Alongside connectivity and power, a third area – the antenna – needs to be given equal attention during the IoT device design process because of the fundamental impact it has on device performance. The antenna is the means by which an IoT device receives and sends signals to the outside world, and is, therefore, a mission-critical element of an IoT device. It connects directly to the RF module. However, antenna decisions are often neglected until the end of the development process, resulting in unnecessary compromises and sub-optimal siting of antennas that could have been avoided with better planning and design.
Embedded or External?
Your first decision must be embedded or external. Embedded antennas, which are integrated within IoT devices, are more complex to design for than external antennas, which are mounted to the outside of devices and are easier to add retrospectively with fewer integration issues.
External antennas are typically a dipole design and are independent of the wireless product they are connected to. In addition, because they are external to the product’s electronics, there is less risk of interference, electromagnetic compatibility (EMC) issues, and fewer size constraints with external antennas.
Eight Tips for Antenna Success
Let’s take a look at the eight considerations listed below to ensure you have properly assessed which antenna will be most suitable for your deployment.
- Understand where the antenna will be positioned and located.
- Design for the type and style of antenna you select.
- Take into account the distance between each antenna if you are using multiple antennas to ensure sufficient isolation.
- Locate a surface mount design (SMD) antenna close to the wireless module to reduce the connecting track/trace length and minimize pick-up noise.
- Use a coplanar waveguide with sufficient ground vias along the transmission line length.
- If using a flexible printed circuit (FPC) antenna with a cable, remember that cable routing is important because it acts as part of the antenna.
- Accommodate 50ohms impedance.
- Match the SMD antenna with the RF module after design completion to achieve 50ohm impedance.
Avoid Common Mistakes
There is no way to fix a bad antenna integration, so the initial preparation is vital. The common mistakes organizations make in the specification and design of devices can readily be overcome provided sufficient attention is devoted early enough to influence the design of the overall device.
An obvious first step for designers is to follow the guidelines in antenna products’ data sheets and those of the RF module. Next, check carefully to review the architecture and design. 3D STEP and Gerber file review are recommended because it is far less time-consuming to identify and rectify any issues at this early stage than later in the field. In addition to the architecture review, a productive step is to check the application notes to ensure the RF module device’s mode of operation is appropriate for the antenna selected before moving on to a full system passive or active test.
Evaluate Your Antenna Integration
This strong evaluation process can highlight and address issues before they have a live impact on deployed devices. There is no substitute for experience here, so seek suppliers that have strong R&D capability and a field application engineer (FAE) base in both antennas and RF modules to support your deployment.