Azimuthal Surface Waves (ASWs) are electromagnetic waves of the surface type, which propagate across an external steady magnetic field in plasma filled metal waveguides. The interaction between extraordinary ASWs and an electron beam that rotates along Larmor orbits in the gap between the plasma column and the metal wall is studied here. The initial stage of the ASW excitation is studied analytically and numerically. Growth rates of the ASW beam instability are analyzed as functions of the parameters of the plasma filled waveguide immersed in a steady magnetic field with toroidal nonuniformity. This nonuniformity leads also to the appearance of corrections to the ASW eigen frequencies. It is shown that the beam-wave interaction in a toroidally nonuniform steady magnetic field is not weaker than in the case of a uniform magnetic field. However, in the studied case, the efficiency of the power transfer from the beam into the excited waves becomes restricted due to the electron drift in the nonuniform magnetic field.

In various technological and scientific applications, different types of coil systems are being used to produce uniform alternating magnetic field. The dimensions of these coil systems are considerably larger than the volume of interest. There is a necessity to reduce the dimension of the coil system without sacrificing the extent of uniformity of the magnetic field. This problem has a wide audience and still remains as a topic of contemporary research in the development of miniaturized devices especially for calorimetric measurements of nano-particles, cancer therapy, and detection of minute surface defects by eddy current probes, etc. In this paper we present how we can modify the shape of a miniature solenoid to produce uniform magnetic field. A Genetic algorithm has been implemented to get the optimum dimension of the miniature solenoid. Our distinct shape design has achieved 97% uniformity for a 60% volume of interest.

The space-variant motion errors are specic to different targets and proportional to the beamwidth of a synthetic aperture radar (SAR) system, which makes them very difficult to be compensated for a SAR system with wide beamwidth. In this paper, a motion compensation (MoCo) algorithm that exploits the features of the geometry of near-range SAR applications is proposed. By dividing the whole range swath into several octave sub-swaths, the effects of space variant motion errors can be greatly reduced, especially for targets at nearer range, with low computational load.

As an emerging technique with a promising application prospect, the device-free passive localization (DFPL) technique has drawn considerable research efforts due to its ability of realizing wireless localization without the need of carrying any device and participating actively in the localization process. Recent technological achievements of the DFPL technique have made it feasible to realize location estimation using the received signal strength (RSS) information of wireless links. However, one major disadvantage of the RSS-based DFPL technique is that the RSS measurement is too sensitive to noise and environmental variations, which incur the misjudgment of shadowed links and degradation of localization performance. Based on the natural sparsity of location finding in the spatial domain, this paper proposes an environmental-adaptive sparsity-based localization method for the DFPL problem in the existence of model mismatch. The novel feature of this method is to adjust both the overcomplete basis (a.k.a. dictionary) and the sparse solution using a dictionary learning (DL) technology based on the quadratic programming approach so that the location solution can better match the changes of the RSS measurements between the node pairs to the spatial location of the target. Moreover, we propose a modified re-weighting l1 norm minimization algorithm to improve reconstruction performance for sparse signals. The effectiveness of the proposed scheme is demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance.

Based on the principle of discone antenna a new UWB monocone antenna is presented. Instead of using traditional cone geometry as a radiator for discone, planar vertical cross strips of aluminum are used as an antenna radiator. This results in wide impedance characteristic and miniaturization of antenna. The simulated model has broadband impedance bandwidth 18:11 form 550 MHz to 18 GHz with Omni directional radiation pattern. The two different antenna models are presented in this paper. Design software CST Microwave Studio, HFSS and Solid works are used for designing and parametric analysis of antenna. Size reduction up to 45 percent is achieved as compared to tradition discone antenna. The N type panel mount connector is used for antenna feeding. As a result of a low profile structure, antenna can be easily mounted for portable application. The antenna radiation pattern is measured in anechoic test chamber. The measured results of antenna are found to be in good agreement with simulation results. The features make the antenna highly suitable for UWB applications.

Quantum properties of a modified Caldirola-Kanai oscillator model for propagating electromagnetic fields in plasma medium are investigated using invariant operator method. As a modification, ordinary exponential function in the Hamiltonian is replaced with a modified exponential function, so-called the q-exponential function. The system described in terms of q-exponential function exhibits nonextensivity. Characteristics of the quantized fields, such as quantum electromagnetic energy, quadrature fluctuations, and uncertainty relations are analyzed in detail in the Fock state, regarding the q-exponential function. We confirmed, from their illustrations, that these quantities oscillate with time in some cases. It is shown from the expectation value of energy operator that quantum energy of radiation fields dissipates with time, like a classical energy, on account of the existence of non-negligible conductivity in media.

A mathematical model of a spherical antenna excited by a slot cut in an impedance endwall of a semi-infinite rectangular waveguide was built using a rigorous solution of the problem. Control of energy characteristics is accomplished by changing impedance distributed on the end-wall of the waveguide section. If the waveguide is excited by the wave H₁₀, the wavelength tuning reaches (30-35)%, i.e. about a half of the wavelength range of single mode waveguide regime.

