Igor Krois

Negative capacitor paves the way to ultra-broadband metamaterials

Experimental demonstration of the overcoming of basic dispersion-energy constraints in metamaterials with the help of active non-Foster negative capacitors is reported. The experimental metamaterial operates in RF regime, and it is based on air transmission line loaded with negative capacitors. Measurement results clearly show almost dispersionless Epsilon-Near-Zero behavior, accompanied with superluminal both phase and group velocities, over a bandwidth of more than four octaves (2 MHz-40 MHz). The principle of periodic loading of transmission line with negative capacitors may find applications in ultra-broadband active metamaterials for antennas and cloaking technology.

A capacitive intrabody communication channel from 100 kHz to 100 MHz

Intrabody communication (IBC) uses the human body as a signal transmission medium. In the capacitive coupling IBC approach, the signal is transmitted through the body, and the signal return path is closed through the environment. The received signal level is affected by the orientation of the transmitter with respect to the receiver, the number of ground electrodes connected to the body, the size of the receiver ground plane, and the surrounding environment. In this paper, we present a characterization of the capacitive IBC channel in the frequency range from 100 kHz to 100 MHz, obtained using a network analyzer and a pair of baluns. In order to better understand the transmission path in the frequency range of interest, we analyze the intrabody channel transmission characteristics using different electrode arrangements, test persons, environments, and body positions and movements. The transmission gain increases with frequency for 20 dB/dec and depends on the transmitter to the receiver distance, and the electrode arrangements. For a proper IBC configuration, the variations of the environment, test persons, body positions, and movements affect the transmission gain less than 2 dB.

Ultra-broadband simultaneous superluminal phase and group velocities in non-Foster epsilon-near-zero metamaterial

Experimental investigation of ultra-broadband simultaneous superluminal phase and group velocity in recently introduced epsilon-near-zero (ENZ) non-Foster metamaterial is reported. The phase and group velocities were extracted both from the measurements of scattering parameters in the frequency domain and the measurements of propagation time of broadband Gaussian pulse in time domain. Reported superluminal effects are extremely broadband (relative bandwidth of 180% (1:20)) and they are fundamentally different from widely reported narrowband experiments based on the anomalous dispersion. The phenomenon of simultaneous superluminal phase and group velocities may find applications in transformation electromagnetic devices and in communication systems.

Intrabody Communication in Biotelemetry

Biotelemetry is remote monitoring, measuring and recording of a living organism’s function, activity or condition. Network of sensor nodes placed on or implanted inside the body of a subject is called Body Area Network (BAN). In this work we will describe the principles of a wireless body area network which uses the human body as a transmission medium, namely intrabody communication (IBC). We will describe the limitations set on the IBC systems, describe dielectric properties of the human body as a transmission medium, specify different ways of transmitting signals through the human body and compare characteristics of the IBC systems found in the literature.

Effect of body positions and movements in a capacitive intrabody communication channel from 100 kHz to 100 MHz

Intrabody communication (IBC) uses the human body as a signal transmission medium. In this paper we examine the influence of body positions and movements of different test subjects on the capacitive intrabody channel transmission characteristics at 1 MHz, 10 MHz and 40 MHz by comparing the mean value and interquartile range of the gain for different combinations of the influential factors. We showed that up to 10 MHz variations in the gain among different test subjects and the variations caused by different body positions and movements of a test subject are comparable, and lower than the variations at 40 MHz.

Broadband superluminal effects in ENZ active metamaterial

Recently, it has been shown possible to construct an (almost) dispersionless active ENZ metamaterials and transmission lines based on non-Foster elements. These structures are inherently extremely broadband (several octaves) and they may support counter-intuitive superluminal phase and group velocities. However, causality is always preserved due to finite bandwidth of any realistic non-Foster element. Here, the measurements of broadband superluminal phase and group velocity of an active transmission line operating in lower RF regime (10 MHz – 40 MHz) are reported.

Application of wireless intrabody communication system to muscle fatigue monitoring

We proposed a wireless approach to electromyography measurements using an intrabody communication concept, which promises to be both easy-to-install and power-efficient. Employing our proprietary intrabody communication hardware we showed that modulated myoelectric signals transmitted through the human body contain enough information for myoelectric signal processing, both in frequency and time domain. We obtained several independent in vivo measurements of isometric and dynamics contractions of biceps brachii muscle, on which we successfully demonstrated the application of muscle fatigue monitoring.

Effects of Transmitter Position and Receiver Ground Plane on Signal Transmission in Intrabody Wireless EMG Measurement System

We investigate relation between the received signal strength and relative positions of the receiver and transmitter in an intrabody communication (IBC) system previously designed for electromyography (EMG) measurements in kinesiology, sports medicine and rehabilitation. The receiver signal electrode was placed on the subject’s left wrist and the transmitter was moved along the arms. We analyze effects of the receiver ground plane size and provide its upper limit beyond which further increase in the received signal strength is insignificant.

Accuracy analysis of dissolved oxygen measurement system realized with Cypress PSoC configurable mixed signal array

In this paper the accuracy analysis of the proposed dissolved oxygen measurement system based on the darks cell and the PSoC configurable mixed signal array chip is performed. In that process critical sources of errors are determined and associated errors are measured. The temperature, as the most affecting parameter of oxygen measurements, is analyzed in greater detail. Monitoring and regulation of temperature of the sample is crucial for precision oxygen concentration measurements. In order to achieve optimal accuracy level, system construction considerations are discussed and averaging algorithm and two point calibration methods are applied.

Effect of transformer symmetry on intrabody communication channel measurements using grounded instruments

Transformers with one winding terminal symmetrical with respect to ground (capacitances between their terminals and ground are the same) are referred to as balun transformers, and are often used for decoupling in the measurements of the intrabody communication (IBC) system transmission characteristics. We measured IBC system amplitude and phase transmission characteristics using three types of galvanic decouplers: non-symmetric RF transformers, balun transformers with center tap grounded and balun transformers with center tap floating. Four possible electrode configurations (AA, AB, BA, and BB) and four electrode arrangements (GSGS, GSSG, SGGS, and SGSG), result in a total of 16 measurement scenarios for each of three measurement setups. We showed that the change in the measured amplitude for different signal and ground electrode arrangements while measuring with non-symmetric transformers is influenced by the transformer symmetry to the ground, and not the capacitive intrabody communication transmission characteristics. The change of the amplitude in case symmetric balun transformers are used is negligible for practical purposes.