The near fields in the proximity of a small ferrite particle with magnetic-dipolar-mode (MDM) oscillations have space and time symmetry breakings. Such MDM-originated fields --- called magnetoelectric (ME) fields --- carry both spin and orbital angular momentums. By virtue of unique topology, ME fields are strongly different from free-space electromagnetic (EM) fields. In this paper, we show that because of chiral topology of ME fields in a near-field region, farfield orbital angular momenta (OAM) can be observed, both numerically and experimentally. In a single-element antenna, we obtain a radiation pattern with an angular squint. We reveal that in far-field microwave radiation a crucial role is played by the ME energy distribution in the near-field region.

Based on space-time duality and through the use of temporal dispersive delay lines, this paper presents a demonstration of temporal cloaking/uncloaking at microwave frequencies. Numerical simulations of pulse generation, continuous wave signal recovery and data recovery are discussed in relation to the proposed system architecture. This paper also suggests a practical means for implementation of real time dual temporal cloaking/uncloaking. Compared to traditional signal processing systems, since the recovered data emerges with a reversed form in time domain before its final decoding, an extra operation named time-reversal is needed to obtain the correct data, which could help protect the significant signals better with the proposed temporal cloaking/uncloaking system. The proposed method and achieved results indicate potential application in secure communications and data multiplexing subject to channel bandwidth requirements.

In this paper we report on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. However, this is not always the case, and a cable with multiple shields may perform similar to or worse than a cable with a single shield. We want to shed more light on these situations, which represent the main focus of this paper.

In this paper, dual-chirped arbitrary microwave waveform has been generated through photonics, incorporated with single dual parallel mach-zehnder modulator (DPMZM) inbuilt mach zehnder interferometer (MZI) structure. We have taken two cases of chirping i.e. linear and nonlinear chirps. A case of linear chirping has been explored previously. However, to the best of the authors' knowledge effect of nonlinear chirping in this paper is evaluated for the first time. Other photonics approaches are also available, such as spectra shaping and wavelength to time mapping. But due to fixed spectral response of spectral shaper, center frequency of linear chirp generated waveform is fixed. To get the large center frequency again we have to use large number of spectral shapers which will increase the system complexity. DPMZM avoids such difficulties. These MZMs are biased at the minimum transmission point to get carrier suppressed modulation. Product modulator (PM) is cascaded to the lower arm of DPMZM. Here by using DPMZM we get two advantages. First we have two complimentarily chirped microwave waveforms and second up conversion of the frequency of microwave carrier. A dual-chirped microwave waveform with centre frequency 6 GHz with bandwidth 200 MHz and 2 GHz is generated. The paper gives specific details about various performance parameters such as input signal frequency and power, output signal parameters viz output frequency, chirp rate, chirp bandwidth, time bandwidth product (TBW), etc. The overall model and its performance parameters are computed through MATLAB simulation.

In this paper, a novel quad-band combination of circularly-polarized microstrip antenna is proposed. This antenna has multi-frequency and quad-polarization with multiple coaxial probes, which cover four bands of the BeiDou navigation system (BDS), meeting different application requirements. By using a stacked structure to achieve feed and using symmetrical slotted method to place the coaxial probes, the multi-frequency antenna is connected together through the middle co-aperture. Meanwhile, the feed position and size are constantly optimized until get the most suitable one, and the necessary perturbation is obtained. We also introduce a broadband stripline 90° bridge. Ultimately, the circularly-polarized and multi-frequency operation is achieved. Furthermore, the novel design enables easy implementation, miniaturization, wide band, which can meet the application requirements and promote the development of the BDS, which can be combined with the Internet of Things technology, applied to life and production.

Electromechanical interaction between slow electromagnetic wave and anisotropic-conducting film is investigated. The physical effects associated with anisotropic-conducting film are revealed by electromagnetic theory and validated by experiment, and they have established the working principles for a class of electromechanical sensors and/or actuators, which have continuously moving part, and are sensitive to the amplitude and the direction of electromagnetic forces or fields and well able to reflect the resonance characteristics. The revealed and validated physical effects may have significance in quite different science and engineering fields and in wide frequency bands from RF to optics.

A main challenge in designing line-start permanent magnet synchronous motors is synchronization analysis and determination. The transient time-step nite element simulations are often required in the design process, which is computationally expensive. An attractive alternative is to use an analytical synchronization model, which is time ecient and thus viable to be included in an optimization procedure. In this paper, two variants of the energy-based analytical synchronization model are proposed. Their viability and performance are compared with those of the existing analytical method and validated by transient nite element simulations. It is shown that the proposed methods have a better resolution and accuracy in determining the synchronization status of line-start permanent magnet motors.

