Negar Tavassolian

Bio: Negar Tavassolian is an academic researcher from Stevens Institute of Technology. The author has contributed to research in topics: Slot antenna & Antenna measurement. The author has an hindex of 15, co-authored 64 publications receiving 723 citations. Previous affiliations of Negar Tavassolian include Georgia Institute of Technology.

Miniaturized Circularly Polarized Square Slot Antenna With Enhanced Axial-Ratio Bandwidth Using an Antipodal Y-strip

Abstract: A novel single-fed, wideband, circularly polarized slot antenna is proposed and fabricated. Wideband circular polarization is obtained by introducing an antipodal Y-strip to a square slot antenna. The feedline is a U-shaped microstrip line that provides a wide impedance bandwidth. The overall size of the antenna is only 28 × 28 mm 2 (0.3 λ o × 0.3 λ o ). A prototype of the antenna is fabricated and tested. The measured bandwidths for the axial ratio (AR <; 3 dB) and relative impedance (|S 11 | <; -10 dB) are 41.3% (from 4.4 to 6.67 GHz) and 84% (from 3.25 to 8 GHz), respectively, and the antenna has a stable radiation pattern and a gain of greater than 3 dBi over the entire circular polarization frequency band.

High-Accuracy Heart Rate Variability Monitoring Using Doppler Radar Based on Gaussian Pulse Train Modeling and FTPR Algorithm

Abstract: This paper presents the theoretical and experimental study of a novel noncontact heart-beat signal modeling and estimation algorithm using a compact 2.4-GHz Doppler radar. The proposed technique is able to accurately reconstruct the heart-beat signal and generates heart rate variability indices at a distance of 1.5 m away from the human body. The feasibility of the proposed approach is validated by obtaining data from eight human subjects and comparing them with photoplethysmography (PPG) measurements. A Gaussian pulse train model is suggested for the heart-beat signal along with a modified-and-combined autocorrelation and frequency-time phase regression technique for high-accuracy detection of the human heart-beat rate. The proposed method is accurate, robust, and simple, and demonstrates an average heart-beat detection accuracy of more than 90% at a distance of 1.5 m away from the subjects. In addition, the average beat-to-beat time intervals extracted from the proposed model and signal reconstruction method show less than 2% error compared to PPG measurements. Bland–Altman analysis further validated the accuracy of the proposed approach in comparison with reference data.

A Concurrent Dual-Beam Phased-Array Doppler Radar Using MIMO Beamforming Techniques for Short-Range Vital-Signs Monitoring

Abstract: This paper presents the theoretical and experimental results of a new approach for multitarget vital-signs monitoring using an electromagnetic-based Doppler radar. A phased-array radar is designed and implemented using a hybrid beamforming architecture to generate two simultaneous beams. The proposed system significantly mitigates the phase collision problem in the presence of multiple targets. Comprehensive discussions on the theory of multibeam systems alongside detailed simulations are provided. For the purpose of demonstration, a prototype dual-beam phased-array continuous-wave Doppler radar has been designed and implemented at 2.4 GHz. The system is fully characterized, and the measurement results confirm the feasibility of the proposed method. The experimental measurements show that for the first time, the breathing rates of two individuals can be monitored at the same time and using the same frequency. Several practical aspects of the system are examined, and a pilot study on the subject tracking is presented. The proposed dual-beam system prevents the phase collision of the signatures of the targets and hence provides multiperson detection capability to the system.

