Search Results (74)

Breast cancer detection through non-invasive and accurate techniques remains a critical challenge in medical diagnostics. This study introduces a deep learning-based framework that leverages a microwave radar system equipped with an arc-shaped array of six antennas to estimate key tumor parameters, including position, size, and depth. This research begins with the evolutionary design of an ultra-wideband octagram ring patch antenna optimized for enhanced tumor detection sensitivity in directional near-field coupling scenarios. The antenna is fabricated and experimentally evaluated, with its performance validated through S-parameter measurements, far-field radiation characterization, and efficiency analysis to ensure effective signal propagation and interaction with breast tissue. Specific Absorption Rate (SAR) distributions within breast tissues are comprehensively assessed, and power adjustment strategies are implemented to comply with electromagnetic exposure safety limits. The dataset for the deep learning model comprises simulated self and mutual S-parameters capturing tumor-induced variations over a broad frequency spectrum. A core innovation of this work is the development of the Attention-Based Feature Separation (ABFS) model, which dynamically identifies optimal frequency sub-bands and disentangles discriminative features tailored to each tumor parameter. A multi-branch neural network processes these features to achieve precise tumor localization and size estimation. Compared to conventional attention mechanisms, the proposed ABFS architecture demonstrates superior prediction accuracy and interpretability. The proposed approach achieves high estimation accuracy and computational efficiency in simulation studies, underscoring the promise of integrating deep learning with conformal microwave imaging for safe, effective, and non-invasive breast cancer detection. Full article

This paper presents the design of a wideband circularly polarized crossed-dipole antenna for multi-GNSS applications, covering the frequency range of 1.16–1.61 GHz. The proposed antenna employs orthogonally placed dipole elements fed by a three-branch quadrature hybrid coupler for broadband and wide gain/axial ratio beamwidth. The design is carried out using CST Studio Suite for a single dipole antenna followed by a crossed-dipole antenna, a feed network, and the entire antenna structure. The designed multi-GNSS antenna shows, at 1.16–1.61 GHz, a reflection coefficient of less than −17 dB, a zenith gain of 3.9–5.8 dBic, a horizontal gain of −3.3 to −0.2 dBic, a zenith axial ratio of 0.6–1.0 dB, and horizontal axial ratio of 0.4–5.9 dB. The proposed antenna has a dimension of 0.48 × 0.48 × 0.25 λ at the center frequency of 1.39 GHz. The proposed antenna can also operate as an LHCP antenna for L-band satellite phone communication at 1.525–1.661 GHz. Full article

This paper presents a novel switchable branch-line coupler (BLC) designed to achieve variable phase shifts while maintaining a constant output power. The proposed design incorporates low stepwise phase shifters with incremental phase shifts of 10° to 20°, covering phase ranges from −3° to 150°. The initial structure is based on a 3 dB branch-line coupler with arm electrical lengths of 3λ_g/2. A novel delay line structure is integrated within the BLC arms, consisting of a λ_g/4 section bridged by a tapered stripline to accommodate a PIN diode switch, thereby altering the current path direction. Additionally, two interdigital capacitors (IDCs), uniquely mounted on a crescent-shaped extension, are implemented alongside the tapered line to elongate the current path when the PIN diode is in the OFF state. By controlling the PIN diode states, the delay time is differentially adjusted, resulting in variable differential phase shifts at the output ports. To validate the functionality, the proposed BLC was integrated with a two-element antenna array to demonstrate differential beam steering. The measurement results confirm that the phased array antenna can switch its main beam between −27° and 25° in the elevation plane, achieving an average realized gain of approximately 7 dBi. The BLC was designed and simulated using CST Microwave Studio and was fabricated on an RO4003C Roger substrate (ε_r = 3.55, 0.406 mm). The proposed design is well-suited for future Butler matrix-based beamforming networks in antenna array systems, particularly for 5G wireless applications. Full article

