Printed circuit boards' radiated emissions pose significant challenges for system-level electromagnetic compatibility design. Source reconstruction methods based on near-field scanning can efficiently predict radiated emissions above the printed circuit boards under the assumption of an infinitely large ground plane. However, existing methods are not suitable for printed circuit boards with irregularly shaped ground planes. In this paper, a novel method is proposed to account for irregularly shaped ground planes. Image theory and the surface equivalence principle are employed to compensate sampled near fields above the ground plane. Compensated near fields are then used to construct an equivalent dipole model, with an optimization technique for dipole positions to improve accuracy. Numerical validations are conducted to demonstrate the capability of the proposed method in predicting radiated emissions both above and below the board. A typical shielding problem is analyzed to show its efficiency and accuracy in system-level EMC simulation.
Accurate dust-storm monitoring is vital in arid regions. This study details the first field deployment of a 94 GHz W-band radar in the Taklamakan Desert to retrieve height-resolved microphysical parameters, including reflectivity, two-way attenuation, and log-normal particle-size distribution. Applying Rayleigh scattering theory, we demonstrate that absorption dominates electromagnetic attenuation at W-band frequencies. Two attenuation estimation methods are introduced, showing low-altitude attenuation reaches 4.5 dB/km during low visibility. To improve weak echo extraction, we optimized Doppler spectrum signal processing by integrating Hildebrand-Sekhon iterative denoising with Kolmogorov-Smirnov testing for robust noise estimation. Height-based attenuation correction effectively recovered near-ground echo strength (up to 10 dBZ), revealing stratified vertical dust transport between 500 and 1000 m. These findings highlight the W-band radar's capability for quantitative dust-storm profiling and microphysical property inversion.
A compact wideband dual-polarized antenna for 5G sub-6 GHz applications is analyzed, designed, and experimentally evaluated. The antenna is a swastika-shaped radiating patch, fed at two orthogonal ports to generate dual polarization. An ultra-wide bandwidth of 154% is achieved over a frequency range of 1-7.7 GHz. Six resonating frequencies at 1.8, 6, 6.7, 10, 12 and 13 GHz are obtained. The achieved interport isolation is better than 30 dB. The antenna is suitable for IEEE L/X/Ku bands and IEEE 802.11 a/n/ac/ax and 5G sub-6 GHz, applications along with IEEE 802.11ax systems. The antenna provides circular polarization in IEEE 802.11 a/n/ac/ax and linear polarization in the IEEE L/X/Ku band. A 3-dB axial ratio bandwidth of 36% is obtained from 4.8 to 6.9 GHz. The antenna exhibits an average realized gain of approximately 6.8 dBi across the operating bandwidth with a peak gain of 9.85 dBi. The simulation and measured results are in good agreement.
This numerical simulation study proposes a broadband, tunable, and angle-insensitive terahertz perfect absorber based on a monolayer MoS2 asymmetric "C" - shaped metasurface. The absorber employs a simplified three-layer architecture: patterned MoS2 layer/SiO2 dielectric layer/Au reflective layer. Finite-difference time-domain simulations demonstrate that the absorber achieves over 91.4% absorption within 0.83-1.43 THz (relative bandwidth of 53.1%), with near-perfect absorption (>99%) across 0.9-1.36 THz, peaking at 99.7% at 1.24 THz. Dynamic modulation is realized by adjusting carrier concentration ( 0.8 & times;10(14) - 1 & times;10(15)cm (- 2) ) through bias voltage (5-10 V). The structure maintains stable performance (fluctuation <4.1%) within a 60 degrees incidence angle range. Electric field and surface current analyses reveal that the broadband absorption originates from the synergistic coupling of magnetic and electric dipole resonances enabled by the asymmetric geometry. This work demonstrates that high-performance terahertz absorption can be achieved through a structurally minimalist design, providing a practical pathway for tunable, easily fabricated terahertz devices.
In this paper, a planar balanced absorptive dual-band bandstop filter (BSF) with inherent common-mode (CM) noise suppressions is proposed. The symmetrical structure consists of four pairs of coupled-lines, with two pairs forming stepped-impedance resonators and the remaining two pairs serving as stubs. Resistors are inserted between coupled-lines to absorb reflected signals. Under CM excitation, the BSF achieves stopbands at 1.7 and 3.62 GHz with 3-dB bandwidths of 23.5% and 10.8%. Under differential-mode (DM) excitation, the reflection coefficient is below -9 dB. The circuit with a size of 58.8 mm & times; 28.2 mm is fabricated and measured to verify the design.
Existing pixelation-based shape synthesis methods are such that the geometrical resolution requirements result in an extremely large number of adjustable variables, even when a considerably smaller number is sufficient to significantly broaden the design space (compared to conventional design approaches), and achieve some required performance subject to design constraints. A new subtractive shape synthesis method is proposed that works directly on the conductor geometry and thus yields a layout completely composed of precisely the conductor material actually intended, without additional processing needed. The way it separates the requisite geometrical resolution from the number of optimization variables needed to shape the circuit layout permits a very fine geometrical resolution with, nevertheless, the number of optimization variables reduced by a very large factor. This makes feasible the use of non-gradient optimizers well-suited to complicated objective functions formed from multiple objectives. The implementation of the method is described, and several example outcomes discussed.
