An S-band bandpass filter based on quarter wavelength stepped-impedance resonator (SIR) is presented in this paper. Two SIRs are loaded to the BPF to obtain wide stopband suppression. The center frequency f₀ of the bandpass filter is located at 2.105 GHz with 3-dB fraction bandwidth (FBW) of 11.9%. It shows that the spurs free upper stopband with 15 dB rejection level can extend to 40 GHz (19f₀). The circuit size of this filter is extremely compact, which occupies only 7.35 mm × 7.5 mm.

In this paper, a novel OLR loaded self complementary dipole antenna (OSCDA) is proposed. Open loop resonators (OLRs) are introduced into the design of a traditional self complementary dipole antenna (SCDA), to evolve it into OSCDA. The antenna is compact and has an impedance bandwidth of 1.1 GHz to 3.3 GHz with VSWR less than 2 across the frequency band. The use of the proposed antenna as a liquid sensor to detect adulteration in liquids is demonstrated from the relationship between concentration and shift in resonant frequency and variation in reflection coefficient. Variation of reflection coefficient due to change in dielectric properties is studied for different cases viz.: (i) dilution of milk with water, (ii) adulteration of coconut oil with rice bran oil, (iii) adulteration of honey with sugar syrup, and (iv) varying concentration of salt and sugar in water. When an adulterant is added to a liquid or concentration of solute in a solution varied, the dielectric properties change. This is reflected in the variation in reflection coefficient and resonant frequency. Experimental results show that the antenna has a good sensitivity to detect adulterated samples.

Exact two-dimensional (2D) analytic expressions for electric and magnetic fields and their potentials created by a linear beam of relativistic charged particles between infinite perfectly conductive plates and ferromagnetic poles are derived. The solutions are obtained by summing an infinite sequence of fields from linear charge-images and current-images in complex space. Knowledge of the normal component of the electric field on the conductor surface makes it possible to calculate the induced electric charge surface density. In addition, we derive within an improved linear approximation new analytical expressions for fields near the beam in the case of an arbitrary beam offset from the median plane. The mathematical features of exact solutions and limitations for the applicability of linear approximations are specified. The primary goals of the future high-luminosity p-p and heavy-ion Large Hadron Collider programme after the Long Shutdown 2 are the search for yet unobserved effects of physics beyond the Standard Model, searches for rare or low-sensitivity processes in the Higgs sector, and probing in more detail the mechanism of electroweak symmetry breaking. This programme relies on the stable operation of the accelerator. However, as the beam luminosity increases, a number of destabilizing phenomena occur, in particular field emission, enhancing the electron cloud effect. For the case of a proton beam, we apply the exact 2D solution for estimating the intensity of electron field emission activated by the electric field of the beam in collimators of the future high-luminosity Large Hadron Collider. Calculation shows that the field emission intensity is very sensitive to a collimator surface roughness. In addition, with a relatively small and accidental beam displacement from the median path, about 20% of the collimator half-gap, the emission intensity increases by a factor of 10⁷. This will partially neutralize the beam space charge, violating acceleration dynamics and enhancing instability effects.

This paper proposes a new method to enhance the impedance bandwidth (IBW), broadside gain, front-to-back ratio, and aperture efficiency of a rectangular microstrip patch antenna (RMPA) printed on a compact artificial magnetic conductor ground plane (AMC-GND). The technique uses large shorted unit cells at the center and a wide slot cut on the unit cells located under the patch to respectively impede the propagation of surface currents and reduce the adverse effect of the loading capacitance that is formed between the RMPA and the AMC-GND on the antenna IBW. The proposed antenna with dimensions of only 1λ₀×0.6λ₀×0.06λ₀, realizes an IBW of 24% (6.07-7.73 GHz), peak gain of 9.93 dBi, and a simulated aperture efficiency of more than 96%. Due to its compact size, good radiation, and wide IBW performances, the presented antenna can be used in various applications, such as MIMO antenna system, wide-angle scanning antenna array and reflector feed antennas operating in satellite C-band 5.9-6.4 GHz and 6.425-6.75 GHz. It is worth mentioning that the main contribution of the current work is the investigation of the detrimental effects of the overlay capacitor on the IBW of a linearly polarized RMPA etched on a compact AMC surface using a simple equivalent circuit model.

