Karim Y. Kabalan

Microwave breast tumor detection relies on the dielectric contrast between healthy and malignant tissue, and the antenna bandwidth affects the cost, complexity and sensitivity of the system. This paper compares an ultra-wideband (UWB) and a narrowband (NB) circular patch antenna that share the same FR4 substrate, 30 × 30 mm² footprint and radiator but differ in their ground plane and feed. Both antennas were fabricated and measured; the simulated UWB antenna covers 3.56–14.73 GHz, and the NB antenna resonates at 7.79 GHz in its TM21 mode; a finite-difference time-domain (FDTD) model with the measured patch dimensions explains the measured NB resonance shift. Sensing is evaluated with finite-element and FDTD solvers, with each antenna 10 mm from a homogeneous healthy or malignant phantom. Both solvers predict the same 140 MHz tumor-induced resonance shift for the NB antenna and a similar peak reflection-coefficient contrast for the two antennas (19.2 and 21.9 dB in the finite-element model; 7.1 and 9.7 dB in the FDTD model), while the UWB antenna is sensitive over a three to seven times wider spectrum and directs 5.5–6 dB more gain toward the phantom. The NB antenna therefore suits low-cost single-frequency detection, whereas the UWB antenna suits imaging systems that exploit frequency diversity.

A multilayer log‐periodic metasurface patch antenna (LPMPA) operating in the 4–9‐GHz frequency range with broadside radiation is presented. This antenna array is characterized by its compact size and low profile. Each element of the LPMPA consists of a 2‐D periodic structure of 4 × 4 square patches, which can be viewed as a metasurface. The array is excited through aperture coupling in the ground plane beneath the radiators. The proper phase progression of the currents for a broadside radiation of the LPMPA′s elements in the active region is obtained by increasing the length of the feed line placed between adjacent radiators. The structure′s stop‐band caused by the excess of length between radiators is eliminated by increasing the characteristic impedance of the feed line to 70 Ω in the proximity of each slot. A prototype of the proposed antenna, consisting of four 2‐D periodic structures, is fabricated and tested. The obtained results show a 76% fractional bandwidth with gain ranges between 8 and 13 dB.

Computation of complex-coefficient complex-solution differential equations is a problem that arises in various domains of science and engineering. This paper aims at applying the Theory of Characteristic Modes (TCM) approach along with the Method of Moments (MoM) in solving these problems with emphasis on procedures for higher differential equations. Several available methods, known in literatures, are available for solving the problem. The complexity of the available methods differs based on the accuracy of the solution. In this paper, the general method is first presented and then a simplified version of it is proposed to solve high order differential equations. Two examples are illustrated, a third and a fourth order complex-coefficients complex-solution differential equations, to show the simplicity of the proposed method. The proposed approach can be also introduced along with other methods to solve these special occurrences differential equations and other boundary value problems.

Cancer is one of the most dangerous diseases worldwide due to difficulty in detection and treatment. However, survival rates are increasing with improved techniques that detect cancer at early stage. Even though numerous techniques already exist to detect cancerous tumors, other replacements are being developed to overcome the problems imposed by the traditional ones such as high cost, exposure to ionizing radiation, physical pain due to breast compression, etc. The implementation of noninvasive microwave radiation for cancer detection has already started. The developments now focus on the improvement of these systems. This paper presents a 48 elements antenna array that improves the resolution of the resulting image making the tumor, its size and its position more visible to the operator.

