A metamaterial sensor that can be applied to detect water content in emulsified oil is proposed, which is reusable in experiment and nondestructive to the sample. Electric field of the original absorber is researched to guide the design of microfluidic. Also, its equivalent circuit model is proposed to validate its ability as a sensor. The calculated sensitivity of the sensor is 339 MHz/ε'_r in the range of 11.26 GHz to 10.044 GHz, indicating its potential for detecting the emulsified oil. The experimental results reveal the reliable process of detection and the linear relationship between frequency shift and water content. This work provides a fast and convenient solution to check the quality of lubricant oil to some extent, which is relatively valuable to modern machinery.

A novel high-swing Class-C VCO with an amplitude feedback loop is presented. The amplitude feedback loop is used to ensure the start-up of the VCO which also makes the proposed VCO always have an optimal phase noise against the PVT variations automatically. The proposed circuit is implemented in a 65 nm CMOS process. The VCO has exhibited a measured phase noise of -128.6 dBc/Hz at 1 MHz offset from the 1.52 GHz carrier frequency with a 1.4 mW power consumption. The variation of measured phase noise at 1 MHz offset is less than 2.3% while temperature changes from -40˚C to 100˚C.

As a kind of complicated targets, the nonrigid vibration of aircraft, their attitude change, and the rotation of their ro-tating parts will induce complicated nonlinear modulation on their echoes from low-resolution radars. These kinds of modulation play an important role in target classification. However, due to the influence of clutter and noise, these kinds of modulation have the characteristics of fuzziness and randomness. As a quantitative to qualitative conversion model based on traditional probability statis-tics theory and fuzzy theory, backward cloud model can be used to model and analyze the modulation characteristics of the conven-tional low-resolution radar echoes from aircraft targets. By considering the sample values of the echo data as individual cloud drop-lets, the paper extracts the cloud digital features such as the expectation, entropy and hyper-entropy of each group of echo data, and investigates the application of these features in aircraft target classification based on support vector machine. The research results show that the backward cloud model can describe the aircraft echoes well, and the echo cloud digital features can be effectively used for the classification and identification of aircraft targets.

The hybrid magnetic bearings (HMB) stabilize suspension in equilibrium position by providing bias flux through permanent magnets. The loss generated during operation causes the temperature of the HMB to rise, which affects the stability of the magnetic bearing. In this paper, the loss and temperature of HMB are analyzed by finite element analysis software. The results show that the loss of HMB is mainly distributed in the rotor part, and the temperature of the rotor part is obviously higher than that of the stator part. The relationship between the structural parameters such as air gap length and pole width, and the loss of HMB is obtained by finite element analysis. According to the analysis results, the structural parameters are optimized by GAPSO. After optimization, the loss and temperature of HMB are significantly reduced.

In this paper, a compact planar mono-band multiple input multiple output (MIMO) antenna with four monopole elements is presented for X-band satellite applications (7.2-7.8 GHz). The MIMO antenna resonates at 7.5 GHz, with high isolation (more than 26 dB) between its ports. It consists of a four closely arranged symmetric monopole antennas with edge-to-edge distance of 7.2 mm (0.18λ). In the top face, different forms are loaded at the rectangular patch. U slot defected ground structure (DGS) has embedded in the ground plane. The prototype of the proposed MIMO antenna is simulated, fabricated and measured to examine the performance of this antenna in terms of S parameters, radiation patterns, the envelope of correlation coefficient (ECC) and the diversity gain (DG). As a result, the presented antenna has a high isolation (S₁₂ < -26 dB) at 7.5 GHz with impedance bandwidths is about 430 MHz (7.28 GHz-7.71 GHz), which covers the X-band applications. The diversity gain is about 10, and the envelope correlation coefficient of antenna is less than 0.02 which means that the antenna has high performance at the resonance frequency.

In recent years, FMCW CSAR (frequency modulation continue wave circular synthetic aperture radar) is more and more widely used in military reconnaissance and sea surface target recognition. However, due to the influence of external factors, it cannot move in an ideal uniform circular trajectory, resulting in low imaging resolution. In this paper, the problem of motion errors caused by nonuniform circular motion is analyzed, and the phenomenon of range unit broadening and sidelobe increase caused by nonuniform circular motion errors is simulated. The echo model is characterized by error parameters. Based on the compressed sensing imaging algorithm, motion error parameters are estimated by parametric sparse representation. The least squares method and gradient descent method are applied to estimate motion error parameters. Simulations are conducted to show that both of the methods can reach the goal that the motion compensation is realized. The result of simulations and measurement data demonstrate that the algorithm can correct nonuniform circular motion errors better and further improve the imaging resolution.

