Design, Performance, and SAR Analysis of a Low‐Profile Metamaterial‐Integrated UWB Antenna for Wireless Body Area Networks

Design and analysis of low profile and low SAR full-textile UWB wearable antenna with metamaterial for WBAN applications

Investigation of SAR reduction and gain enhancement using an all-textile antenna with metamaterial structure for wireless body area network applications

A dual-band, low profile, high gain, and low specific absorption rate (SAR) triangular slotted monopole antenna backed with a 4×4 artificial magnetic conductor (AMC) array is presented for wireless body area network (WBAN) applications. The antenna is printed on a Rogers ULTRALAM 3850 substrate, whereas the AMC array is printed on a RO3003 substrate. The design operates at 3.5 GHz, for WiMAX wireless applications, and at 5.8 GHz for the ISM Band. The proposed antenna preserved the dual-band resonance and exhibited acceptable gain and SAR at a separation of 15 mm from the human body model. To reduce such separation and achieve enhancements to gain and SAR, an AMC array was utilized. In free space, gain enhancements by 6.8 and 3.7 dBi were achieved at both frequencies, respectively. Furthermore, over a gap of 1 mm from the human body, gain enhancements by 23.3 and 13.9 dBi were achieved at both frequencies, respectively. In addition, SAR reductions by almost 99% were attained. The antenna was fabricated and measured where a very good agreement was observed between simulated and measured results, with and without the incorporated AMC array. With such results, the proposed design can be highly recommended for wearable medical applications, specifically for diabetic patients.

PurposeTo improve imaging performance for body MRI with a local transmit array at 10.5T, the geometry of a dipole antenna was optimized to achieve lower peak specific absorption rate (SAR) levels and a more uniform transmit profile.MethodsElectromagnetic simulations on a phantom were used to evaluate the SAR and B1+‐performance of different dipole antenna geometries. The best performing antenna (the snake antenna) was simulated on human models in a 12‐channel array configuration for safety assessment and for comparison to a previous antenna design. This 12‐channel array was constructed after which electromagnetic simulations were validated by B1+‐maps and temperature measurements. After obtaining approval by the Food and Drug Administration to scan with the snake antenna array, in vivo imaging was performed on 2 volunteers.ResultsSimulation results on a phantom indicate a lower SAR and a higher transmit efficiency for the snake antenna compared to the fractionated dipole array. Similar results are found on a human body model: when comparing the trade‐off between uniformity and peak SAR, the snake antenna performs better for all imaging targets. Simulations and measurements are in good agreement. Preliminary imaging result were acquired in 2 volunteers with the 12‐channel snake antenna array.ConclusionBy optimizing the geometry of a dipole antenna, peak SAR levels were lowered while achieving a more uniform transmit field as demonstrated in simulations on a phantom and a human body model. The array was constructed, validated, and successfully used to image 2 individuals at 10.5T.

This paper presents a new design of a sextuple band microstrip antenna for wearable applications a WBAN (Wireless Body Area Network) low SAR (Specific Absorption Rate). The proposed antenna consists of L-shaped slots have been determined based on the frequency bands. For the integration of these techniques six frequency bands consisting of the GSM 1.8 GHz, the WLAN standard IEEE 802.11 ah the band 900 MHz, the ISM band 2.4 GHz and 5.7 GHz, and 3.5 GHz band UWB respectively were considered. The proposed antenna is designed with the purpose of obtaining a low SAR models of the human body, considering both the electromagnetic effect and the shell model in human tissues.

