Circularly Polarized (CP) Wideband on Fabric (Textile) Stealth MIMO Antenna for Wearable Wireless UWB Applications

Stealth wearable wireless devices gained popularity in the personal security and fashion design industry. A multiple-input-output (MIMO) wideband circularly polarized textile is described in the present paper, where a wearable application uses a multiple-input-output (M.I.M.O). It consists of two MIMO antennas, the resonating elements are shaped like a peacock, and the ground plane is similar to a beautiful peacock. A voltage is applied to each antenna element; the ground plane contains a a Peacock-shaped small strip antenna used for circular polarizing. The antenna covers 3dB Axial Ratio Band-Width (A.R.B.W.) of 5.0–7.0 GHz and impedance bandwidth (S11 ≤ −10.5 dB) of 3.7–13.5 GHz. The improved fabric-textile Multple-input-multiple-output antenna showing Channel-Capacity-Loss about (C.C.L) < 0.20 bits/sec/Hz, & Envelope-Correlation-Coefficient (E.C.C) less than 0.021, Total Active-Reflective-Coefficient (T.A.R.C) close to -10.4 dB , DiversityGain (D.G) close to 9.96, Mean-Effective-Gain (M.E.G) ratio close to ±0.5 dB . A Specific-Absorption-Rate(S.A.R) of the proposed antenna for tissues of human specimens is also discussed for different situations pertaining to the human body. The final dimention of the presented The proposed antenna can make unrecognizable because of the beautiful peacock design that can easily mix with the designs of fabric.


Prior Art and Problem Definition
Designers are paying considerable attention to wearable gadgets because of their numerous uses in communication gadgets, and safety devices [1], [2]. The radiating element is a crucial component of a any transceiver system. To radiate efficiently through bending, running, running, and movement, wearable/textile antennas are required. Antennas on textiles must be easy-to-integrate into miniature electronic consumer devices or fashion-clothing and must be low-size, low in weight, non-fragile, durable [3]. Fabrication, antenna placement, and structural deformation are all factors to consider when designing textile antennas [4], [5]. In addition to their flexibility in orientation, movability, and immunity to interference from all drections, wearable applications requiring circularly polarized besides wide-band quality antennas are becoming increasingly in demand [6] - [8]. A growing number of companies are focusing on multi-input-multi-output (M.I.M.O.) and diversity technologies to improve transmission-capacity, especially in complicated multi-path mediums. For establishing reliable channels and dealing with multipath fading, multielement antennas with polarization diversity are the best choice [9]- [11].
There have been several text-tile Multple-Input-Multiple-Output radiating-dipoles with high interelement isolation introduced in the reference [12]- [17]. In ref [12], vias are used to change the modes of resonance of the cavity waveguide with two-band Multple-input-multiple-output antenna generally suitable for W-LAN devices.
An antenna-design with a circular shape and a high impedance surface (HIS) has been described [13], with an excellent isolation of 15-dB between the ports. Wearable applications were demonstrated using a textile MIMO antenna embedded in a single-coated fabric [14] [15].. An Ishaped stub was exploited to get larger interelement isolation on a square-shaped wearable Multpleinput-multiple-output antenna described in [16]. An inverted-L planar strip ground plane was used in [17] to achieve a wide axial ratio bandwidth (ARBW) by feeding a C.P.W wave guide( Coplanar) into a rectangualar slot Multple-input-multiple-output antenna. It was reported in [18] that a dual CP antenna could be formed by combining -shaped strips to achieve polarization of circular nature. The ground plane of [19] was proposed with a twisted -shaped with a defected-ground-structure (D-G-S) combined with a Circularly polarized Multple-input-multiple-output antenna composed of stubs that are clearly grounded. It is shown in [20] that the orthogonal field induction is achieved through the modification of the ground plane of the CP antenna. According to [21], a grounded antenna with wearable on cloths can navigate the phasar differences around orthogonal modes using an implanted in the ground. In [12]- [16], Multple-input-multiple-output antennas showed linear polarization ( ) characteristics, while the referencces [17] to [21], Circularly polarization characteristics were presented. There have been very few reports of wearable/textile antennas that have a wide ARBW. Most wearable on fabric antennas in the literature are Linear-polarization with only single element configurations having very narrow axial ratio bandwidths (A.R.B.W). The ref [31] has given a brief intuition to the present proposed antenna design. The present paper disclosed more attractive, swift anonymous antenna which can be placed disguised as a regular artwork on designer made wearable dress.
An article based on robust, low-sized, wearable-on-cloth, 2-element Circularly Polarized ultpleinput-multiple-output wearable-antennas for mobile communications devices is presented here. It comprises a Peacock-shaped micro-strip(MS) line-fedd antenna and a suitable ground plane. Using an -figured stub, a quad-phase shift is introduced between the vertical & horizontal E-field vectors. Dual-sensor radiation characteristics are achieved by locating the 2-radiating elements in a mirrorimaging configuration. CP (left-hand CP) waves are emitted by port-1, while CP waves (right-hand CP) are emitted by port-2. Due to this property, the presented multple-input-multiple-output antenna is appropriate for polarization-diversity.