In the ongoing search for new materials for microwave absorption applications, Carbon Nanotubes deserve a special consideration due to their outstanding properties. In this paper, microwave absorbing properties of epoxy resin based composites containing commercial MultiWalled Carbon Nanotubes used as fillers have been analyzed. The complex permittivity of the composites was measured in a wide frequency band (3-18 GHz). The absorbing properties of a single-layer absorber backed by a metallic plate considering several concentration of CNTs was simulated taking into account the measured permittivity.

Various interference sources either intentional or unintentional can mask the synthetic aperture radar (SAR) signals and cause image degradation. With a novel data acquisition mode, a new method based on dual-channel SAR is applied to suppress the interference. Using the received dual-channel data, the two-dimensional location of the interference source can be estimated and then the interference can be removed via a Two-Channel Cancelation method. By establishing a linear model of the interference-removed signal, the SAR image is reconstructed based on compressed sensing (CS) theory. Our method requires only a minor change to the traditional SAR system hardware while obtains a higher resolution. Simulation results are shown to demonstrate the validity of the proposed method.

In this paper, frequency-tunable microstrip antennas, for cognitive radio applications, are proposed. The approach is based on electrically tuning the antenna's operating frequency by integrating reconfigurable band pass filters into wideband antenna structures. The design of an open loop resonator (OLR)-based bandstop filter, and its transformation to a bandpass filter, are investigated first. Then, the incorporation of the bandpass filter, with a wideband antenna, is detailed. The same methodology is employed to design cognitive radio pattern and polarization diversity tunable filter-antennas. A good agreement between the simulated and measured results for the different fabricated prototypes is attained.

In this paper, we derive a new geometrical blind corner scattering model for vehicle-to-infrastructure (V2I) communications. The proposed model takes into account single-bounce and double-bounce scattering stemming from fixed scatterers located on both sides of a curved street. Starting from the geometrical blind corner model, the exact expression of the angle of departure (AOD) is derived. Based on this expression, the probability density function (PDF) of the AOD and the Doppler power spectrum are determined. Analytical expressions for the channel gain and the temporal autocorrelation function (ACF) are provided under non-line-of-sight (NLOS) conditions. Additionally, we investigate the impact of the position of transmitting vehicle relatively to the receiving road-side unit on the channel statistics. Moreover, we study the performance of different digital modulations over a sum of singly and doubly scattered (SSDS) channel. Note that the proposed V2I channel model falls under the umbrella of SSDS channels since the transmitted signal undergoes a combination of single-bounce and double-bounce scattering. We study some characteristic quantities of SSDS channels and derive expressions for the average symbol error probability of several modulation schemes over SSDS channels with and without diversity combining. The validity of these analytical expressions is confirmed by computer-based simulations.

This paper proposes a method for the quick estimation of the average voltages at terminal loads when the transmission line translate randomly and analyzes the sensitivities of the loads' voltages to the translation. Because nonuniform transmission lines can be approximated as n-cascaded uniform lines, the study of uniform lines is the basis. Based on the transmission-line equations, the equations are derived to estimate the average voltages, the voltage variations, and the sensitivity of the voltage to the random translation when transmission lines have random translation in their cross sections. With these equations, the average voltages at the loads, the probability distributions of the voltage variations, and the sensitivity of the voltage to the random translation can be obtained quickly. A two-wire line over the ground is studied by using the proposed method. The average voltages and the voltage variations' probability distributions agree well with those via the Monte Carlo (MC) method and the proposed method is more efficient. The results show that the sensitivities of the voltages at the loads to the random height increase with the terminal sources but decrease with the height.

We present Coplanar-Planar Goubau Line (PGL) transitions designed on high-resistivity Silicon to characterize a PGL using microwave probing. These transitions are optimized in the 57-64 GHz frequency band to present excellent electrical performances despite the field disturbance of the measurement setup. As the transitions are positioned on a probe station chuck, a glass substrate is added between the transition under test and the metallic chuck to minimize the disturbance. 3-D full-wave electromagnetic field simulations performed on a commercial software and on-wafer measurements show almost comparable results in term of scattering matrix parameters. Low losses are attained with a measured average transmission parameter of 2.5 dB at 60 GHz for a length of 8 mm of a back-to-back structure with the transitions at the extremities. The measured average insertion loss and return loss per transition are better than 1.36 dB and 11 dB, respectively, with a bandwidth greater than 7% at 60 GHz for a length of 1 mm (about a half of the wavelength at 60 GHz).

This paper presents a new efficient algorithm of filtering and unwrapping phase images for interferometric synthetic aperture radar (InSAR) based on nonlinear phase model. First, we analyzed the statistical and signal properties of interferometric phase, and proposed the concept of nonlinear phase model. The model of reflecting topographic contour is used to approximate the interferometric phase variation occured over the local window. And the lower amplitude bound of the principal vector is decided and the value solution method is given, which can solve effectively and adaptively the nonlinear factor of the phase. Second, we studied the application of nonlinear phase model in interferometric phase filtering. When compared with other advanced filters, the nonlinear phase compensation filter, with a higher computation efficiency and a better phase estimation accuracy in low coherence areas, has a stronger ability to reduce interferometric phase noise in rugged terrain Finally, we introduced the nonlinear phase model to phase unwrapping, which increased the reliability of integration path and the accuracy of the phase gradient, and improved effectively the performance of phase unwrapping. And the real data processing results demonstrated the validity of the proposed nonlinear phase model and of the corresponding solutions.

