Miracle-dz/UniFAR-FTUs huggingface dataset:
Experimental Observation of Lateral Waves Propagation Along Seabed

Effective use of radio frequency (RF) waves propagation in sea environment and development of high-efficiency antennas are crucial to utilize RF waves in seawater which has high attenuation coefficient. Lateral waves are theoretically well known as surface electromagnetic waves propagating along the boundary of lossy and relatively low loss media, which can expand the horizontal propagation distance than direct waves through homogeneous lossy medium. However, lateral waves propagating along seabed has been less experimentally studied than those along sea surface and far from practical realization. Our experimental results at real sea environment show that lateral waves along seabed expand horizontal propagation distance as expected by numerical calculation results. We believe this achievement is a significant step to realize underwater wireless sensor networks on seabed.
Circular Polarized 3D-Printed Enclosed Twist Dielectric Resonator Antenna

This article presents a circular polarized enclosed twist dielectric resonator antenna (DRA) manufactured using 3D-printing, operating at 5.8 GHz. The circular polarization is obtained by twisting the top a rectangular DRA 60 degrees with respect to its base, while the sense of the polarization is given by the turning sense of the twist. The DRA includes a cubic dielectric enclosure to give mechanical stability to the structure. Simulations results shows that the antenna have a gain of around 6.7 dB, and an axial ratio below 3 dB at the operational frequency.
A Compact Dual-Polarized Millimeter-Wave Array with Wide Beam Scanning for Mobile Terminals

This paper describes a compact four-element dual-polarized millimeter-wave array with wide beam scanning for mobile terminals. A modified dual-polarized shorted patch antenna is designed to cover N257 band (26.5–29.5 GHz). The coupled shorted structure is applied to suppress the cross-polarization level in H-plane. The array is constructed with a small element spacing of $0.4 \lambda_{0}$. Three decoupling slots are used to improve isolation for both polarizations. An overlapped −7.5 dB impedance bandwidth of 27–29 GHz is achieved in the array. The proposed array occupies the smallest size of $1.39 \lambda_{0}\times 0.28 \lambda_{0}$ for the four-element dual-polarized array in the open literature. A wide beam scanning range of ±60° with low scanning loss is achieved for both polarizations. The proposed array with superior performance of a small size and a wide beam scanning is promising for mobile terminals.
Broadband Transition from Waveguide to Substrate-Integrated Waveguide with Back-Short Structure in Multilayer Substrate at 300-GHz Band

A broadband transition from a hollow rectangular waveguide to a substrate-integrated waveguide (SIW) was designed in 300-GHz band. The prepreg layers in a multilayer substrate are unified through rectangular apertures opened in the inner printed patterns. A back-short structure was formed at one end of the thick SIW in the multilayer substrate by a via hole arrangement. The back-short length and the locations of matching via holes were optimized to produce double resonance for broadband characteristic. The simulated bandwidth of the proposed transition for $S_{11}$ lower than −10 dB was 71.2 GHz, and the fractional bandwidth was 25.9%.
Circularly Polarized Leaky Wave Antenna for W Band Applications

This paper proposed a W band circularly polarized leaky wave antenna based on a single-layer polarization converter. Linearly polarized waves radiating from longitudinal slots of WR-10 waveguide are converted to circularly polarized waves by an array of metallic patches designed on a thin dielectric slab. The implemented antenna is designed for 92 GHz to 96 GHz frequency band which exhibits a measured gain of 14.5 dBi. The presented robust CP antenna design is a good candidate for various millimeter-wave applications.
A Novel Phase Optimization Method for Sidelobe-Level Suppression of 1-Bit Reconfigurable Reflectarrays

A novel phase optimization method for sidelobe-level suppression of 1-blt reconfigurable reflectarrays (RRAs) is proposed. Simply by switching/reversing the binary phase states of unit cells, the sidelobe level suppression can be attained. Furthermore, to enhance the effectiveness without significantly increasing optimization complexity, the hybrid optimization algorithm, incorporating EM simulated and theoretically calculated results, is used to determine optimal phase distribution over reflectarray aperture. To validate the feasibility, a $15\times 15$ patch reflectarray, which is composed of only two physical lengths to represent two phase states, was experimentally developed and tested, where the sidelobe level is improved from 11.1 dB to 14.3 dB with small peak gain variation from 21.4 dBi to 20.8 dBi.
Modified H-Plane Sectoral Horn for FSS Sensing Applications

