Smart Coat with a Fully-Embedded Textile Antenna for IoT Applications

The Internet of Things (IoT) scenario is strongly related with the advance of the development of wireless sensor networks (WSN) and radio frequency identification (RFID) systems. Additionally, in the WSN context, for a continuous feed, the integration of textile antennas for energy harvesting into smart clothing is a particularly interesting solution when the replacement of batteries is not easy to practice, such as in wearable devices. This paper presents the E-Caption: Smart and Sustainable Coat. It has an embedded dual-band textile antenna for electromagnetic energy harvesting, operating at global system for mobile communication (GSM) 900 and digital cellular system (DCS) 1800 bands. This printed antenna is fully integrated, as its dielectric is the textile material composing the coat itself. The E-Caption illustrates the innovative concept of textile antennas that can be manipulated as simple emblems. Seven prototypes of these “emblem” antennas, manufactured by lamination and embroidering techniques are also presented. It is shown that the orientation of the conductive fabric does not influence the performance of the antenna. It is also shown that the direction and number of the stitches in the embroidery may influence the performance of the antenna. Moreover, the comparison of results obtained before and after the integration of the antenna into cloth shows the integration does not affect the behavior of the antenna.

Sensors 2016, 16, 938 3 of 13 embroidering. Further, the integration of the antenna into a smart coat, by fully embedding it into the material constituting the coat, is described.

Materials
The selection of textile materials for the development of antennas is critical, as discussed in [14]. In this work, all materials used to manufacture the wearable antennas are commercially available and described in the Table 2. For the dielectric substrate, a synthetic fabric with low regain was chosen, in order to minimize the effect of the moisture absorption on lowering the resonance frequency of the antenna.  1 Tex is the unit of the International System of Units used to characterize the linear mass of fibers and yarns. Tex is defined as the mass in grams per 1000 m. The subunit decitex (dtex) is the mass in grams per 10,000 m [23].

Materials
The selection of textile materials for the development of antennas is critical, as discussed in [14]. In this work, all materials used to manufacture the wearable antennas are commercially available and described in the Table 2. For the dielectric substrate, a synthetic fabric with low regain was chosen, in order to minimize the effect of the moisture absorption on lowering the resonance frequency of the antenna.

Manufacturing Techniques
Beyond choosing the textile materials, the construction technique of the antenna is also crucial because the textile materials are highly deformable. The geometrical dimensions of the conductive patch and of the dielectric substrate should remain stable when connecting them, as the mechanical stabilization of both materials is essential to preserve the desired characteristics of the antenna. The geometrical precision of the conductive patch is also critical as the proposed antenna has thin details, as shown in Table 1.
Moreover, the technique to connect the various layers should not affect the electrical properties of the patch, particularly its electrical resistivity. All antennas presented in the following sections were produced assembling the components with the thermal adhesive sheet (JAU Têxteis, Serzedo, Portugal), previously described in the Table 2. The antennas were glued by ironing without steam in a vacuum table. Steam was not used deliberately, especially on materials with copper, to avoid oxidation of the conductive material and the consequent increase of its electrical resistivity.
However, an extra antenna was produced by an ironing process with steam in order to analyse the influence of the steam in the performance of the antenna. Both antennas, with and without steam, were assembled using the same ironing conditions, presented in the Table 3. Additionally, in order to ensure the geometrical accuracy, the patches were cut by an LC6090C CCD (Jinan G. Weike Science & Tecnology Co. Ltd., Jinan, China) laser cutting machine. The obtained results are shown in the Figure 2.