This work is a contribution to the characterization of the electromagnetic properties of high temperature superconductors (HTS) made of Bismuth Strontium Calcium Copper Oxides (BSCCO). The electromagnetic proprieties (critical current density and self-field AC losses) of a tape and a coil are determined experimentally at different frequencies, and compared to analytical models and finite element simulations for a better analysis of the physical phenomena. As shown in this work, the transition from the element to the system is not straightforward, and the characterization of such a material at the system scale is necessary due to their high sensitivity to the magnetic field. Solutions to some measurement problems are also highlighted.

For reducing the computational complexity of direction-finding algorithm in sparse multiple-input multiple-output (MIMO) radar, a low-complexity partial spatial smoothing (PSS) algorithm is presented to estimate the directions of multiple targets. Firstly, by dealing with a partly continuous sampling covariance vector in PSS technology, an incomplete signal subspace can be obtained. Then, a special matrix can be obtained by using this incomplete signal subspace. Meanwhile the incomplete signal subspace can also be repaired by the special matrix. At last, the multiple signal classification (MUSIC) algorithm is used to obtain direction estimations. In the process of obtaining signal subspace, no eigenvalue decomposition (EVD) needs to be performed. Compared with the traditional spatial smoothing (SS) technology, the proposed algorithm has lower computational complexity and higher estimation precision. Many simulation results are provided to support the proposed scheme.

In this paper, a novel microstrip-fed compact antenna with dual band-notched characteristic is presented for ultra-wideband (UWB) applications. Assisted with symmetrical open-circuited stubs, a UWB impedance matching can be achieved. A novel modified capacitively loaded loop (CLL) resonator is proposed to realize the dual notched bands. By symmetrically placing a couple of proposed resonators in the vicinity of the feed line, dual band-notched properties in 3.4-3.7 GHz for WiMAX and 5.15-5.825 GHz for WLAN are generated. The good performance of the dual notched bands, stable gain, and radiation patterns in the operating bands make the proposed antenna a good candidate for various UWB applications.

The aim of this letter is to provide a novel method connecting statistical optimization and information geometry for ship detection in synthetic aperture radar (SAR) imagery. The method consists of two steps: initial detection and iterative optimization. For the first stage, the Weibull clutter model is used for initial detection. For the second step, the metric tensor of the Weibull distribution manifold is constructed for iterative optimization. Experiments show that the proposed method is effective in reducing false alarms and obtains a satisfactory detection performance.

The available polarizers either cannot afford gigawatt-class high-power microwave applications or are large in length. In this letter, a novel grooved polarizer is proposed. The grooves are proposed to be created in an over-mode circular waveguide to improve the power capacity and bandwidth. Moreover, the symmetric elliptical grooves are adopted to suppress high-order modes and realize the desired phase difference. An X-band polarizer prototype is designed and manufactured with length of 91 mm. Simulated results show that the power capacity of the polarizer is more than 1.5 GW. Measured results in accordance with simulations show that the axial ratio is less than 3 dB from 8.6 to 12.2 GHz, with relative bandwidth of 34.6%. The measured return losses are better than -12.7 dB in the same frequency range.