In this paper, three different frequency reconfigurable multiple-input-multiple output (MIMO) antennas are characterized in terms of their channel capacity performance in an indoor environment. Two 2×2 and one 4×4 MIMO antenna configurations are investigated. A complete MIMO system is implemented using software defined radio (SDR) platform. The antenna under test can be used at either transmitter or receiver ends. The channel capacity of the system is evaluated by computing the channel coefficient matrix. The measurements are performed at 2.45 GHz for line of sight (LOS) and non-line of sight (NLOS) scenarios. A comparison of the antennas is performed with an ideal system scenario with totally uncorrelated channels as well as an array of standard monopoles which are half-wavelength apart. The effects of antenna element efficiencies, radiation patterns and spacings on the channel capacity are discussed.

This paper investigates the design of a small antenna on a silicon substrate. The antenna on silicon substrate will be used for integration in a silicon-based GaN TR module. This Co-Planar Waveguide (CPW)-fed antenna has been successfully miniaturized up to λ/4 about 20% reductions by adding a slot to the patch antenna. Promising results are obtained from the antenna simulation and measurement. From the measurement result, the antenna bandwidth is 45% (4.8 GHz-7.5 GHz) with measured gain about 2.5 dBi over frequency range of 5 GHz-7.4 GHz.

An algorithm of solving phase ambiguity of multi-baseline direction finding system based on sparse uniform circular array is proposed in this paper. This sparse uniform circular array whose inter-element spacing is larger than half-wavelength distance suffers from cyclic phase ambiguities, which may cause estimation errors. In order to solve the above phase ambiguities, the corresponding virtual short baselines are acquired by transforming the array element phases that meet with the contraction relationship. The obtained short baselines are used to solve the phase ambiguities according to the virtual baseline and stagger baseline theory. Highly accurate estimates of direction of arrival are herein acquired. Furthermore, the direction of arrival and polarization parameter estimates are automatically matched with no additional processing. The array arrangement problem in high frequency scenario is solved. The estimation accuracy of angle of arrival is improved by means of the phase ambiguity resolution. Simulation results verify the effectiveness of this algorithm.

The parabolic equation (PE) method for estimating propagation characteristics of millimeter wave, which takes into account of attenuation caused by complex meteorological environment, is proposed. The meteorological environment is treated as a mixture composed of hydrometeors and atmospheric gases. Effective permittivity of the mixture is considered in this paper. Based on the effective permittivity, the PE model for estimating propagation attenuation of millimeter wave is developed via modifying the refractive index. Finally, the model is employed to simulate the propagation characteristics of millimeter wave in complex geographical environments of irregular terrain and rough sea surface, and in complex meteorological environments of standard atmosphere, rain and fog.

The high frequency scattering problems of electromagnetic fields scattered from electrically large scatterers are important and challenging. On the calculation of the reflected and diffracted wave fields, the high frequency methods could be classified into the current based method and the ray based method. In this paper, first, we give a review on the progress of the modern high frequency methods for solving the electromagnetic scattering problems. Next, due to the highly oscillatory property of the high frequency electromagnetic scattered fields, we propose the numerical steepest descent path method. Finally, we comprehensively address the high frequency wave physics, including the high frequency critical point contributions, the Keller's cone, the shadow and reflection boundaries and the creeping wave fields.

This paper presents a comprehensive method to analyze negative group delay (NGD) phenomenon at microwave frequency. This method is based on a coupling matrix with finite unloaded quality factor resonators. Unlike conventional NGD circuit topologies that use a lumped resistor R along with bandstop resonators, the proposed topology does not require any R for generating NGD and therefore, provides fully distributed circuit realization. The proposed topology has both source to load and inter-resonator coupling structures. Analytical design equations are provided to obtain predefined NGD with matched input/output ports; the proposed structure therefore does not require any extra matching networks. From analytical analysis, it is also found that the NGD bandwidth as well as magnitude flatness can be controlled by inter-resonator couplings. The proposed design theory is proven through fabrications of NGD circuit at a center frequency of 2.14 GHz. The measurement results are in good agreement with simulations and predicted theoretical results.

In this work, an anisotropic zero index material is designed for use in Vivaldi antennas. The metasurface structures are placed within the aperture of a Vivaldi antenna to improve the directivity and gain of the emitted radiation. The range of operation is in the ultrahigh frequency (UHF) range, between 300 MHz and 3 GHz. Two approaches are presented: a type of resonant metallic metamaterial that belongs to the larger class of anisotropic zero index metamaterials and a non-resonant material. A technique for lowering the dimensions of the resonant metamaterial unit cell is presented and applied. The work presented consists of simulation results obtained with HFSS modelling software from ANSYS.