Manufacturing Techniques
Beyond choosing the textile materials, the construction technique of the antenna is also crucial because the textile materials are highly deformable. The geometrical dimensions of the conductive patch and of the dielectric substrate should remain stable when connecting them, as the mechanical stabilization of both materials is essential to preserve the desired characteristics of the antenna. The geometrical precision of the conductive patch is also critical as the proposed antenna has thin details, as shown in Table 1.
Moreover, the technique to connect the various layers should not affect the electrical properties of the patch, particularly its electrical resistivity. All antennas presented in the following sections were produced assembling the components with the thermal adhesive sheet (JAU Têxteis, Serzedo, Portugal), previously described in the Table 2. The antennas were glued by ironing without steam in a vacuum table. Steam was not used deliberately, especially on materials with copper, to avoid oxidation of the conductive material and the consequent increase of its electrical resistivity.
However, an extra antenna was produced by an ironing process with steam in order to analyse the influence of the steam in the performance of the antenna. Both antennas, with and without steam, were assembled using the same ironing conditions, presented in the Table 3. Additionally, in order to ensure the geometrical accuracy, the patches were cut by an LC6090C CCD (Jinan G. Weike Science & Tecnology Co. Ltd., Jinan, China) laser cutting machine. The obtained results are shown in the Figure 2.

Temperature (°C) Pressure (bar)
Time (s) 200 10 12 (6 for patch + 6 for ground plane) According to the measured results presented on Figure 2, one can see a higher frequency shift in the antenna made using steam in the ironing process. In order to investigate the cause of this shift, the thickness of the antenna was measured, using Kawabata's Evaluation System (KES) for fabrics (KES-F-3 Compressional Tester). For the antenna without steam, the thickness is 0.62 mm, and for the antenna with steam it is 0.60 mm. This difference can be due to the higher compaction of the materials when steam is applied. As one can see in the scanning electron microscope (SEM) images in Figure 3, in the antenna without steam the adhesive sheet (see yellow arrows) remains at the interface between the conductive and dielectric layers. However, when the steam is applied, the adhesive sheet merges with the textile structure (see green arrows).
This effect may be responsible for a decrease in conductivity due to the presence of the glue among the conductive yarns. Moreover, the presence of the adhesive sheet into the Cordura fabric (B. W. Wernerfelt Group, Søborg, Danmark) will presumably change, even if slightly, its permittivity. According to the measured results presented on Figure 2, one can see a higher frequency shift in the antenna made using steam in the ironing process. In order to investigate the cause of this shift, the thickness of the antenna was measured, using Kawabata's Evaluation System (KES) for fabrics (KES-F-3 Compressional Tester). For the antenna without steam, the thickness is 0.62 mm, and for the antenna with steam it is 0.60 mm. This difference can be due to the higher compaction of the materials when steam is applied. As one can see in the scanning electron microscope (SEM) images in Figure 3, in the antenna without steam the adhesive sheet (see yellow arrows) remains at the interface between the conductive and dielectric layers. However, when the steam is applied, the adhesive sheet merges with the textile structure (see green arrows).
Finally, the shift in frequency may be due to other factors, such as the precision of cutting during the manufacturing process.
Nevertheless, it is worth noting that it is important to further study the effect of steam in the performance of the antenna, in order to consider and compensate for it in the design of the antenna.

Laminated Antennas
These antennas are made by superposing fabrics and attaching them with a thermal adhesive sheet. The cutting process of the conductive material is critical, as the antenna has very thin lines; for instance, the Wf dimension (see Table 1). In order to increase the geometrical accuracy, the patches were cut by an LC6090C CCD laser cutting machine. This procedure also reduces the common fraying effect that appears when cutting thin fabrics with scissors.
Two antennas were fabricated with this lamination technique. In order to test the influence of the direction of the structure of the conductive fabric (Zelt) on the performance of the antenna, the patch of antenna A was cut parallel to the warp, and the patch of antenna B was cut at 45° (bias). Figure 4 presents the simulated and measured values of S11 parameter of both antennas, measured with a vector network analyser (VNA). The antennas produced by the lamination technique have shown good results, as the S11 parameter shows. As one can see in Figure 4, the measurements match the simulation fairly well, although there is a small shift of the frequency. This shift of frequency might be due to the narrow manufacturing tolerances that exist even when cutting the fabric by laser. Still, the reflection coefficient (S11) is low at the operating frequencies, meaning that the antenna presents a good impedance mismatch in both GSM and DCS bands. This effect may be responsible for a decrease in conductivity due to the presence of the glue among the conductive yarns. Moreover, the presence of the adhesive sheet into the Cordura fabric (B. W. Wernerfelt Group, Søborg, Danmark) will presumably change, even if slightly, its permittivity. Finally, the shift in frequency may be due to other factors, such as the precision of cutting during the manufacturing process.
Nevertheless, it is worth noting that it is important to further study the effect of steam in the performance of the antenna, in order to consider and compensate for it in the design of the antenna.

