What is the maximum transmit power for a Wi-Fi device operating in each regulatory domain?
Wi-Fi Transmit Power Limits
Understanding the regulatory power limits is essential for Wi-Fi product development, as the maximum power directly determines the coverage footprint and link budget.
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Frequently Asked Questions
Do I need different hardware for different regions?
Usually no. The PA hardware is designed for the highest required power (+30 dBm for FCC). Firmware limits the power for each region. The regional setting is configured during manufacturing or via a software country code. However: some regions require different antenna configurations or DFS implementation, which may require hardware variants. A single-SKU design (one hardware, software-configurable power) is the most cost-effective approach.
What about antenna gain restrictions?
At 2.4 GHz (FCC): the antenna gain can be up to 6 dBi without reducing conducted power. Above 6 dBi: the conducted power must be reduced by the excess gain (e.g., 9 dBi antenna → conducted power must be reduced to 27 dBm). At 5 GHz UNII-1 (FCC): the rule is 1W EIRP regardless of antenna gain. At 5 GHz UNII-3 (FCC): higher gain antennas are allowed with corresponding power reduction. The ETSI approach is typically EIRP-based (no separate antenna gain limit, just a total EIRP cap).
How is transmit power verified during certification?
FCC and ETSI certification testing measures conducted power at the antenna connector (or radiated power for devices with integrated antennas). A calibrated power meter and spectrum analyzer are used. The test measures power at: every supported data rate (MCS0 through MCS13 for Wi-Fi 7), every supported channel, and the lowest, middle, and highest frequency in each band. The measured power must be within the declared power table tolerance (typically ±1 dB over temperature).