Magnetoacoustic tomography with magnetic induction (MAT-MI) is a multiphysics imaging technique that combines electrical impedance imaging with ultrasound imaging. In order to study the influence of parameters on the source of MAT-MI , such as radius and permeability of magnetic nanoparticle clusters, the paper is divided into the following stages. Firstly, this paper analyzes the electromagnetic and acoustic properties of MAT-MI after adding magnetic nanoparticles. Secondly, to determine the suitable simulation conditions, a two-dimensional model is constructed. Thirdly, use the finite element method to solve physical processes of electromagnetic field and acoustic field under conditions of different magnetic nanoparticle clusters' radii and permeabilities, then obtain the magnetic flux density image. Consequently, make the qualitative and quantitative analysis according to the theory and simulation results. The results show that magnetic nanoparticle clusters interact with each other and distort the magnetic field to different degrees; its radius increases with the degree of flux density distortion around it, so does its permeability and magnetoacoustic signal intensity. The research results can play a guiding role in the parameter selection of magnetic nanoparticle clusters in practical applications to a certain extent.

The vibration and noise problems caused by the radial electromagnetic force of the Bearingless Switched Reluctance Motor (BSRM) severely restrict its wide application. The purpose of this paper is to research the electromagnetic vibration and noise of Single-Winding Bearingless Switched Reluctance Machine (SWBSRM). Firstly, the radial electromagnetic force, which is the excitation source of electromagnetic vibration, is analyzed. Secondly, the three-dimensional (3D) model of stator structure is established by ANSYS finite element analysis (FEA) software, and its modal analysis is carried out to obtain its modal shape and corresponding modal frequency, which provides a reference and basis for researching the mechanical vibration of the SWBSRM. Finally, the harmonic response field analysis and sound field analysis model are established, and the vibration and noise of the motor under radial electromagnetic force are analyzed by using the magnetic-solid weak coupling analysis method.

In this article, a solution of the plane wave diffraction problem by two axisymmetric strips with different dimensions is considered. Fractional boundary conditions are required on the surface of eachstrip. Several cases of strip's dimension, configurations, and fractional orders are considered, and numerical results are obtained. The near electric field distribution, Total Radar Cross Section frequency characteristics, and the Poynting vector distribution in the vicinity of these strips are calculated and illustrated. For the fractional order 0.5, the solution is found analytically.

As seen from this article, a novel hepta-band metal-rimmed antenna is proposed. The volume of the proposed antenna is small, and no lumped elements are used. The proposed metal-rimmed antenna is competitive for modern mobile application. The illustrated antenna could be divided into several parts: main ground plane, metal rim, two L-shaped ground slots sharing one open end, an L-shaped branch extended from right edge of main ground, a microstrip feedline located at the top surface of the substrate, a meandered branch located at the back side of the substrate, and a 2mm slot located at the middle of the metal rim's top edge. For lower band, GSM850 and GSM 900 are provided by two bezel loop modes generated through capacitive coupling of feedline. For upper band, DCS, PCS, UMTS, LTE2300, and LTE2500 are covered by multiple modes of two L-shaped slots, a meandered strip and feedline. With the proposed structure, the volume of the proposed antenna could be further reduced. All the mentioned operating bands are achieved in a small area of 620 mm² on a 115x70 mm² system board. Note that the proposed antenna has achieved such a small volume on a relatively small system board without any lumped elements. The rest of this paper will describe the antenna configuration, the analysis of working principle, parametric analysis, and the experimental results are also given and discussed.

This paper presents a new type of vertically stacked substrate integrated waveguide (SIW) filtering antenna. It is composed of an SIW bandpass filtering circuit and an antipodal linearly tapered slot antenna (ALTSA). The filtering circuit consists of two vertically stacked SIW cavity resonators which are coupled with each other by etching slot on the common metal layer. By introducing electric and magnetic mixed coupling structures, close-to-passband transmission zeros can be realized and flexibly adjustable. Due to the partially vertically stacked structure, the proposed filtering antenna also shows a compact physical size. For validation, two vertically stacked SIW filtering antennas operating at 30 GHz with transmission zero at the upper or lower side of the passband are designed, fabricated, and measured. Good agreement is observed between the measured and simulated results.