The use of frequency selective surfaces (FSSs) as sensors has found recent success in the structural health monitoring realm. FSS theory assumes infinite FSS dimensions and planewave illumination. However, in practice, an FSS sensor is finite, and the illuminating field varies across the plane of the sensor. As such, it is of interest to reduce the nonuniformity of the incident electromagnetic energy incident on the sensor. To this end, this work explores the modification of a standard H-plane sectoral horn through the addition of a ridge to generate a uniform electric field over a specified region of interest. In addition to this modified antenna, standard gain (pyramidal) and H-plane sectoral horns were also considered for comparison. The results show that variation in the electric field pattern is reduced for the modified sectoral horn but at the cost of matching properties.
Using Camera Boxes to Build Reproducible CEM Benchmarks with Complex Ducts

A cylindrical hub is inserted into a pipe inside a scaled camera box—a recently introduced structure intended to host differently-shaped ducts behind an aperture. The resulting metallic structure simplifies a commonly used model of jet-engine inlets and is designed to serve as a precisely-defined, easy-to-reproduce simulation and measurement benchmark. Results show that the fields scattered by the structure, while highly sensitive to small changes, can be both measured and simulated accurately even at frequencies with many interior propagating modes.
5G Multilayer Slot Array Antenna Fed by Integrated Substrate Groove Gap Waveguide for 26 GHz Band

We present a 5G multilayer slot array antenna in the 26 GHz band, fed by an integrated substrate groove gap waveguide (ISGGW). In contrast to previous works, we chose to populate the ISGGW and the intermediate “cavity” layers with a printed “Mushroom” type unit cell in order to appropriately guide the electromagnetic wave. The design allows for a multi-layered architecture, that is supported by the configuration of parallel Artificial Magnetic Conductors (AMC) and Perfect Electric Conductor (PEC) structures at the intermediate, in-contact, surfaces of the layers. The presence of parallel AMC and PEC surfaces avoids any electromagnetic leakage among them, regardless of any air gap existence. Unwanted air gaps between the layers of a multilayer structure can be caused by surface roughness and imperfect flat surface presence. The multiple stacked layers of the proposed structure are robust to such gaps underlining the work's significance. The impedance bandwidth $(\mathrm{S}_{11} < -10\ \text{dB})$ of 7.4% covers the frequency range from 25.13 GHz to 27.05 GHz, the realized gain varies between 8–12 dB, and the efficiency ranges between 50% and 80% over the operating band.
Multiband X-Band Frequency for Reflecting Intelligent Surfaces (IRSs)

A multiband reflector is proposed to operate in X-band frequency by employing a multi-ring resonator for an intelligent reflecting surface (IRS). The effect of the incident wave angle is simulated by moving the source signal along the horizontal line to assume the position of the incoming signal relative to the reflector. The simulated results of the proposed reflector show the optimum performance in terms of reflection coefficient and phase at 0 degrees incident wave, which is 0.93 and 32.14° at 8 GHz, 0.78 and -24.14° at 10 GHz, and 0.799 and 5° at 12 GHz. Also, the overall bandwidth for all resonance frequencies is approximately 0.61 GHz at 8 GHz and 0.2 GHz at 10 and 12 GHz respectively.
Characteristics of Terahertz Low Profile Generalized Luneburg Lens Antenna

In this paper, the characteristics of generalized Luneburg lens (GLL) Antenna in terahertz frequency band are studied. According to the definition of GLL, the focus of traditional Luneburg lens (TLL) is designed inside the lens, and subtracts the part of behind focus to reduce the profile. A 220GHz rectangular pyramidal horn is used as the feed. The simulation results of CST Microwave Studio show that although the gain of GLL antenna is lower than that of TLL antenna, the beam scanning angle of feed rectilinear off-focus is improved. We reasonably explain the above phenomena according to the geometric structure of the lens. Finally, the gain is improved by changing the feed beamwidth. This research can not only reduce the lens profile, but also improve the scanning angle.
Creeping Wave on Body for VR Applications

