The spectral coexistence of LPWAN technologies, such as IEEE 802.11ah and LoRaWAN, in the sub-GHz band presents significant challenges for the performance of dense IoT networks. This study analyzes the impact of LoRaWAN interference on IEEE 802.11ah using an NS-3-based simulation environment. To this end, both technologies were integrated within a unified simulation framework, enabling the configuration of PHY and MAC parameters, as well as operating frequency bands consistent with real-world deployments in the US902–928 MHz ISM band and aligned with official standards. The evaluation focuses on fundamental performance metrics—throughput, total packet loss percentage (PPP), and signal-to-interference-plus-noise ratio (SINR)—under varying node densities and payload configurations. Across our sweep, moving from the lowest to the highest LoRa load (from 10 to 8000 LoRa nodes within the specified deployment radius), IEEE 802.11ah throughput decreases by up to 31%, and the packet loss percentage (PPP) increases by up to 79%. Furthermore, an SINR threshold was established as the criterion for packet loss under interference. Overall, this work provides a reproducible methodology for assessing inter-protocol coexistence in unlicensed sub-GHz bands, contributing quantitative evidence to the analysis and design of multi-protocol IoT networks in dense environments.

Design and biocompatibility analysis of an implantable miniaturized antenna in biosfluids for biomedical and ISM band applications

Multiband implantable antennas are crucial components of biomedical implantable devices (BIDs), enabling the establishment of wireless communication links with external base stations. These types of antennas perform various functions such as data transmission, wireless power transfer, and control signaling. However, this scenario requires an external multiplexer in the BIDs to separate various frequency bands, imposing size constraints on the BIDs. This work proposes a self-duplexing circularly polarized implantable (SDCPI) antenna for wireless capsule endoscopy (WCE) application having two separate ports, with port 1 providing a wideband response covering MICS (402 MHz), ISM (433 MHz) band, and port 2 covering ISM (915 MHz) band. The proposed SDCPI antenna achieved a very compact volume of π × (5.1)2 × 0.127 = 10.3 mm3 by semi-circular slots on the radiating patch and shorting pins. The proposed capsule integrated implantable antenna was thoroughly analyzed through simulations in various parts of the digestive tract (stomach, small intestine, and colon) and was later fabricated and tested. The measurements were carried out in minced pork, and the results obtained showed close resemblance to the simulated results. The proposed SDCPI antenna offers a -10 dB impedance bandwidth and CP bandwidth of 151 and 273 MHz, and 10% and 15% at 402 and 915 MHz, respectively. Furthermore, it exhibits measured gain of -36 and − 25 dBi at 402 and 915 MHz, respectively. To evaluate the human safety of the proposed SDCPI antenna, specific absorption rate (SAR) at 402 and 915 MHz was estimated in the stomach, small intestine, and colon, and was found to be within the limits allowed by the IEEE standards. Additionally, the wireless communication link establishment capabilities of the proposed SDCPI antenna were gauged through link margin analysis. This analysis confirmed that at 402 MHz, the presented SDCPI antenna can establish reliable communication up to 25, 9.7, and 4.5 m when placed in the small intestine for bit rates of 1, 12, and 78 Mbps, respectively. Likewise, at 915 MHz, the suggested SDCPI antenna offers seamless communication up to 28, 14.7, and 5.3 m when placed in the small intestine for bit rates of 1, 12, and 78 Mbps, respectively. These results verify that, to the best of the authors’ knowledge, the proposed highly miniaturized SDCPI antenna is the first self-duplexing CP implantable antenna for WCE applications offering simultaneous transmission and reception without requiring an external multiplexer.

Deeply implanted biomedical devices like leadless pacemakers require an antenna with minimal volume and high radiation efficiency to ensure reliable in-body communication and long operational time within the human body. This paper introduces a novel implantable antenna designed to significantly reduce the spatial requirements within an implantable capsule while maintaining high radiation efficiency in lossy media like heart tissue. The design principles of the proposed antenna are outlined, followed by antenna parameters and an equivalent circuit study that demonstrates how to fine-tune the antenna’s resonant frequency. The radiation characteristics of the antenna are thoroughly investigated, revealing a radiation efficiency of up to 28% at the Medical Implant Communication System (MICS) band and 56% at the 2.4 GHz ISM band. The transmission efficiency between two deeply implanted antennas within heart tissue has been improved by more than 15 dB compared to the current state of the art. The radiation and transmission performance of the proposed antennas has been validated through comprehensive simulations using anatomical human body models, phantom measurements, and in vivo animal experiments, confirming their superior radiation performance.