A novel dual-band multi-linear polarization reconfigurable (MLPR) antenna for body-centric wireless communication systems (BWCS) is presented in this paper. The design comprises five symmetrically arranged multi-branch radiating units, each integrating an elliptical patch and curved spring branch for the Medical Implant Communication Service (MICS) band (403–405 MHz), and a pair of orthogonal strip patches for the Industrial, Scientific and Medical (ISM) $2.45$ GHz band (2.40–2.48 GHz). By selectively biasing PIN diodes between each unit and a central pentagonal feed, five distinct LP states with polarization directions of $0^{\circ }$, ${72}^{\circ }$, ${144}^{\circ }$, ${216}^{\circ }$, and ${288}^{\circ }$ are achieved. A dual-line isolation structure is introduced to suppress mutual coupling between radiating units, ensuring cross-polarization levels (XPLs) better than $-15.0$ dB across the operation bands. Prototypes fabricated on a $160\times 160\times 1.5$ mm³ substrate demonstrate measured $|S_{11}|<-10$ dB across 401–409 MHz and 2.34–2.53 GHz and stable omnidirectional patterns despite biasing circuitry perturbations. The compact form and robust dual-band, multi-polarization performance make the proposed antenna a promising candidate for implantable device wake-up signals and on-body data links in dense indoor environments. Full article

To achieve multi-band coverage within limited space, reduce antenna types, and enhance communication capabilities, an eight-unit dual-band 5G MIMO antenna array is proposed based on a monopole structure. The antenna operates in two frequency bands (3.23–4.14 GHz and 4.31–5.3 GHz), covering the n78 and n79 bands for 5G applications. The dual-band and miniaturized design of the antenna elements is achieved through the slotting and branch-loading techniques. The orthogonal placement of corner antenna elements is implemented to reduce coupling and optimize spatial utilization, achieving isolation of over 16 dB between elements. The introduction of a metasurface structure further improved isolation by 2 dB and increased the peak gain of the antenna array to 11.95 dBi. A prototype is fabricated and tested, demonstrating the following performance metrics: isolation exceeding 18 dB, gain ranging from 6 to 12 dBi, envelope correlation coefficient below 0.05, channel capacity greater than 41 bps/Hz, diversity gain of approximately 10 dB, total active reflection coefficient below −24 dB, and radiation efficiency exceeding 72%. These results confirm the superior performance of the proposed antenna design. Full article

This paper presents the design and implementation of a compact, high-isolation, optically transparent 2 × 2 MIMO antenna array. Optical transparency is achieved using a copper-based metal mesh material, which serves as both the radiating element and the ground plane, ensuring high radiation efficiency and minimal visual impact. The array consists of four monopole antennas, and mutual coupling is effectively suppressed through the integration of shorting decoupling branches and a common-ground structure. These techniques address both adjacent and diagonal (non-adjacent) coupling. A prototype was fabricated and experimentally validated. The experimental results demonstrate that the proposed antenna array achieves 20 dB isolation, 3.56 dB antenna gain, and 76% efficiency. Full article

The rapid proliferation of wireless devices and the escalating demand for ultra-reliable, high-capacity communication networks have propelled massive multiple-input multiple-output systems as a cornerstone technology for next-generation wireless standards. Massive multiple-input multiple-output systems deploy hundreds of antennas at both the transmitter and the receiver, leading to high computational complexity in many antenna selection algorithms. Existing approaches often achieve reduced complexity at the expense of partial performance compromise. To address this challenge, this paper proposes an Improved Branch-and-Bound Antenna Selection algorithm that reduces complexity while maintaining the required performance. The algorithm iteratively eliminates the antenna contributing least to channel capacity from the candidate set. Through the mechanism of reverse-stacking nodes, the conventional stack-based search process is modified. Most critically, by employing dynamic stack management and effective pruning conditions, substantial pruning operations can be implemented during subsequent search procedures, significantly accelerating the identification of the optimal antenna subset. Simulation results demonstrate that the improved algorithm reduces computational complexity from an order of 10³ to 10² while maintaining equivalent channel capacity. Furthermore, through a single execution, the algorithm can obtain optimal antenna subsets with varying sizes within specified ranges, effectively overcoming the limitation of the traditional Branch-and-Bound algorithm that requires repeated executions for different subset dimensions. Full article

This work presents a compact four-port MIMO antenna with each radiator consisting of a conventional two-monopole array fed at a single point by a coplanar line and reactively loaded with a stub. The incorporation of a T-stub-loaded tuning technique significantly improves the radiating element’s impedance, leading to deeper port coupling, a broader bandwidth, and an increased electrical length. Consequently, the operating frequency is substantially lower compared to a standalone radiator. By implementing this configuration with two monopoles of different lengths fed at the same end, an ultra-wideband effect is achieved. By placing four of these stub-loaded monopole arrays in an axial symmetric configuration, a MIMO antenna array is formed. The proposed MIMO array operates from 2.89 GHz to 12 GHz, exhibiting a TARC of less than −10 dB, an ECC of less than 0.002, an average diversity gain of 9.999, and port isolations are within a threshold from −18 dB to −50 dB over the entire bandwidth. The array’s footprint is 32 × 32 mm², equivalent to 0.083${\lambda }_0^2$ at the lower cutoff frequency. Full article