The purpose of this study is to present a lightweight wearable (jeans) monopole antenna configuration for body area network (BAN) communication, breast and head tumors detections with back lobe reduction (i.e., low SAR), and it does so without introducing any special methodologies like as, AMC, EBG, HIS. The planned antenna has dual symmetrical slots as well as a ring-shaped slot (DSSRS) at the top, and it is in the form of a radiating rectangular patch with a ground plane. The design procedure has been finished with the help of CST MWS, and the next step will be to fine-tune the parameters of the antenna structure to achieve resonance at the ISM band (5.79 GHz). Testing for BAN, breast, and brain tumor detection was done using this prototype. With the proper impedance matching, the antenna achieves an operational bandwidth of 5.798 GHz (5.739–5.865 GHz), 5.77 GHz (5.715–5.838 GHz), 5.77 GHz (5.718–5.843 GHz) and 5.78 GHz (5.725–5.834 GHz), with an overall peak gain of 8.18 dBi, 7.69 dBi, 5.73 dBi, and 4.59 dBi; when proposed antenna placed on the free space, on the body, on the breast, and the head respectively. The suggested antenna meets the specific absorption rate (SAR) standards given by the FCC (1 gm) and the ICNIRP (10 gm). ABSTRAK: Kajian ini bertujuan untuk membentangkan konfigurasi antena monopole ringan boleh pakai (jenis jeans) untuk komunikasi rangkaian kawasan badan (BAN), pengesanan tumor payudara dan kepala dengan pengurangan lobus belakang (iaitu, SAR rendah), tanpa menggunakan metodologi khas seperti AMC, EBG, atau HIS. Antena yang dicadangkan mempunyai dua slot simetri (dual symmetrical slots) serta slot berbentuk cincin (DSSRS) di bahagian atas, dan berbentuk patch segi empat tepat yang memancar dengan satah tanah. Prosedur reka bentuk telah diselesaikan dengan bantuan perisian CST MWS, dan langkah seterusnya adalah untuk menyesuaikan parameter struktur antena bagi mencapai resonans pada jalur ISM (5.79 GHz). Ujian untuk BAN, pengesanan tumor payudara, dan tumor otak telah dijalankan menggunakan prototaip ini. Dengan padanan impedans yang betul, antena ini mencapai lebar jalur operasi sebanyak 5.798 GHz (5.739–5.865 GHz), 5.77 GHz (5.715–5.838 GHz), 5.77 GHz (5.718–5.843 GHz), dan 5.78 GHz (5.725–5.834 GHz), dengan pencapaian keuntungan puncak keseluruhan sebanyak 8.18 dBi, 7.69 dBi, 5.73 dBi, dan 4.59 dBi; apabila antena yang dicadangkan diletakkan di ruang bebas, pada badan, pada payudara, dan pada kepala masing-masing. Antena yang dicadangkan memenuhi piawaian kadar penyerapan spesifik (SAR) yang ditetapkan oleh FCC (1 gm) dan ICNIRP (10 gm)

This paper presents a compact, low-cost dual-band antenna design with low specific absorption rate (SAR) for Wireless Body Area Networks (WBAN) and Industrial, Scientific, and Medical (ISM) applications. The proposed antenna operates at 2.4 GHz with linear polarization and 5.8 GHz with circular polarization, fabricated on a 1.52 mm thick RF35 dielectric substrate (28 $$\times $$ 40 mm). The design features a coplanar waveguide (CPW) feed integrated with substrate-integrated waveguide (SIW) technology to enhance bandwidth and return loss characteristics. The antenna has broad bandwidths of 0.5 GHz with a 2.4 GHz center and 1 GHz with a 5.8 GHz center. To mitigate back radiation and reduce SAR, a 4 $$\times $$ 4 electromagnetic bandgap (EBG) structure was incorporated, resulting in significant performance improvements. The EBG implementation increased the maximum gain from 3.66 to 8.56 dB at 2.4 GHz and from 3.97 to 10 dB at 5.8 GHz. Additionally, SAR values decreased from 7.34 to 1.62 W/kg for 1 g of tissue at 2.4 GHz and from 2.18 to 0.91 W/kg at 5.8 GHz. Prototype measurements confirm simulation results, demonstrating the antenna’s suitability for WBAN and wearable ISM applications, including sensor networks and Wi-Fi devices. The design offers advantages of independent band tuning, circular polarization at the higher frequencies, and compliance with safety standards for human exposure to electromagnetic fields.

Characterizing specific absorption rate (SAR) of multi-antenna system is a facing challenge for implementing large-scale multiple-input multiple-output (MIMO) communications in mobile devices. For body-worn antennas, active circuit components capable of overcoming dynamic body area network (BAN) channels make MIMO-SAR complex in compliance testing. This study is the first to present the SAR of a body-worn multi-antenna integrated by 2-way microwave power dividers (PDs) with a wide tunable range over 20 dB. Dosimetry analysis was performed using a multi-layer human body model, which was exposed by orthogonally fed antenna arrays with tunable PDs at 2.45 GHz. The dependence of MIMO-SAR on the weight function, i.e., power ratio that is determined by considering the variation in cross-polarization power ratio (XPR) and antenna tilt angle, was investigated. It is found that over a wide tunable power ratio range from 0.1 to 10, the local average MIMO-SAR is dependent on weight function combinations. When the human body is very close to the antenna, the coupling between the microstrip structure of the PD and the human body will affect the local average SAR. The results also show that by increasing the number of array elements, the dependence of the ratio of the average SAR to MIMO channel capacity on the power ratio of the PD will be significantly reduced. The findings of this study provide guidelines for designing integrated structures of wearable antennas and active microwave circuits with low SARs.