Creeping wave on the body surface is critical to the cross-body communication when the Line-of-sight (LoS) path of the two antennas are blocked by the human body. This work focuses on the creeping wave in virtual reality (VR) on-body link. Link loss between head-mount display (HMD) and controller is tested for four antenna locations on head at 8 GHz with full body phantom. Moreover, four simplified phantom block shapes with two PIFA antenna are simulated at 2.4GHz to understand the impact from different bends.
Metasurface-Based Low-Dispersive Leaky-Wave Antenna

In this communication, we present a low-dispersive leaky-wave antenna consisting of a parallel-plate-waveguide structure loaded by a modulated metasurface and a dense medium. The low-dispersive leaky-wave mode is engineered by a proper design of the metasurface and the chosen permittivity of the dense medium. The dispersion analysis is based on the transverse resonance technique and validated through full-wave simulations. A dense medium with a prism shape and a relative permittivity of 12 is used to radiate a beam pointing at 28.3° in elevation in the Ks-band (27–33 GHz) with only 0.5° variation over a 20% relative bandwidth. The leaky-wave mode supported by the structure is efficiently launched by using a compact quasi-optical system. The full antenna dimensions are 225×175×57 mm3 with an expected average gain of 27.5 dBi and total efficiency greater than 55%.
Deep Learning Accelerated Antenna Radiation Pattern Prediction for Undersampled Near-Field to Far-Field Transformation

We present a deep learning model based on U-Net architecture to estimate antenna radiation pattern and accelerate antenna characterization. This process is ordinarily time-consuming and expensive due to the need for an anechoic chamber and precision motion stages scanning through the antenna's 2D/3D near-field space. Significant developments in using deep neural network learning exhibit a non-linear relationship between high- and low-resolution datasets (e.g., images). In this work, we propose to build such a neural network to reconstruct the antenna radiation pattern from undersampled near-field data to accelerate pattern acquisition.
2D Eigenmode Analysis Based on Physics Informed Neural Networks

In this work, a novel deep learning-based approach for identifying the modal field distributions of closed waveguides is introduced. Specifically, physics informed neural networks are used to solve the Helmholtz partial differential equation (PDE) with the imposition of the appropriate boundary conditions. Based on our results, the proposed approach is capable of identifying all the eigenmode distributions of the studied waveguides with an error of less than −12 dB when compared with both analytical and full-wave simulation results.
New Linear Sparse Array for Holographic Millimeter Wave Imaging

The holographic millimeter wave imaging technology for linear sparse array considering phase center error compensation has been verified efficient recently. In this paper, a new linear sparse array layout is proposed, which solves the problem of missing the equivalent samples and has lower phase center error, resulting in higher imaging accuracy. Synthetic imaging results restored by holographic inversion demonstrate the efficiency of the proposed linear sparse array.
Experimental Monitoring of Microwave-Induced Thermoacoustic Signals Generated During Pulsed Microwave Ablation

We experimentally investigate the evolution of microwave-induced thermoacoustic signals generated during pulsed microwave ablation in bovine liver tissue. Using an X-band interstitial ablation antenna and a microsecond pulsed microwave source operating at ~9.4 GHz with an average power of 5 - 10 W, we simultaneously heat tissue and generate thermoacoustic signals. We conduct ablation experiments in both fresh liver tissue as well as boiled liver tissue to decouple the impact of temperature and tissue coagulation on thermoacoustic signal characteristics. We find that the time of arrival of the thermoacoustic signals decreases over the course of microwave ablation due to the change in the temperature-dependent speed of sound as well as tissue shrinkage. Thus, the thermoacoustic time of arrival may be used to monitor microwave ablation in real-time.
Intensity-only OMP-based Direction Estimation for Hybrid Reconfigurable Intelligent Surfaces