A compact tri-band antenna is designed and analyzed to achieve both transmission and reception of direct broadcast service (DBS) and fixed satellite service (FSS) in Ku band. The proposed antenna design consists of a truncated E-shaped slot, eight rectangular slots, two C-shaped slots in the patch and eight defected ground structure (DGS) slots. The three frequency bands of 11.40-12.91 GHz, 13.86-14.53 GHz, and 17.20-17.86 GHz are achieved with impedance bandwidths of 12.32%, 4.73%, and 3.77% respectively. Conversely, the measured frequency bands of 11.40-12.98 GHz, 14.21-14.86 GHz, and 17.41-18.98 GHz with the impedance bandwidth of 12.70%, 4.48%, and 8.63% respectively are obtained. The simulated results of the proposed antenna are compared with the results of fabricated antenna and are found to be satisfactory for reflection coefficient, impedance bandwidth, polarization, efficiency, gain, and radiation pattern. Moreover, the proposed antenna design can be used as an element in an array configuration to achieve high gain in both transmission and reception modes of FSS and DBS.

In this work a reconfigurable Ultra Wide Band (UWB) antenna for Wireless Body Area Network (WBAN) is presented. The antenna is completely composed of fabric materials and is able to switch its topology from a monopole-like structure (for on-body communications) to a microstrip-like structure (for off-body communications) maintaining UWB characteristic stable both on body and in free-space. This antenna presents good radiation properties in both configurations. In order to describe its time domain and frequency domain behavior a System Fidelity Factor (SFF) analysis has been done for both topologies.

Time domain finite element methods (TD-FEM) for computing electromagnetic fields are well studied. TD-FEM solution is typically effected using Newmark-Beta methods. One of the challenges of TD-FEM is the presence of a DC null-space that grows with time. This can be overcome by solving Maxwell equations directly. One approach, called time domain mixed finite element method (TD-MFEM), discretizes Maxwell's equations using appropriate spatial basis sets and leapfrog time stepping. Typically, the basis functions used to discretize field quantities have been low order. It is conditionally stable, and there is a strong link between time step size and mesh dependent eigenvalues, much like the Courant-Friedrichs-Lewy (CFL) condition. This implies that the time step sizes can be very small. To overcome this challenge, we use the Newmark-Beta approach. The principal contribution of this work is the development of, and rigorous proof of, unconditional stability for higher order TD-MFEM for different boundary conditions. Further, we analyze nullspaces of the resulting system, and demonstrate stability and convergence. All results are compared against the conditionally stable leapfrog approach.

This paper presents a practical scheme for threefold stubs etched on the ground plane (GP) to reduce mutual coupling between adjacent patching elements. The multiple input multiple output (MIMO) antenna array consists of two concentric polyhedron annulus patches, a conventional dielectric substrate, threefold fork-shaped stubs (TFSS) and a microstrip line feeder. The equivalent band-stop filtering function of the TFSS suppressing surface wave propagation has been demonstrated in commercial Advanced Design System (ADS) software. The results of previous case studies indicate that the mutual coupling about 5 dB to 47 dB was reduced from 8 GHz to 9.3 GHz (S₁₁ < -10 dB) for antenna arrays. The capabilities of the antenna (in envelope correlation coefficient = 0.018, voltage standing wave ratio = 1.2892, and diversity gain = 20 dB) have been confirmed in a center frequency of 8.97 GHz. An examination of TFSS antennas shows that the side lobes in both the E-plane and the H-plane descends alongside an increasingly broad radiation pattern. The above results demonstrate that the proposed design is highly efficient in MIMO antenna applications.

In this paper, we experimentally demonstrate the performance of a multi-beam antenna based on inductor-capacitor (L-C) transmission line networks. The lumped element parameters of the antenna are derived according to the mapping relations between the Maxwell's equations and L-C network equations. The simulation results are in good agreement with the measurement ones, and the antenna performs well at a wide bandwidth with high directivity. The antenna has potential applications in future communication systems.

Wide axial ratio bandwidth is imparted by placing rigorously designed radial slits on an asymmetrically fed circular radiating patch antenna with parallel bilateral truncations. A partial ground plane with beveling on both the upper corners and a double stepped notch embedded on it makes the antenna suitable for ultra-wideband and X-band applications. The antenna exhibits a −10 dB impedance bandwidth of 8.6 GHz from 3.4 GHz to 12 GHz (111.6%) and a 3 dB axial ratio bandwidth of 8.7 GHz from 3.3 GHz to 12 GHz (113.7%) thereby contributing an effective operating bandwidth of 8.6 GHz (111.6%). The prototype manifests an exceptional far-field radiation pattern and fair gain throughout the passband.