Wireless Body Area Networks (WBANs) are human-centric wireless networks, and implantable antennas represent a vital communication component within WBANs. The dielectric properties of human tissue are highly complex, with each layer exhibiting distinct dielectric constants that significantly influence the performance of implanted antennas. It is therefore imperative that a compact broadband implantable antenna be designed in order to address the instability in communication of medical implant devices. The antenna, coated in silicone, is a single-layer structure fed by a coaxial cable, with a volume of just 6 mm × 6 mm× 0.53 mm. A metallic patch is etched on the upper surface of the substrate, and the compact antenna design is enhanced with the introduction of S-shaped, F-shaped, and rectangular slots on the patch. The bottom side of the substrate is etched with rectangular ground planes, which broaden the impedance bandwidth of the antenna. The simulation results demonstrate that the antenna attains an impedance bandwidth of 23.8% (2.08–2.64 GHz), encompassing the entirety of the Industrial, Scientific, and Medical (ISM) band (2.4–2.48 GHz). In order to simulate the working environment of the antenna within the human body, physical tests were conducted on the antenna in pork tissue. The test results demonstrate that the antenna exhibits a measured bandwidth of 28% (2.3–3.03 GHz), with a radiation pattern that displays omnidirectional radiation characteristics. The antenna’s impedance matching and radiation characteristics remain essentially consistent in both bent and unbent states, indicating structural robustness. In comparison to other implantable antennas, this antenna displays a wider impedance bandwidth, a lower Specific Absorption Rate (SAR), and superior implant performance.

A compact high-isolation diversity and circular polarized (CP) multiple-input multiple-output (MIMO) fabric antenna for 2.4 GHz ISM band applications is presented. A metamaterial (MTM)-inspired radiating element is used for the miniaturization of the presented fabric antenna. The proposed antenna is fabricated on a denim substrate and has a dimension of 58 mm x 23 mm x 1.6 mm. The circular polarization is achieved by trimming the two diagonal corners of the radiating elements. A defected ground structure (DGS) comprising two U-slots is placed underneath each radiator to increase the bandwidth of the presented antenna. The isolation characteristics between the two antenna elements are increased by 20 dB by cutting a slit in a ground plane. The proposed CP-MIMO antenna incorporates an artificial magnetic conductor (AMC) layer to limit backward radiation towards the human body and hence enhances the gain. This antenna has been created on a denim substrate with permittivity εr =1.6 and 1.6 mm thickness. The proposed antenna offers a fractional bandwidth of 6.6 % (2.38-2.54 GHz), and an impedance bandwidth about 160 MHz. The antenna has a peak gain of 2.5 dBi without AMC and 4.5 dBi with AMC. To validate the simulation results, a prototype for the proposed antenna has been fabricated and experimentally characterized. Due to its small size, low specific absorption rate (SAR), ease of integration, and robustness, this antenna is a good option for wireless body area network (WBAN) applications.

This paper presents the design and analysis of a multiple-input-multiple-output (MIMO) textile antenna for wireless body area network (WBAN) applications. The MIMO antenna is comprised of four identical modified rhombus-shaped monopole antenna elements of size of 0.57 λ0× 0.57λ0× 0.015λ0 , where λ0 is the wavelength calculated at the lowest operating frequency. The antenna is backed by a 6 ×6 frequency selective surface (FSS) of dimensions of 0.84 λ0× 0.84λ0× 0.015λ0 to improve gain and to reduce specific absorption rate (SAR). The antenna has an impedance bandwidth (S 11 ⩽ −10 dB) of 8.8 GHz (2.8–11.6 GHz) and isolation of >19 dB between the resonating elements. In order to assess the MIMO antenna’s flexibility, the bending analysis is performed for various bending radii. The obtained diversity metrics are: envelope correlation coefficient <0.5 dB, diversity gain <10 dB, channel capacity loss <0.4 bits s−1 Hz−1, and total active reflection coefficient <−10 dB. The performance of the antenna with and without FSS is investigated for gain enhancement and SAR reduction. With the help of FSS, the antenna gain is increased to 8.44 dBi, and the SAR reduced from 6.99 Watt kg−1 to 0.0273 Watt kg−1. The FSS achieves the highest efficiency of 96%. The designed antenna is suitable for smart textile applications due to its low SAR, high gain, and wider impedance bandwidth.

