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Development of small automatic tunable antenna to enable low transmit power for cellular wireless terminals - Corrects the operating frequency to suit the environment -

2014/07

Overview

Toshiba has developed an automatic tunable antenna which is about 20% smaller than conventional antennas and enables the transmit power level to be reduced. This product can be incorporated in wireless communication terminals such as smartphones, and supports communication methods which accompany fluctuations of the transmit power level. A MEMS (Note 1) variable capacitor (being developed by Toshiba) is used for automatic matching of the antenna, enabling the size to be reduced while raising the communication quality. The details of the product were announced at AP-S (Note 2) at 8:00 (local time), Thursday, July 10 in Memphis, Tennessee.

Development background

The operating frequency of an antenna incorporated in a wireless communication terminal may differ from that of the communication signal due to the influence of objects near the antenna (e.g. desk or user's hand). This may deteriorate the communication quality or increase the level of transmit power. Deterioration in the quality of communication caused by nearby objects becomes more apparent as the antenna becomes smaller. Therefore, a small automatic tunable antenna, which can adjust its operating frequency to that of the radio waves at all times, is needed in order to make terminals smaller and reduce the transmit power level. However, an automatic tunable antenna can work correctly only in a small bandwidth. We also had to make the antenna respond to ever-changing transmission waves under the influence of TPC (Note 3) and nearby objects during automatic matching.

Automatic tunable antenna

Toshiba developed the world's first small automatic tunable antenna which supports TPC and allows low transmission power. A probe close to the end of the antenna can detect an electric wave accurately regardless of its frequency so that automatic matching can be achieved in any bandwidth. The control technology, which uses the change in the electric wave caused by TPC as the trigger, allows the antenna to determine whether the fluctuation of the wave is caused by TPC or the environment (e.g. nearby objects). As a result, automatic matching is made possible without the influence of TPC and communication is achieved without using extra power.
According to our calculation, the new antenna can lower the transmit power by up to 30% compared with conventional antennas and about 10% compared with conventional automatic tunable antennas. Moreover, the antenna is about 20% smaller than the conventional antenna.

Outlook

We are planning to make a prototype IC consisting of individual parts and develop a practical technology by fiscal 2016. We also aim to apply the technology in products which need to be further downsized and whose antennas need to work in accordance with the surrounding environment such as wearable devices and infrastructure monitoring sensor networks.

(Note 1) Micro Electro Mechanical Systems (MEMS): Micro mechanical parts that operate on electricity.

(Note 2) AP-S: IEEE International Symposium on Antennas and Propagation and USNC/URSI Radio Science Meeting: One of the largest forums on antennas and propagation.

(Note 3) Transmit Power Control (TPC): Mechanism to control the power exchanged between a base station and a mobile phone in a mobile phone system.