To meet the demands of terahertz electromagnetic interference suppression and efficient energy absorption, this paper proposes a three-band terahertz metamaterial absorber based on an alumina substrate and vanadium dioxide thin film. Simulations show that in TE and TM modes, nearly perfect absorptions of 99.85% and 99.76% are achieved at 0.833 THz, with secondary absorption peaks at 0.626 THz and 0.874 THz (both >65%). The highly symmetric geometry ensures polarization insensitivity. Parametric studies reveal how bridge width and base side length affect the resonance mode. This design provides new ideas for electromagnetic shielding, energy harvesting, and high-sensitivity sensing in the terahertz band. Its lightweight, thin structure and multi-physics collaboration mechanism demonstrate potential for wearable devices and implantable medical applications. Future work will focus on experimental verification, dynamic frequency reconstruction, and adaptability to extreme environments .
This research article presents a two-element dual-band CP MIMO antenna, intended for n78 (3.3-3.8 GHz) and X-band (8-12 GHz) applications. The design incorporates modified square ring radiators along with modified ground plane. The MIMO antenna engineered to provide 10 dB impedance bandwidth of 3.21-5.82 GHz and 7.23-11 GHz with axial ratio (AR) bandwidth of 2.9-3.88 GHz and 8.93-10.51 GHz. The overlapped impedance and AR bandwidth are 3.21-3.88 GHz in lower band and 8.93-10.51 GHz in upper band. A minimum isolation of 14 dB is achieved without any complex decoupling network. The defected ground structure, open-loop hook-shaped configuration, and rectangular parasitic element positioned at the center of the ground plane for LHCP radiation across both frequency bands. The realized gain ranges from 2.6-3.9 dBic in lower band and 5.6-6.4 dBic in upper band. The total efficiency of the antenna ranges 70 and 88% in lower band and 80-85% in upper band. Within the operating bands, the ECC remains below 0.038 while CCL is less than 0.357 bits/s/Hz. The TARC values remain well below the -10 dB level.
This paper presents the implementation of a via-free shielded half-mode substrate integrated waveguide (S-HMSIW) antenna sensor fabricated using 3D-printing technology. The design employs a fluidic channel built within the substrate, protecting the surface of the antenna sensor from direct contact with the fluids. By injecting the fluid into the channel, the effective permittivity is altered, leading to the switching of the operating frequency. Additionally, copper coating of the sidewalls eliminates the need for vias, simplifying the fabrication. The proposed model is 3D-printed using Polylactic acid (PLA) material. The sensing performance is experimentally validated using ethanol-water solutions with varying concentrations. The fabricated prototype exhibited a measured sensitivity of 0.2%. Additionally, when operated with low-loss fluids, the proposed model functions effectively as an antenna, achieving measured gains in the range of 2.27 - 3.71 dB over the operating band. The observed results demonstrate that the proposed design can be employed for lightweight, low-cost, and adaptive radio frequency (RF) systems with dual-functionality by enabling reconfigurable communication and fluid sensing.
In this paper, we present a method for obtaining a stable-form radiation pattern in a wide frequency range for a small-sized antenna based on a non-symmetrical vertical printed vibrator (a wideband monopole). The method involves using a wideband rectangular radiator and matching it to a 50-Ohm input connector using a quarter-wave transformer based on a microstrip transmission line, along with a specially shaped second arm. Based on the proposed method, we designed a printed antenna with a matching bandwidth of approximately 1600-3700 MHz (similar to 80%) and an impedance matching level no worse than 10 dB, and a stable toroidal radiation pattern in this range. The prototype (PCB without a connector) has a compact size of 60 & times; 22 & times; 1 mm3 or 0.32 lambda max & times; 0.12 lambda max and a small weight of no more than 5 g. The proposed antenna is primarily applicable to wireless communication in aerial systems and is intended for installation on an aircraft.
This paper presents a low-profile, wideband, and high-gain heptagonal-shaped antenna integrated with an artificial magnetic conductor (AMC). The antenna features a heptagonal radiator with a double-sided sigma slot and triangular parasitic patches to enhance bandwidth. The standalone antenna operates from 6.4 GHz to 7.3 GHz (11.4% bandwidth), with a 4 dBi gain. To further boost performance, a square-ring AMC structure with circular patterned rectangular slots is employed. Placing the antenna just 0.02 lambda 0 above the AMC significantly improves performance, expanding the bandwidth to 27.1% (6.3 GHz-8.3 GHz) and doubling the gain to 8 dBi. The combined system achieves a return loss of -40 dB at a center frequency of 7.38 GHz. This design offers a compact, high-efficiency solution for wideband applications.
This paper presents a miniaturized triple-band implantable antenna system operating in the ISM band (2.4-2.48 GHz) and midfield bands (1.45-1.6 GHz and 1.824-1.98 GHz) for sensing and biotelemetry applications. Characteristic mode analysis (CMA) is used during the design process to develop the antenna based on its modal behavior, while conventional full-wave simulations validate the analysis. The antenna achieves impedance bandwidths of 14.19% and 13.58% in the midfield bands and 23.31% in the ISM band. Despite its compact size of 0.000005 $ \lambda_g<^>{3} $ lambda g3, the antenna maintains linear polarization. Triple-band operation is realized through open-ended slots etched on the radiating patch and ground plane, while metallic vias enhance overall performance. In addition, the link margin supports reliable wireless biotelemetry with an external control unit, and the estimated specific absorption rate satisfies IEEE human safety standards. Finally, measurements from the fabricated prototype show good agreement with the simulated results.
The near-field power transfer is analyzed in this paper. It is shown that very basic approximation of electrically small antennas as canonical elements based on the antenna theory can serve well as a simple and efficient tool for both frequency and time characterizations of WPT systems, even in wide-band frequency spectrum of applied antennas. Impulse and pulse responses based on simple analytical formulas that stem from the antenna model are shown for the purpose.
