In this paper, a novel high-order triple-mode half-mode bandpass filter using a single perturbed substrate integrated waveguide (SIW) cavity and a dual-band diplexer are presented. Circular shape metal via-holes are added in the middle of a square SIW cavity as perturbation. The perturbed TE101, TE102 and TE201 resonant modes of the SIW cubic cavity are used to design the proposed filters, which can be shifted to the desired frequency by adjusting the position and size of via-holes. The proposed method reduces the size of the filter, and the measured results indicate that the bandwidth is higher than previous literatures. The dual-band diplexer with a half-mode SIW (HMSIW) structure can be easily implemented based on the proposed BPF through a T-junction, which decreases the number of resonating elements. A triple-mode half-mode filter using a single perturbed SIW cavity with center frequency of 7.43 GHz is obtained. The designed filter and dual-band diplexer are fabricated and measured to validate the present approach.

In this work, computer-aided impedance analysis and genetic-based synthesis of a multiwall carbon nanotube impedance matching section (MWCNTIMS) are proposed. Transmission line model (TLM) of a multiwall carbon nanotube is used for the computer-aided impedance analysis. Continuous parameter genetic algorithm (CPGA) is used for the genetic-based synthesis. A simple, fast and effective impedance analysis and synthesis approach for an MWCNTIMS is presented. The results of the analysis and synthesis for different examples of MWCNTIMS are given and discussed in detail. The results show that the effect of variation of the distance from the ground plane of the outer shell is very small on the values of input resistance and input reactance. The values of input resistance and input reactance decrease while the value of inner radius or the total number of shells increases. Since the diameter increases with the increasing value of inner radius and the total number of shells, the values of input resistance and input reactance decrease with increasing diameter. While the value of nanotube length increases the values of input resistance and input reactance increase.

This paper highlights the effect of millimeter wave (MMW) radiation on biological tissue for prolonged exposure to record thermal effects. The novel method described in this article isthe exposure of millimeter wave on the tissues and study the heat effects resulting from radiation. To simulate this, a setup to uniformly irradiate a tissue of about 2.2 mm thickness is described, and 3D visualization of MMW propagation is modeled using COMSOL Multiphysics radio frequency module at frequencies around 30 GHz. Heat generation and consequent temperature rise in the three layer tissue structure is followed by analysis of temperature variation due to radiation absorption.

This paper presents a novel quintuple-mode wideband lter based on a circular Substrate Integrated Waveguide (SIW) cavity. To implement this filter, a pair of two metallic perturbation vias loaded around the diameter resonator line is used. An Elliptic Dielectric Resonator (EDR) was introduced in the middle of the cavity to shift certain resonant modes and restrain the higher-order modes. The optimal dimensions and dielectric permittivity of the EDR are investigated. A single SIW resonator filter has been designed, manufactured, and measured as an experimental example to verify the proposed design. Simulation and measurement results agree with 51.7% of fractional bandwidth at 10.1 GHz central frequency, with one transmission zero (TZ) at the lower frequency side and four TZs at the upper side.

In this article, a design of two low-profile multiple-input-multiple-output (MIMO) antenna arrays based on left-handed metamaterial (LHM) structures is proposed for multiband wireless applications. The single-element antenna is a monopole antenna fed by a microstrip transmission-line loaded with a single LHM unit cell. The LHM unit cell structure consists of a right-angled bend interdigital capacitor and dual symmetrical right-angled bend shorted stub inductors. The loaded monopole antenna was previously designed to operate in the left-handed (LH) frequency region at three negative-order resconance modes (i.e. 1.39, 1.88, and 2.35 GHz). Herein, to increase the designed antenna performance in wireless communication systems, two- and four-element MIMO antenna arrays having compact sizes with overall dimensions of 21 × 35 mm² and 35 × 35 mm², respectively, are realized. A close uniform edge-to-edge separation between antenna elements of each configuration equals only 2 mm (0.0093λ₀ at 1.39 GHz), and port isolation less than -18 dB over the entire operating bands is obtained without using extra isolation structures. Envelope correlation coefficient is evaluated, showing good field isolation. The performance of the assembled MIMO antenna arrays is verified numerically and experimentally. The given attributes make the proposed antenna arrays a suitable candidate for multiband MIMO applications.