Laminated Antennas
These antennas are made by superposing fabrics and attaching them with a thermal adhesive sheet. The cutting process of the conductive material is critical, as the antenna has very thin lines; for instance, the W f dimension (see Table 1). In order to increase the geometrical accuracy, the patches were cut by an LC6090C CCD laser cutting machine. This procedure also reduces the common fraying effect that appears when cutting thin fabrics with scissors.
Two antennas were fabricated with this lamination technique. In order to test the influence of the direction of the structure of the conductive fabric (Zelt) on the performance of the antenna, the patch of antenna A was cut parallel to the warp, and the patch of antenna B was cut at 45˝(bias).  Finally, the shift in frequency may be due to other factors, such as the precision of cutting during the manufacturing process. Nevertheless, it is worth noting that it is important to further study the effect of steam in the performance of the antenna, in order to consider and compensate for it in the design of the antenna.

Laminated Antennas
These antennas are made by superposing fabrics and attaching them with a thermal adhesive sheet. The cutting process of the conductive material is critical, as the antenna has very thin lines; for instance, the Wf dimension (see Table 1). In order to increase the geometrical accuracy, the patches were cut by an LC6090C CCD laser cutting machine. This procedure also reduces the common fraying effect that appears when cutting thin fabrics with scissors.
Two antennas were fabricated with this lamination technique. In order to test the influence of the direction of the structure of the conductive fabric (Zelt) on the performance of the antenna, the patch of antenna A was cut parallel to the warp, and the patch of antenna B was cut at 45° (bias). Figure 4 presents the simulated and measured values of S11 parameter of both antennas, measured with a vector network analyser (VNA). The antennas produced by the lamination technique have shown good results, as the S11 parameter shows. As one can see in Figure 4, the measurements match the simulation fairly well, although there is a small shift of the frequency. This shift of frequency might be due to the narrow manufacturing tolerances that exist even when cutting the fabric by laser. Still, the reflection coefficient (S11) is low at the operating frequencies, meaning that the antenna presents a good impedance mismatch in both GSM and DCS bands. The antennas produced by the lamination technique have shown good results, as the S 11 parameter shows. As one can see in Figure 4, the measurements match the simulation fairly well, although there is a small shift of the frequency. This shift of frequency might be due to the narrow manufacturing tolerances that exist even when cutting the fabric by laser. Still, the reflection coefficient (S 11 ) is low at the operating frequencies, meaning that the antenna presents a good impedance mismatch in both GSM and DCS bands.
Thus, with the laminated manufacturing technique, by controlling the ironing conditions, the adhesive may remain at the interface of the conductive and dielectric materials, as one can see in the SEM image in Figure 5, showing the cross-section of a laminated antenna assembled without steam. Therefore, in this antenna, made by ironing without steam, the electrical surface resistance of the patch and the relative permittivity of the substrate are not significantly changed. This observation is corroborated by the S 11 measurements previously showed in the Figure 4. Thus, with the laminated manufacturing technique, by controlling the ironing conditions, the adhesive may remain at the interface of the conductive and dielectric materials, as one can see in the SEM image in Figure 5, showing the cross-section of a laminated antenna assembled without steam. Therefore, in this antenna, made by ironing without steam, the electrical surface resistance of the patch and the relative permittivity of the substrate are not significantly changed. This observation is corroborated by the S11 measurements previously showed in the Figure 4.

