Traditional duplexing antennas for implantable biomedical devices often rely on half-duplex or multi-band designs, which allow either transmission or reception at a given time or require separate frequency bands for uplink and downlink. Such configurations result in reduced data rates, increased latency, higher hardware complexity, and potential spectral congestion, thereby limiting their suitability for advanced in-body communication. In this work, an innovative in-band full-duplex (IBFD) concept is introduced in a miniaturized implantable antenna optimized for deep implantation at a depth of 65 mm in a human torso phantom. The antenna operates at 2.4 GHz on both Port 1 and Port 2 with independently controllable bands. A compact volume of 5.81 mm3(π × (2.7)2× 0.254) is achieved through the integration of shorting pins, open-ended slots, and multiple semi-circular slots. High port-to-port isolation of 29.5 dB is obtained using an ultra-thin substrate, superstrate, and a narrow 0.4 mm separation between the radiating patches. The antenna exhibits omnidirectional radiation patterns at both ports, with measured gains of -20.2 dBi and -20.3 dBi for Port 1 and Port 2, respectively. The proposed design demonstrates ultra-miniaturization, high isolation, reliable impedance matching, acceptable radiation performance, and independently controllable duplexing bands. These characteristics make it highly suitable for deeply implanted biomedical devices, significantly improving spectral efficiency and enabling simultaneous transmission and reception for real-time bidirectional communication in next-generation implantable systems.

Wearable Internet of Things (IoT) devices, used in healthcare, fitness, and industrial safety, rely on compact, streamlined antenna systems to achieve high data rates, reliable connectivity, and seamless multi-device operation. This paper introduces a flexible pulse-nexus MIMO antenna (PN-MIMO) design that achieves wideband CP based on a frequency-selective fractal gate absorber (FGA) for mmWave wearable systems. The single antenna is built on a Rogers RT/Duroid 5880 substrate and features compact dimensions of 0.48λ0×0.16λ0×0.02λ0at 24 GHz. The antenna is further configured into a quad-element MIMO system with a minimal port-to-port spacing of 0.048λ0. A novel concept is introduced whereby distinct resonance frequencies, one generated by the PN-MIMO antenna (23.4–24.2 GHz) and the other by FGA (24–26 GHz), are combined to achieve a wide impedance bandwidth (IBW) of 3.5 GHz (22.2–25.7 GHz) through constructive interference. The integration also results in low mutual coupling (≤ 25 dB), high gain (≥ 7.5 dBi), and a wider 3-dB axial ratio bandwidth (ARBW) of 2.5 GHz. The on-body performance and bending behavior of the antenna are evaluated on the chest, hand, and leg of a human model, demonstrating stable operation under structural deformation and body loading. Later, the simulation results are validated through measurements, showing good agreement. The proposed PN-FGA-MIMO antenna exhibits excellent radiation characteristics while maintaining SAR levels significantly below the US (1.6 W/kg) and EU (2 W/kg) safety limits, indicating its strong suitability for mmWave wearable applications.

Retinal prosthetic devices (RPDs) require miniaturized, biocompatible, and energy-efficient wireless links to enable reliable power delivery and data communication under harsh intraocular environments. This paper presents a smart-glass-enabled intraocular wireless power transfer (WPT) and communication platform based on an interdigitated spiral antenna integrated with an on-substrate rectifier, coated with an oil-infused biocompatible elastomer. The proposed implant is fabricated on a Rogers RT Duroid 6010 substrate with a compact size of 6.3 mm × 6 mm × 0.25 mm and achieves ultra-wideband (UWB) impedance matching from 2.2 to 8 GHz. Unlike conventional RPDs that rely on inductive coils or narrowband architectures, the proposed design enables simultaneous radiative near-field WPT and wideband communication within a single compact intraocular structure. A detailed electromagnetic analysis is conducted using a realistic eye model, which demonstrated robust impedance matching and stable transmission performance under eye rotation and transmitter (Tx)-receiver (Rx) antenna separation variations. The proposed WPT system achieved -22 dB power transfer efficiency with a Tx-to-Rx separation of 17 mm. The UWB Rx achieved a maximum measured peak gain greater than -14 dBi with a measured radiation efficiency of more than -24 dB across the 2–7 GHz frequency range. Furthermore, sensitivity analysis confirms that the antenna maintains reliable operation under ±20% variations in tissue permittivity and conductivity to account for inter-subject physiological variability. In addition, a WPT Tx is integrated into glasses to ensure wearability and to validate real-time rectification and LED illumination under saline-loaded conditions experimentally. To ensure compliance with safety regulations, a comprehensive safety analysis is conducted, including specific absorption rate and tissue heating. To assess long-term functional stability, in vitro aging studies of the oil-infused elastomer in phosphate-buffered saline at physiological and accelerated temperatures are conducted, followed by gravimetric, radio-frequency (RF), and spectroscopic analyses to verify sustained surface integrity, functional stability, and the absence of oil leaching over time.