ABSTRACTThis research introduces a compact, flexible, and lightweight ultra‐wideband (CFL UWB) wearable antenna for IoT‐based health monitoring systems with low SAR, where the antenna serves as a key component. This design emphasizes broad bandwidth performance of 4.80–19.20 GHz, covering the 5.8‐GHz ISM band commonly used for Wi‐Fi, as well as the 10.40‐GHz band, which falls within the X‐band (8–12 GHz) used for high‐resolution microwave imaging, remote sensing, satellite communication, and high‐speed data links. The antenna features a rectangular patch with strategically introduced notches, a defective ground structure (DGS), L‐shaped slots at the ground plane edges, and a central vertical slot in the DGS to enhance impedance performance via optimized current distribution. Fabricated on a jeans substrate, it achieves a compact size of 17.5 × 15 × 1.7 mm3 and an impedance bandwidth of 120%. The design delivers a peak simulated gain of 5.11 dBi at 20 GHz and maintains 99.9% radiation efficiency at 5.8 GHz under bending conditions. SAR values remain within safe limits, measured at 0.693 and 0.817 W/kg for 1‐g tissue, and 0.693 and 0.701 W/kg for 10 g tissue, respectively. These results demonstrate the compatibility of the antenna for efficient, safe, and high‐data‐rate wearable IoT‐based health monitoring applications.

This research explores the design and simulation of a unidirectional double E-shaped microstrip antenna (MSA) operating at 5.8 GHz. The antenna was designed using CST Studio Suite, with Rogers RT 5880 as the substrate material due to its favorable dielectric properties. The design process involved adjusting the patch geometry by introducing slots to enhance bandwidth and gain. Simulation results show a return loss of −38.05 dB and a VSWR of 1.025, both indicating excellent impedance matching. Additionally, the antenna exhibits a directional radiation pattern with a peak gain of 7.63 dBi. These findings highlight the antenna's potential for compact and high-performance wireless communication systems in the ISM frequency band.

This paper presents a compact wideband implantable antenna developed for wireless capsule endoscopy (WCE) functioning in the 2.4–2.48 GHz ISM band. The antenna’s miniaturized design is achieved through the integration of E - and L - shaped slots in the circular radiator, a shorting pin and defective ground structure with an inclined T – shaped slot. The final structure has compact dimension of :pi::times::{3}^{2}:times::0.254:m{m}^{3}, and the Rogers RO3010 (:{epsilon:}_{r}=10.2,text{tan}delta:=0.0035) material serves as both substrate and superstrate. Performance was assessed in homogeneous muscle and heterogeneous human phantoms, and experimentally validated by implanting the device in minced pork. At 2.45 GHz the antenna delivered − 20.8 dBi gain, and a 44.02% impedance bandwidth. The specific absorption rate (SAR) values are recorded as 216.8 W/kg (1 – g) and 30.2 W/kg (10 – g). The study demonstrates that the antenna reliably supports wireless links beyond 10 m, maintaining a 10 dB margin at 2.45 GHz.

This research introduces a two-port MIMO antenna suitable for 5G, demonstrating enhanced data rates, throughput, capacity, and resistance to multipath fading. The antenna operates within the sub-7 GHz frequency range and adheres to the standards for 5G connections employed in many countries. The antenna possesses a wideband response spanning from 3.7 to 7.60 GHz and demonstrates an isolation surpassing 20 dB among its components. The singular component consists of interlinked circular patches and a partial base with a rectangular extension. The dimensions are minimal, measuring 22 × 28 mm² (0.27λ × 0.35λ) for a single element and 28 × 60 mm² (0.35λ × 0.74λ at 3.7 GHz) for the two-port arrangement, with a substrate height of 0.8 mm. Hardware prototyping demonstrates MIMO compliance with a maximum gain of 4.6 dBi and an ECC of less than 0.001. The evaluation of diversity gain (DG) and mean effective gain (MEG) further confirms its compatibility across several communication bands, including unlicensed LTE band 46, ISM bands, WLAN bands, 5G NR bands n77 and n79, and 5 GHz WLAN within the sub-7 GHz spectrum. Additionally, it is compatible with Wi-Fi 6, the Indian National Satellite System INSAT-C, and V2X/DSRC services, highlighting its adaptability across many communication standards and frequency bands.

