Sasan Ahdi Rezaeieh

Bio: Sasan Ahdi Rezaeieh is an academic researcher from University of Queensland. The author has contributed to research in topics: Dipole antenna & Wideband. The author has an hindex of 9, co-authored 28 publications receiving 273 citations.

Lung cancer detection using frequency-domain microwave imaging

Abstract: A frequency-domain algorithm for the early detection of lung cancer is presented. The algorithm predicts the distribution of scattered fields inside the imaged domain (torso) using the measured fields around that domain. That prediction is based on using the first-order Bessel function of the first kind to relate the fields outside the imaged domain to the fields inside that domain. The predicted field distribution shows the relative differences between the dielectric properties of tissues within the torso and thus enables detecting lung cancer, which has a significantly larger dielectric constant that the lung's healthy tissues. To validate the proposed algorithm, an integrated imaging system, which includes a three-dimensional slot-rotated antenna that circularly scans an artificial torso phantom using the band 1.5-3 GHz, a wideband microwave transceiver and a laptop for control, processing and image generation, is built. The obtained experimental results confirm the reliability of the proposed method in lung cancer detection.

Pattern Reconfigurable Metasurface Antenna for Electromagnetic Torso Imaging

Abstract: A pattern reconfigurable metasurface antenna for an electromagnetic torso imaging system operating at the ultrahigh frequency (UHF) band is presented. To meet the requirements of electromagnetic torso imaging, the antenna can scan the human chest with steerable unidirectional radiation patterns. The designed antenna consists of three rectangular microstrip-fed slot radiators illuminating a metasurface layer with $7\times 5$ unit cells to cover the whole chest. Six p-i-n diodes are used to switch the radiating slots creating different beams. The unit cell dimensions are $0.125\lambda _{0}\times 0.125\lambda _{0}$ and the antenna has a low profile of $0.9\lambda _{0}\times 0.7\lambda _{0}\times 0.06\lambda _{0}$ ( $\lambda _{0}$ is the wavelength of the lowest operating frequency of the antenna). The antenna creates three distinct beams with a peak gain of 8 dBi at 1 GHz and 2 dBi gain variations across different beams over its measured wide operating frequency bandwidth of 27% at 0.8–1.05 GHz. A complete electromagnetic torso imaging system, which utilizes the designed antenna, is built and is successfully tested to detect 20 mL of fluid (water) inside the torso, thus differentiating between healthy and unhealthy cases.

Microwave System for the Early Stage Detection of Congestive Heart Failure

Abstract: Fluid accumulation inside the lungs, known as cardiac pulmonary edema, is one of the main early symptoms of congestive heart failure (CHF). That accumulation causes significant changes in the electrical properties of the lung tissues, which in turn can be detected using microwave techniques. To that end, the design and implementation of an automated ultrahigh-frequency microwave-based system for CHF detection and monitoring is presented. The hardware of the system consists of a wideband folded antenna attached to a fully automated vertical scanning platform, compact microwave transceiver, and laptop. The system includes software in the form of operational control, signal processing, and visualizing algorithms. To detect CHF, the system is designed to vertically scan the rear side of the human torso in a monostatic radar approach. The collected data from the scanning is then visualized in the time domain using the inverse Fourier transform. These images show the intensity of the reflected signals from different parts of the torso. Using a differential based detection technique, a threshold is defined to differentiate between healthy and unhealthy cases. This paper includes details of developing the automated platform, designing the antenna with the required properties imposed by the system, developing a signal processing algorithm, and introducing differential detection technique besides investigating miscellaneous probable CHF cases.

Bandwidth and Directivity Enhancement of Loop Antenna by Nonperiodic Distribution of Mu-Negative Metamaterial Unit Cells

Abstract: The theory, design, analysis, and verification of a wideband and unidirectional loop antenna loaded with mu-negative (MNG) metamaterial unit cells is presented. It is shown that by nonperiodic positioning of MNG unit cells on the loop structure, the amplitude of the surface current can be modified in a desired section of the loop, and hence, unidirectional radiation is achievable at the mu-zero resonance frequency. Moreover, it is demonstrated that as a result of the capacitive MNG loading, a 90° phase difference occurs between the vertical arms of the loop. Therefore, its radiation mechanism can be characterized as an array of two dipole antennas positioned a quarter wavelength apart, thus creating unidirectional radiation. To further improve the performance of the antennas, a quarter-wavelength strip is located in the vicinity of the loop to act as a resonator and director at higher frequencies. With the proposed structure, the final design is at least 50% smaller, in terms of the occupied area, than recent antenna designs of conventional loops, MNG loaded loops, and loop–dipole composite antennas. It also achieves a wide fractional bandwidth of 52% from 0.64 to 1.1 GHz, which is 50% wider than recent MNG metamaterial unit cell loaded loops, with a measured peak front-to-back-ratio and gain of 13 dB and 4.8 dBi, respectively.