This paper proposes a miniaturized frequency-scanning antenna with high scanning rate. To overcome the OSB (open stopband) of traditional leaky wave antenna, CRLH-TL (Composite Right/Left-Handed-Transmission Line) is adopted. Furthermore, an antenna unit consisting of two symmetrically curved microstrip lines with two short branches is employed, whose second mode exhibits excellent transmission characteristics. The measurements demonstrate that the antenna can achieve scanning from −67.5° to 35.5° in the frequency band range of 5.65–6.5 GHz, with a scanning rate of 7.3. During scanning, the highest gain in the band is 12.3 dBi, the lowest is 10 dBi, and the gain fluctuation is within 2.3 dB, showing good scanning characteristics. Additionally, the length of the proposed antenna is approximately 3.84λ₀ for a central frequency of 5.95 GHz. Full article

In this paper, based on bionics, a flexible multi-band antenna is designed to mimic the structure of a spider’s web, which supports various communication standards such as 4G, 5G, and GPS. The antenna lays out multiple loop branches in a limited space to achieve wideband operations from 1.31 GHz to 2 GHz (42.4%), from 3.4 GHz to 4 GHz (16.2%), and from 5.1 GHz to 5.78 GHz (12.5%). The antenna selects 40 × 50 × 0.1 mm³ polyimide as the dielectric substrate and trapezoidal coplanar waveguide feed. A simulation and experimental analyses demonstrate that the antenna exhibits consistent performance when subjected to different bending scenarios. The design scheme utilizing a flexible dielectric substrate streamlines the integration process, offering a promising avenue for deployment in smart wireless devices. The results of the consistent tests and simulations demonstrate that the device meets the requisite standards for wireless communication. Full article

In this paper, a novel topology and method for designing a multi-band rectenna is proposed to improve its RF-DC efficiency. The rectifier achieves simultaneous rectification using both series and parallel configurations by connecting two branches to the respective terminals of the diode, directing the energy input from two ports to the anode and cathode of the diode. Six desired operating frequency bands are evenly distributed across these two branches, each of which is connected to antennas corresponding to their specific operating frequencies, serving as the receiving end of the system. To optimize the design process, a low-pass filter is incorporated into the rectifier design. This filter works in conjunction with a matching network that includes filtering capabilities to isolate the two ports of the rectifier. The addition of the filter ensures that each structure within the rectifier can be designed independently without adversely affecting the performance of the already completed structures. Based on the proposed design methodology, a dual-port rectenna operating at six frequency bands—1.85 GHz, 2.25 GHz, 2.6 GHz, 3.52 GHz, 5.01 GHz, and 5.89 GHz—was designed, covering the 4G, 5G, and Wi-Fi/WLAN frequency bands. The measured results indicate that high-power conversion efficiency was achieved at an input power of −10 dBm: 43.01% @ 1.85 GHz, 41.00% @ 2.25 GHz, 41.33% @ 2.6 GHz, 35.88% @ 3.52 GHz, 22.36% @ 5.01 GHz, and 19.27% @ 5.89 GHz. When the input power is −20 dBm, the conversion efficiency of the rectenna can be improved from 5.2% for single-tone input to 27.7% for six-tone input, representing a 22.5 percentage point improvement. The proposed rectenna demonstrates significant potential for applications in powering low-power sensors and other devices within the Internet of Everything context. Full article

Radar imaging is a technology that uses radar systems to generate target images. It transmits radio waves, receives the signal reflected back by the target, and realizes imaging by analyzing the target’s position, shape, and motion information. The three-dimensional (3D) forward-looking imaging of missile-borne radar is a branch of radar imaging. However, owing to the limitation of antenna aperture, the imaging resolution of real aperture radar is restricted. By implementing the super-resolution techniques in array signal processing into missile-borne radar 3D forward-looking imaging, the resolution can be further improved. In this paper, a 3D forward-looking imaging algorithm based on the two-dimensional (2D) super-resolution algorithm is proposed for missile-borne planar array radars. In the proposed algorithm, a forward-looking planar array with scanning beams is considered, and each range-pulse cell in the received data is processed one by one using a 2D super-resolution method with the error function constructed according to the weighted least squares (WLS) criterion to generate a group of 2D spectra in the azimuth-pitch domain. Considering the lack of training samples, the super-resolution spectrum of each range-pulse cell is estimated via adaptive iteration processing only with one sample, i.e., the cell under process. After that, all the 2D super-resolution spectra in azimuth-pitch are accumulated according to the changes in instantaneous beam centers of the beam scanning. As is verified by simulation results, the proposed algorithm outperforms the real aperture imaging method in terms of azimuth-pitch resolution and can obtain 3D forward-looking images that are of a higher quality. Full article