In this paper, the slot-shape and slot-size introduced on the radiating surface of a microstrip antenna as well as the inserted air-gap between the substrate sheet and ground plane are predicted, simultaneously. This synthesizing-prediction is carried out using knowledge based neural network (KBNN) model as this approach requires very less amount of training patterns. The suggested approach is validated by fabricating and characterizing three prototypes. A very good agreement is attained in measured, simulated and predicted results.

An extended transmission-line model is presented for an inset-fed rectangular microstrip patch antenna. The transmission-line model agrees to the cos4 impedance variation for inset-fed microstrip antennas with an addition of a corrective extended feed length upto the inner radiating edge. Verification of the model's complex reflection coefficient is concluded with good agreements with measured results. Further extension of the transmission-line model with for or more thin shorting post connected to multiple varactor diodes have been conducted. Fourty two test cases across five independent antenna designs have been worked upon. Results obtained using the transmission-line model are compared with those obtained with a 3D full-wave solver and measurements. In 69% of the test cases, the transmission-line models have less than 3% deviation to the measured or simulated results. 41% of them have less than 1% deviation. For the first two antennas, both simulated and measured results were compared with the transmission-line model. For the rest of three, results from the transmission-line model were compared to the simulated ones.

In this paper, we present an efficient meshing scheme for physical optics calculation of electromagnetic scattering from bodies of revolution. Piecewise linear approximation is used to represent the generatrix and circular perimeter of the body's cross section. This results in quadrilateral meshes and enables the application of multilevel search algorithms for efficient determination of the illuminated portion of the surface. Besides, the physical optics surface integral is reduced to a closed form expression using the Gordon's method. Simulation results conrm the proper accuracy and efficiency of the presented algorithm.

An active reconfigurable Radar absorbing structure (RAS) with the pin diode was proposed to reduce the radar cross section (RCS) of antenna. The operating states of the RAS reflector can be switched by using the pin diode. For ON-state and OFF-state diodes, the reflection coefficients of the RAS reflector were less than -25 dB and more than -0.8 dB around 8.3 GHz, respectively. The RAS reflector with ON-state diodes can be used as a dipole antenna reflector and has the same radiation performance as a dipole with a metal reflector, while the RAS reflector with OFF-state diodes can be used as a radar absorber for RCS reduction. Meanwhile, chessboard-like geometry RAS reflector was proposed to achieve wideband RCS reduction. The RCS reduction band covers the working band and is extended to 5-18 GHz. The results show that the reconfigurable RAS reflector can contribute to the antenna RCS reduction at working frequency without loss of radiation performance of dipole antenna.

A low-profile wideband bowtie antenna backed by artificial magnetic conductor (AMC) ground is presented for gain enhancement.The proposed bowtie antenna, loaded with an open stub in the upper layer, has broadband property. By using an AMC reflector,consisting of 6×9 metallic patches, the bidirectional radiation of the bowtie antenna is changed to unidirectional radiation. The distance between the bowtie antenna and the AMC surface is onlyλ/10 at 3.75 GHz. Both the bowtie antenna and the AMC surface are fabricated and measured. The measured results demonstrate good and stable performances, including maximum gain of 8.27 dBi, and flat gain response with variation of 0.6 dB in the wide impedance matching (S11 < -10 dB) band from 3.05 GHz to 4.35 GHz(35.1%). Furthermore, the maximum cross-polarization level is -17 dB for both E and H planes, and the measured front-to-back ratios are more than 18 dB.Good agreement between the simulated and measured results validates the proposed design approach.

In this paper, a combination of the Jerusalem cross (JC) as a fractal load and fractal Minkowski slot antenna for dual-band application is investigated. The prototype slot antenna has a Minkowski fractal formation with four Jerusalem cross (JC) loads to achieve dual-band application with compact size to improve the bandwidth. A T-shaped feed line is implemented in the final modeled antenna. The fabricated antenna has a bi-directional pattern with sufficient bandwidth at 2.4-3.1 GHz and 5.1-5.9 GHz with VSWR<2 for Wi-Fi, WiMAX, Bluetooth application as well as an IEEE WLAN protocol with a gain of 5-6 dBi, respectively. The size of the prototype patch antenna is 40×40 mm², and the antenna is designed and fabricated on an FR-4 low cost substrate with ε_r=4.4 and thickness of 1.6 mm. It is simulated by HFSS full wave software. In addition, the VSWR, pattern and axial ratio of experimental results are presented and compared with simulation models. As a result, improvements of the Jerusalem cross compared with conventional cross have been achieved with some parameter tuning to improve the band width.