In this paper, an integrated switchable and tunable bandpass filter is designed, simulated, and fabricated. This integrated bandpass filter is able to switch as well as tune in the ultra-wideband (UWB) as well as 2.4 GHz band. At first, a UWB bandpass filter is developed which consists of two bent shorted quarter-wavelength stubs and a connecting half-wavelength stub. Subsequently, a 2.4 GHz bandpass filter is realized by connecting another half-wavelength stub on top of the UWB filter. RF pin-diodes are used for switching the bands between UWB and 2.4 GHz bandpass filter. The switchable bandpass filter converts into a tunable filter by changing the inductance or the length of shorted stubs through the pin diodes. A detailed parametric analysis is done for calculating different stubs lengths of the UWB as well 2.4 GHz bandpass filter. The simulation results show a high rejection level of >40 dB at the lower frequency and a low insertion loss of 0.8 dB in the passband for UWB filter. For 2.4 GHz bandpass filter, the simulation results show an insertion loss of 0.42 dB and a 3 dB bandwidth of 796 MHz. The filter is fabricated on a Rogers 4003 substrate, and the measurement results of the switchable filter in the UWB band show an insertion loss of 2.1 dB and a 3 dB bandwidth of 7 GHz. In the case of 2.4 GHz bandpass filter, the insertion loss is 0.78 dB.

In this paper, a dual-polarisation shared-aperture duplex antenna is presented for satellite communications at the standard microwave Ku-band, based on the integrated filtering-antenna concept and co-design approach. The design relies on the use of resonators coupled to the radiating dual-band dual-polarisation antenna. The resonant patch antenna forms one pole of each channel filter, resulting in a third-order filter in the Rx channel and a second-order filter in the Tx channel. The Rx and Tx ports of the antenna take in horizontal and vertical linear polarisations, respectively. The integrated duplexer helps to increase the isolation between the ports and the selectivity of each channel. The integration between the filter and the antenna is achieved by electromagnetic coupling, without the need of external matching circuits. Thus it attains a compact footprint. The operation frequencies of the demonstrated duplexantenna are from 11 to 12.5 GHz (12.8%) for the downlink to the Rx port, and from 13 to 14.4 GHz (10.2%) for the uplink at the Tx port. High port-to-port isolation of over 40 dB is realized to reduce channel interference. Flat in-band average gains are achieved to be 8.3 and 8.6 dBi, for the low- and high-bands, respectively.

In this paper we revisit the condiagonalization of the Sinclair backscattering matrix, to overcome the Huynen decomposition issues, so as to correctly extract scatterer polarimetric properties. The correct extraction of scatterer polarimetric properties will lead to the correct classification of the scatterer predominant scattering mechanism. Huynen used the congruence transformation by a special unitary matrix to diagonalize the Sinclair matrix into a real and nonnegative diagonal matrix. He also expressed the special unitary matrix in terms of the polarization ellipse parameters and associated them with the scatterer orientation, asymmetry, and skip angle. Unfortunately, this association was found misleading. As a result, it makes the scatterer classification ambiguous, for it is based on the scatterer skip angle and the diagonal matrix. To overcome these ambiguities, we perform the diagonalization procedure founded on the consimilarity transformation by a special unitary matrix, as proposed by Lüneberg. In order to correctly extract the scatterer asymmetry degree and orientation, we express the special unitary matrix in terms of an asymmetry operation and a pure rotation operation. Moreover, we integrate the scatterer skip angle in the diagonal matrix of the consimilarity transformation by having it complex, leading to an unequivocal scatterer characterization.

The self-interference problem of linear frequency modulated continuous wave (LFMCW) radar is a known issue that limits the radar's detection range. Analog adaptive interference cancellation (AIC) technique is effective to mitigate the self-interference problem. However, we find that the phase difference between the error signal and reference signal paths may significantly deteriorate the stability of the AIC system. Therefore, in this paper, we analyze the effect of phase difference on system stability through the mathematical modeling and simulation. We find that the system is stable when the phase difference is between -90 and 90 degrees, and diverges when it is between 90 and 270 degrees. Therefore, to avoid system instability, we propose to add a phase shifter in the reference signal path to compensate the phase difference. The experiment results show that compared with the traditional delay-based compensation method, our phase compensation based method can increase interference cancellation ratio (ICR) by 15 dB for a single-antenna system and 12 dB for a dual-antenna system.