Wearable antennas play a critical role in the continuous health monitoring capabilities of Wireless Body Area Networks (WBANs), necessitating compact, conformal designs that ensure both high performance and user safety. However, many existing designs suffer from bulky form factors, limited dual-band functionality, and elevated Specific Absorption Rate (SAR) levels. In this work, a conformal, dual-band circular-ring slot antenna is proposed, fabricated on a flexible denim substrate characterized by a relative permittivity of εr = 1.6, a loss tangent of tan δ = 0.002, and a thickness of 0.7 mm. The antenna operates within the 2.45 GHz and 5.85 GHz ISM bands, employing a simple microstrip feed and a partial ground plane to achieve realized gains of 6.1 dB and 7.2 dB, along with return loss minima of –31 dB and –26 dB, respectively. Experimental measurements and full-wave electromagnetic simulations demonstrate consistent impedance characteristics, uniform gain performance, and SAR values of 0.197 W kg−1 and 0.6413 W kg−1 well below the FCC safety threshold of 1.6 W/kg. Furthermore, conformal bending tests over radii ranging from 50 mm to 70 mm reveal negligible degradation in antenna performance, underscoring its mechanical robustness under realistic wearable conditions. The antenna’s ultra-thin profile, low SAR, and efficient dual-band operation position it as a promising candidate for integration into compact, safe, and scalable wearable devices targeting healthcare and Internet of Things (IoT) applications.

Implant body area networks (BANs) have so far drawn considerable attention in biomedical applications. Although implant BANs require high throughput performance of wireless communication due to real-time data transmission, the transmit power is strictly regulated in order to satisfy a safety guideline in terms of specific absorption rate (SAR). In this paper, we evaluate the local peak SAR based on required bit error rate (BER) performance for implant BANs at 400 MHz medical implant communication service (MICS) band. To begin with, we first perform finite-difference time-domain (FDTD) simulations for implant BAN propagation with a numerical human body model, and derive the propagation characteristic of implant BAN signals. Then, we calculate the BER performance under this implant propagation channel and derive the required transmit power to secure a permissible BER. Finally, we calculate the local peak SAR under the required transmit power when the implant transmitter moves along the digestive organs. Based on such an approach, we attempt to determine a threshold transmit power which could be used to ensure the induced SAR not exceeding the safety guideline.

Background: Specific Absorption Rate (SAR) is radiofrequency power delivered to tissue duringa Magnetic Resonance Imaging (MRI) examination, expressed as watts per kg (W/kg). Radiofrequencypower deposition results in increased heating of patient tissues; thus, the use of MRI has to becontrolled to ensure patient safety.&#x0D; Objective: The study aimed to evaluate SAR among patients using the 3 Tesla MRI (MRI 3T) and 1.5Tesla MRI (MRI 1.5T) machines.&#x0D; Methods: Data were obtained from patients who were examined using MRI 3T (1,159 patients, 8,225series) and MRI 1.5T (1,423 patients, 8,605 series) machines. Age, body weight, SAR, repetition time(TR), type of radiofrequency (RF) pulse and anatomical region exposed were studied.&#x0D; Results: Average SAR for all patients using the MRI 3T was lower than that of the MR 1.5T in everypart (p &lt;0.001) = 0.92 ± 0.57 W/Kg, 2.45 ± 1.01 W/Kg, accordingly. The SAR that the patients receivedusing the spin echo technique revealed that T2 weighted image had lower SAR than T1 weighted imagefrom both MRI 3T and MRI 1.5T (p &lt; 0.001), 0.87 and 0.98 W/kg for MRI 3T, 2.20 and 2.83 W/kg forMRI 1.5T, respectively. For underweight patients, the lowest SAR was 0.89 W/Kg (MRI 3T) and 2.40W/Kg (MRI 1.5T), respectively. Whereas, among overweight patients, the SAR was the highest at 0.97W/Kg (MRI 3T) and 2.52 W/Kg (MRI 1.5T). For SAR categorized by the flip angle of the RF pulse,and patients evaluated by the MRI 3T, the study revealed that the group with the flip angle of the RFpulse &lt;75 degrees had lower SAR than the flip angle of the RF pulse &gt;75 degrees, 0.77 W/Kg and 0.94W/Kg, accordingly (p &lt; 0.001) similar to the MRI 1.5T.&#x0D; Conclusion: The average SAR of patients evaluated using the MRI 3T was lower than those of patientsevaluated using the MRI 1.5T in every body part examined. SAR was lower when the TR was increasedand flip angle was decreased.

In this study, a metamaterial (MTM)‐based high‐gain compact‐wearable antenna for 2.45 GHz industrial, scientific and medical radio band application has been proposed. To achieve the flexibility of the antenna, textile material felt fabric has been chosen as the substrate of the antenna as well as MTM. An omega (Ω) like structure has been taken as MTM unit cell design. High value of permeability is utilised for the gain enhancement of the antenna. In addition, very low specific absorption rate (SAR) is obtained using the MTM which makes the proposed antenna suitable for the biomedical application. The proposed antenna has achieved about 3 dB gain enhancement along with SAR value of 0.405 W/kg (1 g tissue). The design has been optimised and the prototype with the optimised parameter has been fabricated and tested over the semi‐solid phantom and human body. Further, the proposed antenna over different type of textile material has also been validated.