Compact Wideband Loop Antenna Partially Loaded With Mu-Negative Metamaterial Unit Cells for Directivity Enhancement

Abstract: A wideband and unidirectional loop antenna partially loaded with mu-negative (MNG) metamaterial unit cells is presented. To reduce the electrical size of the antenna, its first resonance is formed by capacitively loading a conventional one-wavelength loop antenna to excite the mu-zero resonance that is independent of the resonator's size. As a result of partial loop loading using properly designed and distributed slots, the amplitude of the surface current can be engineered to be higher in the feeding arm while achieving a zero phase shift along each arm of the loop structure. Consequently, unidirectional radiation with a moderate front-to-back ratio (FBR) is achieved without using any reflectors. Moreover, as a result of the capacitive loading, the loop antenna is divided into an array of dipoles that are excited with a 90° phase difference, enabling unidirectional radiation at the loop-mode resonance. To both enhance the impedance matching of the antenna at lower frequencies and excite an additional resonance, a strip patch is added in the vicinity of the loop. The proposed structure is smaller by 80% than similar MNG loaded loops and achieves a wide fractional bandwidth of 52% (0.64–1.1 GHz) with a peak FBR and gain values of 12 dB and 3.2 dBi, respectively.

Fast Frequency-Based Multistatic Microwave Imaging Algorithm With Application to Brain Injury Detection

Abstract: A multistatic microwave imaging technique is presented for fast diagnosis of medical emergencies pertaining to brain injuries. The frequency-based imaging method utilizes Bessel functions to estimate the scattered power intensity inside the imaged region from measured multistatic scattered signals outside the imaged region in a quasi-real-time manner. A theory is used to prove that the relation between the scattered fields outside the imaged object (the head) and the internal scattering profile follows the first order of first type Bessel function. To reconstruct the internal scattered power intensity accurately, the average-trace subtraction method is used to remove the skin reflections and clutters. The presented algorithm is verified using realistic numerical simulations and experimental measurements, which are performed using a radar-based head imaging system that includes an antenna array containing eight elements, microwave transceiver, and switching network. To emulate different brain injuries, realistic head phantoms are utilized. The obtained results using frequency steps that meet Nyquist criterion confirm the reliability of the proposed method in the successful detection of different sizes and locations of injuries inside the head phantom in a fast and consistent way. In comparison with existing multistatic time-domain methods, the presented approach is faster and more accurate.

3-D Wideband Antenna for Head-Imaging System with Performance Verification in Brain Tumor Detection

Abstract: A 3-D slot-rotated antenna for a microwave head- imaging system is presented. The antenna is designed to have a wideband and unidirectional performance at the low microwave frequency band that are the requirements of the specified imaging system. Starting from a traditional wide-slot antenna, several conventional techniques are applied to enhance its bandwidth and directivity while miniaturizing its size. In that regard, four series of staircase-shaped slots are applied to lower the operating frequency, whereas a folding process is used to enhance the directivity and reduce the overall size. In addition, two parasitic patches are connected to the slot area to increase the operating bandwidth. The final design has the dimensions of ${\hbox {0.11}} \lambda \times {\hbox {0.23}} \lambda \times {\hbox {0.05}} \lambda $ . ( $\lambda $ is the wavelength of the lowest measured operating frequency.) It has a measured VSWR fractional bandwidth of 87% (1.41–3.57 GHz) and a peak front-to-back ratio of 9 dB. To verify the suitability of the antenna in head imaging, it is connected to a wideband microwave transceiver and used to circularly scan an artificial head phantom in $20^\circ$ angle steps in a monostatic mode. The collected backscattered data are then processed and used to generate an image that successfully shows brain tumors. The compact size, wide operating bandwidth, unidirectional radiation, and detection viability are merits of the presented antenna and the subsequent system.

Miniaturized Dual-Band and Dual-Polarized Antenna for MBAN Applications

Abstract: This paper presents a novel miniaturized antenna with a dual-band resonance covering the medical body-area network (MBAN) and a 5.8-GHz industrial scientific medical band. Owning to its stacked-patch structure, the proposed antenna generates an omnidirectional radiation pattern with vertical polarization and a broadside radiation pattern with circular polarization at the two bands, respectively, thus fulfilling the requirements for both on- and off-body channels simultaneously. This antenna is designed on a multilayer tissue model, and is then validated on the Gustav voxel model. The footprint of the proposed antenna is only $0.18\lambda _{0} \times 0.18\lambda _{0} \times 0.04\lambda _{0}$ . The proposed design is fabricated and its performance is investigated in various scenarios. When measured on the pork trunk, impedance bandwidths of 2.8% at the lower band and 9.0% at the upper band are achieved, fully covering the two bands. Besides, the transmission performance at the MBAN band is also studied by conducting measurements on the human body, and the measurement results agree well with the simulation. The obtained robust antenna performance reveals that the proposed design is suitable for MBAN applications.

Compact CPW-Fed Planar Monopole Antenna With Wide Circular Polarization Bandwidth

Abstract: The design and implementation of a coplanar waveguide-fed planar monopole antenna with circular polarization and broadband operation is presented. The antenna operates in the Industrial, Scientific, and Medical (ISM) and wireless local area network (WLAN) (5 GHz) bands with circular polarization (CP) in both bands. It is demonstrated that a fractional bandwidth for CP larger than 33% can be attained simply by introducing an inverted L-shaped slot in the ground plane and parallel-aligning an inverted-L-shaped strip. The advantages of the proposed antenna are the simple yet efficient design of the radiator, a wide 3-dB axial-ratio operating band, and a compact size.

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.