1) DESIGN PROCESS
The Generation phases of the textile radiator elements is shown in Figure.2. Figure. Figure.2-d, one can improve the axial ratio of the radiating element (ANTENNA-4) in step-4. To cover the lower frequency range, the RADIATOR resonating band required to change to the left-side. The antenna element therefore has a rectangular slot (with dimensions L3*W3) etched in its ground plane, as can be observed in Figure. 2e. Therefore, the current operating frequency band moves to the downward diirection when the path length grows. In addition, the proposed ANTENNA-5 achieves superior CP performance. In Table-1, you will find the simulation results (impedance band width & ARBW) of every stage.

2) CIRCULAR POLARIZATION (CP) PERFORMANCE
Antenna stages are illustrated in Fig.3(b) indicating the axial ratios and frequency. The ANTENNA-1 vector @ stage-1 is Linearly Polarized as the vector Phase-Contrast(PC) between the E-field vectors is never 90 degrees. Likewise, ANTENNA-2 is also Linearly Polarization.  Furthermore, a square ground-plane (Antenna-3 and Antenna-4) is joined to a series of Letter-Lfashioned strips of various widths & lengths to obtain a 90-degree differences of phase among the Efield vectors. X-axis fiels(Ex) and y-axis field(Ey) amplitudes become almost equal when they are separated by 90* phase deviation [17]. An illustration of the current distributions on surface for the presented wearable antenna (at wt=270degrees, wt=180degrees, wt =0degrees,&wt=90degrees) is given in Figure 4. The orthogonal current vectors A1 and A2 are symbolized by A1, and their sum is represented by A2. Figure.4(a) shows that at wt at 0degrees the current density on surface on the upper place of the antenna (A1) and the outer-ends of the L-fashioned antenna (A2) raises. The summation (A3) of these 2-vectors is going upward. Fig.4(b) illustrates that at wt=90degrees, the vector sum A3 shifts downward to the right side lower, showing clockwise ratating vectors over a duration.. The sum (A3) also proceeds clockwise in Fig.4(c) and (d) at wt=180* and 270*, respectively. As a result, the proposed textile antenna can operate in the broadside direction. In Fig.5(a) and (b), we show the| jEx/Eyj | and phase difference plots of ANTENNA5 and ANTENNA-1. By introducing the phase difference of 90degrees between the vertical & horizontal E-field vectors, the L-shaped strip on the ground plane balances the magnitude of both. By etching process a rectangular slot giving the flow of Current that is increased on the ground plane, thus shifting to the left side of the resonating frequency band.    .7(a) shows how the MIMO Antenna A's L-shaped strips are mirrored imaged into a T-shaped body near the middle caused by the Mirrored-Image pattern. The presented MIMO antenna's S12 parameters are stable without any decoupling. As long as there are no decoupling elements between the antenna elements, the proposed Circularly polarized Multple-input-multiple-output radiator has stable S12 parameters. A. and B., respectively, show Fig. 8(a) and (b) the S-parameters and axial ratio curves for the Circularly polarized Multple-input-multiple-output antennas. Antenna elements are separated by a T-shaped stub that offers superior isolation of more than 16dB.