Endometriosis is a gynecological disease for which the diagnostics are difficult and often invasive; therefore, non-invasive diagnostic methods using sensitive and specific parameters present in easily available body fluid such as blood serum are needed for the detection of this disease. Our study aimed to answer the question of whether there are any differences between women with advanced endometriosis (AE), patients with gynecological diseases other than endometriosis (NE), and healthy women (control) in terms of the number of antennas of N-glycans from serum IgG. The degree of branching of IgG N-glycans was determined by a modified lectin ELISA with biotinylated lectin Con A (Canavalia ensiformis agglutinin) recognizing α-linked mannose, specifically reacting with biantennary N-glycans. The PHA-L/Con A ratio was calculated from the obtained N-glycan reactivities with Con A and PHA-L (Phaseolus vulgaris leucoagglutinin, specific to tri- and/or tetra-antennary N-linked glycans). The expression of Con A-reactive biantennary N-glycans in serum IgG was significantly lower in the control group than in the NE group (p = 0.045). The values of the PHA-L/Con A ratio were significantly higher in the NE group than in the AE and control groups (p = 0.019 and p = 0.022, respectively). The PHA-L/Con A ratio could be taken into account as a parameter helpful in the non-invasive diagnosis of advanced endometriosis, thus differentiating this disease from other gynecological diseases with an inflammatory background. Full article

Radio frequency interference (RFI) analysis is crucial for ensuring the proper functioning of a radio telescope and the quality of astronomical observations, as human-generated interference can compromise scientific data collection. The aim of this study is to present the results of an RFI measurement campaign in the frequency range of 4–5.8 GHz, a portion of the well-known C-band, for the Sardinia Radio Telescope (SRT), conducted in October–November 2023. In fact, this Italian telescope, managed by the Astronomical Observatory of Cagliari (OAC), a branch of the Italian National Institute for Astrophysics (INAF), was recently equipped with a new C-band receiver that operates from 4.2 GHz to 5.6 GHz. The measurements were carried out at three strategically chosen locations around the telescope using the INAF mobile laboratory, providing comprehensive coverage of all possible antenna pointing directions. The results revealed several sources of RFI, including emissions from radar, terrestrial and satellite communications, and wireless transmissions. Characterizing these sources and assessing their frequency band occupation are essential for understanding the impact of RFI on scientific observations. This work provides a significant contribution to astronomers who will use the SRT for scientific observations, offering a suggestion for the development of mitigation strategies and safeguarding the radio astronomical environment for future observational campaigns. Full article

Dendrolimus superans (Lepidoptera: Lasiocampidae) and Lymantria dispar (Lepidoptera: Lymantriidae) are two important forest defoliators in northeast China, with the former being a specialist on Larix spp. and the latter being a generalist feeding on >500 species of plants. The morphology and ultrastructure of antennal sensilla of both male and female D. superans and L. dispar were examined using scanning electron microscopy (SEM). In both sexes of D. superans, the following five types of antennal sensilla were found: sensilla trichoidea, s. chaetica, s. coeloconica, s. gemmiformia, and s. basiconica. In males of L. dispar, six types of antennal sensilla: sensilla trichoidea, s. chaetica, s. coeloconica, s. basiconica, s. styloconica, and s. auricillica, were identified. In addition to the six types found in males, a seventh type of sensilla, s. squamiform, was only detected on L. dispar female antennae. For s. chaetica of D. superans, a unique ultrastructure of sub-branches that have one branch, two branches, and three branches was observed on their tips, which has not yet been reported on other insects. s. styloconica, s. auricillica, and s. squamiform, not found in the specialist D. superans, may be related to the euryphagy of L. dispar. Potential functionalities of these sensilla were discussed with reference to moth feeding habits, and their morphology, distribution, and ultrastructures on both species. Full article