In this paper, we present a novel design for an end-fire antenna, which generalizes the concept of conventional Yagi-Uda antenna by introducing multiple driven elements. Through using the method of maximum power transmission efficiency, the optimal distribution of excitations for the multiple driven elements can be obtained, and the end-fire gain of the array can be significantly improved in comparison with the conventional Yagi-Uda antenna with a single driven element. In order to demonstrate the new idea, two different types of antenna arrays are designed and fabricated. The first design uses a split-ring resonator (SRR) as radiating element. Compared to similar planar Yagi-Uda SRR antenna arrays previously reported, the number of antenna elements can be reduced from fifteen to eight, and the longitudinal dimension is significantly reduced by 46% while the same performances are maintained with the gain reaching 11.7 dBi at 5.5 GHz. In the second design, printed half-wavelength dipoles are used as the antenna elements. It is shown that an eight-element dipole array with four driven elements has a peak gain of 13.4 dBi at 2.45 GHz, which is 1.8 dB higher than the conventional printed Yagi-Uda dipole antenna array with the same number of elements.

This document presents an evaluation of a near-field contactless inductive link, examined from a radiated disturbance standpoint, whose sources are low-power Analog Front End (AFE) circuits. Two basic types of AFE rectifiers based on Shottky diodes and Mosfet transistors were tested. Due to selective interference measurement, a map of distortions regarding the position of the coil was created. The obtained results referred to the analytical model, providing sufficient convergence to quickly assess the optimum position of the receiving coil.

Ultra-wideband antennas covering 1-18 GHz are required for Direction Finding (DF) and phased array applications in electronic warfare and communication systems. Several antennas such as Archimedean spirals, Log periodics, Ridged horns have been extensively used for ESM-DF applications. In this paper an all metal Vivaldi antenna covering 3-18 GHz is designed using HFSS software, and hardware has been realized. A measured VSWR of less than 2.5 over 3-18 GHz is obtained. Radiation patterns are satisfactory both in simulations and measurements. There is fairly good agreement between the two. Further parametric studies are carried out on the single antenna with side and back walls, and this design is optimized for VSWR of less than 2.5 over the band. This antenna is used in a linear array of 8 elements. For this array in simulations, scanned patterns devoid of grating lobes are obtained from 3.0 GHz to 9.0 GHz, and results are presented.

We provide herein open-form, double series formulae describing the diffraction of electromagnetic waves by a dielectric, dissipative wedge of finite radius a: Our procedure bypasses altogether any attempt to enforce boundary conditions at wedge faces, and relies instead on volume self-consistency for the total electric field, incident plus self-consistently radiated by polarization/ohmic currents distributed throughout the wedge interior. Self-consistency of this sort is formulated as an integral equation over the wedge cross-sectional area, an equation wherein are implicitly subsumed all necessary boundary conditions. The crux of the ensuing solution depends upon a decomposition within the wedge interior of both incoming (here taken as plane) wave field and the underlying Green's (Hankel) function into standard functional buildings blocks individually compliant with the Helmholtz equation as adapted to the reference, exterior medium. With such decomposition in hand, the remainder of the solution follows a more or less routine, Ewald-Oseen route, one eased by function orthogonality, by cancellation across the board of the total field when similarly so decomposed throughout the wedge interior, and an almost rote reading off of interior expansion coefficients against those found on the exterior. The incoming field series decomposition across the wedge interior, it should be noted, avoids the pitfall of a naive recourse to Fourier series, and invokes instead a root-mean-square minimization. That such a procedure enjoys a measure of validity is confirmed in Appendix C, wherein it is shown that the present analytic apparatus, when permitted to confront a degenerate wedge having its exterior angle γ tending to zero, γ→0+; which is to say, a bona fide dielectric cylinder, recovers the classical, boundary-value solution as to its every detail. All in all, while we do hope that the present work will serve to broaden the prevailing viewpoint as to permeable wedge scattering, we nevertheless admit to a measure of regret as to the complexity of the resulting formulae, whose numerical implementation bodes ominously to be a formidable task in its own right. It would seem that we reach here a frontier of diminishing returns as to the applications of classical analysis, a point at which its intellectual allure can honorably surrender to direct, computer-driven point matching methods.

