Omar Mustafa Ramahi

A novel shared through-port architecture for a compact, broadband, and reconfigurable integrated coupler/ power divider is proposed in this letter. By structurally fusing two three-branch couplers, the design intrinsically integrates multiple functions. Reconfiguration among three operating modes—left- or right-channel coupling and equal power division—is achieved using p-i-n diodes. A hybrid miniaturization approach employing T-shaped equivalent stubs and meandered lines ensures the wideband performance. Fabricated at 2.45 GHz with a compact size of $28.46\times 38.42$ mm, the circuit exhibits measured the coupling mode operation from 2.30 to 2.65 GHz ( $-3.5\pm 0.2$ dB output and >23 dB isolation) and power-division mode operation from 2.0 to 2.97 GHz ( $-5{\,}\pm{\,}0.2$ dB output, >18.1 dB isolation, and phase imbalance ±0.6°). Compared with conventional cascaded solutions, this work provides a significantly more integrated and flexible building block for reconfigurable RF front-ends.

This paper presents a design strategy for a low-profile, low-cost, uniformly 3D-printed dielectric spherical lens antenna, tailored for high-gain communication applications. The proposed approach employs a cost-effective and modified fabrication process inspired by the Hedgehog form to simplify the traditional gradient-index (GRIN) permittivity distribution. This simplification is achieved through a spherical array of tapered dielectric rods with constant relative permittivity exposed to air, utilizing the concept of effective permittivity equivalence over conventional GRIN techniques. The incorporation of traveling-wave dielectric conical rods facilitates broadband operation by accommodating a wide range of phase velocities and enabling gradual impedance transitions, making the lens intrinsically wideband; in practice, the overall system bandwidth is limited by the impedance bandwidth of the feeding antenna. When integrated with an X-band horn antenna, full-wave electromagnetic simulations show a peak realized gain of 21.7 dB at 10 GHz, representing a 9.1 dB improvement over the horn alone, together with a 3-dB gain bandwidth of 40%. To compensate for phase variations in the GRIN distribution, the spherical lens employs a slightly asymmetric Hedgehog configuration with deliberately overlapped unit cells, which improves field concentration and primary radiation, yielding an aperture efficiency of 60%. A prototype was fabricated, and its performance was validated in a real-world lab setting through S-parameter analysis, closely matching simulation results and confirming the design’s high effectiveness and efficiency.

This paper presents a novel low-frequency electromagnetic system for enhanced breast tumor detection. The proposed setup utilizes a loop array integrated with spiral resonators as a magnetic field-driven transmitter, and a metasurface antenna as the receiver. Operating at 200 MHz, this system achieves deeper tissue penetration due to its low frequency and enhances sensitivity to anomalies because of the conductivity contrast between tumor and healthy tissues under magnetic fields. The uniform illumination of the entire breast volume eliminates the need for mechanical scanning. Furthermore, integrating the loop array with the spiral resonators enhances the magnetic field strength, while the single-feed-point design simplifies the system. Numerical simulations were conducted using a realistic dense breast model, demonstrating that the proposed setup can detect tumors of various locations, sizes, and depths within the dense breast tissue. The complete system was fabricated, implemented, and validated through experimental measurements.

This work introduces an electromagnetic energy scanning technique with specific application to the detection of breast cancer. The technique is based on a metasurface field detector probe composed of an ensemble of electrically small elements resonating at 700 MHz, where the middle single element represents the field detector. The sensor scans the two-dimensional plane that contains the energy transmitted through the breast. Once the scan is completed, we generate a contrast image composed of N X N pixels that represent the different components of the breast tissue. We then compile a dataset of these contrast images to train a convolutional neural network (CNN) to differentiate between healthy and unhealthy breast tissue. Thie probe provides a resolution that cannot be matched by either electrically small probes or resonance-based probes that have dimensions comparable to the wavelength. The field emanating from a specific structure, such as a human female breast, can be scanned by the proposed probe to achieve a resolution in the millimeter range while operating in the low-microwave frequency spectrum. The probe was tested numerically, and a prototype was tested experimentally, demonstrating its effectiveness in providing a field resolution of approximately 5 mm.

This article presents a design methodology to enhance the radiation efficiency of compact modular radar systems by employing an advanced spherical dielectric gradient-index (GRIN) Luneburg lens with tunable refractive index gradients. The proposed design utilizes computationally optimized dual-beam masks, implemented as two exponentially tapered rods, to modify the conventional permittivity distribution of the Luneburg lens. This approach enables the use of a single lens for both transmitter (TX) and receiver (RX) radar microstrip antennas while addressing beam tilting issues. To validate the design, a prototype of the GRIN modified Luneburg lens (MLL) was manufactured using a cost-effective and uniform 3-D-printing technique and seamlessly integrated with a commercially available X-band radar module. The experimental evaluation was conducted in a laboratory setting, measuring transmitted power using a standard X-band horn antenna connected to a spectrum analyzer and strategically positioned within the radar’s radiation field at various aperture-to-aperture distances. Received power measurements were also recorded at the radar RX antenna, demonstrating significant improvements in both transmitted and received power. These enhancements collectively contribute to a substantial increase in the radar’s signal-to-noise ratio (SNR) for high-gain communication systems. The MLL-enhanced radar module achieves a realized gain of 17.2 dB at 10.4 GHz, resulting in a 3.2-fold extension of the radar’s detection range in both elevation and azimuth directions. Additionally, the integration of the GRIN MLL leads to a 10-dB enhancement in received power, corresponding to a tenfold improvement in SNR when operating along the boresight. These findings validate the effectiveness and robustness of the proposed design in radar sensing enhancement.