A compact and low-correlation multiple input multiple output antenna system covering 1710-2690 MHz band for wireless communication standards is proposed. It comprises two identical elements with coupled feeding plate and radiating strip, and each element has a volume of 24.5×15×1.2mm³. Simulated and measured results show that it has good potentials for high-band-only mobile phone. 45% bandwidth (based on S₁₁ < -6 dB), -20 dB isolation, over 70% efficiency and less than 0.15 correlation coefficient are achieved in the frequency ranging from 1710 MHz to 2690 MHz. Several key parameters are also discussed in this study to better understand the antenna principles.

In this work we examine, for the first time, the use of classification algorithms for early-stage tumor detection with an experimental time-domain microwave breast screening system. The experimental system contains a 16-element antenna array, and testing is done on breast phantoms that mimic breast tissue dielectric properties. We obtain experimental data from multiple breast phantoms with two possible tumor locations. In this work, we investigate a method for detecting the tumors within the breast but without the usual complexity inherent to image-generation methods, and confirm its feasibility on experimental data. The proposed method uses machine learning techniques, namely Support Vector Machines (SVM) and Linear Discriminant Analysis (LDA), to determine whether the current breast being scanned is tumor-free. Our results show that both SVM and LDA methods have promise as algorithms supporting early breast cancer microwave screening.

A new thin electromagnetic soft surface of strips in which ledge edges are used to reduce the strip period width and in turns a miniaturized structure is achieved. The designed surface is tested to reduce the mutual coupling between microstrip patches separated by a half wavelength. A 20% relative bandwidth of the bandgap is achieved. Study of the effect of different parameters is presented. The measurements show good agreement with the computed results.

Based on two orthogonal linear sparse arrays (LSA) which consist of the coupled-sensors (CSs), a high resolution and no ambiguity (HRNA) method is proposed to estimate the two-dimensional (2D) angles of single source. The HRNA method first constructs a new covariance matrix to achieve no ambiguity independent angles estimation by using the covariance matrix generated by each LSA, and then computes joint elevation and azimuth angles by utilizing both the estimated independent angles and triangular relationship. For large array aperture of the LSA, the HRNA method earns a high angle resolution; however, its independent angles estimation accuracy is slightly lower than the multiple signal classification (MUSIC) with a uniform linear array (ULA). In order to enhance the independent angle estimation performance, first improved HRNA (FI-HRNA) method is developed based on the HRNA and MUSIC methods. Further, in order to decrease the computational cost, second improved HRNA (SI-HRNA) method is presented based on FI-HRNA and MUSIC methods. The proposed SI-HRNA method obtains high angle resolution, high angle estimation accuracy and low computational load. In addition, the spacing between two adjacent CSs is not limited, and thus the angle resolution and estimation accuracy can be set according to practical demand. Numerical experiment and comparison with the other existing algorithms verify the effectiveness and superior performance of the method proposed in this paper.

In this paper, a computational model is established for the finite-difference time-domain analyses of induced voltage on the overhead line at oil exploiting port under lightning strike. The MTLL approximate formulation is used to simulate the lightning strike, and convolutional perfectly matched layers are used to truncate the computational domain. A two-step method is established to calculate the coupling to the overhead lines to reduce the huge computational domain of the conventional 3-D FDTD simulation. Parallel implementation is introduced for the second-step calculation to overcome the memory storage limit of a single computer. With this model, the electromagnetic field at the adjacent areas and the induced voltage on the overhead line are studied when lightning strikes an oil derrick. It is demonstrated that the electromagnetic field decreases as the distance from the oil derrick increases, but the vertical field decrease much slower than the horizontal field. It is also shown that the transversely located overhead line will introduce lower voltage than the radially located line. As the length of the overhead line increases, the induced voltage increases and the low-frequency induction is strengthened. The overhead line should be set as low as possible to reduce the induced voltage.

In this paper, two novel vector sensors using a reduced number of radiating elements are proposed to estimate the directions of arrival of incoming electromagnetic signals in the 3D space, azimuth and elevation angles. The first one uses co-located radiating elements while the other one is based on distributed antenna elements. These two sensors combine only two half-loops and one linear monopole placed on a metallic plate in view of embedded applications. Full wave electromagnetic simulations are performed to take into account the electromagnetic coupling effects between the antenna elements. The directions of arrival estimation accuracy of electromagnetic signals incoming in arbitrary directions in the full 3D space are computed from the MUSIC algorithm. For experimental validation purpose, a prototype is manufactured and the directions of arrival measurements are performed. Then a novel vector sensor design with a reduced number of antenna elements is presented. The antenna elements are spatially distributed. An analysis is carried out to determine the largest distance between the antenna elements without causing ambiguous estimations in the 3D space . The estimation accuracy of the resulting sensor is reported. Finally the performances of these two vector sensors are compared.