ISSUE 03 2014


DEVICES


29


What are the ideal and latest materials used for internal antennas and how do their properties differ from earlier 2G/3G components? Taoglas: Ideal and latest materials have not changed; there’s nothing different between LTE and 2G and 3G for materials – ceramic was superior then and it is now. Our proprietary and unique ceramic recipes – we are actuallxy one of the few antenna vendors selling internal ceramic antennas in the M2M market – are always going to have an advantage over fibreglass-printed antennas because you have intrinsically higher dielectrics. Higher dielectrics drive the physical size of the antenna down, but you have low losses, which keeps the performance of the antenna up while, at the same time, physically shrinking the antenna. It’s no different than when you have a 2G or 3G system; it’s just that now you need more bandwidth on lower bands.


What are the performance specs and standards you are trying to achieve in such antennas? Taoglas: The antenna performance is largely dictated by the total radiating power (TRP) requirements that come from the various carriers. Each carrier specifies a particular TRP requirement and we can calculate the antenna efficiency required to meet that. In reality, for LTE and the majority of the bigger carriers specifying TRP (mainly US carriers), a 40 per cent antenna efficiency is good enough. We don’t see European carriers being so specific as it’s an open market. There are no mandatory TRP and TIS requirements for the general M2M device market, although there are targets for specific countrywide, operator-led projects with their own serviced devices.


Explain the manufacturing process for the latest LTE internal antennas illustrating the degree to which miniaturisation is a factor as smartphone and tablet device sizes have now done an ‘about turn’ and increased in size? EMSS: Device form factor definitely plays a role in the antenna design challenges. For example, larger devices mean that larger separation and pacing of individual or MIMO elements is possible, which could reduce coupling. However, the ongoing trend towards thinner devices can have an adverse impact on performance and, in some cases, result in poor antenna gain, or higher SAR values.


Taoglas: Although tablets and smartphones may be increasing in size, they are getting thinner. If you look at the displays on the latest Android devices or Samsung, the whole front is a display. There’s virtually no place to put an antenna and this complicates design. Even if the devices are getting bigger, on the antenna side you are still getting less space for an antenna. In terms of manufacturing process, it’s not any different now. If you are going to build something with an integrated internal antenna, you start out by designing your antenna and mechanicals together as your starting point and then you worry about where you are going to put electronics and where you will put the battery. The first thing you ask is, ‘what basic fundamental form factor will I have’, and based on that, you then ask ‘what antenna am I going to try to use?’ Then, you design your mechanicals around the antenna. For M2M products it makes much more sense to pick an off- the-shelf (OTS) antenna and design the mechanicals around it. In general, M2M manufacturers have to design custom mechanicals anyway; they are not starting out with a standard box and, in most cases, have to have a custom enclosure. If you design an enclosure after the fact, you may need both a custom enclosure and a custom antenna, which is more


With the growth in complexity of design and integration aspects there has been an increase in the use of simulation from concept prototype stage, right through to compliance estimation studies


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