In order to evaluate the electromagnetic environment of the 750 kV four-circuit transmission lines accurately, and design the optimal tower type and phase sequence of the four-circuit lines, the finite element method is used to analyze the distribution characteristics of power frequency electromagnetic field under the line. The excitation function method and the empirical formula method are used to calculate the radio interference and audible noise distribution under the line respectively. Electromagnetic environment parameters of various phase sequences of two tower types are analyzed to determine the optimal phase sequence of 750 kV four-circuit transmission lines. The results show that the electromagnetic environment of transmission lines is strongly influenced by different tower types and phase sequences. The magnetic flux density and radio interference of the various phase sequences of the two tower types reach the limit of code, and 43.52% and 64.81% phase sequences reach the audible noise limit conditions respectively. Electric field intensity is a main influence factor of electromagnetic environment. The optimal phase sequence layouts of the two tower types are 1661 and 1522, and the electric field intensities are 9.66 kV/m and 9.12 kV/m. The calculation method and results can be used for reference in practical engineering.

This study proposes the idea of a thermotherapy device for the treatment of human knee joint disorders by the thermal effect of microwave radiation. The device is composed of a circular array of dipole antennas operating at 2.45 GHz. A high resolution three dimensional geometric, electric, and thermal model for a human right knee is constructed. Electromagnetic simulations are performed to calculate the specific absorption rate (SAR) distribution within the tissues of the human knee using the finite difference time domain (FDTD) method. The SAR distributions are calculated for four and eight elements circular arrays. The FDTD is applied to calculate the rise in temperature within different tissues of the human knee due to the exposure to different levels of heating microwave power. The effect of the tissue thermoregulatory response on the temperature rise is investigated for each individual tissue type. Moreover, the dependence of the induced steady state rises in tissue temperatures on the absorbed SAR is studied in the case of the SAR at a point in the muscle tissue (local SAR), and the SAR averaged over 1 g (SAR_{1 g}) and over 10 g (SAR_{10 g}). The rise in temperature distribution due to radiation from the circular array of dipoles is calculated at different cross sections.

In this paper, a compact printed monopole antenna with periodic H-shaped slots for WLAN application is proposed, designed and fabricated with standard flexible printed circuit board process. By cutting four H-shaped slots in the radiation patch of the printed monopole antenna, the resonant frequency of the monopole antenna can be reduced; therefore, a compact antenna is realized. The radiator size of the antenna is 0.07λ_g×0.19λ_g, which is much smaller than that of a traditional printed monopole antenna. By utilizing electromagnetic simulation software CST, the antenna is simulated and optimized. Moreover, the performance of the proposed antenna is discussed taking into consideration the possible effects of deformations due to the flexibility of the substrate. A sample antenna is manufactured and measured to prove the predicted performance of our proposed antenna. The measured results agree well with the simulations. Hence, the proposed method in this paper is a promising candidate for the design of compact antennas.

The problem of evaluating the shielding effectiveness of a thin metallic circular disk with finite conductivity against an axially symmetric vertical magnetic dipole is addressed. First, the thin metallic disk is modeled through an appropriate boundary condition, and then, as for the perfectly conducting counterpart, the problem is reduced to a set of dual integral equations which are solved in an exact form through the application of the Galerkin method in the Hankel transform domain. A second-kind Fredholm infinite matrix-operator equation is obtained by selecting a suitable set of basis functions. A low-frequency solution is finally extracted in a closed form. Through a comparison with results obtained from a full-wave commercial software, it is shown that such a simple approximate solution is accurate up to the frequency where the surface-impedance model of the thin disk is valid.

For microwave computational imaging (MCI), the reduction of measurement matrix's coherences permits better reconstruction performance. Therefore, frequency diverse apertures (FDAs) have become a major option of antennas for MCI due to their frequency-varying radiation patterns. The frequency diversity in the patterns reduces coherences; however, the losses in practical materials and the finite sizes of apertures impose upper limits on frequency diversity. For further coherence reduction, the polarization diversity (PD) of aperture elements is as a new approach introduced in this paper. We present an electromagnetic formulation of scattering aperture elements' PD. In the formulation, the PD brings an additional degree of freedom in the generation of the measurement matrix, given the apertures being illuminated with varying polarizations. This new degree of freedom enables a potential of reducing the coherences. Two complementary electric-field-coupled (cELC) scattering apertures, which differentiate in the polarizations of elements, are fabricated for validation. A set of comparisons yielded by the near-field scanning data of these apertures shows that the PD effectively reduces coherences and improves reconstruction performance.