This paper is a design and fabrication of an UWB filter (band pass filter) with two notched (rejection) bands. Ultra-wideband (UWB) systems are systems with the electromagnetic spectrum from 3.1 GHz to 10.6 GHz. The designed filter removes WLAN and satellite signals which are 5.8 GHz and 8 GHz. For designing filter, we use a stepped-impedance stub-loaded resonator. To provide two notched bands, a radial stub loaded resonator with a defected microstrip structure (DMS) is used. The presented filter has more analytic relations and simpler structure than prior works. This filter is fabricated on an RO4003 substrate with dielectric constant of 3.55. The dimensions of the filter are 10*25 mm which are more compact than prior structures. The measurements have a good agreement with predicted results which verifies the feasibility of the UWB filter.

A new miniaturized microstrip branch-line coupler with wide suppression band is proposed in this paper. The new structure has two significant advantages, which not only effectively reduces the occupied area to 12.3% of the conventional branch-line coupler at 0.6 GHz, but also has high 11th harmonic suppression performance. The measured results indicate that a bandwidth of more than 125 MHz has been achieved while the phase difference between S₂₁ and S₃₁ is within 90° ± 1.0°. The measured bandwidths of |S₂₁| and |S₃₁| within 3 ± 0.4 dB are 145 MHz and 150 MHz, respectively. Furthermore, the measured insertion loss is comparable to that of a conventional branch-line coupler. The new coupler can be easily implemented by using the standard printed-circuit-board etching processes and is very useful for wireless communication systems.

This work presents an approach for the design of a quad-band substrate integrated waveguide (SIW) bandpass filter based on multilayer process. TE₁₀₁/TE₁₀₂/TE₁₀₃/TE₁₀₄ modes are used to characterize the four passbands, respectively. Firstly, the locations and band ratios of the passbands are chosen based on the effective width-length of the SIW resonator and its ratio. Then, vertical couplings of the modes and source-load are designed on the middle metal layers between the dielectric layers, which provides a relatively independent bandwidth tuning and high selectivity. To demonstrate the proposed design method, a quad-band SIW bandpass filter is fabricated and measured. Experimental results agree well with the simulated counterpart. The proposed quad-band SIW filter presents good selectivity and compact size.

Recently, consumer drones have encroached upon airports and pose a potential threat to aviation safety. Radar is an effective remote sensing tool to detect and track flying drones. Radar echoes from flying birds are assumed to be clutters when a radar is detecting drones. Yet, few studies have reported how radar echoes from flying birds interfere with the detection of drones,how similar radar cross section (RCS) and flight feature of birds and drones are,and why the flying birds cause trouble when radar identifies signals from the drone. In this study, we collected 3900×256 of Ku-band radar echoes of flying birds and consumer drones. The targets consist of a pigeon, a crane, waterfowl, and a DJI Phantom 3 Vision drone. We compared the maximum detectable range of birds and drones, the time series and the Doppler spectrum of radar echoes from the birds and the drone, considering oncoming and outgoing radar data with respect to radar location. The statistical results indicate that flying birds have similar RCS, same velocity range, similar signal fluctuation, and approximate signal amplitude. Our results of radar automatic target recognition (ATR) illuminate that the identification probability of airborne drones will be lower due to the interference of the radar signal by flying birds. Above all, these facts confirm that flying birds are the main cause of interference when a radar is detecting and identifying airborne drones.