B. MIMO ANTENNA
In spite of this, the antenna's ACBW variations really due to Surface-Wave-Coupling. The MIMO antenna A is therefore etched with a rectangular slot (size ls*wsmm2) to improve its 3-dB ARBW as shown in Figure 7(b) (Multple-input-multiple-output Ant-B). In addition to improving isolation (>18.5dB), the slot would improve MIMO antenna performance. ARBW is realized by optimizing the dimensions of the rectangular slot. Antenna B's simulated impedance bandwidth and ARBW are shown in Table-2.  .8 (d) shows both the computer-generated and calculated efficiency for the proposed radiating element, with the highest efficiency at 9.5GHz. Due to the loss-dielectric, mini surface area of the radiator, the efficiency appears to be low.

4) DUAL-SENSE CP PERFORMANCE
Wearable Circularly polarized Multple-input-multiple-output antenna with dualsense irradiation capability for two ports has been proposed. A diagram of the surface current distribution of the textile antenna is shown in Fig.9 (@wt=0degrees, wt=90degrees, wt=180degrees, and wt=270degrees).Two orthogonal vectors of current are represented by A1 and A2, while their sum is represented by A3. FIG10. computer-generated surface current circulation at 8.49 GigaHz Fig.9(a) shows that the resultant (A3) has been inclined to the upside right at wt==0 DEGREES, while the vector addition (A3) has been inclined toward the low-side right at = /2 degrees.In contrast, in Figure.-b, the vector addition (A3) orients itself towards the up-left at Wt=zero degrees, while the vector addition (A3) is oriented to the low-left at = /2•.The load of 50-OHMS is supplied to port-two when port-one is excited, and vice versa. An animated representation of the exterior current circulation of the anticipated Multple-input-multiple-output antenna at 8.5 ℎ can be seen in Figure-10. Despite the patch element in the middle, the current circulation is even all the way through the radiator area, validating the antenna gain.

RESULTS DISCUSSION
2038 v is utilized to measure the performance of the anticipated wearable "Multple-input-multiple-output antenna". As revealed in Figure.11-), the wearable Multple-Input-Multiple-Output radiator's measured and simulated reflection coefficients. Approximately 113% (3.6-13 GHz) and 121% (3.3-13.6 GHz) of the measured and simulated bandwidths exceed 10 dB. According to Figure 11(a), the measured isolation between ports 1 and 2 is GROUND SURPASSING 17dB, whereas the simulated isolation is over 19 dB. The decoupling structure is designed to operate between 4-6 GHz to minimize coupling at lower frequencies.
A plot of the calculated and computer-generated gain of the anticipated wearable(radiator) antenna can be seen in Figure-11c. At 8.5 GHz, the calculated peak gain is 5.69dB. Antenna measurements and simulations agree well. Because the textile materials and copper part are joined by adhesives, there is a small difference.

B. EMISSION PERFORMANCE(radiation)
The anticipated CP wearable Multple-input-multiple-output antenna is illustrated with calculated and computer-generated radiation patterns for both 5.25Ghz & 6.3 GHz in Fig.12. Using a 50-OHMS load on port-2 & port-1, the MIMO antenna shows LHCP characteristics. MIMO antennas operate in the same manner as RHCP capabilities when port-two is excited and port-one is coordinated to a 50-OHM load. Figures 12(a)

2) TARC
Multi-port antenna elements can interfere with each other's performance when they operate simultaneously. This effect is considered by TARC, which is presented as the . A TOTAL ACTIVE REFLECTIVE COEFFICIENT (TARC)may be calculated based on the following equation [26] for the proposed two-port MIMO antenna. The simulated and measured curves of the TOTAL ACTIVE REFLECTIVE COEFFICIENT (TARC)are shown in Figure 13 The study illustrates how the wireless environment impacts diversity. The MEG [22] can be premeditated using the subsequent equations.