Embroidered Antennas
Embroidering is a promising method in terms of repeatability and mass-manufacturing [24], as the embroidered antennas do not need a cutting or lamination process, thus reducing the production costs. For this reason, several embroidered antennas have been proposed; for instance, spiral antennas [25,26], RFID tags [27,28], and antennas without a ground plane [29][30][31]. This paper explores the embroidering technique to produce antennas that can be easily applied in clothing as an emblem. This way the embroidering technique might enlarge the dissemination of the textile antennas into clothing.
As the antenna considered in this paper is a printed monopole antenna which requires a ground plane, the manufacturing process has to be adapted in order to eliminate the short cuts caused by the embroidering technique in both sides of the dielectric material. Therefore, the construction technique of the embroidered antenna was: firstly, embroidering the patch in a thin textile; secondly, cut the embroidery; and, finally, attach the embroidery to the dielectric substrate using the thermal adhesive sheet. This process is the same one used to produce the traditional emblems for cloth customization.
Five antennas were developed with this technique, using a SWF MA-6 automatic embroidering machine. The patches were embroidered in the Atlantic fabric (B. W. Wernerfelt Group, Søborg, Danmark) using Silverpam yarn (Tibtech Innovations, Pierre Mauroy, France) (see Table 2). The parameters of the embroidery are described in Table 4. The orientation of the stitch was considered by performing stitches along four different directions for antennas 1, 3, 4, and 5. The number of stiches was considered by varying the float of the stitch for antennas 2 and 3. To avoid differences in the fringe effect on the feed line (Wf × Lf) due the different directions of the stitches, all antennas have feed lines embroidered with a horizontal step stitch. Figure 6 shows the simulated and measured values of the S11 parameter of these antennas, measured with a VNA. It is clean that the measurements match closely to the simulations. Where

Embroidered Antennas
Embroidering is a promising method in terms of repeatability and mass-manufacturing [24], as the embroidered antennas do not need a cutting or lamination process, thus reducing the production costs. For this reason, several embroidered antennas have been proposed; for instance, spiral antennas [25,26], RFID tags [27,28], and antennas without a ground plane [29][30][31]. This paper explores the embroidering technique to produce antennas that can be easily applied in clothing as an emblem. This way the embroidering technique might enlarge the dissemination of the textile antennas into clothing.
As the antenna considered in this paper is a printed monopole antenna which requires a ground plane, the manufacturing process has to be adapted in order to eliminate the short cuts caused by the embroidering technique in both sides of the dielectric material. Therefore, the construction technique of the embroidered antenna was: firstly, embroidering the patch in a thin textile; secondly, cut the embroidery; and, finally, attach the embroidery to the dielectric substrate using the thermal adhesive sheet. This process is the same one used to produce the traditional emblems for cloth customization.
Five antennas were developed with this technique, using a SWF MA-6 automatic embroidering machine. The patches were embroidered in the Atlantic fabric (B. W. Wernerfelt Group, Søborg, Danmark) using Silverpam yarn (Tibtech Innovations, Pierre Mauroy, France) (see Table 2). The parameters of the embroidery are described in Table 4. The orientation of the stitch was considered by performing stitches along four different directions for antennas 1, 3, 4, and 5. The number of stiches was considered by varying the float of the stitch for antennas 2 and 3. To avoid differences in the fringe effect on the feed line (W fˆLf ) due the different directions of the stitches, all antennas have feed lines embroidered with a horizontal step stitch. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.  Figure 6. Simulated and measured return loss of embroidered antennas.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the patternmaking of the coat, thus being part of it. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.  Figure 6. Simulated and measured return loss of embroidered antennas.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the patternmaking of the coat, thus being part of it. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.  Figure 6. Simulated and measured return loss of embroidered antennas.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the patternmaking of the coat, thus being part of it. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.  Figure 6. Simulated and measured return loss of embroidered antennas.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the patternmaking of the coat, thus being part of it. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.  Figure 6. Simulated and measured return loss of embroidered antennas.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the patternmaking of the coat, thus being part of it.  Figure 6 shows the simulated and measured values of the S 11 parameter of these antennas, measured with a VNA. It is clean that the measurements match closely to the simulations. Where antenna 3 is the one with the best match of the reflection coefficient. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the patternmaking of the coat, thus being part of it. The antenna 3 presents the closest result to the simulation line. This can be due to the fact the embroidery stitch direction is parallel of the feed line, homogenizing the current flow [24]. Antennas 4 and 5 present very similar behavior that might indicate the angle of the diagonal direction is not influencing it. Coherently, antenna 1 shows the higher shift of the frequency that can be due to the fact the direction of the embroidery stitch is perpendicular to the feed line. Additionally, antenna 2 was made using a vertical stitch, as was antenna 3, having however, a higher number of stitches. This makes the current flow less continuous, due the constant breaks and higher number of air gaps in the embroidery [15], reducing the conductivity of the patch, which may explain the difference between the magnitudes of the return loss of antennas 3 and 2.