Painless, cuffless and continuous blood pressure monitoring sensors provide a more dynamic measure of blood pressure for critical diagnosis or continuous monitoring of hypertensive patients compared to current cuff-based options. To this end, a novel flexible, wearable and miniaturized microstrip patch antenna topology is proposed to measure dynamic blood pressure (BP). The methodology was implemented on a simulated five-layer human tissue arm model created and designed in High-Frequency Simulation Software “HFSS”. The electrical properties of the five-layer human tissue were set at the frequency range (2–3) GHz to comply with clinical/engineering standards. The fabricated patch incorporated on a 0.4 mm epoxy substrate achieved consistency between the simulated and measured reflection coefficient results at flat and bent conditions over the frequency range of 2.3–2.6 GHz. Simulations for a 10 g average specific absorption rate (SAR) based on IEEE-Standard for a human arm at different input powers were also carried out. The safest input power was 50 mW with an acceptable SAR value of 3.89 W/Kg < 4W/Kg. This study also explored a novel method to obtain the pulse transit time (PTT) as an option to measure BP. Pulse transmit time is based on obtaining the time difference between the transmission coefficient scattering waveforms measured between the two pairs of metallic sensors underlying the assumption that brachial arterial geometries are dynamic. Consequently, the proposed model is validated by comparing it to the standard nonlinear Moens and Korteweg model over different artery thickness-radius ratios, showing excellent correlation between 0.76 ± 0.03 and 0.81 ± 0.03 with the systolic and diastolic BP results. The absolute risk of arterial blood pressure increased with the increase in brachial artery thickness-radius ratio. The results of both methods successfully demonstrate how the radius estimates, PTT and pulse wave velocity (PWV), along with electromagnetic (EM) antenna transmission propagation characteristics, can be used to estimate continuous BP non-invasively.

Summary: This article presents a complete design procedure for planar slotted waveguide antennas (SWA). For a desired sidelobe level ratio (SLR), the proposed method provides a pencil shape pattern with a narrow half power beamwidth, which makes the proposed system suitable for high power microwave applications. The proposed planar SWA is composed of only two layers, and uses longitudinal coupling slots rather than the conventional inclined coupling slots. For a desired SLR, the slots excitation in the radiating and feeder SWAs are calculated based on a specified distribution. Simplified closed‐form equations are then used to determine the slots nonuniform displacements, for both the radiating and feeder SWAs, without the need to use optimization algorithms. Using simplified equations, the slots lengths, widths, and their distribution along the length of the radiating and feeder SWAs can be found. The feeder dimensions and slots positions are deduced from the dimensions and total number of the radiating SWAs. An 8 × 8 planar SWA has been designed and tested to show the validity of the proposed method. The obtained measured and simulated results are in accordance with the design objectives.

With the prevalence of breast cancer among women and the shortcomings of conventional techniques in detecting breast cancer at its early stages, microwave breast imaging has been an active area of research and has gained momentum over the past few years, mainly due to the advantages and improved detection rates it has to offer. To achieve this outcome, specifically designed antennas are needed to satisfy the needs of such systems where an antenna array is typically used. These antennas need to comply with several criteria to make them suitable for such applications, which most importantly include bandwidth, size, design complexity, and cost of manufacturing. Many works in the literature proposed antennas designed to meet these criteria, but no works have classified and evaluated these antennas for the use in microwave breast imaging. This paper presents a comprehensive study of the different array configurations proposed for microwave breast imaging, with a thorough investigation of the antenna elements proposed to be used with these systems, classified per antenna type, and per the improvements that concern the operational bandwidth, the size of the antenna, the radiation characteristics, and the techniques used to achieve the improvement. At the end of the investigation, a qualitative evaluation of the antenna designs is presented, providing a comparison between the investigated antennas, and determining whether a design is suitable or not to be used in antenna arrays for microwave breast imaging, based on the performance of each. An evaluation of the investigated arrays is also presented, where the advantages and limitations of each array configuration are discussed.

This paper presents a procedure for the design of a 2D Slotted Waveguide Antenna (SWA) array having circular polarization. The 2D array is formed by a defined number of 1D branchlines broadwall SWAs, which are fed using an extra broadwall SWA. The SWA branchlines have cross-shaped slots that radiate with a circular polarization. The dimensions of these slots are optimized for best performance. The feed SWA is made with rectangular slots, which are designed to achieve a low SLL. An example SWA with 10 χ 10 slots is designed using this procedure, and the design results are reported in this paper.

In this paper, a ladder shaped microstrip patch antenna with an average size, suitable for most mobile phones, is proposed. The proposed antenna has a size of 120*50 mm2 for a ladder patch with coaxial cable feeding. It covers a bandwidth of approximately 30 MHz from 685 MHz to 715 MHz that is in the UHF band. Various dimensions of the ladders were investigated to attain the best possible matching conditions. This antenna is designed, simulated using HFSS, fabricated and tested. Results are then compared and good agreement was obtained.