Finally, One Size Fits All

The fast pace, ever changing evolution of the wireless industry puts an enormous time-to-market pressure on the engineering of every new mobile device. Being in the heart of every mobile product, the design of the RF front-end and in particular, the antenna, becomes specially cumbersome as every product currently requires a fully customized antenna. Fractus new Virtual Antenna technology has been conceived to address this particular issue, proposing a new standard antenna element, the miniature mXTEND Antenna Booster, to virtually replace every customized antenna in virtually every mobile product.

Handset antennas have significantly evolved from the original external antennas covering one or two bands to internal antennas featuring multiple bands enabling smartphones to operate in 2G, 3G, and 4G standards in multiple regions of the world

The market pressure is currently focused on demanding handset devices capable of supporting sophisticated services requiring considerable high quality, high data rates, such as video on demand, video streaming, video conference, voice over IP, etc. The integration of all these services and functionalities inside current handset platforms featured by strict constraints in terms of size, weight, profile, and energy consumption increases the challenges for antenna engineers.

Following the state-of-the-art approach in handset antenna design, the complexity of the antenna solution increases together with an increase in the number of operating frequency bands. Generally, the larger the number of operating bands the greater the dimensions of the antenna and its geometrical complexity. The current technological trend has been precisely to take advantage of geometrical complexity to optimize the size and performance of every antenna in every single mobile device. In general terms, the greater the number of bands, the greater antenna complexity to pack all radio wavelengths in the available space inside the mobile platform.

Such a design approach is subject to the well-known physical limit in the performance of small antennas. A well-known fundamental principle in antenna design is that an antenna must keep a minimum size relative to the longest operating wavelength to radiate efficiently. Beyond a certain size limit, a further antenna reduction results in a rapidly decreasing bandwidth and efficiency. It is known that an antenna enters into the ‘small antenna’ regime when its overall size is smaller than l/p. In a mobile system and considering a longest operating wavelength at a frequency of 824 MHz, such a limit is around 120mm, right about twice the top edge of a mobile phone where the antenna is usually located. Following this thought, this means that about every modern mobile phone antenna, even those integrated in current large smartphones, operates well within the small antenna regime and it is therefore understood to be subject to the bandwidth and efficiency constraints of small antennas. In other words, to further reduce the antenna size an antenna engineer needs to face overcoming a fundamental wall that has constrained antenna evolution for decades.

Besides those fundamental limits, other practical constraints introduce additional hurdles when integrating an antenna into a mobile platform. For instance, the performance of a handset antenna solution is strongly conditioned by the architecture of the handset platform and the components integrated thereof, such as battery, display, shieldings, covers, and alike. When customizing the antenna inside the phone, the antenna engineer needs to bear in mind not only the bands, bandwidth, size, and efficiency constraints inherent to the design of every antenna, but the co-existence of all those neighboring elements that might interact with antenna near fields. This results in an iterative design, integration, and optimization processes, which supposes a time-consuming and costly approach

Fractus Virtual Antenna solution aims to throw some light into this landscape by simplifying the design process while reducing the time-to-market and cost of the final mobile product. Fractus solution based on the mXTEND antenna booster is capable of replacing conventional handset antennas of large dimensions by miniature and off-the-shelf, standard mobile antenna components. The solution can be effectively standardized across multiple handsets sharing the same platform while featuring different form factors. The proposal has been specially thought to simplify the migration process from 3G to 4G, and it becomes a radical step forward in the evolution of handset engineering.


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