In this study, the physical relationship between the shape parameter v of the K-distribution and the spatial correlation of a sea clutter signal received with a radar is demonstrated through simulation results. The spikiness of the sea clutter is well modeled by the shape parameter v of the K-distribution. According to a well-known empirical formula, the shape parameter v changes with the radar resolution based on a constant power-law relation. However, as with most empirical findings, this finding is valid only for the environmental conditions under which the formula was developed. In other words, the existing power-law models for the shape parameter of the K-distribution for sea clutter do not consider the relative ratio of the cross-range resolution R_c to the spatial decorrelation length R_dec of the sea surface. Our study investigates this relation using statistical simulations based on the principle of superposition for backscattered signals that represent sea clutter within a resolved area on the sea surface. This study shows that the constant factor α in the power-law relation must be modified to a function of the ratio R_c/R_dec. The findings of this study will be useful for the evaluation of detection performance in designing radar systems operating in the maritime environment.

According to theory, once certain conditions are fulfilled, current and voltage pulses propagate along ideal transmission lines with the speed of light. One can reach such a conclusion only when the conductors are assumed to be perfectly conducting, which cannot be realized in practice. A wave can only propagate along a transmission line with the speed of light if no energy has to be spent in establishing the current in the conductor. However, in establishing a current in a transmission line, energy has to be supplied to the electrons to set them in motion since they have a mass. The energy transfer to the electrons manifests itself in the form of an inductance which is called the kinetic inductance. The effect of the kinetic inductance has to be taken into account in signal propagation along high carrier mobility conductors including super conductors. In the case of transmission lines, the kinetic inductance leads to a change in the characteristic impedance and a reduction in the speed of propagation of waves along the transmission line. The goal of this paper is to show that the kinetic inductance will set an upper bound to the speed of propagation of waves along transmission lines, which is smaller than the speed of light.

In this paper we present an analytical method, employable with commercial full-wave electromagnetic CADs, which allows full-wave simulations of electromagnetically (EM) large structures, in terms of wavelength, such as linear accelerator cavities (LINACs) and a very accurate estimation of their operating frequency. The proposed technique is based on the exploitation of rotational symmetry through the definition of equivalent axially-symmetric volumes which replaces the non axially-symmetric ones inside the structure being analyzed. After a theoretical study, we show the successful application of the method in the real case study of a Drift Tube Linac (DTL) cell.

In this paper, a switchable beam and super-directive Electrically Small Antenna (ESA) dipole deployed at an IoT network gateway at 868 MHz is presented. It consists of one fed dipole and one loaded parasitic dipole. The nature and value of the load are obtained using the Uzkov equations, allowing determining current weighting coefficients in the case of two separately fed antennas, in order to maximize the gain and the directivity in a given direction. Reconfigurability in two directions is achieved using a pair of anti-parallel PIN diodes to steer the beam to the desired direction. The array final dimensions are 109 × 43 mm² (0.3λ × 0.1λ) generating a high directivity of 6.8 dBi in simulation and 6.7 dBi in measurement at 868 MHz for each beam in the azimuth plane.

In this paper, a broadband reader antenna is designed and manufactured for wearable ankle strap applications. The frequency range covered for S₁₁ < -10 dB is from 850 MHz to 1650 MHz with dipole like radiation pattern in free space. The proposed broadband antenna is manufactured with a semi-flex (Taconic RF-35) and flexible (Kapton) substrates. A good agreement between simulations and measurements has been achieved. Prototypes performances have been tested by measuring the reading distance. The maximum reading distance obtained is about 1.46 m at 865 MHz with an output power of the transmitter (P_TX) of 25 dBm. Results of functional RFID test show that the proposed antenna can be used as an RFID reader antenna when it is placed on the ankle of the human body.