In this article, an efficient technique of the effective complex permittivity estimation of different human body models for in vitro measurement of implantable antennas at different medical frequencies (402 MHz and 2.45 GHz) using transmission matrix method (TMM) is proposed. This computational electromagnetics-based method can overcome some shortcomings of popular measurement techniques. TMM considers both reflection and transmission coefficients in different tissue layers present in multilayered human body models to predict effective complex permittivity. To check the prediction accuracy of the proposed method, two different antennas operating at two Federal Communications Commission (FCC)-prescribed medical bands (402-MHz MICS and 2.45-GHz ISM bands) are designed and placed within two popular human models-three-layer heart model and seven-layer brain model. The accuracy of prediction is observed by recording antenna performances within generalized multilayered model and predicted homogeneous model. The results show that this TMM-based method can predict equivalent complex permittivity of any human body model with 98.46% accuracy which is better than many related works. The variations in effective complex permittivity due to +/- 20% variations in thickness, relative permittivity, and conductivity at 402 MHz and 2.45 GHz have also been studied here. This method is independent of the number of body layers and their relative permittivity, conductivity and thickness, structure of implantable antenna, and its operating frequencies etc.

In the context of in-vitro testing of implantable medical devices, multi-layered body phantom development poses significant challenges in terms of complexity, cost and possible formation of unwarranted air gaps between two layers or mixing chemicals of two layers while one layer is placed on other layer in hot semi-solid form. Therefore, it is recommended to use its equivalent homogeneous phantom with same dielectric properties. In this article, equivalent complex permittivity of three-layer human-body-model at 2.45 GHz is estimated by using Transmission Matrix Method (TMM) and FEM solver. The transmission matrix of the required body model is calculated based on the electrical properties of each layer. Solving nonlinear equations from TMM, multiple solutions of complex permittivity values are obtained. A two-antenna system is designed in FEM solver where one of the antennas is placed within homogeneous phantoms with obtained complex permittivity values and other is in free space to choose exact complex permittivity using scattering parameters. To validate the final phantom properties practically, the simulated setup is replicated. The practical results show good agreement with simulated responses. This approach can reduce complexity of designing multilayer-models considering only 0.53

The growing demand for multi-frequency wireless communication systems has significantly increased research interest in multi-band radio frequency (RF) and microwave filters. Designing multi-band RF and microwave filters that are efficient, affordable, compact, lightweight, and easy to fabricate presents a significant challenge. Multi-band bandpass filters (BPFs), including dual-, tri-, and quad-band variants, are pivotal in simplifying RF systems by reducing component count, particularly in multi-band transceivers. Creating compact and efficient dual-band filters is essential for modern electronic devices operating in dual frequency bands. This article presents a thorough analysis of prior research on microstrip dual-band bandpass filter designs, emphasizing current developments and the challenges encountered. A detailed comparison of several design strategies is provided and discussed to offer researchers insights into the benefits and drawbacks of each technique for specific applications. This article also outlines the challenges and future research directions for dual-band microstrip BPFs to meet various performance goals in current and future wireless systems.

The design and development of a novel scalp-implantable, nan-invasive, battery free, hybrid wireless sensor system for continuous intracranial pressure (ICP) monitoring are presented. Traditional methods for ICP measurement are highly invasive and pose risks such as infection and trauma. In contrast, the proposed system comprises a radio frequency (RF) powered, hybrid RF biosensor utilising a miniaturised implantable antenna and a wearable non-invasive transceiver. The dual-band operation at 2.45 GHz and 4.55 GHz enables high-data-rate transmission suitable for real-time brain telemetry and for energy harvesting. Electromagnetic simulations utilising human tissue phantoms exhibit robust impedance characteristics, featuring reflection coefficients of − 20.61 dB at 2.45 GHz and − 12.48 dB at 4.55 GHz, alongside fractional bandwidths of 20.42

In this article, a low-profile, compact (1.36 lambda 0 x 1.24 lambda 0 x 0.04 lambda 0), microstrip, annular leaky wave antenna, with beam scanning capacity, (-44 degrees to +45 degrees) has been proposed in the frequency band of 5.5-6.5 GHz. The leaky wave structure consists of four annular microstrip rings arranged in a circular manner. The 2D cylindrical leaky wave propagates outward radially from the source along the interfaces of this structure. The periodic repetition of the rings in a circular pattern results in a compact structure compared to the linear repetition in leaky wave structures, adding to the novelty of the design. The dimensions of the ring are so chosen as to excite the dominant TM mode of the structure and thereby generate directive radiation patterns with beam scanning property. The operating frequency band covers the sub-6 GHz band, which is suitable for automated vehicular communications. Most of the antenna designs earlier reported for vehicle-to-vehicle communications produced omnidirectional patterns. On the contrary to this, the structure presented in this work, prevents unnecessary dissemination of signals by producing a directional pattern that gives wider angular coverage through beam scanning. A symmetric beam scan is obtained in the frequency band of interest, with a measured gain of 1.2 dB and a gain variation between 0.6 dB and 2.62 dB.

