How to Optimise RF Performance in Wireless Metal Devices
With new wireless technologies ever emerging, engineers are creating devices for ever widening variety of applications. This growth in the Internet of Things has been made possible by achieving sufficient wireless antenna performance.
Metallic product housings and enclosures do not form antenna friendly environments. For components that are wholly a product of operating environment, conductive surfaces are detrimental.
Innovative devices push the boundaries of possibility. That's where the biggest market potential lays. Here's what you need to do to ensure antenna performance is not impacted.
Metallic enclosures aren't antenna friendly
Needless to say, but antenna are the elements of a device that connect it. Many new devices are virtually redundant if they cannot connect as they promise.
This makes metallic enclosures an important design decision. Conductive materials (including carbon fibre and fibreglass), can block electromagnetic transmissions and generate noise.
Electromagnetic fields create currents on conductive materials, effectively turning them into radiators. This will detune and block RF transmissions. Even when enclosures are 'windowed' with nonconductive panels, performance is usually highly limited.
This necessitates a higher radiated power, as the antenna is working less efficiently and drawing more power. In low powered devices, this can wreck havoc to battery life.
This is the challenge many engineers face. So what can you do to reduce this effect?
Clarify your design brief
Wireless products require a holistic design approach - that's where RF performance is considered alongside all design decisions.
Understanding how the device will be used and what its requirements are is essential. It may be necessary to get clarity beyond a simple design brief to get this right first time.
There are many variables in antenna integration - all of which could render your product unable to work. The variables of your design will determine what the best approach is to get the most efficient performance.
Your choice of antenna will go some way to determining the best design for performance. The physical form of your device may determine a particular solution to be the most effective.
Embedded antenna are still the preferred option for wireless connectivity. However, embedded antenna are the most challenging to integrate within a metal enclosure.
In larger devices, with large nonconductive panel windows to allow radiation, they can achieve better levels of performance. In smaller devices, performance parameters are rarely sufficient, at worst, these devices can fail to work.
To use an embedded antenna, you may need to significantly compromise on your initial designs. This reaffirms the need to consider RF performance throughout every stage of your development cycle.
Mounted multilayer antenna
In modern, innovative applications, the performance of an embedded antenna is sometimes unsuitable. This requires a different antenna selection - particularly in devices that cannot afford to have large windows to allow radiation, large external antenna attached to them or nonconductive enclosures.
It is possible to use a multilayer antenna and mount it to the enclosure of a device. These antenna feature ferrite-like layers to isolate noise and allow for the antenna to perform as if it was in free space.
Furthermore, these are easily hidden due to their small footprint. Unlike embedded dipole antenna they are not thick (just 1.6mm) and do not create bulges. Carbon fibre bicycle frames could hide these antenna behind a badge or branding with little impact on performance.
In these challenging applications, the positioning of an antenna becomes all the more important. For embedded antenna, the radiation will be highly concentrated, thus will need to be pointed towards the source for any type of performance. Without this careful positioning, embedded antenna can fail to work.
Likewise, multilayer antenna require some of the same considerations. The in-situ use and materials nearby in the operating environment can negatively impact wireless performance. For example, in SMART metering applications, it may be necessary to point the antenna away from detuning conductive objects. This is why a location that is easily seen is recommended.
As more metallic SMART devices hit the market, the challenge of creating an environment suitable for antenna performance has not got easier. There is no perfect solution for all metallic products, so it’s important you are aware of the characteristics that will enable efficient RF performance.
Now devices can be powered by single-cell batteries, efficient antenna performance has become more vital. Yet, in metallic enclosures, the natural operating environment poses challenges to achieving this goal.
If wireless performance is an important criteria of your brief, then a multilayer antenna may be the cost-effective solution you need to increase performance. For more information about multilayer antenna, click below to read more about the Antenova REFLECTOR range of antenna.