Antennas as Afterthoughts

Mistake: The device form factor is finalized, the RF module is chosen, and the PCB is laid out. Time to bring in the antenna, right?

Wrong. When choosing an embedded antenna weeks or months into the project, go ahead and start scheduling time for rework. For instance, the smaller the device, the more likely that the processor, memory, battery, and other components will need to be moved to free up PCB space for the antenna. And even when the design left room for the antenna, that doesn’t necessarily mean that spot is the ideal board position to optimize performance and pass carrier certification. All of that rework takes time, which is money.

Solution: Treat embedded antennas as a day one decision, not day 90. They’re not just another component. Instead, the choice and integration are fundamental, system-level decisions that directly affect the device’s time to market, time to revenue, performance, service life, sustainability, and competitiveness. All of those aspects directly affect your brand reputation and bottom line because if a device doesn’t perform well or isn’t even available when customers need it, competitors will get that business instead.

The Taoglas Antenna Integrator tool facilitates and expedites this process. Simply input a custom PCB size and then select and place multiple Taoglas antennas on the digital board. Once configured, the design is submitted to Taoglas, and users receive a technical report within 24 hours that includes detailed antenna performance parameters, including return loss and efficiency.

Incorrect Integration

Mistake: The embedded antenna is placed in a spot that undermines performance, to the point that the device can’t meet customer requirements or pass carrier certification or both. Correcting that mistake requires expensive, time-consuming rework or having a custom antenna developed to accommodate those PCB limitations.

Solution: Every Taoglas antenna has an integration guide with detailed guidance for PCB location, minimum ground plane size, and other aspects to ensure optimal performance. When comparing antennas, read their integration guides to help identify the right model. It’s another example of why antennas should be a day one consideration.

For example, chips and other small antennas are highly sensitive to their PCB placement due to limited impedance bandwidth and efficiency. The PCB boosts the antenna’s radiation because currents are excited on the PCB ground plane. (For a deeper dive, see “Why Antenna Placement on PCBs is Critical for Chip Antenna Radiation Performance.”)

When researching antennas, read each one’s integration guide recommendations for PCB location and minimum ground plane size. This helps narrow down the options and pinpoint the model that the device’s and PCB’s form factors can support.

Poor PCB Design

Mistake: When the PCB doesn’t have the size or shape necessary to support the antenna, something has to change. Either the PCB has to be redesigned or a custom antenna must be used to accommodate the form factor limitations. Both options take time and money.

Solution: The device’s form factor ultimately determines the PCB’s size and shape. Use those measurements to help identify the antennas that can perform well on that board. Of course, that’s possible only when the antenna is a day one consideration.

Suppose the integration guide for one of the antennas under consideration recommends placement mid-point on the long side of the PCB with a minimum ground plane of 90×50 mm. Can the device form factor accommodate a PCB capable of providing that? If not, then see if any of the other candidate antennas can work with that size and shape.

The integration guide also provides the keep-out area specs. Use those determine where the processor, memory, battery can, and other metallic components can be placed without compromising antenna performance and reliability. Apply the keep-out parameter to all relevant layers.

Make sure that width and thickness of the transmission line traces, as well as the PCB thickness, are all capable of achieving 50 ohms. This maximizes performance and battery life by minimizing signal reflection and can help maximize component life by keeping heat to a tolerable level. Proper impedance matching also is key for achieving passing carrier certification on the first submission.

Overlooking Matching

Mistake: Setting and forgetting. Just because the antenna is in exactly the right place on a perfectly engineered board doesn’t guarantee optimal system-level performance.

Solution: Antennas are highly sensitive to their surrounding environment. That’s why their real-world tuning often differs from that of the design target or development board implementation.

An antenna’s resonant frequencies typically can be adjusted with small physical modifications to the antenna itself or by implementing a lumped element electrical matching network. To ensure that the latter is an option if it turns out to be necessary, leave space on the board for the matching components.

Not Calling in the Experts

Mistake: Hubris or embarrassment.

Solution: Whether you’ve designed dozens of successful wireless devices or embarking on your first, someone else always has more experience. Leverage that.

Taoglas has spent nearly a quarter century helping device OEMs and system integrators develop and refine hundreds of different types of devices for cellular, GNSS, Wi-Fi, and other technologies. Taoglas’ engineering services are a convenient way to leverage that expertise to keep projects on time and on budget.

For example, CSA.30 and CSA.31 services help identify and correct integration mistakes such as designing a device enclosure flush against the top of a patch antenna. This creates a dielectric gap that detunes the antenna, shifting its frequency and reducing gain. In less than a workweek’s worth of tests, these two services help devices pass carrier certification and get to market faster.

Another example is the Taoglas AntennaXpert suite of tools. Antenna Integrator helps optimize RF performance, component placement, and PCB size, while simplifying mechanical integration and reducing development time.

Get in touch for orders or any queries: sales@rfdesign.co.za / +27 21 555 8400

Courtesy of Taoglas