antennas with higher gain than 0dBi, conducted power should be reduced.
Measurements were performed on an EFR32MG13 based reference board (BRD4158A Rev A01).