This work describes a theoretical study of filters using a defect in one-dimensional photonic comb-like structure. This photonic comb-like structure is constituted by finite or infinite segments which have negative permeability and grafted in each site by a finite number of lateral branches (play the role of the resonators), which consists of a negative permittivity. Numerical results exhibit the permissible bands which are separated by gaps (forbidden band). These gaps originate not only from the periodicity of the system but also from the resonance states of the grafted lateral branches. We study the effect of the presence of a resonator defect on the transmission behavior, phase, and phase time. The electromagnetic band structure shows that there is a defect mode in the gap. The transmission rate and the reduced frequency of this mode are related to the variation of defect length. Similarly, we calculate, for the first time, the quality factor evolution of this defect mode when the defect length varies. This structure can be used as a new optical filter in the microwave range with a high factor of quality and of transmission.

In this paper, a differentially fed, structurally simple, patch antenna, operating at 5.2 GHz is presented. The proposed antenna is particularly designed for a base station, Gallium Nitride (GaN) transmitter. The antenna is composed of an H-shaped patch, backed by a ground plane, with two differential feeds placed at the longitudinal edges. The size of the antenna is 0.55λ₀ x 0.49λ₀ x 0.27λ₀ (where λ₀ is the free space wavelength at the center frequency). A prototype of the stand-alone antenna is designed, fabricated, and measured. The antenna offers a voltage standing wave ratio (VSWR) bandwidth of 4% and a differential impedance of 100, which matches most of the differential integrated circuits. The measured gain and directivity of the proposed differential antenna are 5.3 dBi and 7 dB, respectively. From simulation it is observed that the proposed antenna possesses a front to back ratio of 15.69 dB and a 3 dB beamwidth of 84˚. The measured peak efficiencies of the antenna in the lower and higher bands are 84% and 59%, respectively. Details of the design and lumped model, along with the experimental and simulated results, are presented and discussed. The effect of scaling different design parameters for operation at different frequency bands is considered as well.

Microwave induced thermoacoustic imaging (TAI) is a hybrid imaging technique combining microwaves and ultrasound waves to achieve both superior spatial resolution and high image contrast. Here, we present results from a hybrid finite element model and an experimental setup using a microwavem peak power of less than 5 kW (average power of only 4.5 W), significantly less than for comparable imaging performance in previous works. Microwave pulses with a duration less than 1 μs are used to excite ultrasound waves with a frequency higher than 1 MHz. Experimental measurements show agreement with simulation results using hybrid finite element modeling capturing microwave heating and acoustic wave propagation. Simulations suggest targets with a conductivity of approximately 0.9 S/m yield the strongest thermoacoustic signatures. Both B-mode images and time-reversal based reconstructed images are obtained and clearly demonstrate the enhanced contrast and high resolution by exploiting the dielectric absorption properties of microwaves and the sub-millimeter resolution of ultrasound. The use of a time reversal algorithm on recorded data demonstrates the effectiveness of TAI for biomedical applications. Standing wave patterns are identified in targets and their relation to the target characteristics and their effect on the resulted images are investigated. The novelty of this work is in lowering the microwave average power while still being able to detect induced acoustic signals, along with developing a numerical model to provide an insight into the imaging process and analyze anomalies in image reconstruction.

In this paper, a gain and front-to-back ratio (FTBR) enhanced vertically polarized 1 × 3 series-fed linear array for Airborne SAR-X application has been presented. The proposed antenna prototype is designed at 9.65 GHz X-band. The proposed antenna design consists of a square radiating patch, substrate, quarter wave transformer 50 Ω matched transformer, and series feed line (SFL). The simulated antenna prototype is fabricated and successfully measured. The final antenna prototype has a dimension of 80 × 50 × 1.587 mm³ or 2.574 × 1.6087 × 0.051λ₀³ (Free space wavelength) or 3.256 × 2.035 × 0.0645λ_g³ (Guided wavelength) at 9.65 GHz. The results indicate that the proposed antenna prototype yields an impedance bandwidth >140 MHz (from 9.591 to 9.712 GHz) defined by S₁₁<-10 dB. The low profile/cost antenna prototype has a fully directional radiation pattern with measured gain up to 12.2 dBi and estimated radiation efficiency of 89%, respectively. A brass plate with 0.8 mm thickness has been fabricated to attach to the antenna ground plane for improving FTBR of more than 30 dB. All these features make the proposed antenna array have good potential applications in X-band system, especially in 9.65\,GHz Airborne SAR systems. The aperture of the antenna is 80 mm x 50 mm, which equals 31 wavelengths at 9.65 GHz.