Abstract A dual-band dual-polarized wearable antenna that applies to two different operating modes of wireless body area networks is proposed in this letter. The antenna radiates simultaneously in the ISM band at 2.45 and 5.8 GHz. It consists of a rigid button-like radiator and a flexible fabric radiator. At 2.45 GHz, an omnidirectional circularly polarized pattern is radiated by the flexible radiator, which is suitable for the on-body communication. At the same time, a linearly polarized broadside pattern for off-body communication is generated by button radiator at 5.8 GHz. The antenna has been validated in free space and human body environments. The impedance bandwidth at 2.45 and 5.8 GHz are 5% and 35%, and the gain is measured to be 0.15 and 5.95 dBi, respectively. Furthermore, the specific absorption rates are simulated. At 2.45 and 5.8 GHz, the results averaged over 1 g of body tissue are 0.128 and 0.055 W/kg. The maximum value at both bands is below the IEEE C95.3 standard of 1.6 W/kg.

Bluetooth technology has become foundational for short-range communication in a wide range of Internet of Things (IoT) applications, encompassing both Bluetooth Low Energy (LE) and Classic protocols. With the 2.4 GHz ISM band increasingly congested by coexisting technologies such as Wi-Fi, Zigbee, and proprietary wireless protocols, Bluetooth now faces critical challenges in delivering consistent Quality of Service (QoS) for time-sensitive and bandwidth-intensive use cases. In contrast to Wi-Fi, which benefits from robust QoS frameworks like IEEE 802.11e and Wi-Fi Multimedia (WMM), Bluetooth's current design lacks built-in mechanisms for traffic prioritization, deterministic latency, or adaptive scheduling. This paper identifies core limitations of Bluetooth’s transport architecture under interference-prone conditions and proposes a novel cross-layer QoS framework. Our design introduces traffic classification at the application layer, connection event prioritization at the link layer, coexistence-aware adaptive frequency hopping, and enhanced controller-host coordination through vendor-specific HCI extensions. We validate the proposal using simulations and empirical tests involving mixed BLE/Classic traffic and controlled Wi-Fi interference. The results demonstrate improvements in latency, jitter, and reliability, especially for critical IoT use cases such as voice, telemetry, and health monitoring. The framework provides a scalable path forward for integrating Bluetooth QoS into future specifications and enabling its use in high-density, real-time applications.

Abstract A miniaturized antenna for use in wearable applications is proposed which delivers an ultra-wide bandwidth of 4.6 GHz (from 21 to 25.6 GHz). A frequency selective surface (FSS) based reflective plate is placed below the antenna to significantly reduce the rear-side radiations towards the human tissues. The combined use of an Antenna and a Frequency selective surface (FSS) plate improved the gain from an earlier value of 5.5 dB to 8.1 dB, and directivity increased from 6 dB to 9.15 dB. The Front-to-back-ratio (FTBR) also improved substantially from 3.5 dB to 28 dB without much increase in antenna dimensions. Also, the combined structure provides a wider 3-dB axial ratio bandwidth (ARBW) of 2.45 GHz (from 22.15–24.6 GHz). The design achieves an ultra-small dimension of 10 × 15.5 × 3.864 mm3 to suit wearable applications. Finally, to ensure human tissue protection, Specific absorption rate SAR (1 g) analysis is also performed, which delivers low value of 0.784 W Kg−1 and 1.4 W Kg−1 at a distance of 1 mm and 6 mm from the skin layer. The proposed design offers all essential characteristics of wearable antennas, namely, high gain and directivity, high FTBR, low SAR, ultra-small size, wide 3-dB ARBW, and wide impedance bandwidth in a single design which makes it a promising candidate for portable wearable applications at 24 GHz (24.05–24.25 GHz ISM band).