Integration into Clothing
When developing smart textile products, bringing technologies to the consumer in an acceptable and desirable format is a challenge. Some authors have been integrating textile antennas in products in a pleasing way, for instance, as wearable antennas for commercial advertisement proposes, dissimulated in brand names and logotypes [32,33]. However, until now, the microstrip patch textile antennas have been built ex situ and then posteriorly integrated in the lining of the garment or into pockets or simply glued to the cloth. This paper proposes an innovative solution that presents the first antenna prototype manufactured directly in the clothing as it is made with the same textile materials composing the cloth. This cloth is a smart coat for electromagnetic harvesting-the E-Caption: Smart and Sustainable Coat, in which the antenna has a substrate that is continuous and was cut according to the pattern-making of the coat, thus being part of it.
This innovative solution to integrate antennas into cloths is illustrated in Figure 7. The antenna is integrated into the clothing by manipulating it as a simple emblem. In the future, the antennas can be incorporated into patterns and drawings, mixing conductive and non-conductive embroideries, creating fashionable emblems that function as antennas. These "emblem" antennas may be accessible to the end user for customization of smart cloth, for several applications. This innovative solution to integrate antennas into cloths is illustrated in Figure 7. The antenna is integrated into the clothing by manipulating it as a simple emblem. In the future, the antennas can be incorporated into patterns and drawings, mixing conductive and non-conductive embroideries, creating fashionable emblems that function as antennas. These "emblem" antennas may be accessible to the end user for customization of smart cloth, for several applications.

E-Caption: Smart and Sustainable Coat
The integration of textile antennas for energy harvesting into smart clothing emerges as a particularly interesting solution when the replacement of batteries is not easy to practice, such as in wearable devices. A fully-embedded antenna in clothing contributes for the integration of electronic devices in less obtrusive ways, improving the good aesthetic and the technical design, making the garment more comfortable and desirable to the final consumer. This might enhance niche markets where form and function work together in order to create new attractive textile products that can assist the user in many aspects of their daily routine.
The E-Caption: Smart and Sustainable Coat was developed combining these concepts, integrating antenna A produced by the lamination manufacturing technique presented in previous sections. It is the first prototype of a smart coat with a printed monopole antenna fully integrated, as its dielectric is the textile material composing the coat itself. The coat is made of Cordura and of a 3D fabric (Reference 3003-3D fabric, from LMA-Leandro Manuel Araújo, Ltda.). Figure 8 shows the E-Caption coat with the textile antenna for RF energy harvesting.
In the past years, some authors have been analyzing the influence of the human body on the performance of textile antennas [34,35]. However, no one has analyzed the influence of its integration on clothing on its performance. Therefore, the analysis of the integration of antennas and the evaluation of their behavior after integration into clothing are discussed in Section 3.

E-Caption: Smart and Sustainable Coat
The integration of textile antennas for energy harvesting into smart clothing emerges as a particularly interesting solution when the replacement of batteries is not easy to practice, such as in wearable devices. A fully-embedded antenna in clothing contributes for the integration of electronic devices in less obtrusive ways, improving the good aesthetic and the technical design, making the garment more comfortable and desirable to the final consumer. This might enhance niche markets where form and function work together in order to create new attractive textile products that can assist the user in many aspects of their daily routine.
The E-Caption: Smart and Sustainable Coat was developed combining these concepts, integrating antenna A produced by the lamination manufacturing technique presented in previous sections. It is the first prototype of a smart coat with a printed monopole antenna fully integrated, as its dielectric is the textile material composing the coat itself. The coat is made of Cordura and of a 3D fabric (Reference 3003-3D fabric, from LMA-Leandro Manuel Araújo, Ltda.). Figure 8 shows the E-Caption coat with the textile antenna for RF energy harvesting.

