COVER STORY
Considerations for successful antenna selection
Antenna selection is often one of the most challenging parts of a design even for the most experienced RF engineers. It will be no surprise that it is also fundamental to the performance of any wireless connection and hence one of the most important aspects. Without a well- functioning antenna, the radio link may not be stable and the user’s experience and therefore market acceptance of the product will likely suffer.
Perhaps because it is thought of as hard, we often find that the choice of antenna is often left till last, which can mean compromises in performance, costly redesigns and delays getting a product to market. Sometimes, a project could have adopted a standard design if the selection had been made early but is forced to commission a more costly custom solution to fit the space left over to accommodate it.
But how do you ensure you are selecting the best antenna for your device? The answer to this question is often complex and dependent on many factors relating to how the device is built and deployed. Andrew Pockson, divisional engineering manager at Anglia, has been working with a world leader in antenna design, Taoglas to identify the key considerations that designers need to bear in mind when choosing the right antenna for their product.
Taking the right first steps
The most crucial point is to ensure that the antenna selection is considered at the concept stage of the development cycle because it will influence so many aspects of the electronic and mechanical design. At the concept stage the housing dimensions and PCB layout have not yet been finalised meaning the design can be adapted giving a wider choice of off-the-shelf antenna options to meet the application requirements. This also makes it much easier to achieve an optimal RF performance within the mechanical and electrical constraints of a system as they can be adjusted to suit. Don’t assume an antenna which worked on a previous design will also be suitable for a new design, even minor changes like the layout of the PCB tracks or the enclosure material, including pigments, fillers and coatings can have a substantial influence on the antenna performance. Mechanical complexity can also hamper antenna efficiency due to parasitic coupling from metals nearby the antenna, or from metals blocking the radiation path around the antenna.
It is possible to integrate the antenna during later stages of the design cycle, however design flexibility will be constrained and there is a much greater risk of failing to meet the performance metrics in the finished design leading to potentially expensive redesign and additional compliance testing.
At the concept stage when the RF performance and mechanical specifications are being defined, we recommend designers contact us for help achieving
8 June 2022 Components in Electronics
performance goals, good RF performance in the field and to meet any regulatory and operator approvals that may be required. By utilising Anglia and Taoglas experienced engineers, real industry experience and an unparalleled range of antennas we can help customers achieve a solid reliable process to ensure product success.
Types of antennas
There are many diverse types of antennas, but for the most part they can be separated into one of two categories: embedded or external. Generally, a combination of the aesthetic design and RF performance will influence the type of antenna selection, for example on a portable device such as a tablet or phone, embedded antennas are desirable because they can be hidden out of sight inside the enclosure, conversely for vehicles or industrial equipment the only viable option may be to use an external antenna in order to achieve suitable performance due to the common use of metal enclosures around the electronics.
In the case of embedded antenna, it should also be noted that performance loss is not an uncommon occurrence at the lower bands especially when the antenna is coupled to a short host circuit board such as those used in compact devices like telematics, tracking, medical and metering products. Taoglas have a new patent pending “Boost” innovation which helps compensate for these losses in the lower bands by making the PCB ground plane look electrically longer to the antenna, while not physically lengthening it. Boost
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technology can improve performance by 1.5dB to 2dB in critical lower band efficiency for embedded on board antenna applications. This equates to efficiency boosts of 20%+ and can be used for any antenna to improve efficiency particularly in the 600-1000MHz regions where the common ISM bands are found. Taoglas have produced a whitepaper detailing how Boost technology can be used to improve antenna performance, click or scan the QR code to download the whitepaper.
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