We analytically model single-, two-, and three-wires above ground to determine the decay lengths of common and differential modes induced by an E1 high-altitude electromagnetic pulse (HEMP) excitation. Decay length information is pivotal to determine whether any two nodes in the power grid may be treated as uncoupled. We employ a frequency-domain method based on transmission line theory named ATLOG - Analytic Transmission Line Over Ground to model infinitely long and finite single wires, as well as solve the eigenvalue problem of a single-, two-, and three-wire system. Our calculations show that a single, semi-infinite power line can be approximated by a 10 km section of line and that the second electrical reflection for all line lengths longer than the decay length are below half the rated operating voltage. Furthermore, our results show that the differential mode propagates longer distances than the common mode in two- and three-wire systems, and this should be taken into account when performing damage assessment from HEMP excitation. This analysis is a significant step toward simplifying the modeling of practical continental grid lengths, yet maintaining accuracy, a result of enormous impact.

In order to solve the problem of strong coupling between torque and suspension force of bearingless switching motor and the strong chattering of sliding mode control, a direct suspension force control method for hybrid stator bearingless switched reluctance motor based on 1uasi-continuous third-order sliding mode is proposed. According to the special structure of hybrid stator bearingless switched reluctance motor, the direct decoupling of torque and suspension force is realized. The suspension force control system adopts the direct suspension force control of the third-order sliding mode. By comparing with the second-order sliding mode control system under the condition of interference source and non-interference source, the results show that the designed control strategy has high precision, strong robustness, fast convergence speed, and it can effectively decrease vibration.

A compact Multiple Input Multiple Output (MIMO) antenna of size 41×30×0.8 mm³ is proposed in this paper for Ultra-Wideband (UWB) application with high isolation. The proposed UWB-MIMO antenna consists of two Semi-Circle Antennas (SCA) which acts as a radiating patch for achieving UWB operation. The frequency range of UWB is from 3.04 to 10.87 GHz. The high isolation is achieved by inserting an E-shaped slot in the radiating patch, and further enhancement is achieved by inserting a narrow slot in the ground plane. It can be seen that there is good agreement between the simulated and measured results which indicates that the proposed antenna is suitable for UWB applications.

Ground penetrating radar is an effective nondestructive method for exploring subsurface object information by exploiting the differences in electromagnetic characteristics. However, this task is negatively affected by the existence of ground clutter and noise especially if the object is weak or/and shallowly buried. Therefore, this paper proposes a novel method for suppressing the clutter and background noise simultaneously in both flat and rough surfaces. First, the ground clutter is removed mainly by applying a simplified least square fitting background method, which remains the residual random noise signal. The remaining signal is then decomposed by singular value decomposition, which assumes that the decomposed signal contains four main components including strong target, weak target, very weak target, and accumulated noise signals. The powered singular values and their differences are clustered by K-means to extract the target signal components. The simulation results indicate that the proposed method is able to enhance the target signal with satisfactory results under both flat and rough surfaces as well as in a high-level background noise. Besides, this method also shows its superiority to the latest existing proposed methods.

