Aswathy K. Sarma

Bio: Aswathy K. Sarma is an academic researcher from Anna University. The author has contributed to research in topics: Microstrip antenna & Slot antenna. The author has an hindex of 4, co-authored 5 publications receiving 257 citations.

Dual-Band EBG Integrated Monopole Antenna Deploying Fractal Geometry for Wearable Applications

Abstract: This letter presents the design of a dual-band wearable fractal-based monopole patch antenna integrated with an electromagnetic band-gap (EBG) structure. The prototype covers the GSM-1800 MHz and ISM-2.45 GHz bands. The EBG structure reduces the radiation into the human body over 15 dB. It also reduces the effect of frequency detuning due to the human body. The performance of the antenna under bending, crumpling, and on-body conditions has been studied and presented. Specific absorption rate (SAR) assessment has also been performed to validate the antenna for its usefulness in wearable applications.

Polygon-Shaped Slotted Dual-Band Antenna for Wearable Applications

Abstract: This letter presents the design of a wearable dual-band patch antenna for operating in the GSM-900 and 1800 bands. The proposed polygon patch antenna comprises a circular slot and vertical slits embedded on jeans substrate. This structure provides two paths for currents, making it viable for dual bands. The effect of patch length, slot radius, and slit length on the overall antenna performance is analyzed by performing a comprehensive parametric study. Further bending, crumpling, wetness, and on-body measurements have been performed to validate the structure. Specific absorption rate (SAR) values ranging between 0.00039-0.0035 W/Kg have been obtained for two different analyses.

Deployment of Modified Serpentine Structure for Mutual Coupling Reduction in MIMO Antennas

Abstract: This letter deals with the design and implementation of modified serpentine structure (MSS) for isolation enhancement in microstrip antenna arrays. The antenna array is constructed using square patch radiators and is designed to operate at 2.45 GHz (ISM band) specially used for multiple-input-multiple-output (MIMO) communications. The proposed MSS acts like a band-reject filter to reduce the coupling between the radiators in the antenna array. The design and characterization of the modified serpentine structure is done, and its validity in MIMO scenario is verified through simulation and measurements. Experimental results show an isolation improvement of 34 dB for an array with reduced edge-to-edge spacing of 6 mm (λ0/20). The envelope correlation coefficient (ECC) is within the acceptable limit, making the solution viable for MIMO applications.

A Fractal-Based Circularly Polarized UHF RFID Reader Antenna

Abstract: This letter presents the design of a coplanar waveguide (CPW) circularly polarized antenna for the central frequency 900 MHz, it comes in handy for radio frequency identification (RFID) short-range reading applications within the band of 902-928 MHz where the axial ratio of proposed antenna model is less than 3 dB. The proposed design has an axial-ratio bandwidth of 36 MHz (4%) and impedance bandwidth of 256 MHz (28.5%).

Polarisation diverse multiple input–multiple output antenna with enhanced isolation

Abstract: In this article, two-element monopole multiple input–multiple output (MIMO) antenna with polarisation diversity for 4G and other applications has been presented. The designed antenna covers 16% (1701–2001 MHz) of bandwidth around the design frequency (1850 MHz) which includes both DCS-1800 and DCS-1900 bands. The two antennas are placed orthogonally and symmetrically with edge-to-edge spacing of 5.5 mm (λ 0/30). With the placement of interconnected swastika-shaped resonator between the two monopole antennas, there is an isolation enhancement of 60 dB thus reducing the envelope correlation coefficient value ranging from 0.016 to 6.12 × 10−10 and improving the diversity gain ranging from 9.9 to 10 dB within the −10 dB bandwidth. A prototype has been fabricated and validated using measurements.