This paper studies the nonlinear effects induced by a TVS limiter on an entire system illuminated by a high power electromagnetic (HPEM) pulse through a simple model. The relations between the load responses and the incident electric field under different conditions are obtained numerically. The results show that the TVS limiter not only protects the circuit which it is intended to but also may increase the response of the other end which is connected to the circuit by a transmission line. The nonlinear effect of the TVS limiter on the other end is dependent on the incident direction of the external HPEM pulse, TVS location, line length, electric field level, and shielding cavity. When the effective coupling length (ECL) of a load is longer than the line length, or its coupling with external HPEM is much weaker than the other end, its response will be affected by the other end connected with a TVS limiter and will become nonlinear. The addition of a shielding cavity will increase the effect because the cavity will increase the duration of the field which results in a larger ECL. Due to the nonlinear effect of the TVS limiter, special attentions, such as considering different incident directions as many as possible in the real testing and setting more margins, should be paid in the protection design.

In this paper, a novel broadband high-isolation dual-polarized antenna is proposed for 5G application. The proposed antenna consists of L-shaped elements, Γ-shaped feeding strips, and a box-shaped reflector. The use of simple L-shaped antenna elements not only simplifies the manufacturing process, but also greatly increases the isolation between the two ports. Stable gain and radiation patterns are achieved by using box-shaped reflectors. Results show that an impedance bandwidth of 50.6% for S₁₁ < -10 dB & S₂₂ < -10 dB from 3.1 to 5.2 GHz was achieved, and port to port isolation was higher than 45 dB within the bandwidth. The gains of the measured antenna were 8.7±1.1 dBi in the whole operating frequency band. In addition, stable radiation pattern with low cross polarization, low back radiation was achieved.

Direction of arrival estimation (DOA) is critical in antenna design for emphasizing the desired signal and minimizing interference. The scarcity of radio spectrum has fuelled the migration of communication networks to higher frequencies. This has resulted in radio propagation challenges due to the adverse environmental elements otherwise unexperienced at lower frequencies. In rainfall-impacted environments, DOA estimation is greatly affected by signal attenuation and scattering at the higher frequencies. Therefore, new DOA algorithms cognisant of these factors need to be developed and the performance of the existing algorithms quantified. This work investigates the performance of the Conventional Minimum Variance Distortion-less Look (MVDL), Subspace DOA Estimation Methods of Multiple Signal Classification (MUSIC) and the developed estimation algorithm on a weather impacted wireless channel, Advanced-MUSIC (A-MUSIC). The results show performance degradation in a rainfall impacted communication network with the developed algorithm showing better performance degradation.

In this paper, a compact triangular defected ground plane monopole antenna with 5G, WLAN, and a downlink/uplink of X-band notched characteristic for UWB applications is presented. The initial design consists of a CPW rectangle-shaped patch with a triangular, slotted ground plane to obtain ultra-wideband feature. The 3.3-3.7 GHz for the 5G band is eliminated by inserting dual symmetrical T-shaped slots at the upper edge of the ground plane. Further, a metamaterial as dual symmetrical single split ring resonator slits is etched at the bottom edge of the ground plane to suppress electromagnetic interference at IEEE upper WLAN band from 5.72 to 5.84 GHz. To restrict the interferences with the existing downlik and uplink for X-band signals from 7.1 to 8.39 GHz, we load a single I-slot to the radiator patch. The small size of the presented triple band eliminated antenna makes it a candidate suitable for recent communication systems.

An improved mixed phased/retrodirective array is presented. The phase conjugation technique will be achieved in base band instead of in intermediate frequency (IF) band. Canceling the need to the intermediate frequency stage in the receiver will reduce the complexity and cost of the system. The ability to the entire processing of the tracking array function to be applied using software defined radio (SDR) system is added. The effect of the phase errors at each channel is compensated phased array, and the noise performance of the tracking array is improved. Also an expanded analytical study of the noise performance of the array to include the impact of the phase errors on the array performance is presented. The proposed equivalent one-channel model of the N-channel array provides a clear and efficient way to characterize the noise performance of array receiver systems with any amplitude tapering and also considering the phase errors. The improvement provided by the mixed phased/retrodirective array compared to the traditional phased array is evaluated. The of array size on the tracking array performance in the presence of phase error is discussed. A monopulse tracking array is taken as an example.