BENDING EFFECT ANALYSIS
If worn in clothing on human body parts like the arms and thighs, the wearable antenna can bend. We ran simulations of the antenna at different radii to ensure its structural integrity, including 15 MilliMeters, 25 MilliMeters, 35 MilliMeters, and 45 MilliMeters. Table 15 and Table 16 illustrate the results from a simulated S11 antenna and an axial ratio for diverse winding radii. To facilitate analyze MIMO antennas, bending of the antenna for both the E-plus the H-plane are analyzed. A simulation for the bending of the original antenna, compared with that of the simulated results presented in Figures 15(a) and (b). By comparing the results with the original results, it can be seen that the curves tend to lean to the elevated frequency side by roughly 710 MHz's . The Multple-input-multiple-output radiator performs best at several bending circumstances, exhibiting both an equal bandwidth and an excellent S11 result; however, the results deteriorate as the bend radius decreases because of an unbalanced impedance between the feed line and the port. Similar results are also observed in bending analyses in the Horizontal-plane(H), where the resonating band shifts right as the bending radius decreases. An antenna bending model simulating the axial ratio, shown in Fig. 16, the radius changing between 16 MilliMeters and 46 MilliMeters is illustrated. At 6 GHz, the 3-dB ARBW degrades owing to the feed line offset, shifting to the down-ward as the bending radius grows.AxialRatio and S11 of the anticipated wearable radiator in the (E)plane have been measured in Fig.17(a&b), with nice conformity amid the computer-generated and calculated outcome. Additionally, the antenna on the body is analyzed. The 4-level human being arm revealed in Figure-18a has fundamental values of density, conductivity, and LossTangent permittivity as shown in Table 4. As can be seen in Fig.18(b), the simulated S11 results for different bending radii are moved to the right, due to the loss character of the human arm and the reduced length of the current path.

S.A.R CHARACTERISTICS (Specific-Absorption-Rate)
This relation [27] can be utilized to define the SAR value as follows.
The incremental mass is dm, the incremental energy is dE, and the volume element is dA. Based on the calculation of the antenna's maximum input power, 367.86 mW is the maximum power for 10 grams of tissue at 2Watts input powers, exceeding the highest standard limit. Accordingly, the anticipated radiator(CPMIMO) can work within its acceptable boundaries. An analysis of textile MIMO antennas and recent textile wearable antennas is shown in Table5. These parameters such as substrate material, antenna size, ARBW, operating bandwidth, sense of polarization, fractional bandwidth, gain, and isolation are compared. In [12]- [16], wearable antennas were presented as LPAs. Circular polarization showed in [11], while [17]- [21] were dual-sense CP antennas, but their operating bandwidth was small. Circular polarization showed in [11], while [17]- [21] were dual-sense CP antennas, but their operating bandwidth was small. The proposed textile antenna has a smaller size and axial ratio than the reported antennas and has a dual-sense (Left hand circular polarization L.H.C.P /Right hand circular polarization R.H.C.P) design.

CONCLUSION
A II-port stealth CP wearable Multple-Input-Multiple-Output radiator for Circularly polarized wideband operation is proposed in this paper. An overall size of 34.5X42X1 mm3 can be found on the textile antenna. ARBW and impedance bandwidth of 113% are observed in the anticipated Multple-Input-Multiple-Output antenna. DIVERSITY.GAIN (D.G) is greater than the value 9.96dB, Envelope.Correlation.Coefficient-E.C.C below the value 0.0200, and Channel Capacity Loss(CCL) slightly below the value 0.2b/s/Hz are displayed on the antenna. Without any additional decoupling elements, the isolation obtained exceeds 18 dB. Human tissue models are also used to analyze SAR of the presented radiator, which is found to be within the allowed range of frequencies. This radiator is best usable for C-band up-link and down-link applications in wireless networks on and off the body, including WLAN, Bluetooth, and WiMAX.