This paper details the work of the LAPLACE Electromagnetism Research Group to develop an original measuring setup dedicated to the detection of an EMDrive like force. Recent peer-reviewed experimental results [1, 2] were obtained using similar setups based on a torsion pendulum combined with an optical sensor. These very accurate measurement setups are appropriate for measuring such an extremely weak force. They also appear costly, which may discourage other research teams from working on this topic. Our main goal is then to provide an alternative configuration, based on a commercial precision balance, in order to build a measuring setup more affordable, handy, and accurate enough to measure an EMDrive like force. Our experimental system is capable of feeding a truncated cone shaped 2.45 GHz resonant cavity with power up to 140 W. To calibrate the EMDrive force and avoid false positive thrusts, an original setup has been proposed and evaluated. It allows us to really consider that the parasitic effects do not alter the hypothetical force measurement by the use of force direction switching during the measurement.

High resolution wide swath (HRWS) imaging and ground moving target indication (GMTI) are similar in terms of system architecture and are based on a multi-channel system in the azimuth direction. However, in order to achieve their respective performance requirements, the HRWS SAR requires a lower pulse repetition frequency (PRF), and the GMTI system requires a relatively higher PRF. In consideration of this contradiction, the parameters of the moving target are introduced into the reconstructed filtering vector constructed by each signal reconstruction algorithm, so that the HRWS imaging of the moving target can be realized. In this paper, considering the characteristics of the Relax algorithm, a motion-adapted signal reconstruction algorithm is proposed, and the iterative process of the new method is described in detail. This method can perform GMTI on moving targets with a lower PRF without changing the PRF of the HRWS SAR system. By the simulation of point target echo, and comparing with the traditional signal reconstruction algorithms, the reliability and effectiveness of the new method are verified.

A single-layer substrate integrated waveguide (SIW) is developed to design a dual-band band-pass filter (BPF) operating below the cut-off frequency of the SIW, known as evanescent-mode excitation. Gap-coupled excitation is used to demonstrate multiple transmission poles (TPs) and transmission zeros (TZs) below the cut-off frequency of the SIW. The structure is reported to realize two independent evanescent-mode poles on a single-layer SIW which reduces the size and complexity of the structure compared to those of the recent multi-layer evanescent-mode structures. Lumped-element equivalent circuit is employed to describe the EM behavior of the structure for TZs and TPs realization. A compact single-layer dual-band SIW filter is fabricated based on the proposed structure. A good agreement is reported between the measured and simulated performances.

Matrix completion (MC) theory has attracted much attention for its capability of recovering a low-rank matrix through its partial entries. In this paper, we investigate the novel suppression methods of wind turbine clutter (WTC) and introduce the application of MC in WTC suppression for weather radar. First, the vectors of weather signals contaminated by WTC are sequentially constructed into a low-rank snapshot matrix satisfying random undersampling, and then, the weather data can be accurately recovered by minimizing the nuclear norm in the inexact augmented Lagrangian multiplier (IALM) method. The proposed algorithm can effectively suppress not only the wind turbine clutter but also the noise, greatly improving the signal-to-noise ratio of the echo. An experimental test validates the effectiveness of the proposed MC algorithm, and its performance is superior to the widely-used multiquadric interpolation algorithm with potential engineering applications.

In this paper, the double-walled carbon nanotube composite material (DWCNTs-composite) and bundle of DWCNT-composite material (CB-DWCNTs) for antenna applications at terahertz frequency range are presented and investigated. The mathematical modeling and analysis of DWCNTs-composite material is presented for the purpose of modelling and simulation approach. The bundle of DWCNTs-composite material is constructed and designed, based on this modeling approach. The DWCNT-composite material consists of double-walled carbon nanotube coated by a thin jacket of another different material. The dependency of the electrical conductivity of B-DWCNTs-composite on the different parameters is presented and investigated. The performance evaluation of B-DWCNTs-composite and CB-DWCNTs materials are presented based on their electromagnetic properties. For this purpose, the dipole antennas of these composite materials are designed and implemented using CST (MWS), where the cross sections of B-DWCNTs-composite and CB-DWCNT materials are circular geometry. Furthermore, comparative studies are performed to show the dependency of size and frequency of the DWCNT-composite material. The results obtained from the DWCNTs-composite and CB-DWCNTs dipole antennas are presented based on S₁₁ parameters, resonant frequency, gain, bandwidth, and efficiency.