Future wireless networks are envisioned to benefit from adaptive electromagnetic wave propagation by leveraging reconfigurable intelligent surfaces (RISs) that programmably redirect signals toward intended users. This reconfigurable wireless environment is only possible when the directions of the transmitters and the receivers with respect to RISs are known. This information can be efficiently retrieved using hybrid reconfigurable intelligent surfaces (HRISs) that can sense a portion of the incident signal. However, HRIS structures are most beneficial when the integrated sensing circuitry can be implemented in a simple and low-cost manner. In this paper, we propose and numerically demonstrate a process to only use the intensity of the sampled incident signal to detect the angles of arrivals (AoA) on the HRIS. Toward this goal, we deploy an orthogonal matching pursuit (OMP) algorithm which can robustly recover data from sparsely sensed samples-a condition also applicable to HRISs. The proposed estimation approach will reduce the complexity of the sensing components of HRISs and will bring them one step closer to real-world applications.
Sub-6 Ghz Rotman Lens for Underground Mines Using Machine Learning

The paper introduces a new approach of using machine learning in the design of a sub-6 Ghz Rotman lens for underground mine applications. The lens, optimized through machine learning technique, showed good results in terms of insertion losses. The design is optimized to operate in the sub-6 GHz frequency range, especially at the 3.5 GHz band. In order to be employed in underground mining. The final lens structure and port placement were both generated using machine learning.
Efficient Design of Thinner Broadband MRAM Using Novel Formulation of Cost Function

Modern military and civic applications require broadband microwave radar absorbing material (RAM). Such a RAM is multilayer and invariably increases the surface thickness of platforms (viz., aircraft, ship, vehicle) and thereby increases the overall body weight. So, all RAM design methods do some kind of optimization of layer parameters. In this paper, we study the effect of commonly used cost function formulations on obtaining global optima. We also explore formulation for thinner design of RAM and propose a new cost function. Our proposed formulation effectively works as a two-step optimizer and is able to provide thinner results without increasing the complexity of the algorithm employed for optimization.
An Accurate Retrieval Method for Complex Electrical Parameters of Materials Based on Partially Filled Waveguide

Determination of the permittivity and permeability for penetrable materials is very important in many applications. There exist several common techniques such as resonant cavity method, free space method, and waveguide method presently. Partially filled waveguide method is another one which enjoys the feature of reduced fabrication precision requirement for the dielectric sample under test. In the original paper proposing the partially filled waveguide method, only TM modes are considered. Through mode matching analysis, we show in this paper that both TM and TE modes shall be considered so as to give correct results.
Arctic odyssey - Five years of data buoys in AIDJEX. [Arctic Ice Dynamics Joint Experiment

The Arctic Ice Dynamics Joint Experiment of 1975-1976 used data bouys in conjunction with tracking satellites to study the interaction of Arctic Sea ice with the environment, and, more specifically, to define the motion of ice on the perimeter of the area of interest and to measure surface barometeric pressure over the same area. Charts are presented, indicating the position of the buoy array along with a table detailing buoy characteristics. The position fix accuracy of RAMS (Random Access Measurement System) buoys is discussed together with position errors due to the along-track motion of the observing satellites. Polar satellite data collection and tracking efficiency is assessed together with satellite system flexibility concepts.
A Broadband Low Profile SIW H-Plane Horn Antenna with Improved Performance

This paper is presenting a broadband, low-profile ($0.008 \lambda_{0}$) substrate-integrated waveguide (SIW) H-plane horn antenna with the reduced side lobes and improved front-to-back ratio (FTBR). This is achieved implementing three rectangular slots near the coaxial feed. The hexagonal slots in front of the horn aperture are used to improve impedance matching. The measured fractional impedance bandwidth of 29.5% (3.25 GHz), the maximum gain of 5.52 dBi (minimum: 2.85 dBi), the maximum radiation efficiency of 95.99 %, the FTBR of 15.83 dB, and the low cross-polarization level have been achieved at the frequency of 9.85 GHz.
Pattern Reconfigurable Capped Patch Antenna for mm-Wave 5G Applications

