Connection in a Wireless World: Comparing Custom and Off-the-Shelf Antennas

March 19, 2024

Blog

Have you ever had a smart watch that has – yet again – lost its connection to your phone, or a wireless controller that keeps on blinking instead of linking to your gaming console? Even though our world has fully embraced wireless technology, performance issues persist.

When you design a wireless device, the antenna becomes a gateway to the outside world – a component that transforms your smartphone into something more than an overpriced pocket calculator. Your choice of an antenna boils down to two options, either you design a custom antenna, or you go for an off-the-shelf (OTS) component. Both options have their merits and drawbacks, but only one of them ensures the best possible user experience.

An Off-the-Shelf Option for an Off-the-Shelf Situation

There’s no denying that a well-integrated OTS antenna can offer great results. When used in its ideal environment, an OTS component offers good performance, while lowering the design and manufacturing costs of the device. It is an especially attractive option when a project is trying to meet its cost and schedule targets. Those “ideal environments” can, however, become a crux, achieving correct input impedance and better performance requires a matching circuit. With wearables and IoT devices, the limitations of the ground plane and circuit effects also present their own problems. A misstep in the decision process lowers the reliability and overall efficiency of the device considerably.

As the landscape of IoT devices and consumer electronics evolve, customization becomes more crucial than ever. The growing consumer demands require constant modifications, which in turn requires several electrical and mechanical factors to be considered. More complex devices also mandate more compact designs for antenna size and placement, since devices tend to stay the same size, or get even smaller. All of this will naturally bring its own limitations and challenges.

And it’s not like product design is easy to begin with. Optimal antenna placement varies from device to device. Have you ever wondered how many antennas a modern smartphone requires, with every connection from 5G to Wi-Fi? With wearables, antenna engineers need to also take the unique size, placement, and material characteristics into account.

Comparing Antenna Options

Engineers evaluate antenna options based on multiple factors, such as non-recurring engineering (NRE) and bill of materials (BOM) costs, project schedule, unit requirements, dimensions, placement, and application. A simple comparison between OTS and custom antennas summarizes the differences:

	OTS Antenna	Custom Antenna
NRE cost	Low	High
BOM cost	High	Low
Performance (following design rules)	Excellent	Excellent
Performance (breaking design rules)	Poor	Good
Durability	Product dependent	Good

Custom antennas may have higher NRE costs, but efficient design work results in significantly lower BOM costs. OTS solution on the other hand saves on development and design costs, but the material costs will be higher due to lack of optimization. While both antennas have excellent performance in ideal conditions, only custom antennas maintain their performance in diverse environments. Customization can also address specific challenges to enhance durability.

Overcoming OTS Challenges: A Practical Example

To illustrate the difference between antenna solutions, we compare the efficiency between three different options. The first one features an OTS antenna on a plain PCB with appropriate clearance for the antenna. The second one also shows an OTS antenna on a PCB, but this time we have added a metallic display frame to it. This is an example of a typical modification. Finally, there’s a similar metallic frame, but this time the antenna has been customized.

 

(Figure 1, Figure 2 and Figure 3. OTS antenna on plain PCB. OTS antenna on PCB and metallic display frame. Custom antenna on PCB and metallic display frame.)

Let’s compare the results. The first OTS antenna works well on a plain PCB, since that is the environment in which it’s been designed to operate in. However, once we introduce the metallic display frame, it covers the antenna clearance on the PCB. The change in the antenna environment drops the performance significantly. This problem does not appear in the scenario with the custom antenna. The antenna volume and performance can be optimized by using all of the space available from mechanics. This example is illustrative, but it represents a common real-life problem. Modifications to the original design may seem insignificant, but they can still affect the performance drastically.

 

	Antenna Efficiency (699-960MHz)
OTS antenna on plain PCB	30% (-5dB)
OTS antenna with display frame	3% (-15dB)
Custom antenna with display frame	25% (-6dB)

Quality of the Connection = Quality of the Device

The success of any wireless device depends on the quality of the connection. With poor antenna performance, other features will perform poorly or be rendered completely useless. Even though an OTS component can offer similar performance in ideal settings, a customized solution offers many advantages.

1. Custom antennas ensure better wireless performance
   • Custom antennas offer significantly better performance on compact devices. This improved performance does not require any extra space.
2. You can fit more operating bands into the product
   • Due to improved performance, a larger number of operating bands can be covered with a single custom antenna, compared to a single OTS antenna. This might remove the need for active antenna tuning or product variants, leading to cost savings or access to new markets.
3. Better environmental tolerance
   • Custom antennas endure environmental effects better than OTS antennas. With custom antennas, there is no need for a trade-off between performance and durability.
4. Higher degree of integration
   • A higher level of integration with the mechanics is possible for custom antennas. Mechanical parts such as frames, screws or cables can be used as the antenna. You might not even need any separate antenna component when your device has been custom designed.
5. Custom antennas are cost-efficient
   • Despite the lower NRE cost of OTS antennas, custom antennas may become cheaper in volumes. When the custom antenna has been integrated to such a degree that there is no component left, cost-saving in bill-of-materials is obvious. A common example is a custom PCB trace antenna, where the cost of the antenna has been reduced to zero thanks to PCB supplier quality control and RF testing.

To find out more about different antenna solutions, contact Radientum’s antenna design services. If you want to learn more about antenna design and testing or EMC, check out Radientum’s blog.