In order to reduce the underwater electric field generated by corrosion of ship, a boundary element method (BEM) combined with nonlinear polarization curve was employed to investigate the influence of output current of compensate anode in an electric field protection system on underwater electric field. Moreover, the BEM model was verified by physical scale modeling (PSM). The distribution characteristic of electric field and the variation trend of electric field with compensate current obtained by simulation are consistent with the experimental results. Moreover, the errors of peak-to-peak value of electric field obtained by experiment and simulation are within 20%. Compared with 0 mA compensation current, the peak-to-peak values of X component, Y component, Z component, and modulus are reduced by 52%, 70%, 72%, and 62% respectively when compensation current is 40 mA. The phenomenon of over-compensation will occur if compensation current is greater than 40 mA.

A frequency continuous reconfigurable microstrip patch antenna with operation band covering S-band and C-band is introduced. The antenna consists of a central rectangular patch and four parasitic patches with a symmetrical structure, connected by four varactor diodes in the middle position of the edge of each patch. With help of HFSS microwave studio simulation, results have shown that, by altering the bias voltage on varactor diodes, the operated frequencies vary continuously within a wide range from 3.29 to 4.01 GHz and 5.35 to 7.00 GHz, which cover S-band and C-band. Further measurement, which verifies the simulation by reasonable agreement, has been carried out. Besides, this frequency reconfigurable antenna maintains broadside radiation and stable radiation pattern. Specifically, the gain is basically maintained at around 4.5 dBi with the working frequency increasing from 3.60 to 7.00 GHz. Compared with other frequency-reconfigurable antennas available in previous literature, the proposed antenna has advantages of a wide frequency tuning range, high frequency selectivity, simple and stable structure, low cost, and miniaturization, which make it a promising candidate as cognitive radio and future wireless communication systems.

Refractive index (RI) measurements find extensive use in biochemical sensing field. However, currently available RI sensors exhibit excessive temperature crosstalk and have low sensitivity in the low RI range. To solve this, a high-sensitivity and temperature-insensitive refractometer based on a tapered no-core-hollow-core fiber (TNHF) structure is proposed for low-range RI measurement. The TNHF comprises two Mach-Zehnder interferometers that are introduced within the tapered no-core fiber and hollow-core fiber, thereby establishing a composite interference. The results of an experimental evaluation demonstrate that maximum sensitivities of 482.74 nm/RIU within an RI range of 1.335~1.3462 can be achieved, which is greater than that achieved using a traditional modal interferometer structure. Significantly, the refractometer exhibits ultra-low temperature sensitivities of 0.062 dB/°C and 6.5 pm/°C, which can alleviate the temperature crosstalk. The refractometer can be realistically applied in many fields requiring high precision RI measurement due to its advantages of low cost, ease of manufacture, high sensitivity, and temperature insensitivity.

In this paper we are concerned with a microwave imaging problem for a non-magnetic two-layered background medium, where objects are buried in the lower half-space, and the scattered field is collected in the upper one according to a multi-monostatic configuration. In particular, we are interested in estimating the achievable transverse resolution. As well known, range resolution mainly depends on the working frequency band whereas transverse resolution depends on the geometrical parameters of the configuration and is usually computed in correspondence to the highest (or even the average) adopted frequency. Determining transverse resolution is much more difficult, and closed form estimations have been actually found only for the case of unbounded observation domain. However, in real scattering scenarios measurements have to be necessarily collected under an aspect limited setup. Therefore, in order to fill such a theoretical gap, here the focus is on the estimation of transverse resolution for bounded observation domains. To this end, we consider a single-frequency 2D scalar prototype configuration where the buried scattering object domain is represented by a strip parallel to the half-space interface. More in detail, we succeed in finding an analytical estimation of the transverse resolution which highlights the role of the configuration parameters as well as the dielectric permittivity of the lower half-space.

Partitioning large arrays into subarrays can reduce system cost. In this paper, we use identical subarrays to partition a large rectangular aperture. The periodical structure in a large array is broken down by changing the orientations of the subarrays. In each subarray, the element positions are optimized by particle swarm optimization (PSO) to obtain low sidelobe levels. In order to reduce the coupling among the elements, the minimum element distance measured in Euclidean space is restricted in the procedure of optimization. And a modified PSO is proposed to solve the optimization problem with this constraint. Better results can be obtained than the element distance constraint measured in Chebyshev space. This simple but efficient subarray design method is demonstrated through several numerical simulations.