A simple design for a pattern reconfigurable antenna is presented in this paper. The proposed antenna is a typical rectangular patch with an inverted U-shaped trace of metal (called a cap) printed around the patch. To achieve pattern reconfiguration, a cut is made on either side of the cap. Different beam tilting was achieved depending on the position of the cut along the cap. When the longitudinal distance between the center of the cut and the center of the patch is small, a maximum scanning angle of 60° is obtained. The pattern tilting was achieved without any active devices. The antenna achieves a gain and directivity of 6 dBi and 7 dBi respectively, and an impedance bandwidth of 1.8 GHz (28–29.8 GHz). Additionally, the cap and the cut did not affect the antenna's performance, although a slight shift in resonance is observed. The antenna can be employed for mm-wave 5G/6G antenna array applications.
Calculating Power Wave S-Parameters Using Only Port Voltages or Currents

A method is presented for calculating the power wave S-parameters of a multiport network using only the voltages or currents evaluated at the port terminals with one port driven by a Thévenin or Norton equivalent circuit with its impedance matched to its respective reference impedance and the other port(s) loaded with their respective reference impedances. The calculations can be performed using general mathematical analysis software; specialized RF software is not required.
Beyond Word Embeddings: Heterogeneous Prior Knowledge Driven Multi-Label Image Classification

Multi-Label Image Classification (MLIC) is a fundamental yet challenging task which aims to recognize multiple labels from given images. The key to solve MLIC lies in how to accurately model the correlation between labels. Recent studies often adopt Graph Convolutional Network (GCN) to model label dependencies with word embeddings as prior knowledge. However, classical word embeddings typically contain redundant information due to the imperfect distributional hypothesis it relies on, which may degrade model generalizability. To tackle this problem, we propose a novel deep learning framework termed Visual-Semantic based Graph Convolutional Network (VSGCN), which alleviates the negative impact of redundant information by utilizing heterogeneous sources of prior knowledge. Specifically, we construct both visual prototype and semantic prototype for each label as heterogeneous prior label representations, which are further mapped to multi-label classifiers via two Multi-Head GCNs separately. The Multi-Head GCN mechanism proposed in this paper aims to guide the information propagation between prototypes for each label, which constructs multiple correlation graphs to simultaneously model the label correlation in different subspaces. Notably, we alleviate the negative influence of needless information by decreasing the inconsistency of predictions that come from visual space and semantic space. Extensive experiments conducted on various multi-label image datasets demonstrate the superiority of our proposed method.
Miniaturized Millimeter Wave Resonators with Self-Biased BaM Films

Miniaturized millimeter wave resonators that are based on the ferromagnetic resonance (FMR) of M-type barium hexagonal ferrite (BaFe12O19, BaM) films are proposed and simulated. The operating frequency can be up to 50 GHz without external biasing magnetic fields by virtue of the internal anisotropy field of BaM films. A novel strip line ridge structure is utilized to couple energy from transmission line to the ferromagnetic resonators. An equivalent circuit is used to optimize the design, and simulation results from full-wave simulator (HFSS) agree with circuit simulation results from ADS.
A Signal Processing Framework for Rapid Detection of Tree Defects via a Standoff Tree Radar System

This paper proposes a framework for processing the B-scans of tree trunks and revealing the presence of trees' internal defects (i.e., cavities and decays) from the signatures of their reflections. The framework uses the B-scans obtained by a standoff step frequency continuous wave radar system, moved in straight trajectories at a standoff distance facing the tree trunks' surfaces. In particular, the proposed framework first applies an antenna calibration to the raw B-scans to suppress the antenna's internal reflections. Then, it leverages a column-connection clustering (C3) algorithm to remove the signatures of the reflections from the trunk surface. Finally, it applies a Kaiser window to the Fourier-transformed A-scans of the processed B-scan to further increase the signal-to-noise ratio (SNR). The application of the proposed framework to measured (raw) B-scans shows that the proposed framework improves the SNR by more than 30 dB and reveals the signatures of the defects in the B-scans. The proposed framework can be used for many other standoff radar applications, such as through-the-wall imaging, defect/anomaly detection in concrete walls, in which the magnitude of the reflection from the main target is two/three orders smaller than the magnitude of the unwanted reflections from the surfaces or other objects.