ISSUE 03 2014
DEVICES
27
F
rom antennas to transmit, antennas to receive, antennas for positioning, antennas for Wi-Fi connectivity and NFC, all must be accommodated in the smallest of new mobile devices and work
with minimal interference between them. And they must also operate without emitting too much energy beyond that already allowed by the regulatory authorities in different markets. But be in no doubt, without the capabilities of the ‘humble’ antenna functioning optimally, whether at the base station or in the latest smartphone, the mobile industry simply would not be and running your Facebook page from your latest Samsung or Apple smartphone would be impossible.
To find out more, LTE Today sought the views of ElectroMagnetic Software and Systems, (EMSS), whose application engineer, Peter Futter, gave us some qualified thoughts from a company which provides a 3D simulation tool for antenna design. Called FEKO, it’s used by a range of mobile and tablet manufacturers around the world with whom the company works closely, and this has given EMSS a comprehensive understanding of what the typical challenges are. Futter and his colleagues have published several studies on LTE antenna design and integration aspects in various journals and will be presenting their latest study in April at EDI CON, in Beijing, entitled Antenna Performance of LTE Enabled Hand-Held Tablets. With frequencies ranging from 400 to 4000MHz and bandwidths up to 20MHz, their paper will, amongst other things, look at how LTE utilises multiple antennas on both ends of the wireless channel i.e. multiple input multiple output (MIMO) to support high data rate 4G applications.
For a manufacturer’s view Taoglas, a leading antenna player, stepped up to the plate with Ronan Quinlan, joint managing director, and Chris Anderson, the company’s vice president of engineering delivering their views. Taoglas, whose terminal antennas include the TG30, sells almost all of its LTE products to customers in North America where LTE has taken off faster than Europe and other regions. The company provides a comprehensive range of external, embedded and base station antenna solutions for M2M applications such as smart-grid, metering and telemetry applications, as well as remote monitoring, medical applications and many more. Its PA series ceramic PIFA antennas include its newest and patent pending PA.700.A Internal – LTE-Cellular SMT Antenna, designed to work in the 4G LTE 700MHz band but also in 2G/3G bands. Another patent pending internal antenna is its Maximus FXUB66 flexible ultra wideband antenna, designed to cover all working frequencies in the 700-6000MHz spectrum, including all cellular, Wi-Fi, ISM and GNSS bands.
What are the general challenges faced when designing internal antennas for cellular devices? EMSS: Achieving good antenna radiation performance with minimal volume allocated for the antenna is a classic challenge. Furthermore, modern devices typically contain multiple and/or multiband antennas, so coupling and interference needs to be managed carefully. The design must be robust, and insensitive to a range of in-use scenarios including in talk position, various hand grips, and within vehicles. One of the major advantages of simulation is that these concepts can be tested numerically, ultimately reducing the number of prototypes and simplifying antenna integration.
Taoglas: The physical size of the device is one of the biggest challenges, and the expectations of consumers mean that the size of modern devices is shrinking – they expect things to be iPhone-sized or smaller. LTE in the US is deployed at lower frequencies, which means the antennas need to be bigger and that complicates the design and cost. Europe is similar, with deployments heading towards 800MHz.
The second biggest issue is certification. There are not a lot of organisations out there that are building these devices – they don’t have people with the skill set to build products with embedded antennas. Most machine-to-machine (M2M) hardware implementations needing an internal antenna are designed by people who have never designed a radio product and because carriers enforce minimal performance rules for the whole device, which includes the antenna, the bar is quite high. Carriers are saying ‘your product has to work very well, you can’t make something that sort of works; this is how well it has to work’. Carriers are enforcing those rules and if your device does not meet that minimal performance, you can’t sell
Dermot O’Shea, joint managing director, Taoglas
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