Innovative technologies and an expanded Internet of Things (IoT) ecosystem have transformed how the world connects, computes and communicates today. Consumer adoption of connected devices has exponentially increased and this can lead to potential issues with electromagnetic interference if the devices being sold do not conform to regulatory guidelines. Imagine a doctor’s handheld device’s signal interferes with the operation of a medical equipment that was being used to monitor a patient in intensive care!
Electromagnetic interference (EMI) consists of any spurious, conducted, or radiated signals of electrical origin and occurs when the electromagnetic field of one device impacts the operation of another device. IoT devices are EMI sources too since they transmit or utilize electrical energy and their operation generates conducted or radiated signals (WiFi/BT signals for example) that can cause equipment performance degradation.
IoT devices must thus meet applicable emission regulations as applicable to the geography where they are being sold. Products that contain radio transmitters must also comply with RF exposure criteria in order to ensure the safety of the end user and bystanders. Specific Absorption Ratio (SAR) is a measure of the rate at which radio frequency (RF) energy is absorbed by the human body and products that make body contact including wearables have to conform to SAR regulations.
In the United States, devices have to comply with FCC’s guidelines for unintentional emissions from equipment. For the EU region, devices with RF transmitters or receivers must comply with Radio Equipment Directive (RED) as well as meet any EMC criteria that apply to non-radio functions of the device. RED compliance ensures the efficient use of the radio spectrum which is critical to allow IoT devices to coexist without interfering with one another.
Qualcomm’s expertise in connectivity and compute enable them to integrate their Snapdragon platforms with their own WiFi and BT modules to create products with controlled RF emissions. Although the software implementation and features vary across Qualcomm WLAN solutions, they all incorporate a common design principle for ensuring regulatory compliant operation in all target markets: During run-time, Qualcomm WLAN implementations set transmit power to the highest value that does not exceed any of the power data described in the infographic below – for the currently configured country of operation, channel, modulation/rate, bandwidth and MIMO mode.
The design components that limit the transmit power on a device are elaborated below.
- Each board design includes calibration data or rate-to-power data. This board-specific data includes maximum transmit power that the board is capable of outputting. This data is determined by Qualcomm for each reference design and stored in the Board Data File (BDF).
- Qualcomm WLAN software contains a table (regulatory domain tabe) of allowed 2.4 and 5 GHz operating channels applicable to each country. This is used by the WiFi subsystem to allow access point and client devices to be configured for global operation. These domain limits are set to lenient levels to avoid unnecessarily limiting power.
- The Conformance Test Limit data scheme is the primary means by which end-products are limited to operate within conformance requirements for all target regions of operation. The CTL table is stored in the product BDF during manufacturing and is always product-specific.
SMART Wireless’ SoMs will typically have a modular grant so that host devices that use our SoM need not undergo any extra testing or certifications if there are no additional RF sources outside of our SoM. A few of our SBC products, like the Inforce 6620 and Inforce 6309 are FCC and/or CE certified out of the box. Shielding is the use of conductive materials to reduce radiated EMI reflection or absorption and all our products have been provisioned to have EMI shields.
Device manufacturers are not obligated to create/sell globally compliant products. Having said that, Qualcomm’s processor design coupled with SMART Wireless’ expertise in creating product solutions that can pass FCC Class A/Class B, CE including RED 2014/35/EU and all regulatory compliances applicable in multiple countries across the world, enable manufacturers to productize in all geographies seamlessly.