Stretching Effect on Textile Antenna for Spacesuit Tahmid Rashid, Sima Noghanian, Reza Fazel-Rezai Department of Electrical Engineering University of North Dakota Grand Forks, North Dakota, USA tahmid.rashid.und@gmail.com, sima.noghanian@und.edu, reza.fazeleza@und.edu Pablo de León Department of Space Studies University of North Dakota Grand Forks, North Dakota, USA deleon@space.edu Abstract— Textile and flexible antennas are prone to stretch. This is especially important in spacesuit applications where the suit is pressurized. In this paper we propose a monopole textile antenna placed on a flexible electromagnetic band gap (EBG) ground that is made on flexible substrate. The antenna is designed for on- body communication system of spacesuit. The system is designed for 5.8 GHz band. In normal condition the antenna gain with the EBG structure at 5.8 GHz is 7.02dBi. Simulation results are shown for the antenna under stretching individually and when it is integrated with the EBG. I. INTRODUCTION Research and development of body-worn communication systems and electronics have become very prominent in recent years. Some applications include intelligent garments equipped with wireless communication devices for sports, astronauts’ spacesuits [1], and fire fighters’ uniforms [2]. These systems are unthinkable without different kinds of body-worn textile or flexible antennas. Acceptable performance in single frequency band wearable antennas has been shown in late nineties [3]. Later dual frequency designs were developed to support mobile network systems. Recent developments were on antennas with electromagnetic band-gap structures (EBGs) integrated with antennas [4]. In this paper a planar monopole antenna is proposed. Although planar monopoles offer a wide band impedance matching, their gain is usually low due to their omnidirectional radiation pattern. Frequency-detuning problem might appear due to the high dielectric properties of the human body, as the antenna works close to human body in wearable applications. Furthermore, reduction of the back radiation from the antenna is important safety consideration in body worn applications. EBGs are being considered in suppressing surface wave, eliminating the detuning effects, reducing back radiation, and therefore, increasing the gain. The performance of the textile or flexible antenna can be affected by many factors such as bending, crumbling, stretching, temperature change, and humidity. Specifically, the effect of stretching of the textile or flexible antennas is of interest in spacesuit applications, since spacesuit will be pressurized in space. The pressure inside the spacesuit is of the order of 4.5 psid. This pressure normally causes the textile material to stretch up to 2%. In this paper we will discuss the stretching effects on the performance of the antennas for 1%, 2% and 3% of width and length. Simulation results are presented for a single antenna element and antenna mounted the EBG layer, and on spacesuit. CST Microwave Studio has been used for the simulations. II. ANTENNA AND EBG DESIGN A co-planar waveguide (CPW) fed textile monopole antenna was designed and simulated using CST Microwave Studio. Pellon was chosen as the substrate, with a thickness of 3.6 mm, and relative dielectric permittivity (ε r ) of 1.08. Fig. 1 (a) shows the design structure of the antenna. RO3003, flexible material of relative dielectric constant 3, was used for the EBG layer. The thickness 1.52 mm was used. Fig. 1 (b) shows the design variables of a single cell of the EBG structure. We used 3 × 2 EBG cells. Table I shows the parameter values of the antenna and EBG structure. Fig. 1. (a) Top view of the antenna (b) One cell of the EBG. TABLE I. ANTENNA DIMENTIONS IN MILIMETER Parameters L W Lp Wp Lt Wt G Dimensions 34.00 34.00 20.00 20.00 4.00 0.35 0.46 Parameters D Wg A B Wm Wg S Dimensions 4.00 0.90 14.80 13.60 4.00 6.96 0.20 Parameters EL EW SL SW SG ST Dimensions 31.60 61.10 26.40 7.00 3.10 2.70 III. ANTENNA PERFORMANCE UNDER STRETCHING The antenna is stretched up to 3% of its original size. The stretching was simulated for 3 cases: width only, length only, and width and length together. W is the width stretch factor, and L is the length stretch factor. In non-stretching condition the CPW fed textile monopole antenna is shows the -31.2dB S 11 at 5.8 GHz. Antenna gain is 1.17 dBi. From Table II one can see that F r (resonance frequency) changes as the antenna is stretched in length. When the antenna is stretched in width the performance of the antenna drops drastically and it does not work at the intended frequency anymore. Similar results are (b) (a)