PDMS is frequently utilized in the biomedical field because of its biocompatibility. The PDMS finds applications in medical implants, cardiovascular flow replication, and in the biomedical industry. This paper presents an innovative antenna design optimized for biomedical applications operating in the Industrial, Scientific, and Medical (ISM) band (2.4–2.5 GHz). The proposed antenna features a compact, flexible structure utilizing a Polydimethylsiloxane (PDMS) substrate to prioritize patient safety and comfort. For PDMS, the loss tangent is 0.0134 and the dielectric constant is 2.71. The design process employs parametric optimization to achieve a low-profile configuration with a wide impedance bandwidth and better radiation characteristics. Simulations and experimental validation using a multi-layered tissue phantom demonstrate superior performance, achieving a return loss below -10 dB across the ISM band. Additionally, Specific Absorption Rate (SAR) measurements confirm compliance with international safety standards, ensuring minimal electromagnetic exposure. PDMS-based flexible antennas hold promise for biomedical applications, but many existing designs face challenges related to limited gain, narrow bandwidth, and poor mechanical stability under continuous body movement. This highlights the need for more reliable and adaptable antenna solutions for on-body use. This study underscores the potential of the proposed ISM-band antenna to enhance the functionality and efficiency of biomedical communication systems, driving advancements in telemedicine and personalized healthcare solutions.

Radio-Frequency Energy Harvesting (RFEH) can be considered a promising solution for powering devices in the Internet of Things era, such as low-power wireless sensors, since RF electromagnetic waves are commonly found in diverse environments, due to different communication systems. To harvest the electromagnetic waves energy and convert them into Direct Current (DC), rectennas, which are composed of an antenna together with a rectifier, are used. However, the design of such rectifiers has two major challenges: the low spectral power density available and the dependence of circuit behavior on the operation temperature. To overcome the former, the Power Conversion Efficiency (PCE) of the circuit should be as high as possible, using, for instance, devices with low drop voltage. To improve the energy transfer from the antenna to the load, an Input Matching Network (IMN) is generally used. However, the rectifier input impedance varies with the temperature, which can degrade significantly the circuit performance. For this reason, to improve the circuit behavior, it would be desirable to have an RF design with low-temperature dependence. Schottky diodes are a common choice for RF rectifiers owing to their low conduction voltage and fast switching capability. Nevertheless, aiming to provide a better integration into commercial CMOS processes, such that the rectifier is placed together with the circuit it aims to power, it would be interesting to substitute Schottky with diode-connected MOSFETs. Therefore, this work aims to design rectifiers using a commercial RF 65nm CMOS process focusing on RFEH systems and considering the temperature influence.Two circuits were considered in this work: one basic Dickson charge pump, as presented in Fig. 1, and a 3-stage Dickson charge pump. In Fig. 1, VRF represents the RF source, M1 and M2 are the diode-connected transistors, CL is the load capacitance, and Cc is the coupling capacitance. In this circuit, the two diode-connected MOS operate alternately, one conducting at each half cycle of the input AC signal. Therefore, the voltage at CL is increased. For a 3-stage circuit, each basic cell of Fig. 1 is connected in cascade to the previous one. By using multiple stages, the output voltage can be further increased. However, there is a voltage drop at each device, in order to start its conduction, which can be a limiting factor for the circuit operation. For the determination of the devices width and length, an optimization tool incorporating the Imperialist Competitive Algorithm (ICA) has been used. The algorithm considers a Gaussian profile applied to the lower limit, center value, and upper limit fitness functions aiming to search for robust solutions regarding the variations of the manufacturing processes and environmental conditions. In the optimization process, the focus was a low temperature dependence while maximizing the output voltage. The TSMC RF CMOS 65nm PDK has been used, considering low threshold voltage transistors. The optimization was performed for the 3-stage circuit, whereas the one with just the first stage (parameters taken from the 3-stage optimization) was simulated for a comparison between their performances. A load of 1kW was considered, and the operation frequency was chosen as 2.45 GHz (ISM band).Fig. 2 presents the PCE as a function of the input power (Pin) for both circuits operating at different temperatures. It can be observed that the 1-stage circuit has provided a higher PCE than the 3-stage one. This can be understood by the fact that there are more transistors in the latter circuit and there is a voltage drop in each transistor, reducing the circuit efficiency. On the other side, the temperature has not affected the circuit behavior, which is significantly different from the rectifiers using Schottky diodes, in which the temperature increase results in a significant PCE reduction. In Fig. 3, the output DC voltage (Vout) obtained by these two circuits is presented as a function of the RF signal peak input voltage (Vin) at different temperatures. From this figure, it is clear that when increasing the number of stages, a higher output voltage can be obtained, making the 3-stage Dickson charge pump more adequate for supplying a low-power circuit. Nevertheless, a higher possible output voltage does not mean higher efficiency as previously demonstrated.In summary, in this work two MOS rectifiers, one with a single stage and a second one with 3 stages, were designed using commercial 65nm PDK aiming at RFEH applications operating at 2.45 GHz. The circuit has shown a low-temperature dependence. The higher the number of stages, the higher the output voltage. However, an efficiency reduction was observed for the multiple-stage rectifier. Figure 1

