Publications de Denys Nikolayev

Novel 2-D Beamsteerable Rectenna with Improved Power Receptivity for mm-Wave RF-WPT Applications

Anja Skrivervik, Denys Nikolayev, German Augusto Ramirez Arroyave, Amir Mohsen Ahmadi Najafabadi

This paper introduces a novel 2-D beam-steerable rectenna designed for mm-wave RF wireless power transfer (RF-WPT) applications. The 2-D beamsteering capability of the proposed rectenna is achieved by integrating an on-chip 4 × 4 Butler matrix, which is co ...

2025

Physical insights and design principles for efficient wireless implantable bioelectronics

Anja Skrivervik, Denys Nikolayev, Mingxiang Gao

Implantable bioelectronics require highly efficient wireless connectivity for autonomous operation and closed-loop control, yet power constraints, safety regulations, and data transmission limitations continue to hinder advancements in medical device innov ...

2025

Analysis of Non-Canonical Body-Conformal Arrays with Polarization Decomposition

Anja Skrivervik, Denys Nikolayev

Conformal phased arrays can be found in many applications due to their ability to fit tridimensional surfaces and, thanks to their scanning performance, can excel planar arrays. However, most of the previously proposed analysis methods can be applied only ...

IEEE2023

Theoretical Efficiency and Dosimetry of Buffered On-body Transmitter Antennas for Wireless Powering of In-body Devices

Anja Skrivervik, Denys Nikolayev

The viable and safe application of wireless power transfer for powering bioelectronic implants requires understanding the wave propagation in heterogeneous and dispersive media, the electromagnetic exposure assessment, and the optimum design of the system ...

IEEE2022

Reconfigurable Dual-Band Capsule-Conformal Antenna Array for In-Body Bioelectronics

Anja Skrivervik, Denys Nikolayev

Wireless in-body bioelectronics offer powerful biosensing and therapeutic capabilities. Efficient and robust in-body antenna designs are required to ensure a reliable through-body link, increase data rates, and reduce power budgets. This study proposes and ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2022

Wireless Powering Efficiency of Deep-Body Implantable Devices

Anja Skrivervik, Denys Nikolayev, Mingxiang Gao, Zvonimir Sipus, Erdem Cil

The wireless power transfer (WPT) efficiency to implanted bioelectronic devices is constrained by several frequency-dependent physical mechanisms. Recent works have developed several mathematical formulations to understand these mechanisms and predict the ...

Institute of Electrical and Electronics Engineers2022

Physical Bounds on Implant Powering Efficiency Using Body-Conformal WPT Systems

Anja Skrivervik, Denys Nikolayev, Mingxiang Gao, Zvonimir Sipus

The efficiency of an on-body wireless power transfer system for implant powering is defined by how the electromagnetic energy interacts with the lossy, heterogeneous, and dispersive body tissues. The objective of this study is to discuss the methodology an ...

IEEE2021

Rules of Thumb to Assess Losses of Implanted Antennas

Anja Skrivervik, Denys Nikolayev, Mingxiang Gao, Zvonimir Sipus

Fundamental limits for implanted antennas should be able to evaluate the bounds on losses with the knowledge of physical limitations from antenna and tissue parameters. In this work, rules of thumb to assess losses of deeply implanted antennas are presente ...

IEEE2021

Propagation-Loss Characterization for Livestock Implantables at (433,868,1400) MHz

Denys Nikolayev

Automated systems based on wearable sensors for livestock monitoring are becoming increasingly popular. Specifically, wireless in-body sensors could yield relevant data, such as ruminal temperature. The collection of such data requires an accurate characte ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2021

Application of Fundamental In-Body Radiation Limitations to Practical Design of Antennas for Implantable Bioelectronics

Anja Skrivervik, Denys Nikolayev

Fundamental in-body limitations on achievable radiation efficiency could provide decision-making assistance to engineers working on antennas for implantable bioelectronics. In this study, proof-of-concept conformal microstrip antennas are proposed based on ...

IEEE2020

Optimal Frequency of Operation and Radiation Efficiency Limitations of Implantable Antennas

Anja Skrivervik, Denys Nikolayev, Zvonimir Sipus

Fundamental limits on radiation performance of implantable antennas serve as the design quality gauge, facilitate the choice of the antenna type, and provide simple design rules to maximize the radiation performance. This study obtains the limits using two ...

IEEE2020

Joint Antenna-Channel Modelling for in-to-out-Body Propagation of Dairy Cows at 868 MHz

Denys Nikolayev

In this paper, for the first time, the in-to-out-body path loss between a capsule antenna placed inside the cows' rumen and a distant gateway was characterized at 868 MHz. Measurements were conducted on five different fistulated cows in a dairy barn. The i ...

IEEE2020

Design Concerns for In-body Antennas Based on Frequency Analysis of Fundamental Radiation Limitations

Anja Skrivervik, Denys Nikolayev, Zvonimir Sipus

Fundamental radiation limitations of in-body or implantable antennas should give us an estimate on the feasibility of some desired system. It was shown that near-field effects and distance to the body - freespace boundary are critical aspects, while the sh ...

IEEE2020

Rapid Analysis of Arbitrary-Shaped Conformal Beam-Scanning Arrays

Anja Skrivervik, Denys Nikolayev

Conformal antenna arrays are able to fit seamlessly on curved 3D-shaped surfaces, which are found ubiquitously on vehicles, aircraft, a human body, etc. In addition, conformal structures can overcome the scan loss limitations of conventional planar arrays. ...

IEEE2020

Influence of Body-Implanted Capsule Dimensions and Materials on Achievable Radiation Efficiency

Anja Skrivervik, Denys Nikolayev

Fundamental bounds on achievable radiation efficiency serve as the design quality gauge, facilitate the choice of the antenna type considering the available dimensions, and provide simple rules to check the feasibility of a given design. This study quantif ...

IEEE2019

Millimeter-Wave Heating in In Vitro Studies: Effect of Convection in Continuous and Pulse-Modulated Regimes

Denys Nikolayev

Shallow penetration of millimeter waves (MMW) and non-uniform illumination in in vitro experiments result in a non-uniform distribution of the specific absorption rate (SAR). These SAR gradients trigger convective currents in liquids affecting transient an ...

WILEY2019

Dielectric-Loaded Conformal Microstrip Antennas for Versatile In-Body Applications

Anja Skrivervik, Denys Nikolayev

Wireless implantable bioelectronics and accurate in vivo characterization of path loss require efficient and robust in-body antennas. Loading electric antennas with the effective permittivities higher than that of surrounding tissues is a promising solutio ...

2019

Radiation Performance of Highly Miniaturized Implantable Devices

Denys Nikolayev

Miniature wireless implantable bioelectronics provide powerful capabilities for biotelemetry, therapeutics, and neural interfacing. These technologies rely on antennas to communicate with external receivers, yet existing systems suffer from poor radiation ...

IEEE2019

Ensuring robust and tissue-independent operation of implantable, ingestible, and injectable antennas

Denys Nikolayev

In-body bioelectronics relies on antennas to interface with external on- or off-body equipment. In this paper, we address the impedance detuning of in-body antennas caused by nondeterministic electromagnetic properties of biological tissues. The impedance ...

IEEE2019

Optimal Radiation of Body-Implanted Capsules

Denys Nikolayev

Autonomous implantable bioelectronics requires efficient radiating structures for data transfer and wireless powering. The radiation of body-implanted capsules is investigated to obtain the explicit radiation optima for E- and B-coupled sources of arbitrar ...

2019