Implantable devices play a vital role in IoT-based healthcare, creating the need for compact, multi-band antennas that support high data rates for biotelemetry. This study presents a miniaturized dual-band, dual-port MIMO implantable antenna designed for wireless capsule endoscopy (WCE) and deep tissue applications. The antenna is integrated within a capsule-type device and has compact dimensions of 11.5×6×0.6mm3. It operates in the Industrial, Scientific, and Medical (ISM) bands of 433.1–434.8 MHz and 902–928 MHz. The proposed antenna supports the transmission of high-quality images and video over a considerable distance. Miniaturization and high isolation are achieved using carefully designed meandered lines. This design avoids the use of shorting vias or ground-plane slots, which simplifies the structure and reduces back radiation. As a result, it eliminates the need for a complex decoupling network to enhance isolation. This antenna is the first reported MIMO implantable design to operate in the lower ISM bands while maintaining an ultra-compact size. Following a detailed simulation-based analysis, a prototype was fabricated. The measured results showed excellent agreement with simulations. The antenna provides impedance bandwidths of 61 MHz (466–405 MHz) and 112 MHz (846–958 MHz), and measured gains of –40.2 dBi and –35 dBi at 433 and 915 MHz, respectively. Specific absorption rate (SAR) analysis was conducted to ensure compliance with IEEE safety standards. A link margin study was also performed, demonstrating reliable communication for high data rates of 1, 78, and 120 Mbps, with a minimum coverage distance of 10 meters based on SAR constraints. To assess diversity performance, envelope correlation coefficient (ECC) and diversity gain (DG) were evaluated and found within acceptable limits. The antenna also exhibits pattern diversity at both operational bands. The proposed design offers a reliable and compact solution for high-data-rate, SAR-compliant biotelemetry in modern IoT-based healthcare systems.

Leadless cardiac pacemakers (LCPs) enhance health technology by offering a minimally invasive and reliable solution for cardiac pacing; however, their reliance on batteries poses a challenge to achieving extended device longevity. This study proposes an efficient wireless power transfer (WPT) system for LCP devices, in which the dynamic misalignments caused by the natural contraction and relaxation of heart muscles during cardiac cycles and respiratory movements are characterized for the first time. The system comprised an off-body transmitter (Tx) and an in-body rectifier-integrated conformal receiver antenna (Rx). A single-band Tx is optimized to deliver the power wirelessly in the 915 MHz frequency band, whereas the Rx element is configured to offer dual-band characteristics at 433 MHz (data-telemetric mode) and 915 MHz (power reception mode). In addition to the peak gains of −30.6 and −24.8 dBi at the respective lower and higher frequency bands, the Rx exhibited a wireless power reception efficiency of up to 0.53% with a harvested voltage of more than 3 V at 55 mm Tx-Rx separation. The simulation results were experimentally validated in a heart-mimicking phantom, demonstrating the effectiveness of the proposed WPT system in maintaining robust power delivery even in the presence of misalignments induced by physiological motions. Moreover, the rectifier’s measured efficiency of 82% emphasizes its effective power delivery from the perspective of commercial pacemakers. In addition, a WPT-enabled real-time wireless biotelemetric communication link was established, highlighting the system’s potential as a versatile Internet of Medical Things (IoMT) platform for monitoring various real-time physiological parameters.