This work presents the application of a planar microstrip metamaterial (MM)- motivated sensor in the form of a split-ring resonator (SRR) for the detection and quantification of water adulteration in honey samples. The proposed sensor utilizes inexpensive software-defined radio (SDR) measurements, offering a cost-effective solution. Unlike previous MM sensors employing SRR configuration, our proposed MM-motivated sensor is integrated with a microstrip feedline and an additional vertical bar, enhancing its sensing capability. To enable accurate measurements, a simple calibration procedure based on baseline normalization is implemented, allowing for amplitude-only transmission measurements (|S₂₁|) using the SDR. A special sample holder was designed to increase repeatability of measurements. We separately employ two post-processing techniques, namely the rolling average (RA) approach and the Savitzky-Golay (SG) filter, to effectively eliminate ripples in the measured |S₂₁| data obtained from the SDR. For validation and evaluation of the proposed sensor and post-processing techniques, measurements of flower honey samples with water adulteration levels (δ) up to 10% (mass-to-mass basis) were also performed using a vector network analyzer. The resonance frequency of |S₂₁| is utilized as the basis for analysis. We establish a metric function (linear function) that correlates the shift in resonance frequency with the δ. It is observed that this function fits to measured resonance frequency values with an R² value greater than 0.96 for both post-processing techniques with or without the sample holder. By inverting this function, we can predict δ with considerable accuracy for a given resonance frequency by using another linear function. It is observed that percentage variations between predicted and measured δ values are between 1.54% and 6.46% for testing samples with δ = 5% and δ = 7%.

This paper presents an attractive microwave technique for permittivity (ε_r = ε′ r−jε′′ r) extraction of nondispersive or weakly dispersive dielectric materials. The technique uses amplitude-only transmission |S₂₁| measurements at multiple frequencies without requiring the information of the sample thickness (d). To achieve this goal, the state transition matrix was first applied for determining |S21|, and then the least minimum square procedure was implemented to the derived objective function for unique ε_r determination. Numerical analyses were performed to validate the proposed extraction technique and evaluate the effect of inaccurate d information on ε_r determination by other similar techniques in the literature. Its performance is examined by numerical analyses based on number of frequency points M within a given frequency band and based on different frequency bands for the same M. Not clear. Waveguide measurements at the S-band (2.60−3.95 GHz) and the G-band (3.95−5.85 GHz) of four low-loss non-dispersive or weakly dispersive samples (dioxane, cyclohexane, polyethylene, and chloroform) and two lossy dispersive samples (ethanol and dimethyl sulfoxide) with different lengths were carried out to validate the proposed extraction technique and compare its accuracy against other similar methods in the literature. From measurements of low-loss non-dispersive or weakly dispersive samples, it is noted that the accuracy of our extraction method does not change much with d. For instance, extracted ε_r of the cyclohexane (chloroform) sample with three different lengths differs from the reference value by less than 1% for ε′ r and 3% for ε′′ r . Although the accuracy of the proposed method lowers for dispersive samples, it can still find applications for low-cost accurate ε_r determination of nondispersive and/or weakly dispersive dielectric samples.

Honey is a rich source of sugar and is one of the indispensable ingredients in infant foods. Thus, it can be subjected to adulteration due to its cost. Measurement techniques such as liquid chromatography and near-infrared spectroscopy, used for detecting any adulteration, are expensive and need to be conducted by highly trained personnel for off-line analysis. Microwave measurements, as a fast, simple, and relatively inexpensive analysis, have recently shown great potential in detecting adulteration within honey samples. Nonetheless, sensor types used in such measurements are conventional. In this study, a reflection-type sensitive microwave sensor terminated by a metal back is proposed for the first time in the literature for detection and quantification of water percentage (δ) level (mass-to-mass basis) within water-adulterated honey samples. When compared with other resonance-based microwave cavity sensors, thanks to its eight strips located at the centers of two closed circular loops, it demonstrates superior frequency selectivity and sensitivity (S = 5.13%) validated by full-wave 3D simulations performed by the CST Microwave Studio and equivalent circuit analysis carried out by the ADS software. For example, for ethanol, the proposed sensor gives a frequency shift of more than 1 GHz in the X-band. Resonance frequency shift and variation of the reflection coefficient amplitude (|S11|) are measured at X-band to detect honey samples with up to 8% adulteration level. Three different honey samples (flower honey, highland honey, and thyme honey) were examined to test the performance and applicability of the proposed sensor.