Possibly the only thing proliferating faster than smart home devices is the wireless protocols they support, including Bluetooth® Low Energy (BLE), 4G/5G cellular, Thread, Wi-Fi®, Ultrawideband (UWB), and Zigbee. Matter has increased the number of active radios operating within homes by facilitating interoperability across ecosystems. Shoehorning multiple disparate technologies into compact form factors is a major challenge for engineers, who must get them to co-exist not only within the same enclosure, but also with other nearby smart home devices using the same bands.
Protocols have coexistence techniques at the MAC layer but not the physical layer. That means engineers must develop their own strategies for integrating multiple antennas in multi-protocol devices. Achieving sufficient isolation between those antenna elements while preserving radiation efficiency is no small task.
For example, when multiple radios share common ground structures and a space-constrained enclosure, mutual coupling can quickly degrade receiver sensitivity. That undermines performance, reliability, and user experience, and in turn jeopardizes the device’s brand reputation and revenue potential.
Some smart home applications use bands in the 800 MHz range, such as thermostats and EV chargers that link to the utility meter outside to support energy monitoring or special electric rates. These low signals are better able to penetrate drywall, siding, and other physical obstructions than those at 2.4 GHz or 5.8 GHz. The catch is that they require physically larger antennas, bigger ground planes, and greater clearance from metal enclosures.
Another major challenge is that anechoic chambers and other lab tests can’t accurately replicate the range and complexity of modern homes, from detached single-family houses to lofts to high-rise apartments. Drywall, concrete, stucco, and windows all create attenuation, reflection, multipath, and fading. So do large appliances such as refrigerators. Meanwhile, microwaves, garage door openers, Wi-Fi routers, and other devices raise the noise floor. It’s impossible to predict and then test for all of these factors that could be present in a customer’s home.
Control What You Can Control
Instead, engineers should focus on the variables that they can directly control. One example is ensuring adequate space between the antennas and metal such as the enclosure, internal shielding, mounting hardware, battery cans, and even decorative metallic finishes. All of these can detune an antenna, reducing its efficiency and shrinking the effective range — problems that can remain hidden during early validation before emerging during certification or in customer homes.
To mitigate these kinds of problems, one tip is to use the final enclosure and operating environment to guide antenna topology and front-end architectural decisions, as well as PCB layout. For example, shared antennas reduce cost and conserve space, but be aware o tradeoffs such as additional filtering, switching complexity, and isolation challenges. Giving each radio a dedicated antenna can improve reliability and performance but is difficult or impractical when the device has a small and/or unusually shaped form factor.
Impedance mismatch often is overlooked or underestimated even though it directly affects radiation efficiency and the load presented to the RF front end. Poor matching increases return loss, reducing effective radiated power and lowering the relative received signal (RSSI) at the peer devices. This is particularly problematic for battery-powered devices such as doorbell cameras because it increases power consumption. Short battery life is something that user reviews flag, putting those devices at a competitive disadvantage.
To mitigate these kinds of problems, one tip is to use the final enclosure and operating environment to guide antenna topology and front-end architectural decisions. For example, shared antennas reduce cost and conserve space, but with tradeoffs such as additional filtering, switching complexity, and isolation challenges. Giving each radio a dedicated antenna can improve reliability and performance but is difficult or impractical when the device has a small and/or unusually shaped form factor.
Tuning and Testing Tips and Tools
Antenna tuning shouldn’t be done with an isolated PCB, which provides an incomplete picture of the finished device. Instead, wait until the complete mechanical and electrical system is in place, including cabling, power architecture, and sources of conducted or radiated noise.
Confirm link margin, coexistence robustness, and receiver sensitivity under realistic conditions such as mockups of houses and apartments. This helps ensure certification on the first attempt and in turn keeps the product on schedule and on budget by avoiding expensive re-engineering.
Taoglas developed a variety of online integration and simulation tools to facilitate and streamline these processes. The latest example is the AI Product Recommendation Engine, which filters and ranks antenna options based on technologies and application requirements. This minimizes design time, effort, and uncertainty in the initial product development stages.