This study examines how the effective dielectric characteristics of the human torso affect the carrier-link-margin (CLM) and data-link-margin (DLM) of a biocompatible gelatin-encapsulated implantable medical device (IMD) that consists of a small implantable antenna, battery, printed circuit board (PCB), camera, and sensor operating at 2.5 GHz. The specific absorption rate (SAR) and the radio frequency (RF) link performances of the IMD are tested for ±20% changes in reference to the mean values of the effective relative permittivity, ɛeff, and the effective conductivity, σeff, of the human body model. An artificial neural network (ANN) with two inputs (ɛeff, σeff) and five outputs (SAR_1g, SAR_10g, fractional bandwidth, CLM, and DLM) is trained by 80% of the total scenarios and tested by 20% of them in order to provide reliable dependent analyses. The highest changes in 1g SAR value, 10g SAR value, fractional bandwidth, CLM, and DLM at a 4 m distance for 100 Kbps are 63%, 41.6%, 17.97%, 26.79%, and 5.89%, respectively, when compared to the reference effective electrical properties of the homogeneous human body model. This work is the first to accurately depend on the electrical analyses of the human body for the link margins of an implantable antenna system. Furthermore, the work’s uniqueness is distinguished by the application of the CLM and DLM principles in the sphere of IMD communication.

This letter presents a nonlinear phase modulated (NPM), dual-beam, circularly polarized (CP) scalar impedance modulated (SIM) metasurface-based leaky-wave antenna (LWA) with butterfly-shaped beamforming, operates at fr = 15.5 GHz. A comprehensive NPM technique is analytically presented to obtain proposed metasurface-based LWA. The proposed NPM function is numerically realized by its magnitude and phase response. Using NPM, a dual-beam linearly polarized (LP) surface impedance (Zsurf) is analytically mapped into CP impedance with simulated and measured data validation of proposed dual beam, CP LWA. An overall dimension of 15 lambda 0x 7.5 lambda 0 yields highly directive dual beam (i.e., {theta s, cps} = {(-35(degrees), 0(degrees)), (32 degrees, 0(degrees))}) with a maximum realized gain (g(max)) of 21.52 dBic and half-power beamwidth of 4.2(degrees) each. A wideband axial ratio beamwidth of 1.8 GHz is obtained with an overall axial ratio of <1.2 dB.

A triple-band, coaxial-fed, slotted microstrip patch antenna with metasurface loading is presented in this article. The first frequency band covers the 865-868MHz European UHF-RFID band, the second frequency band partially covers the 3300-4200MHz n77 and 3300-3800MHz n78 5G communication bands. Finally, the third frequency band partially covers the 3.7-4.2GHz satellite communication band. The S 11 <=-10 dB regions of the antenna-metasurface system lie between 833-885MHz, 3400-3550MHz and 4059-4164MHz. The system exhibits right circular polarization within the first and third frequency bands with a 3dB axial ratio bandwidth of 41MHz (5%) within the first band and 111MHz (2.7%) within the third band. The 3dB axial ratio beamwidth is +/- 60(0 )within the RFID band and +/- 30(0) within the satellite communication band. Moreover, the system also exhibits a dual-linear polarization within the second band. The radiation efficiency remains within the 75-85% region for all the three bands. The dimensions of the system are 0.28 lambda(0) x 0.28 lambda(0) x 0.023 lambda(0) at 865MHz. The proposed antenna-metasurface system is therefore very versatile, finding use as an UHF-RFID reader as well as for 5G and satellite communication.