With the advancement of the Internet of Things (IoT), networks of intelligent systems formed by sensors are becoming increasingly prevalent in various applications worldwide. However, some obstacles hinder their applicability, especially in scenarios where these networks need to cover large areas, particularly in hard-to-reach locations. In such cases, powering the devices becomes unfeasible due to factors such as distance, positioning, and geographical dispersion. To address these challenges, various energy harvesting technologies have been explored, such as the use of radio frequency (RF), which enables the powering of these sensors, making it possible to develop ultra-low-power (ULP) energy-autonomous systems. Currently, with the presence of numerous RF signals in the environment, energy harvesting from RF waves is a promising area of study. For energy harvesting, antennas connected to ultra-low-power RF-DC converter circuits are used to increase the DC voltage available for powering the sensors. Most of these circuits use conventional transistors (MOSFETs) or Schottky diodes to convert the captured signals, as these devices have a lower conduction voltage compared to PN junction diodes. Schottky diodes are a common choice for RF rectifiers due to their fast-switching capability and low conduction voltage. However, to position the rectifier directly within the circuit it is intended to power, it is advantageous to replace Schottky diodes with MOSFETs configured as diodes, which allow for a larger integration density. Therefore, this work aims to design RF rectifiers and analyze the output voltage behavior when multiple rectifier stages are coupled in a cascade.A Dickson charge pump was considered in this work. Initially, a single-stage circuit was simulated in Eldo tool using SPICE Level 3, with the topology presented in Fig. 1. In this figure, Vin1 represents the RF source, operating at the ISM band of 2.45 GHz, M1 and M2 are the diode-connected transistors, C1 is the coupling capacitance, C2 is the load capacitance and R1 is the load resistance. In this circuit, the two diode-connected MOS transistors operate alternately, with one conducting in each half-cycle of the transient input signal, which increases the voltage across R1. In the sequence, a cascade configuration was schemed. Circuits with 2 up to 6 stages were evaluated forming multi-stage RF-DC converters. Each single-stage charge pump is connected in cascade with the previous one. It is worth noting that each stage also receives an RF signal source. In this way, the DC signal output of one stage becomes the DC level for the subsequent stage, and so on.Fig. 2 shows the DC output voltage as a function of time at the output of each stage in the six-stage Dickson charge pump. It can be observed through the figure that the total DC voltage in the output stage is in the order of 3.2 mV, which is equally divided among the output of all the previous stages. Fig. 3 shows the DC voltage as a function of time for single- to six-stage circuits, always taken in the output capacitor. This demonstrates that, when a two-stage circuit is applied instead of a single-stage one, there is an increase in the output voltage. However, for circuits with a large number of stages, the output voltage saturates around 3.2 mV, which can be observed in the left axis of Fig. 4. Anyway, it is interesting to observe that the increase in the number of stages leads to a faster response as the output reaches 3.2 mV in a smaller interval. This behavior could be related to the operation of the transistors in the subthreshold regime due to the small RF signal amplitude. In the right axis of Fig. 4, the normalized efficiency with respect to the single-stage circuit is presented as a function of the number of stages. It is noted that the fewer the number of stages, the higher the efficiency of the converter. This could be expected since each stage inserts new devices in the circuit, which need to be supplied.In summary, in this work, six MOS rectifiers, from single- to six-stage circuits connected in cascade topology, were designed to focus on RF energy harvesting (RFEH) applications operating at the ISM band of 2.45 GHz. The circuits with a larger number of stages showed a faster time response with the drawback of a reduction in efficiency. However, for circuits with more than two-stages, the output DC voltage is no longer dependent on the number of stages. Figure 1

An integrable high isolation MIMO antenna for wireless and ISM band applications: design and evaluation

