Textile Antenna for Electromagnetic Energy Harvesting for GSM900 and DCS1800 bands Ricardo Gonc ¸alves 1,2 and Nuno B. Carvalho 1,2 1 Instituto de Telecomunicac ¸˜ oes, Aveiro, Portugal 2 Universidade de Aveiro, Aveiro, Portugal rgoncalves@av.it.pt, nbcarvalho@ua.pt P. Pinho 1,3 , Caroline Loss 4 and Rita Salvado 4 3 Inst. Sup. Eng. Lisboa - ISEL, Lisboa, Portugal 4 Universidade da Beira Interior, Covilh˜ a, Portugal ppinho@deetc.isel.pt, m4280@ubi.pt, rita.salvado@ubi.pt Abstract—Energy harvesting is the process by which energy is derived from external sources captured, and stored for small, wireless autonomous devices, like those used in wearable elec- tronics and wireless sensor networks. This paper presents the design of two textile antenna suitable to harvest energy in the GSM900 and DCS 1800 bands. The antennas gain, are of the order 2 dBi and efficiency 80%. I. I NTRODUCTION Energy harvesting will allow for recharging batteries or super capacitors, and will have a great impact on the lifetime of wireless sensor networks (WSNs). This has particular importance as the network size increases and the replacement of the batteries is not always practical. The common sources of energy harvesting include the following [1]: mechanical, ther- mal, electromagnetic, natural and human motion. Nowadays, energy harvesting devices efficiently and effectively capture, accumulate and store energy, to power up the sensor nodes for short periods of time, in order to perform helpful tasks. However, in a not too distant future, they will enable to supply all the nodes of WSN without the need of replacement of batteries. This energy can be used continuously to increase the battery charge or prevent power leakage. In [2], the authors present the state-of-the-art of energy harvesting techniques for low power systems such as power conversion, power manage- ment, and battery charging, as well as the advances in energy harvesting from vibration, thermal, and radio frequency (RF) sources. Prototypes for the energy harvesting from the ambient RF spectrum have been proposed in [3], [4], enabling to power supply low-power systems. In the context of wireless body area networks (WBAN) electromagnetic energy harvesting is accomplished by using wearable antennas allowing for power supply the sensor nodes [5]. The remaining of this paper is organized as follows. Section II presents the motivation of our work as well as the average received power for different RF sources. Section III describes the design of single and dual band antennas for collecting RF energy. Finally, Section IV draws the main conclusions. II. RF ENERGY SCAVENGING AND RECEIVED POWER Nowadays, RF energy is currently broadcast from billions of radio transmitters (e.g., mobile communications base stations and television/radio stations) that can be collected from the ambient. Our vision is that this energy holds a promising future for power supply wireless electronics devices. One of the contributions from this work is the measurements of the electromagnetic spectrum availability from 350 MHz to 3 GHz. The field trials were performed by using the NARDA- SMR [6] and PROLINK 4-4C signal meter [7], as shown in [8], in different locations, which led to the average results depicted in Figure 1. From which, we conclude that the best set of frequency bands for energy harvesting is the mobile phone bands. Fig. 1. Average received power for all measurements. III. ANTENNAS FOR RF ENERGY HARVESTING Considering the previous analysis regarding the best fre- quencies for energy harvesting, it is proposed in this section, a possible implementation of two textile antennas suitable to be introduced within clothes for body worn applications, a single band antenna to harvest in the GSM900 band and a dual band antenna to harvest in GSM900 and DCS1800. The proposed antennas design is shown in Figure 2. Table I presents the corresponding dimensions. A Cordura cloth type was considered for the substrate, it presents a permittivity (ǫ r ) of approximately 1.9 and a loss tangent (tan δ) of 0.0098, having a relative height of 0.5 mm. For the conductive sections of the antenna an electrotextile (Zelt), with an electric conductivity of 1.75105 S/m was con- sidered. The return loss obtained from numerical simulations of the proposed antennas is presented in Figure 3. From which is observed that these antennas present an operating frequency 1206 978-1-4673-5317-5/13/$31.00 ©2013 IEEE AP-S 2013