A Compact, Low-Profile Fractal Antenna for Wearable On-Body WBAN Applications

Abstract: A compact and low-profile wearable antenna is presented for on-body wireless body area network (WBAN) applications. The proposed triangular patch antenna is designed using low-cost widely available vinyl polymer-based flexible substrate. The final antenna topology is obtained by the combination of the Koch fractal geometry, meandering slits, and defected ground structure, to achieve a novel hybrid structure with compact footprint, good structural conformability, and enhanced impedance bandwidth (BW) to operate in the Industrial, Scientific, and Medical band with center frequency at 2.45 GHz. The fabricated prototype of the antenna has shown a good agreement between numerical and experimental results. In comparison to state-of-the-art prototypes, our design has more compact form factor of 0.318λo × 0.318λo × 0.004λo, along with 7.75% impedance BW, a peak gain of 2.06 dBi, and overall radiated efficiency of 75%. For the assessment of a specific absorption rate (SAR) performance of our design, it is tested on realistic heterogeneous HUGO voxel model. Both numerical and experimental investigations revealed extremely good robustness to both human body loading and structural deformation, making it an ideal candidate for flexible and body-worn devices.

Wearable Antennas: A Review of Materials, Structures, and Innovative Features for Autonomous Communication and Sensing

Abstract: Wearable antennas have gained much attention in recent years due to their attractive features and possibilities in enabling lightweight, flexible, low cost, and portable wireless communication and sensing. Such antennas need to be conformal when used on different parts of the human body, thus need to be implemented using flexible materials and designed in a low profile structure. Ultimately, these antennas need to be capable of operating with minimum degradation in proximity to the human body. Such requirements render the design of wearable antennas challenging, especially when considering aspects such as their size compactness, effects of structural deformation and coupling to the body, and fabrication complexity and accuracy. Despite slight variations in severity according to applications, most of these issues exist in the context of body-worn implementation. This review aims to present different challenges and issues in designing wearable antennas, their material selection, and fabrication techniques. More importantly, recent innovative methods in back radiations reduction techniques, circular polarization (CP) generation methods, dual polarization techniques, and providing additional robustness against environmental effects are first presented. This is followed by a discussion of innovative features and their respective methods in alleviating these issues recently proposed by the scientific community researching in this field.

Wearable Circular Ring Slot Antenna With EBG Structure for Wireless Body Area Network

Abstract: A wearable circular ring slot antenna with electromagnetic bandgap (EBG) structure for wireless body area network application is proposed in this letter. According to the analysis of equivalent circuit model, the volume of the EBG element is miniaturized for wearable applications. The measured impedance bandwidth of the proposed antenna is observed to be 2.28–2.64 GHz, which covers the 2.4 GHz Industrial Scientific Medical (ISM) band. The measured half-power beamwidths are 60° and 54° in the H -plane and the E -plane, respectively, and the front-to-back ratios are 17 and 13 dB in the H -plane and the E -plane, respectively. The specific absorption rate calculated values for tissue in 1 g (for the U.S. standard) and 10 g (for Europe standard) are both less than the limitations. In conclusion, it is proper to use the proposed antenna in wearable applications.

Dual-Band EBG Integrated Monopole Antenna Deploying Fractal Geometry for Wearable Applications

Abstract: This letter presents the design of a dual-band wearable fractal-based monopole patch antenna integrated with an electromagnetic band-gap (EBG) structure. The prototype covers the GSM-1800 MHz and ISM-2.45 GHz bands. The EBG structure reduces the radiation into the human body over 15 dB. It also reduces the effect of frequency detuning due to the human body. The performance of the antenna under bending, crumpling, and on-body conditions has been studied and presented. Specific absorption rate (SAR) assessment has also been performed to validate the antenna for its usefulness in wearable applications.

Compact and Low-Profile Textile EBG-Based Antenna for Wearable Medical Applications

Abstract: A compact wearable antenna with a novel miniaturized electromagnetic bandgap (EBG) structure at 2.4 GHz for medical application is presented in this letter. The design demonstrates a robust, compact, and low-profile solution to meet the requirements of wearable applications. The EBG structure reduces the back radiation and the impact of frequency detuning due to the high losses of human body. In addition, the structure improves the front-to-back ratio (FBR) by 15.5 dB. The proposed compact antenna with dimensions of ${\text{46}}\,\times \,{\text{46}}\,\times \,{\text{2.4 mm}}^{3}$ yields an impedance bandwidth of 27% (2.17–2.83 GHz), with a gain enhancement of 7.8 dBi and more than 95% reduction in the specific absorption rate. Therefore, the antenna is a promising candidate for integration into wearable devices applied in various domains, specifically biomedical technology.