D-dot sensor is a type of differential sensor that is widely used in the measurement of ultra-wide band (UWB) pulse electric field. The output of the sensor needs to be integrated to rebuild the original electric field. According to the methods of integration, the measurement system based on D-dot sensor can be classified into software integral D-dot measurement (SIDM) system and hardware integral D-dot measurement (HIDM) system. For an SIDM system, the accuracy of calibration, which is influenced by the integral error of the recovery signal, unfortunately, remains an impediment to its practical application. In this paper, a calibration uncertainty evaluation method based on a standard field generating equipment of time-domain electromagnetic pulse is investigated. The level of the integral error is determined by constructing a noise model using the calibration method. In the process of modeling, the characteristics of the background noise are analyzed first. Additionally, a random signal model taking background noise into account is built, and the integral value of the background noise is derived. Moreover, the integral error model is verified by a statistical method using tested data. After modeling, the uncertainty of the equivalent area for a real D-dot sensor in a software integral system and the methods for reducing the uncertainty are illustrated according to the integral error model.

L-band one-dimensional (1-D) synthetic aperture radiometer is a passive microwave imager that aims to produce global sea surface salinity and soil moisture maps. Two instrument concepts for the L-band 1-D synthetic aperture radiometer have been proposed and selected as candidate payloads for future Chinese space missions, including MICAP (Microwave Imager Combined Active and Passive) for the Chinese Ocean Salinity Mission and IMI (Interferometric Microwave Imager) for the Water Cycle Observation Mission (WCOM). For a synthetic aperture radiometer, spatial imaging error is defined as the difference between the original brightness temperature (BT) and the retrieved BT images within the alias-free field of view (AF-FOV). The main causes of image spatial error in the L-band 1-D system are antenna elements spacing and antenna patterns error. Flat target transformation (FTT) algorithm is always useful for correcting radiometer imaging, but there is still a concave residual error in the retrieved image. An improved calibration algorithm is proposed, which replaces the cold sky view in the FTT with a stable reference scene BT image. A task simulator has been set up to evaluate the new method. The proposed calibration algorithm is shown to reduce the spatial bias and improve the quality of the retrieved BT image.

In order to improve the efficiency of the quasi-optical mode converter, two methods to design mirror systems for a 170 GHz gyrotron operating in TE_32,9 mode are presented in this paper. The first method is to use Katsenelenbaum-Semenov Algorithm (KSA) to design the structure of the mirror. The second method to design the mirror system depends on the phase difference on the mirrors, so we name it PD method. The mirror system consists of three mirrors, and the mirror center position and mirror size are the same for both methods. For the first method, the scalar and vector correlation coefficients obtained at the window are 99.45% and 98.12%, respectively, and the mirror system has been designed with a transmission efficiency of 97.25%. The scalar and vector correlation coefficients and mirror system transmission efficiency are 99.73%, 98.85%, and 97.67% respectively for the second method. Simulation results of the two methods are compared and analyzed, which provide a reference for the design of gyrotron quasi-optical mode converter mirror system.

In this work, a Complementary Folded Triangle Split Ring Resonator (CFTSRR) loaded triband mobile handset planar antenna is presented. The proposed antenna consists of a dumbbell-shaped radiating element and two CFTSRR metamaterial unit cells. The dumbbell-shaped radiating element resonates at 5 GHz. The presence of CFTSRRs additionally offers two lower band resonance. The CFTSRR-1 and CFTSRR-2 exhibit negative permittivity at 1.8 GHz and 2.4 GHz, respectively. The proposed antenna is designed to resonate at 1.8 GHz (GSM1800 MHz), 2.4 GHz, and 5 GHz (IEEE802.11ax) for voice and Wi-Fi applications of the mobile handset, respectively. The proposed antenna demonstrates compactness up to 88.6% at 1.8 GHz. The parametric studies are investigated to optimize the antenna in desired frequency bands by using Ansys HFSS19 software. The simulated and measured results are discussed. The measured result shows -10 dB reflection coefficient with bandwidth about 250 MHz (1.6 GHz-1.85 GHz), 50 MHz (2.375 GHz-2.425 GHz), and 225 MHz (4.925 GHz-5.15 GHz) which are 14.5%, 2%, and 5% respectively around their center frequencies. The measured maximum gain is approximately 1.7 dBi, 8 dBi, and 11.5 dBi for 1.8 GHz, 2.4 GHz, and 5 GHz, respectively.