Multichannel neural monitoring systems are crucial in the accurate diagnosis and treatment of epilepsy by continuously recording neural activity, allowing precise identification of epileptic zones. These systems demand an ultrawideband (UWB) antenna with wireless power reception capability to facilitate high-data-rate communication and battery-free operation for the development of compact and long-lasting neural devices. This articel introduces a compact ($9\times 11\times 0$.25 mm3) battery-free implantable UWB system with an integrated rectifier for multichannel epilepsy monitoring, wirelessly powered by a novel 2.4 GHz smart cap-based transmitter (Tx) antenna. Extensive simulations and measurements are conducted to analyze the system’s performance. The implantable system exhibits a measured ultrawide bandwidth of 6.8 GHz (1.2–8 GHz) with peak gain values of −16.5, −23, and −24.1 dBi at 2.4, 4.8, and 5.8 GHz, respectively. The proposed wearable smart cap-based Tx antenna efficiently transfers power to the UWB implant system in various scenarios, including lateral and rotational misalignments, achieving a measured transmission coefficient$(|S_{21}|)$of −20.06 dB at a 15 mm distance while ensuring user comfort and mobility. Moreover, the compact rectifying circuit achieves a maximum conversion efficiency of 78.4% at a low input power of 6 dBm across a 2 k$\Omega $load. In addition, the safety of the system was validated using a realistic human head model to ensure compliance with the IEEE specific absorption rate limits. The features and performance metrics demonstrate that the proposed UWB implant system, powered by a wearable smart cap, offers a promising solution for safe, continuous, and battery-free multichannel epilepsy monitoring applications.

We introduced a circularly arranged Vivaldi endfire antenna array combined with nona-band rectifiers to enhance the capability of receiving electromagnetic power to supply power for Internet of Thing (IoT) devices. The rectifier encompasses frequencies of 0.9, 1.4, 1.8, 2.1, 2.4, 2.6, 3.5, 4.9, and 5.8 GHz, primarily covering telecom and Wi-Fi operating frequencies. Higher efficiency values at a lower input power of -10 dBm were achieved as 73.98%, 54.54%, 63.16%, 27.14%, 59.58%, 56.60%, 46.62%, 21.43, and 20.64% at 0.9, 1.4, 1.8, 2.1, 2.4, 2.6, 3.5, 4.9, and 5.8 GHz, respectively. In addition to the rectifier, we designed a wideband endfire Vivaldi antenna with a 3–8 dB gain over the operating frequencies, with an efficiency exceeding 80%. To further boost the received power, the antenna rectifier was transformed into an eight-element-based circular array, enabling multibeam and full-azimuth power reception coverage. We validated the performance of the rectifier and antenna by fabricating an energy-harvester array. Furthermore, we demonstrate the IoT device operation to illustrate the practical application of our proposed system.

Textiles integrated with electronics and long-range (LoRa) wireless technology are revolutionizing e-healthcare by enabling remote patient monitoring through wireless body area networks. This article presents a smart textile-based LoRa technology system for monitoring heart rate and predicting body temperature over both short and long distances. The system incorporates a LoRa module integrated with a smart textile, featuring sensors for photoplethysmography, electrocardiography, and body temperature monitoring. An embroidered monopole antenna seamlessly integrates into clothing, offering triple-band wideband operation at 433, 610, and 915 MHz with minimal susceptibility to human body effects and structural deformations. The proposed wearable antenna, assessed through specific absorption rate analysis, exhibits minimal exposure to electromagnetic radiation, ensuring user safety. The smart textile LoRa-enabled healthcare application (STLHA) monitors the received signal strength indicator, heart rate, and temperature data. Experimental results demonstrate effective outdoor communication ranges of up to 250 m at 915 MHz and 350 m at 433 MHz, with indoor ranges of up to 50 m. The STLHA offers a wireless solution for wearable devices, which enhances their functionality and usability in e-healthcare applications.

This paper presents a wireless link between an intraoral Tongue Drive System (iTDS) and a nearby receiver. The iTDS is a wireless and wearable assistive technology (AT) detects tongue gestures and allows individuals with severe physical disabilities to issue a set of user-defined tongue commands to access computers, smart-phone, and navigate powered wheelchairs. To mitigate the effects of external RF interference, the Tx can switch between three transmission bands (27 MHz, 433MHz, and 915 MHz), while sharing a dual-band antenna for the upper two bands and a coil for the lower band and battery charging to reduce size. Additionally, two adaptive matching networks are incorporated with the Tx at 433 MHz and 915 MHz, respectively, to maintain robustness of wireless link in the dynamic mouth environment. The adaptive matching mechanism utilizes a feedback for auto-tuning of the antennas' matchings. The adaptive triple-band Tx chip is implemented in a 5 V 0.35-pm standard CMOS process and a combination of simulation and measurement results have been presented.