The Implantable Medical Antenna (IMA) is extensively used for continuous patient health monitoring. For in-vitro testing of IMA, the development of human-body-phantom is a necessary task before implantation within the torso. The phantom can be developed by mixing different chemicals. Evaporation from liquid phantom and bacterial activities in semi-solid phantom during in-vitro measurement can change the electrical properties (relative permittivity and conductivity) of the phantom model which may lead to variation in implantable antenna performance. From a realistic point of view, the overall permittivity and conductivity of the human body can change due to variations in water content, blood properties, collagen content, hormones, development of diseases especially cancer, Madelung's disease, etc. Therefore, it is required to have knowledge about the dependence of IMA performance on equivalent electrical properties of homogeneous body phantom which has been studied in this article. From this study, it is observed using a curve-fitting technique that mathematical formulation between IMA parameters and variable effective permittivity and conductivity of equivalent body model are difficult. That's why; an Artificial Neural Network (ANN) has been developed here for proper estimation considering only similar to 1% and 1.5% errors with respect to the simulated and measured responses, respectively.

Quantum dot (QD) solar cells are promising for enhancing photovoltaic performance by improving light harvesting and charge carrier dynamics. This study introduces TiO2 quantum dots (QDs) as a novel UV-absorbing top layer in tandem solar cells—selected for their wide, tunable bandgap ( 3.7 eV), high photostability, non-toxicity, and compatibility with mesoporous TiO2 transport layers. Unlike traditional absorbers, TiO2 QDs target the underutilized UV spectrum, acting both as a power-generating absorber and a protective optical filter. Synthesized via a low-cost sol–gel method, the TiO2 QDs exhibited a crystallite size of 5.02 nm and strong UV absorption peaks at 360 and 378 nm. The fabricated cell achieved a PCE of 4.68

This letter introduces a miniaturized dual-band implantable antenna (volume of 21.53 mm(3)) to adapt C-band 5G biotelemetry in wireless capsule endoscopy (WCE). Open-ended slots were engraved on a patch to tune the antenna efficiently. The antenna, along with the battery, printed circuit board (PCB), camera, and data-management system was placed within a biocompatible polyvinyl alcohol capsule. This antenna was communicating with fractional bandwidths of 20.42% and 13.85% and realized gains of -24.08 dBi and -26.11 dBi up to 12 m and 6 m distances at 2.45 GHz and 4.55 GHz within the human body phantom, respectively. The antenna system was fabricated and placed within two homogeneous body models to verify its performance at both frequencies. The proposed system shows the known best performance reported on wireless capsule endoscopic systems. Introduction of 5G facility in WCE biotelemetry is also a novel approach in this application to improve the quality of smart patient monitoring.

This paper presents the effects of effective dielectric properties of human torso on carrier-link-margin (CLM) and data-link-margin (DLM) of an experimentally validated miniaturized corner-chamfered meander-line implantable antenna placed within an implantable system prototype consisting of battery, PCB, camera and sensor encapsulated by biocompatible gelatin at 2.5 GHz. Specific Absorption Rate (SAR) and link margin performances of the implanted antenna are analyzed for 2500 scenarios (±20% variations in reference to the mean values of the effective relative permittivity, ɛeff, and conductivity, σeff, of the human body). For accurate dependence analyses, an artificial neural network (ANN) with two input variables (ɛeff, σeff) and five output variables (SAR_1g, SAR_10g, fractional bandwidth, CLM and DLM) is trained by 80% and tested by 20% of the total scenarios. Compared with the reference effective electrical properties of the homogeneous human body model, respective maximum variations of 63%, 41.6%, 17.97%, 26.79%, and 5.89% are observed in 1 g SAR value, 10 g SAR value, fractional bandwidth, CLM and DLM at 4 m distance for 100 Kbps. This work pioneers accurate dependences of link margins of body-implantable antenna system on effective relative permittivity and conductivity analyses.

Implantation depth of Implantable Medical Devices (IMDs) is an important factor of communication quality between implantable antennas in IMDs and external devices. Therefore, it is required to study the effect of implantation depth on implantable antenna performance. In this article, dependence of resonant frequency and scattering parameters of a two-antenna system where one miniaturized meander-line antenna is placed within human muscle tissue layer operating at 2.45 GHz ISM (industrial, scientific and medical) band and a rectangular patch antenna placed outside human body, are tested. Here 15 values of implantation depth ranging over 5-35 mm inside muscle layer are taken and for each case resonant frequency and scattering parameters (S-11 and S-21) of the system are recorded. Statistical analysis has been performed to observe how these performance parameters are dependent on depth of implantation which may be varied at the time of surgery.

