Wi-Fi thermal challenges for RF front-end designers

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Cees Links is a Wi-Fi pioneer and the founder and CEO of Greenpeak Technologies and currently General Manager of Qorvo’s Wireless Connectivity business unit.

There are two main design challenges when it comes to thermal management in the Wi-Fi front-end. The first is the increased demand for smaller, sleeker routers, access points and wireless speakers that must be aesthetically pleasing. Consumers are migrating away from one wireless router per home and toward a mesh-networked home, driving the need for a smaller and less obtrusive product. Additionally, Wi-Fi is designed into set-top boxes, speakers and voice assistant devices that are also becoming smaller and sleeker. Smaller and more pleasing to the eye is good for the consumer, but it creates additional pressure on the design as the devices inside have less space to properly dissipate the heat they create.

The second challenge is in the enterprise market, where the power source for Wi-Fi products is in the Ethernet connection. This Power over Ethernet (POE) connection is limited, so the challenge for product designers is to maximize the RF output power of the RF front-end with a limited POE. Efficient power dissipation is key.

Power dissipation is defined as the amount of power consumed and converted to heat. Electronic devices produce heat, as an unwanted by-product, which is a waste of energy. The desired state of any RF circuit is to reduce this wasteful heat and provide extensive RF output power, system efficiency and RF signal range.

This means RF front-end designers must create products that function using a low power source but produce high RF output power. And they also need to ensure their products efficiently remove the unavoidable excess heat created, to maximize RF output and reduce unwanted cooling fans or bulky heat sinks. These fans and heat sinks hinder the manufacturer’s ability to meet the sleek, small, aesthetically pleasing product criteria.

To solve the thermal heat/dissipation challenge, an innovative plan of attack is needed, one that focuses on efficiency, low current consumption and maximum power output. This design approach can help reduce thermal dissipation by 25–50 percent per RF stream while maintaining output power requirements and RF range.

Wi-Fi 5 and Wi-Fi 6 routers and access points with multiple RF multiple-input multiple-output (MIMO) streams are typically subjected to average temperatures of 60 °C or higher, even when the room is a moderate 25 °C. Additionally, more functionality and more data throughput in a smaller product footprint all contribute to the same problem: more heat.

Fortunately, there are some innovative 2.4 and 5 GHz products in the market that address both Wi-Fi 5 and Wi-Fi 6 solutions with multiple RF streams and voltage requirements. These RF front-end (RFFE) products address the thermal and power dissipation challenge, but they also meet the small form factor requirement. They help enable a broad range of end-products and market sectors, such as retail, operator, enterprise and consumer, in a form factor that’s acceptable to customer requirements.

Heat can degrade overall system performance, impacting throughput, range and the ability to prevent interference. So, when designing Wi-Fi systems, it’s important to choose RFFE components that mitigate heat-related problems. Product designers should also consider using fully optimized, integrated front-end modules (FEMs) instead of discrete front-end components. These modules reduce line lengths and the need for tedious tuning of the design, which contributes to insertion loss and system heat.

By choosing RFFE modules that provide a complete solution – that meet the stringent thermal and RF range requirements and integrate filter, PA, LNA, switch, detector and coupling in one package – designers can remove the expense and tedious task of piecing these individual components together. Instead, the design process can be streamlined, costs reduced, products certified faster, and most importantly: time to market is reduced and stringent schedules can be met.