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When a PCB antenna for Bluetooth device is the right choice?
Bluetooth2,4GHz ISM2.4 GHzPCB trace
When you are developing a connected, wireless product, the antenna is one of the most critical design areas. Because the user experience depends on how well your product connects! Whether you are making an IoT device, smartphone, or smart ring, you can choose between two alternatives: design a custom antenna, or use an off-the-shelf (OTS) antenna. Both have their pros and cons, but here are five reasons why you should go for custom antenna design to deliver your customers a superior user experience!
The custom antenna is the need of the IoT world
Antenna experts are helping you with integrating the standard off-the-shelf (OTS) antennas and also providing a solution to customize the antenna in the RF and wireless communication market. Standard antennas offer a promising performance in ideal environments even without the matching circuit. OTS antennas can lower the cost for designing (simulations and optimization) and manufacturing (tooling and testing) of the device. Meanwhile, it also helps the engineers to meet the cost targets and delivery schedule. But a wrong decision in the selection of antenna lowers the reliability and overall efficiency of the device.
The rapid growth of the Internet of Things (IoT) and the customer’s application require some special modifications in the existing model to perform effectively. Several electrical and mechanical factors to be considered to customize an antenna and to fulfill those requirements.
Custom antenna vs. Off-the-Shelf antenna comparison
In recent time, the demand for wireless products and IoT devices have shown a rapid growth which compelled the antenna engineers to confront in choosing the available options of antennas.
OTS antennas offer better gain and efficiency in ideal conditions. But the matching circuit is required to attain correct input impedance and better performance. Usually, the standard antennas have enough ground plane surface to neglect the external interference but in wearables and IoT devices, antenna designers must figure out the limitation of the ground plane and circuit effects.
From the cost-effective point, engineers try to optimize the PCB with a thinner layer of the stack and avoid the expensive materials i.e. Rogers materials. Our team also focuses on the following factors: What is the application of the antenna? What are the desired antenna dimensions? Where should the antenna be placed? How many units are required? Non-recurring engineering (NRE) and bill of materials (BOM) cost? What is the schedule of the project?
| 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 |
As the number of IoT devices and consumer electronics is increasing to connect over Wi-Fi, the complexity of wireless devices is also increasing which compacts the antenna size and antenna placement.
Several options for placement of antenna have been established to achieve the desired antenna performance i.e. placement of antenna within the device or on PCB or external. For example, a smartphone has more than six antennas and all are compact inside the body to ensure calls, Bluetooth, Wireless Fidelity (Wi-Fi), Long Term Evolution (LTE) wireless communication standard, Global Positioning System (GPS), Near-Field Communication (NFC).
In the wearable industry, special materials for antenna designing have been introduced according to the application. Antenna size, placement and material characteristics for environmental ruggedness in wireless communication lead the antenna engineers to the development of custom antennas that meet the requirements of the customer with respect to their application.
A practical example of how Custom antenna overcomes OTS challenges
In the pictures below, there are three different situations. First is an example of an Off the Shelf (OTS) antenna on plain PCB with antenna appropriate clearance. The second is OTS on PCB and display metal frame followed by a custom antenna with display metal frame. A comparison of efficiencies is presented to understand the importance of custom antenna.
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Figure 1. Off the Shelf Antenna on plain PCB Off-the-shelf antenna on a PCB that has metallic display frame under the antenna which contradicts design rules. |
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Figure 2. Off the Shelf Antenna on PCB and metallic display frame Custom antenna with PCB and display frame that contradicts off-the-shelf antenna design rules. |
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Figure 3. Custom antenna on PCB and metallic display frame |
Off the shelf antenna works well on plain PCB, which provides the environment the antenna is designed to operate in. Once the display metal frame is introduced, it covers the antenna clearance on PCB and changes the antenna environment therefore the performance drops significantly. With a custom antenna design, the antenna volume can be optimized using all the space available from mechanics, and performance is improved.
| 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) |
The 5 ways a custom antenna can improve your product’s wireless performance
With any wireless device, the quality of connectivity has a huge impact on the user experience, and; how your product succeeds in the market.
Here are 5 reasons why a custom antenna enables you to create a better product – compared to taking a shortcut with an OTS antenna:
- The custom antenna provides better wireless performance.
The custom antenna will offer greatly improved performance on real compact devices as they are designed specifically to that environment when using the same volume of space as the OTS antenna. - You can fit more operating bands into the product.
Due to the 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 simply give access to new markets. - Better environmental tolerance.
Custom antennas can be made to be even more rugged against environmental effects than OTS antenna. You don’t need to make the trade-off with durability and performance. - A higher degree of integration
A higher level of integration with the mechanics is possible for custom antennas than OTS antennas. Mechanical parts such as metal frames, screws, or even cables can sometimes be used as the antenna. You might not even need any component that could be called the antenna when the custom antenna has been integrated into your device. - Custom Antennas are more cost-efficient
Despite the lower NRE cost of OTS antennas custom antenna becomes cheaper in volumes if that has been the design target. When the custom antenna has been integrated to such a degree that there is no component left, cost-saving in bill-of-material is obvious. A common example is a custom PCB trace antenna where the cost of the antenna has been reduced to zero at the expense of more detailed PCB supplier quality control and RF testing.
In Conclusion
Wireless connectivity is becoming ubiquitous. IoT devices are equipped with wireless connectivity because it simply is more cost-efficient. More often than not, consumer products are enabled with wireless connectivity to deliver greater user experiences. However, competition is fierce and only those devices and products with smooth and robust wireless connectivity can win customers’ hearts! This comes down to how well your antenna performs – contact Radientum to hear more about antenna design!
Disclaimer: The views and opinions expressed in this article are those of the author. It is intended only as a sharing of antenna design knowledge for educational purposes.