This paper presents the design and simulation of a microstrip patch antenna for Internet of Things (IoT) applications in the 5.8 GHz ISM band, using an FR4 substrate to ensure cost-effective prototyping. A baseline inset-fed rectangular patch is compared with three optimized geometries: an inset-modified patch, a notched patch, and a U-shaped slotted patch. Simulations were conducted in CST Studio Suite using the frequency domain solver. Important performance metrics that were evaluated include return loss (S₁₁), gain, bandwidth, directivity, and radiation efficiency. This inset-optimized design yielded the best results with a radiation efficiency above 57%, a return loss of –49.8 dB, a bandwidth of 250 MHz, and a gain of 3.97 dB. The notched design also showed good performance, offering bandwidth (237 MHz) and strong impedance matching (–44.8 dB) with only minor gain trade-offs. Despite having the highest directivity, the slotted patch's lower efficiency (54%) and gain (3.55 dB) limited its applicability for low-power IoT nodes. All of the designs outperformed the 150 MHz target bandwidth, confirming that FR4-based antennas are feasible for small IoT systems. The study demonstrates how simple geometric changes can improve performance while maintaining low cost and ease of fabrication.

The growth of IoT and wearable electronics demands sustainable energy solutions beyond short-lived, waste-generating batteries. RF energy harvesting offers a self-powered alternative by capturing ambient RF energy. However, implementing this technology on textile substrates remains challenging due to material incompatibility, ink toxicity, substrate porosity, and scalability constraints. This study addresses these challenges by developing optimized fabrication techniques for printed textile rectennas operating at 2.45 GHz. It focuses on conductive ink formulations tailored for textiles, scalable integration methods such as screen-printing and doctor blade techniques, and improved attachment methods for lumped components, ensuring full integration of a microstrip patch antenna and rectifier circuit onto fabric. The research systematically examines the impact of substrate porosity, ink adhesion, material losses, mechanical deformation, dielectric variability, and surface roughness on energy harvesting efficiency. Additionally, it promotes environmentally sustainable solutions by reducing reliance on volatile organic compounds (VOCs) and complex fabrication processes. Electromagnetic simulations and experimental validations confirm the rectenna’s capability to harvest 2.4 GHz ISM band energy, despite challenges such as dielectric sensitivity and conductive ink losses. This work establishes a scalable, cost-effective framework for next-generation wearable and IoT applications, advancing flexible electronics and self-sustaining smart textiles.

Microstrip patch antennas are widely used in wireless communication due to their low profile and ease of fabrication. This makes them useful in the 2.4GHz ISM band. In this paper, the effects of different geometrical notches and slots on a basic rectangular microstrip patch antenna are analysed. Triangular, rectangular and hexagonal slots; and notches on only two corners and on all four corners are investigated using High Frequency Structure Simulator (HFSS) to determine which produce the most improvement on the operation of a rectangular microstrip patch antenna. The simulated results show that hexagonal slots and notches on two corners produce the most improvement.

In this paper, a small size multistubs resonator based flexible wearable antenna is demonstrated for dual-band operation. The proposed antenna is composed of vertically aligned multistubs resonator, a 50 Ω microstrip feed and a defected ground structure (DGS). This configuration of antenna resonates at 2.4 and 5.8 GHz Industrial, Scientific, and Medical (ISM) sub-6 GHz bands. It has a small footprint of 32 × 17 × 0.508 mm3 (0.256 λL × 0.136 λL × 0.004 λL at fL = 2.4 GHz), with measured reflection coefficient magnitudes (|S11|) of − 15.81 dB with bandwidth of 280 MHz (2.3–2.58 GHz) and − 33.06 dB with bandwidth of 580 MHz (5.42–6 GHz) at 2.425 and 5.72 GHz, respectively. Moreover, it has bidirectional and omnidirectional radiation features due to DGS with a measured peak gains of 1.317 dBi (2.425 GHz) and 4.759 dBi (5.72 GHz). This study also explored a widespread investigation on a parametric study, specific absorption rate (SAR), diverse bending conditions and its interaction with diverse on-body circumstances (by placement on the chest, hand, and leg). The SAR values are 1.29 W/kg (1 g) and 0.88 W/kg (10 g) at 2.43 GHz whereas at 5.8 GHz, the SAR values are 0.507 W/kg (1 g) and 0.257 W/kg (10 g), which well within SAR safe limits. The antenna adhere the effective robustness, stable performance during bending deformations and on-body scenarios which validated the antenna effectiveness for wearable sub-6 GHz ISM band applications.

A compact circular slotted radiator for ISM and wireless bands