Textile antennas power efficiency

For wearable systems, including textile antennas, power efficiency represents a crucial matter, especially for the so-called autonomous systems, where the necessary power for the system operation is ideally obtained entirely by means of energy harvesting [16] from the surrounding environment, and no additional power supply is needed. Even in the case of wearable systems equipped with wearable battery units, it is very important to keep power consumption as low as possible. To this aim, several techniques were recently envisaged, by means of innovative textile antennas, such as active antennas as well as the use of multiantenna-processing techniques, such as diversity with multiple wearable antennas. 

Introduction of microelectronic microwave components close to the antenna demands for appropriate interconnect technologies on textiles. This aspect has been dealt with in various publications, both with woven and non-woven materials However, only little data is available on the microwave properties of different woven and non-woven materials This deficiency must be overcome. Interconnection to the microwave monolithic integrated circuit is an important area of research and development. One possible approach is the implementation of ribbon type interconnects, which can efficiently be used for power supply and low ficquency outyut signals. 

Efficiency to maximize the radiated power, the antenna designer wiU aim at a large radiation efficiency. As previously discussed, the total efficiency is the product of two terms. The first one, the impedance mismatch factor M, can he maximized by minimizing the reflection coefficient. The second term, the conductive-dielectric efficiency Ced can be maximized by using textile materials with low ohmic and dielectric losses, ie, electrotextiles with high conductivity and textile dielectric substrates with low tan 6. 

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