Results
The performance of the antenna of the E-Caption: Smart and Sustainable Coat was tested in the anechoic chamber, as shown in Figure 9.  Figure 10 presents the variation in the S11 parameter obtained through numerical simulation and measured in free space, before and after the integration into the smart coat. It is possible to see the agreement between the simulated and measured values even in the on-body measurements. The textile antenna presents an operating frequency range capable of completely covering the GSM900 (880-960 MHz) and the DCS1800 (1710-1880 MHz). In the past years, some authors have been analyzing the influence of the human body on the performance of textile antennas [34,35]. However, no one has analyzed the influence of its integration on clothing on its performance. Therefore, the analysis of the integration of antennas and the evaluation of their behavior after integration into clothing are discussed in Section 3.

Results
The performance of the antenna of the E-Caption: Smart and Sustainable Coat was tested in the anechoic chamber, as shown in Figure 9.

Results
The performance of the antenna of the E-Caption: Smart and Sustainable Coat was tested in the anechoic chamber, as shown in Figure 9.  Figure 10 presents the variation in the S11 parameter obtained through numerical simulation and measured in free space, before and after the integration into the smart coat. It is possible to see the agreement between the simulated and measured values even in the on-body measurements. The textile antenna presents an operating frequency range capable of completely covering the GSM900 (880-960 MHz) and the DCS1800 (1710-1880 MHz).  Even after integrated into clothing, the radiation pattern of the antenna is clearly omnidirectional. The Figure 11 shows the radiation pattern of the antenna fully integrated into the smart coat structure and also measured on-body. The results depicted in Figure 11 correspond to the XZ plane. This is the only measurable plane (see Figure 9), due to the configuration and placement of the antenna on the coat. Nevertheless, it is the most relevant plane in order to evaluate the omnidirectional characteristic of the antenna.
Moreover, given the position of the antenna on the coat, previously shown in Figure 8, it is clear that the direction at which the antenna will present less influence from the coat or from the person occurs at nearly 30° in the broadside direction. This is confirmed by the results depicted in Figure 11. According to the results presented in Figure 11, one may conclude that, as expected, the mass of the coat and mainly of the person influence the radiation characteristic of the antenna. In the measurement of the empty jacket, when the coat places between the probe antenna and the test antenna, around 160°, there is a reduction in the gain of the antenna, which is due to the presence of a large dielectric body, that is, the coat. Nevertheless, the antenna shows a nearly omnidirectional pattern.
The on-body antenna performs differently. Since the human body is conductive, it absorbs and reflects radiofrequency waves. The results on Figure 11 show that when the body is behind the test antenna, at 30° broadside, a slight increase in gain is measured. However, when the body is between the probe and the test antenna, at 160°, it will absorb a high amount of radiation and will reflect the Even after integrated into clothing, the radiation pattern of the antenna is clearly omnidirectional. The Figure 11 shows the radiation pattern of the antenna fully integrated into the smart coat structure and also measured on-body. The results depicted in Figure 11 correspond to the XZ plane. This is the only measurable plane (see Figure 9), due to the configuration and placement of the antenna on the coat. Nevertheless, it is the most relevant plane in order to evaluate the omnidirectional characteristic of the antenna. Even after integrated into clothing, the radiation pattern of the antenna is clearly omnidirectional. The Figure 11 shows the radiation pattern of the antenna fully integrated into the smart coat structure and also measured on-body. The results depicted in Figure 11 correspond to the XZ plane. This is the only measurable plane (see Figure 9), due to the configuration and placement of the antenna on the coat. Nevertheless, it is the most relevant plane in order to evaluate the omnidirectional characteristic of the antenna.
Moreover, given the position of the antenna on the coat, previously shown in Figure 8, it is clear that the direction at which the antenna will present less influence from the coat or from the person occurs at nearly 30° in the broadside direction. This is confirmed by the results depicted in Figure 11. According to the results presented in Figure 11, one may conclude that, as expected, the mass of the coat and mainly of the person influence the radiation characteristic of the antenna. In the measurement of the empty jacket, when the coat places between the probe antenna and the test antenna, around 160°, there is a reduction in the gain of the antenna, which is due to the presence of a large dielectric body, that is, the coat. Nevertheless, the antenna shows a nearly omnidirectional pattern.
The on-body antenna performs differently. Since the human body is conductive, it absorbs and reflects radiofrequency waves. The results on Figure 11 show that when the body is behind the test antenna, at 30° broadside, a slight increase in gain is measured. However, when the body is between the probe and the test antenna, at 160°, it will absorb a high amount of radiation and will reflect the Moreover, given the position of the antenna on the coat, previously shown in Figure 8, it is clear that the direction at which the antenna will present less influence from the coat or from the person occurs at nearly 30˝in the broadside direction. This is confirmed by the results depicted in Figure 11.
According to the results presented in Figure 11, one may conclude that, as expected, the mass of the coat and mainly of the person influence the radiation characteristic of the antenna. In the measurement of the empty jacket, when the coat places between the probe antenna and the test antenna, around 160˝, there is a reduction in the gain of the antenna, which is due to the presence of a large dielectric body, that is, the coat. Nevertheless, the antenna shows a nearly omnidirectional pattern.
The on-body antenna performs differently. Since the human body is conductive, it absorbs and reflects radiofrequency waves. The results on Figure 11 show that when the body is behind the test antenna, at 30˝broadside, a slight increase in gain is measured. However, when the body is between the probe and the test antenna, at 160˝, it will absorb a high amount of radiation and will reflect the rest in the opposite direction, shielding the test antenna and, thus, create a null of radiation at this point. This happens for both frequencies, being clearer at 1800 MHz.

