Today’s global society relies heavily on technology and the access it delivers. Whether for personal consumption or for work, wearable and wireless devices such as smartphones, tablets and laptops are used daily. Therefore, it is imperative that devices provide robust connectivity while maintaining safety compliance.
Global standards have been adopted by the various international regulatory agencies that all devices must adhere to. Specific Absorption Rate, commonly referred to as SAR, provides a straightforward means of measuring the RF energy absorption by the body from the source being measured. SAR ensures that the RF emissions from connected devices—such as smartphones, tablets and laptops—are within the safety guidelines set by the Federal Communications Commission (FCC) and other international regulatory agencies. With the rise of 5G devices hitting the market, there’s a bigger need for leading device manufacturers to build products with high-quality connectivity in 5G/Wi-Fi 6. So how do these manufacturers design products that deliver on performance while keeping consumers safe?
The answer lies with the embedded smart sensors found inside (Figure 1). By leveraging these sensors, connected devices can intelligently detect human presence and enable advanced RF control when the user is in close proximity without compromising the user’s experience.
SAR Compliance Guidelines
In 1996 , the FCC introduced SAR standards that require device manufacturers to regulate the levels of RF power emitted. In order to maintain an optimal balance of connectivity on the device, as well as safety for the end-user, manufacturers have had to continually improve performance while adhering to global safety standards.
Before consumer connected devices are sold, each design must be tested for compliance with standards set by regulatory agencies in each region. In the United States, the FCC sets the exposure limit for the general public to be a SAR level of 1.6W/kg averaged over 1 gram of tissue with a maximum separation distance of 25 mm from the user. The European standard, however, is 2W/kg (over 10g of tissue) with a separation distance limited to 5mm from the body.
Since the introduction of these standards, the complexity of RF system designs has advanced and the usage of these wireless devices has become increasingly widespread. Therefore, it is important to have standards reviewed and updated regularly—based on usage—in order to maintain an optimal balance of connectivity and RF safety (Figure 2). Here are a few key factors that leading manufacturers must keep in mind as regulations evolve:
- The current/projected SAR limits and certification process in the targeted country where the product is to be sold
- The importance of early-stage SAR testing in order to optimize the RF design and minimize risk of delay in development cycle
- The best solution to optimize performance while maintaining safety compliance
Reliable Intelligent Sensors
Intelligent SAR sensors help deliver better consumer experiences and are most commonly used for RF optimization. When incorporated into connected devices, smart sensors offer a variety of benefits such as improved performance and adherence to global regulations.
An effective way to balance performance with safety compliance is to implement a SAR sensor that manages the power output of the device dynamically based on proximity to the user. This delivers a vastly superior customer experience. For example, when a smartphone in is your pocket, the sensors reduce RF power to minimize exposure to the user. When the user pulls the smartphone out of their pocket, the sensors recognize the increased distance from the user to the phone and boosts the signal for a better connection.
With the increase in 5G devices hitting the market, there are new design complexities and more compliance challenges for leading manufacturers. To enable ultra-high speed 5G devices, smartphones, tablets and laptops are designed with high-performance RF systems often containing an increased number of antennas to support the demand for more reliable connectivity and greater bandwidth. Instead of compromising the performance that consumers are expecting from 5G, the use of SAR sensors provides manufacturers an effective solution to ensure a good customer experience while also maintaining the stringent global safety compliance.
For wearables—earbuds, smartwatches and fitness trackers—smart sensors improve user experience by providing “wear and go” features such as auto on/off. These sensors provide the rapid response functions that users desire including smart assistant activation, noise cancellation control and media player management. According to Statista , the number of devices is forecast to reach more than 1 billion by 2022. The increased demand for more intelligent wearable devices will drive the need for smart sensor designs in order to support intuitive gesture control and extended battery life.
As consumer devices rapidly evolve, device manufacturers are challenged with delivering solutions that leverage the best available technologies to deliver both high performance and user safety. The companies who lead the charge will be the leading manufacturers that continue to innovate and develop the best performance without compromising compliance.
Semtech | www.semtech.com
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • JANUARY 2021 #378 – Get a PDF of the issue
David Wong is senior director of consumer sensing products for Semtech’s Wireless and Sensing Products Group. He’s responsible for the newly launched PerSe intelligent sensor platform for enhanced connectivity and SAR compliance in mobile devices (5G/Wi-Fi) and intuitive control in wearables applications.