KBA_BT_0410: TX power limitations for regulatory compliance (ETSI, FCC)
03/85/2019 | 12:34 PM
Without Adaptive Frequency-Hopping (AFH)
ETSI EN 300 328
It is generally true that ETSI EN 300 328 allows 20 dBm RF output power in all such cases when equipment is using wide band modulations other than FHSS (Frequency Hopping Spread Spectrum). In these cases PSD (Power Spectral Density) also must be tested, which allows 10 dBm / 1 MHz.
These restrictions apply to those BLE devices, where adaptive frequency hopping is not enabled. In the case of 125 kbps, 500 kbps and 1 Mbps PHY (~1 MHz bandwidth) it means that the maximum radiated power allowed is 10 dBm. In the case of 2 Mbps PHY it is a few tenths dB more.
FCC 15.247
Based on FCC part 15.247 in the case of wideband digital modulation the output power can go up to 30 dBm and the power spectral density must be below 8 dBm / 3 KHz.
In the case of 500 kbps (coded), 1 Mbps and 2 Mbps PHY 30 dBm limitation is applied.
In the case of 125 Kbps coded PHY the device doesn’t pass the 8 dBm/ 3 KHz PSD limit with full power, thus the maximum output power allowed is 14 dBm.
Summary
Since Bluetooth stack takes the strictest regulation, thus the maximum output power is 10 dBm in those cases when AFH is not enabled (or AFH is enabled but no more than 15 channels are available). This stack limitation (10 dBm EIRP) is valid in for all PHYs and devices.
Power Limits Without AFH
EIRP [dBm]
FCC
125 kbps coded PHY
500 kbps, 1Mbps and 2 Mbps
14
30
ETSI
10
Supported by stack
10
With Adaptive Frequency-Hopping (AFH)
ETSI EN 300 328
When adaptive frequency hopping is allowed (and at least 15 channels is available) the only one limitation is maximum 20 dBm EIRP. There isn’t any restriction for PSD.
FCC 15.247
If AFH is used, the maximum output power, which is allowed by FCC, can be 30 dBm and there isn’t any PSD limitation. FCC contains a restricted band from 2483.5 MHz to 2500 MHz and due to this in several cases power limitation is needed on the edge channels.
Summary
Considering regulations of FCC and ETSI, when AFH is applied and at least 15 channels are available, the maximum conducted output power, which is allowed by BLE stack, is 20 dBm on all channels except of on channel 37 and 38 (physical channels not logical channels) . The output power is limited to 18 dBm on channel 37 and 15.3 dBm on channel 38 in the case of all PHYs. There isn’t any limitation on channel 39, because the upper channel is only used for advertisements, so with the low duty cycle correction advertisements can be sent at full power.
Power Limits With AFH
EIRP [dBm]
FCC
channel 37
channel 38
all other channels
18
15.3
30
ETSI
20
Supported by stack
18
15.3
20
Bluetooth Low Energy
Knowledge Base Articles
RF Hardware
If customer only need to pass FCC, if they can set TX power greater than 10dbm without AFH for advertising? For example 14dbm since it is the lowest power for all phys.
0
To indicate the region, you would probably need different hardware for different regions. Not worth it for 4 dB. The stack uses the strictest restriction, so that the device is compliant in all regions.
0
To be in conformance with ETSI,
In case of non connectable beacon (TX only), is it possible to advertise at EIRP 20 dBm with a specific duty cycle ?
So with Silabs stack and a specific duty cycle it is possible to advertise (EIRP dBm) 18 (channel 37), 15.3 (channel 38), 20 (channel 39)?
thanks for your kind reply
0
No, you can only advertise up to 10dBm.
0
Just to be clear, are you saying you can only advertise at 10dBm because the stack limits you...or is it because the ETSI/FCC regulations limit you to 10? I.e, would it be and ETSI violation if you send a single iBeacon at 20dBm?
KBA_BT_0410: TX power limitations for regulatory compliance (ETSI, FCC)
Without Adaptive Frequency-Hopping (AFH)
ETSI EN 300 328
It is generally true that ETSI EN 300 328 allows 20 dBm RF output power in all such cases when equipment is using wide band modulations other than FHSS (Frequency Hopping Spread Spectrum). In these cases PSD (Power Spectral Density) also must be tested, which allows 10 dBm / 1 MHz.
These restrictions apply to those BLE devices, where adaptive frequency hopping is not enabled. In the case of 125 kbps, 500 kbps and 1 Mbps PHY (~1 MHz bandwidth) it means that the maximum radiated power allowed is 10 dBm. In the case of 2 Mbps PHY it is a few tenths dB more.
FCC 15.247
Based on FCC part 15.247 in the case of wideband digital modulation the output power can go up to 30 dBm and the power spectral density must be below 8 dBm / 3 KHz.
In the case of 500 kbps (coded), 1 Mbps and 2 Mbps PHY 30 dBm limitation is applied.
In the case of 125 Kbps coded PHY the device doesn’t pass the 8 dBm/ 3 KHz PSD limit with full power, thus the maximum output power allowed is 14 dBm.
Summary
Since Bluetooth stack takes the strictest regulation, thus the maximum output power is 10 dBm in those cases when AFH is not enabled (or AFH is enabled but no more than 15 channels are available). This stack limitation (10 dBm EIRP) is valid in for all PHYs and devices.
500 kbps, 1Mbps and 2 Mbps
With Adaptive Frequency-Hopping (AFH)
ETSI EN 300 328
When adaptive frequency hopping is allowed (and at least 15 channels is available) the only one limitation is maximum 20 dBm EIRP. There isn’t any restriction for PSD.
FCC 15.247
If AFH is used, the maximum output power, which is allowed by FCC, can be 30 dBm and there isn’t any PSD limitation. FCC contains a restricted band from 2483.5 MHz to 2500 MHz and due to this in several cases power limitation is needed on the edge channels.
Summary
Considering regulations of FCC and ETSI, when AFH is applied and at least 15 channels are available, the maximum conducted output power, which is allowed by BLE stack, is 20 dBm on all channels except of on channel 37 and 38 (physical channels not logical channels) . The output power is limited to 18 dBm on channel 37 and 15.3 dBm on channel 38 in the case of all PHYs. There isn’t any limitation on channel 39, because the upper channel is only used for advertisements, so with the low duty cycle correction advertisements can be sent at full power.
all other channels
To be in conformance with ETSI,
In case of non connectable beacon (TX only), is it possible to advertise at EIRP 20 dBm with a specific duty cycle ?
So with Silabs stack and a specific duty cycle it is possible to advertise (EIRP dBm) 18 (channel 37), 15.3 (channel 38), 20 (channel 39)?
thanks for your kind reply
Just to be clear, are you saying you can only advertise at 10dBm because the stack limits you...or is it because the ETSI/FCC regulations limit you to 10? I.e, would it be and ETSI violation if you send a single iBeacon at 20dBm?
thanks