Ultra-Wideband Millimeter-Wave Dielectric Characteristics of Freshly Excised Normal and Malignant Human Skin Tissues

Abstract: Millimeter waves have recently gained attention for the evaluation of skin lesions and the detection of skin tumors. Such evaluations heavily rely on the dielectric contrasts existing between normal and malignant skin tissues at millimeter-wave frequencies. However, current studies on the dielectric properties of normal and diseased skin tissues at these frequencies are limited and inconsistent. In this study, a comprehensive dielectric spectroscopy study is conducted for the first time to characterize the ultra-wideband dielectric properties of freshly excised normal and malignant skin tissues obtained from skin cancer patients having undergone Mohs micrographic surgeries at Hackensack University Medical Center. Measurements are conducted using a precision slim-form open-ended coaxial probe in conjunction with a millimeter-wave vector network analyzer over the frequency range of 0.5–50 GHz. A one-pole Cole–Cole model is fitted to the complex permittivity dataset of each sample. Statistically considerable contrasts are observed between the dielectric properties of malignant and normal skin tissues over the ultra-wideband millimeter-wave frequency range considered.

Pulse Transit Time Measurement Using Seismocardiogram, Photoplethysmogram, and Acoustic Recordings: Evaluation and Comparison.

Abstract: This work proposes a novel method of pulse transit time (PTT) measurement. The proximal arterial location data are collected from seismocardiogram (SCG) recordings by placing a micro-electromechanical accelerometer on the chest wall. The distal arterial location data are recorded using an acoustic sensor placed inside the ear. The performance of distal location recordings is evaluated by comparing SCG-acoustic and SCG-photoplethysmogram (PPG) measurements. PPG and acoustic performances under motion noise are also compared. Experimental results suggest comparable performances for the acoustic-based and PPG-based devices. The feasibility of each PTT measurement method is validated for blood pressure evaluations and its limitations are analyzed.

Ganong's review of medical physiology

Abstract: Ganong's review of medical physiology , Ganong's review of medical physiology , کتابخانه دیجیتال جندی شاپور اهواز

Advances in Photopletysmography Signal Analysis for Biomedical Applications

Abstract: Heart Rate Variability (HRV) is an important tool for the analysis of a patient’s physiological conditions, as well a method aiding the diagnosis of cardiopathies. Photoplethysmography (PPG) is an optical technique applied in the monitoring of the HRV and its adoption has been growing significantly, compared to the most commonly used method in medicine, Electrocardiography (ECG). In this survey, definitions of these technique are presented, the different types of sensors used are explained, and the methods for the study and analysis of the PPG signal (linear and nonlinear methods) are described. Moreover, the progress, and the clinical and practical applicability of the PPG technique in the diagnosis of cardiovascular diseases are evaluated. In addition, the latest technologies utilized in the development of new tools for medical diagnosis are presented, such as Internet of Things, Internet of Health Things, genetic algorithms, artificial intelligence and biosensors which result in personalized advances in e-health and health care. After the study of these technologies, it can be noted that PPG associated with them is an important tool for the diagnosis of some diseases, due to its simplicity, its cost–benefit ratio, the easiness of signals acquisition, and especially because it is a non-invasive technique.

Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays

Abstract: Massive MIMO (multiple-input multiple-output) is no longer a "wild" or "promising" concept for future cellular networks - in 2018 it became a reality. Base stations (BSs) with 64 fully digital transceiver chains were commercially deployed in several countries, the key ingredients of Massive MIMO have made it into the 5G standard, the signal processing methods required to achieve unprecedented spectral efficiency have been developed, and the limitation due to pilot contamination has been resolved. Even the development of fully digital Massive MIMO arrays for mmWave frequencies - once viewed prohibitively complicated and costly - is well underway. In a few years, Massive MIMO with fully digital transceivers will be a mainstream feature at both sub-6 GHz and mmWave frequencies. In this paper, we explain how the first chapter of the Massive MIMO research saga has come to an end, while the story has just begun. The coming wide-scale deployment of BSs with massive antenna arrays opens the door to a brand new world where spatial processing capabilities are omnipresent. In addition to mobile broadband services, the antennas can be used for other communication applications, such as low-power machine-type or ultra-reliable communications, as well as non-communication applications such as radar, sensing and positioning. We outline five new Massive MIMO related research directions: Extremely large aperture arrays, Holographic Massive MIMO, Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive MIMO.