Written by Mathieu Pigeot
If you have spent days, weeks, months developing your IoT solution, and have finally arrived at a design that you are satisfied with, choosing the right antenna for your wireless communication devices can seem like an insignificant task.
However, experience has too often shown that doing this without consideration can compromise the function of your whole system and even, in some cases, can lead to considerable overheads (e.g. cost of sending out technicians to the field to install an antenna when a simple right-angle would have been sufficient) and time wasted; if deploying on a large-scale, you don’t want to make the mistake of underestimating the importance of your antenna!
So how should you choose the right antenna for your IoT application? What factors need to be taken into consideration and what are the mistakes to avoid? Here are some points for consideration:
If you are in the process of choosing the antenna, it is very likely that you have already designed your network map, and already know what network/communication technology you will be working with.
Most IoT applications will include either one or a combination of: cellular 4G/3G; WiFi and other WLAN technologies such as Bluetooth, Zigbee; LPWAN such as LoRaWAN/NB-IoT/Sigfox; GNSS technologies for location services; or Satellite networks such as Iridium or Orbcomm. All wireless networks use a dedicated frequency range, which your antenna must cover. Always make sure that you check the antenna specifications in order to ensure that your antenna covers the modem frequencies. See the following illustration to understand where your network stands on the frequency spectrum.
Antenna gain is all about the capability of your antenna to focus on the radiated signal, in order to increase your network coverage. This is particularly relevant to cellular networks and short range technologies such as WiFi or Zigbee, where the range of emission is limited. (As opposed to satellite networks with global coverage).
The higher the gain of the antenna, the further away from the source of emission you can go. Note however, that gain is not the only factor to influence your antenna performance; 3D pattern of reception, (which is determined by the shape of your antenna) is another big factor – therefore, be sure to always purchase a couple of samples to do a field survey before you go ahead with a large order and roll out; antenna performance is also extremely dependent on environmental conditions, so you’d better do your homework! See the illustration below for an abstract representation of the relation between gain and 3D pattern.
Form factor/Mounting option
Physical qualities of your antenna, (such as shape of the body/radome and mounting options) are things that can also seem superficial, but they have important repercussions on your application performance and can potentially translate into costly overheads.
Here are a couple of options to keep in mind:
- Right-angle antennas are small antennas that directly screw into the modem. They are a great option for internal use where reception is no issue; they are so simple to install that a child could do it!
- “Hockey puck” or low-profile style antennas are often used for in-vehicle applications, and applications utilised in busy public areas (such as in digital signage solutions and kiosks) where the antenna might be exposed to damage by passers-by, and other similar perturbation. Most manufacturers will offer either magnet adhesive pads for mounting, which can sometimes be secure enough to be used on vehicles and easy to install, or screw-mount options for a more secure installation and the advantage of being practically theft-proof. Installation is slightly more difficult, as it requires that a hole be drilled into the enclosure.
- Whip antennas will generally offer the highest performance, and will also generally be ground-independent, which means that they do not require mounting to a flat surface to work properly. This offers greater flexibility when working in tricky environments, such as on boats and electric poles.
- Other form factors include Panel mountable antennas (flat and designed to be mounted to a horizontal wall) or dome-shaped radome, designed for specific applications. Consider what is used in other similar applications to help assist when making your choice.
- When choosing a lead always be careful to use the shortest possible lead. The longer the lead, the more signal loss you will get. You should also avoid extending the lead by connecting an extension cable, as the connectors are yet another source of signal loss.
Those are very basic things to consider when choosing the right antenna for your IoT application (although we hope that they were helpful for those who are getting started in the field!). Be sure to do your research well and talk to a professional before you make your choice. There are some valuable resources online for getting more detailed tips; remember that each network has its properties, and these will affect the function of your antenna.