Madelung's disease occurs due to defective lipid metabolism. Non-encapsulated systematic fat accumulation in adipose tissue in the neck, torso, abdominal area, hips etc. causes Madelung's diseases which may cause difficulty of swallowing, breathing and speaking. It is difficult to differentiate Madelung's disease and tumor generation by observing its growth from outside the body due to doppelganger nature. In this manuscript, a novel two-antenna system has been proposed for Madelung's disease detection where one of the antennas is implanted within muscle layer to study rapid fat growth in subcutaneous layer and other is placed at outside of the body. Characteristics of wireless link between these antennas vary with fat thickness variation. Here, dependence of transmission $(\mathrm{S}_{21})$ and reflection $(\mathrm{S}_{11})$ coefficients of the system on fat thickness variation are studied. Madelung's disease can be detected by observing similar dependence observed in receiving end while implanted antenna placed within patient's body, communicating with receiver.

In this article, a novel method of fault detection in nonuniformly excited linear antenna array has been reported. This method uses an evolutionary algorithm-based technique to generate approximate radiation pattern in tune with reference faulty pattern for a nonuniformly excited linear antenna array. Based on the approximation, a binary sequence-based method of exact fault detection has been developed. In order to illustrate the effectiveness of the method, 12- and 20-element Dolph Tschebyscheff linear antenna array with amplitude fault has been considered. Superiority of the proposed method has been demonstrated through comparative study.

Intraocular lymphomas represent a diverse group of malignant lymphoid neoplasms, characterized by their heterogeneity. These neoplasms can be classified into two main categories: (1) those originating from the vitreoretinal tissue and (2) those that emerge within the uveal tract [1], [2]. The lymphomas affecting the retina and/or vitreous are considered primary tumors and are often associated with central nervous system (CNS) disorders [1], [2]. Primary vitreoretinal lymphomas (PVRLs) were previously referred to as primary intraocular lymphomas (PIOLs). PVRL predominantly involves the retina, vitreous body, and retinal pigment epithelium, whereas PIOL encompasses a broader range of intraocular structures, including the retina, vitreous body, choroid, and optic nerve, and can manifest as either vitreoretinal lymphoma or uveal/choroidal lymphoma. Both conditions share similar clinical presentations but differ in their specific intraocular involvement [1], [2]. Although rare, PVRLs constitute the most prevalent form of intraocular lymphoma. The estimated annual incidence is 0.46 per 100 000 individuals [1], [3]. This aggressive high-grade non-Hodgkin lymphoma is strongly associated with primary CNS lymphoma (PCNSL). According to the current World Health Organization (WHO) lymphoma classification, the majority of PVRL cases are categorized as diffuse large B-cell lymphomas [4]. Approximately 80% of PVRL patients will ultimately develop PCNSL, while 20% of PCNSL cases initially present with PVRL. Consequently, PVRL is typically fatal due to its eventual correlation with the CNS [5]. Despite its rarity, PVRL poses significant challenges in terms of diagnosis and treatment. The lack of effective therapeutic options and delays in diagnosis can contribute to a poor prognosis [1], [2].

In this article, a low-profile, microstrip-based, periodic leaky wave antenna has been proposed for vehicle-to-vehicle (V2V) communications. The leaky-wave structure, loaded periodically with stepped impedance resonator stubs operates in the 5.4-6.2 GHz frequency band, which includes the WAVE (Wireless Access in Vehicular Environments) band (5.85-5.925 GHz) required for automated vehicular communications. The S11 obtained in the spectrum is below -12.68 dB. While the majority of the antennas designed for V2V communications produced omnidirectional patterns, the structure proposed in this work yields a directional pattern, preventing unnecessary outages of signals. The periodic structure gives an added advantage of beam scanning, resulting in a wider, yet directive coverage in the desired frequency band. A backward beam scan from -13 to -31 is obtained in the frequency range of 5.4-6.2 GHz with a gain variation of around +/- 0.6 dB only.

The development of sensing technologies and miniaturization allows for the development of smart systems with elevated sensing performance. Silicon-based hydrogen sensors have received a lot of attention due to its electrical conductivity and the mechanical endurance. With this motivation, we have proposed a two-terminal silicon-based device in a crossbar architecture as a hydrogen gas sensing platform. In this work, we have adopted a multi-layer modeling approach to analyze the performance of the proposed system. Technology computer-aided design models have been used to capture device performance. A gas sensor model based on hydrogen adsorption on the Palladium surface and a crossbar model has been adopted to understand the Palladium work function variation with gas pressure and the performance of the proposed crossbar system respectively. We have shown the impact of parameters like interconnect resistance and array size on the whole system's performance. Finally, a comprehensive analysis has been provided for the design rule of this architecture. A fabrication process to spur future experimental works has also been added. This work will provide computational insight into the performance of a crossbar hydrogen sensor system, optimized against some critical parameters.