Discussion
In the future, garments will not only communicate social conditions or protect the human body against the extremes of nature, but will also provide information and communication tools. Clothes are becoming able to communicate wirelessly without the need of large and expensive equipment. This is possible because textile technologies can produce new types of sensors and antennas that are so small, flexible, and inexpensive that they can be applied in different types of clothing, shoes, and accessories.
The effective integration of wearable systems contributes to the advance of the IoT. The innovative concept of producing textile antennas to integrate into clothing by simply manipulating it as an "emblem" may improve the usage of the wearable technologies. In the future, the wearable antennas can be incorporated into textile patterns and drawings, creating fashionable antennas. These "emblem" antennas may be easily acceded by the end user, for customization of smart cloth for several applications.
The E-Caption: Smart and Sustainable Coat is the first prototype of this concept, integrating an "emblem" antenna capable of completely covering GSM900 (880-960 MHz) and the DCS1800 (1710-1880 MHz) bands, for IoT applications. In this context, the integration of textile antennas for energy harvesting into smart clothing can be a solution for recharging wearable devices, such as low-power electronics and WBSN.

Conclusions
Embedding antennas in clothing contributes for the advance of the integration of electronic devices in less obtrusive way making the smart clothes more comfortable. In the E-caption, the antenna is manufactured directly on the clothing, having a continuous dielectric substrate made with the textile materials composing the coat. Therefore, a continuous substrate of the antenna does not influence its performance. Moreover, the presented results show that, despite the masses of the coat and of the body influencing the radiation characteristic of the integrated antenna, it still shows a nearly omnidirectional pattern.
This work shows that "emblem" antennas, including the ones having ground planes, may be manufactured by lamination and embroidering techniques. When laminating, the ironing process without steam seems to be preferable as it better preserves the electromagnetic performance of the materials. Additionally, this work shows the orientation of the conductive fabric used for the patch is not influencing the performance of the laminated antenna. In addition, it shows the direction and number of the stitches in the embroidery may contribute to increasing the conductivity of some elements, thus improving the performance.
Other techniques to produce "emblem" antennas may be considered in the future, for instance, transfer, screen printing, and inkjet methods. Finally, this innovative concept of textile antennas for energy harvesting might open new horizons in the clothing development and in sustainable communication.