Antenna selection is a complex process even for experienced design engineers who work regularly on wireless enabled products. That complexity is driven by many factors:
- Each design project has specific performance objectives that will define which antennas are and are not well suited to that product, so engineers often cannot use the same antennas as in past projects
- The shape, materials and design of each product have a significant impact on the performance of antennas, making it critical to implement antennas that are suited to those specific RF dynamics
- Many products rely on multiple wireless technologies working alongside one another, adding complexity to the antenna selection process by requiring engineers to find the right performance on a number of bands
- The use cases and implementation environments for each product creates a unique RF environment that needs to be factored into the selection process, adding yet another layer of selection criterion to the process
Each of those on their own would make antenna selection complex. But taken together, those combined factors make the selection process a daunting task. This article is intended to provide some clear road signs to help you navigate through that process. Before we go further, we should note that we will focus on embedded antennas in this article. For projects that require an external antenna, we typically advise engineering teams to choose an off-the-shelf antenna. There are many reasons for that, including minimizing the impact on the exterior design of the wireless product, simplifying the installation process and cost-effectiveness. An off-the-shelf antenna is almost always the right choice for those engineering teams.
In contrast, there is a lot more variability when it comes to embedded antennas. In some cases, an off-the-shelf antenna can meet an engineering team’s needs. In other cases, a custom antenna will be the only way to achieve the performance goals of a design project. Here are 6 tips to help you navigate the process:
- Think About the Antenna Early – The biggest misconception we see is that antenna selection comes after a product is well down the road of the design process. Waiting until late in the process to think about antennas has a number of potential negative impacts. One pitfall is that an engineering team may make design decisions that paint them into a narrow corner when it comes to the antenna. That may mean they have limited options or no viable option that meets their technical or financial criteria. That can lead to delays as the team has to go through additional design cycles to resolve that roadblock. More frequently, though, the impact of not thinking early enough about antennas is that engineering teams underestimate how long it will take to select, implement and test the antenna. That can lead to delays even if no design tweaks are necessary. For those reasons, talking about antennas earlier is the single most important thing your team can do to ensure the antenna selection process avoids those issues.
- Don’t Go It Alone – The second most important thing an engineering team can do to successfully navigate this process is to have an antenna and testing partner that can serve as an advisor at key moments in a design project. We are not saying that the do-it-yourself approach can’t work. We are engineers ourselves and know how satisfying it is when we figure something out on our own. In the case of antenna selection, though, engaging with an antenna supplier typically leads to far better outcomes in terms of product performance and hitting deadlines than solely using an antenna database and datasheets to make a selection. Not only will the antenna partner help steer the selection process in the right direction, but it will also be able to help with the testing process, which is so important to making sure the antenna and the product perform as needed.
- Look at More than Gain – One of the most valuable things an antenna supplier will advise engineering teams to do in antenna selection is to expand their selection criteria. Too often, an antenna’s gain becomes the dominant factor in the selection process, but that is a problematic. An antenna may produce a lot of gain, but does it produce a radiation pattern that matches what you need the product to do? Yes, an antenna may have a high gain, but does it only achieve that in one point in space or in a small solid angle – neither of which are helpful for the use case? There is an inherent tension between gain and radiation patterns – with higher gain often reducing or altering the radiation pattern in ways that may provide inadequate coverage and performance. For that reason, I recommend that engineers look beyond just gain by looking for a combination of gain, radiation patterns and efficiency that best suit how and where the device will be used. Other important selection criteria include return loss and the physical/mechanical spec. This longer list of criteria will help steer the selection process in a more successful direction, including helping your team decide whether an off-the-shelf antenna or custom antenna is the best choice.
- If You Find an Off-the-Shelf Antenna – With that more-detailed list of selection criteria, your team and the antenna supplier can jointly review potential off-the-shelf antenna options and determine if any solutions will meet your needs. Their guidance will be valuable in interpreting data sheets, narrowing down candidates and determining if any off-the-shelf antennas are a good fit. If there are good candidates, your antenna advisor should be able to not only help you make a final choice (after testing, which we will discuss below), but also provide valuable guidance about how to implement it. Those instructions they provide will be invaluable because no antenna is an island. How they are implemented can have a dramatic impact on performance, so the guidance the supplier provides will be pivotal for a successful project.
- If You Need to Go Custom – In an ideal world, there would be an off-the-shelf antenna for every project, but that is sometimes not the case. The evaluation process outlined above can end up being a dead end, where no off-the-shelf antennas can do what a wireless product and its use case need the antenna to do. In that scenario, a custom antenna may be the right option. For engineers who have not done custom projects, there may be the perception that custom antennas are only for companies doing mass production of consumer products. The reality is that custom antennas can quickly be designed and implemented for small-scale initiatives where speed-to-market is a priority. Your antenna supplier will walk you through the process for designing the custom antenna and optimizing it for your implementation. Testing will be critical, which brings us to our last piece of advice.
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Test, Test, Test – If you do take the custom antenna route, testing will be critical. It will give you and your antenna supplier the ability to adjust the antenna design as needed not only for how it works when attached to the product but also for how it will perform in the real-world environment. RF modeling can give you a lot of valuable information, but only a well-designed testing process can replicate real-world performance and give you information about how to optimize the antenna for the RF environment in which it will be implemented. The fine-tuning can include adjustments to improve return loss, increase energy efficiency and more. The testing might also reveal minor design improvements that can be made by the engineering team to the product itself before it goes to manufacturing.
Biographies:
Gordon Barber is the Director of Product Management for the Antenna Business Unit at Laird Connectivity, which provides a full range of antennas, modules and product development services that simplify the process of using wireless technology. As Director of Product Line Management, Gordon oversees product development and strategic innovation initiatives for Laird Connectivity’s Antenna Business Unit across all market segments, including 5G, small cells and emerging cellular technologies. Gordon works with telecommunications companies and integrators to implement wireless solutions that increase connectivity for users and pave the way for the future of wireless networks. For nearly 20 years, he has worked in wireless engineering and antenna design, and he is currently leading special design projects at Laird related to Massive MIMO, 5G and other emerging technology. He earned his Electrical Engineering degree from the University of Massachusetts Dartmouth.
Ted Hebron is Senior Product Manager for Laird Connectivity, which provides a full range of embedded wireless modules and other solutions that simplify the process of using wireless technology. In this role at the company, Hebron leads development of Laird’s FirstNet-related solutions among other families of connectivity products. Hebron has 36 years of experience in RF design and antenna engineering utilizing a range of wireless technologies including cellular, radar, radio, television and low-power connectivity. He has managed engineering teams in six Laird operations centers around the globe, and his work prior to Laird includes positions at Boeing and Harris Broadcast. He earned his BSEE degree from the University of Kansas.