The specific features of TM-polarized surface electromagnetic waves in a finite structure fabricated by a periodic alternating semiconductor and dielectric layers are investigated. Dispersion characteristics of eigenwaves are analyzed numerically and analytically. The complex Poynting energy flux and the surface wave's distribution are calculated. The influence of geometrical and physical parameters of the structure on the properties of surface waves is studied.

Multifractal correlation, which studies the spatial correlation characteristics of two points with different singularity indexes, is a generalization of multifractal single point statistic. This paper introduces multifractal correlation theory into the characteristic analysis of aircraft echoes from low-resolution surveillance radars, and discusses the application of multifractal correlation characteristics in target classification. Firstly, on basis of introducing multifractal correlation theory, the multifractal correlation characteristics of aircraft echoes from surveillance radars are analyzed in detail by means of the multifractal correlation analysis. Secondly, on basis of the foregoing analysis, several characteristic parameters of the echo multifractal correlation spectrum are defined, and the support vector machine (SVM) based on the defined characteristic parameters is taken as the classifier to classify different types of aircraft targets. Finally, real recorded aircraft echo data are adopted to do the classification experiments, and the experimental results validate the proposed method.

A robust direct data domain least squares (D3LS) beamforming algorithm that is capable of reducing the sidelobe level of the beam pattern is presented. By exploiting the sparsity of the desired beam pattern, the proposed method can enhance the performance with its lower sidelobe level and deeper null for interference while the robustness against steering vector mismatch is increased when a proper regularization parameter is selected. Simulation results demonstrate the effectiveness of the proposed method.

Based on a construction of concentric deformed annular slots with a stepped microstrip feed line, two designs of dual-band dual-sense circularly polarized slot antenna are proposed in this paper. Compared with the first antenna, the second design possesses the merits of simple structure by devising a twin-slot with less adjusted parameters to achieve the same satisfactory output responses. The results from simulations and measurements demonstrate that both of the antennas have good quality of impedance matching and dual-sense circular polarization at 1.6 GHz and 2.5 GHz.

Measurements of mm-wave excitation spectra of high-order whispering gallery modes in free-space cylindrical disk resonators as functions of resonator thickness have been made. Resonators in the form of tight stacks of thin dielectric disks excited via dielectric waveguides have been used in the experiment. Experimental conditions for the excitation of thin-disk resonators have been found. A simple approach for the modeling of resonator spectra and recovery of dielectric parameters has been proposed.

In this paper, 60 GHz millimeter-wave indoor propagation characteristics are simulated and analyzed using the method of SBR/IM (shooting and bounding ray tracing/ image). And the simulated and measured results agree well, so the correctness of the method has been validated. Some propagation parameters are obtained in the simulation, such as the indoor reception power distribution, distribution of phase angle of received power, root mean square (RMS) delay spread, direction of arrival, RMS angular spread, Doppler shift, etc. The analysis of the above results provides the foundation for the indoor coverage of millimeter-wave communication system.

The Medium-Earth-Orbit SAR（MEOSAR）is one of the potential next-generation spacebarne SAR for its excellent performance, however, due to ionospheric effects, a MEOSAR may not be able to produce data useful for science applications. So study of ionospheric effects is one of the critical techniques for the development of MEOSAR. In this paper, we present ionospheric effects on azimuth imaging for MEOSAR. First, we establish an analysis model for ionospheric effects on azimuth imaging of MEOSAR based on the system characteristics of MEOSAR and the temporal-variability of ionosphere. Then, based on the analysis model, we analyze the effects caused by the quadratic and cubic phase errors induced by temporal-variability of ionosphere on azimuth imaging. According to the results of our analysis, we conclude that both the quadratic phase error and the cubic phase error neglected for Low-Earth-Orbit SAR(LEOSAR) will deteriorate the azimuth imaging for MEOSAR and ionospheric effects become more and more serious with the increase of SAR altitude and the improvement of azimuth resolution designed.

Dynamics of interference interaction of counter-propagating electromagnetic pulses on a magneto-dielectric slab is studied in time domain. Energy redistribution in the counter-propagating pulses with arbitrary waveforms is considered. The maximal energy redistribution in the diffracted field takes place under certain conditions. The conditions are found and their physical explanation is supplied. The problem of transient electromagnetic wave diffraction on homogeneous magneto-dielectric slab is solved analytically by means of Laplace transform. The analytical solution is in agreement with numerical simulation based on finite difference time domain approach.

Sidelobes of strong targets substantially impact image quality of synthetic aperture radar (SAR) using linear frequency modulation (LFM) waveform, especially in urban areas. A novel space-borne azimuth multi-channel SAR scheme with ultra-low range sidelobe-ratio (RSLR) performance was proposed, employing complete complementary sequence (CC-S) coding waveform. The CC-S waveform was utilized to acquire ultra-low RSLR performance in range direction. Azimuth multi-channel scheme was introduced, to compensate reduction of effective PRF due to employing CC-S, and to mitigate azimuth resolution lost resulted from strong azimuth weighting, in order to implement low side-lobe performance in both range and azimuth direction. The method for pre-processing the CC-S based multi-channel SAR data was proposed, which would both compensate receiving time difference of sub-sequences and reconstruct azimuth spectrum of multi-channel SAR data. Furthermore, the corresponding image formation algorithm for accurately focusing raw data of the SAR system was also proposed. Computer simulation results were presented, which demonstrated the validity of the proposed SAR scheme and image formation algorithm.

This paper proposes a Synthetic Aperture Radar (SAR) vehicle target detection algorithm based on contextual knowledge. The proposed algorithm firstly obtains the general classification of SAR image with a Markov Random Field (MRF)-based segmentation algorithm; then modifies the prior target presence probability utilizing terrain types, distances to boundary and target aggregation degree; finally gains the detection results using improved Cell Averaging-Constant False Alarm Rate (CA-CFAR). Detections with real SAR image data show that this algorithm can effectively improve target detection rate and reduce false alarms compared with conventional CA-CFAR.

A 1.3 m piecewise reflectarray demonstrator has been designed, manufactured and tested, that radiates a contoured beam coverage over North America. A very good agreement is obtained between the theoretical and measured radiation patterns. Many innovative techniques and processes were developed in order to meet the challenging specifications of a space telecommunication antenna.

Software Defined Radar is the latest trend in radar development. To handle enhanced radar signal processing techniques, advanced radars need to be able of generating various types of waveforms, such as frequency modulated or phase coded, and to perform multiple functions. The adoption of a Software Defined Radio system makes easier all these abilities. In this work, the implementation of a Software Defined radar system for target tracking using the USRP platform is discussed. For the first time, an experimental characterization in terms of radar application is performed on the latest USRP NI2920, demonstrating a strongly improved target resolution with respect to the first generation platform.

High-performance dual-band Doherty power amplifier and non-uniform circularlypolarizedantenna array require impedance-transformingunequal dual-band 90° branch-line couplers forpower dividing and phase shiftingin the feed networks.In this paper, an analytical design methodology of generalized impedance-transforming dual-band branch-line couplers for arbitrary coupling levels is proposed. The coupler features wide range of realizable frequency ratio, multiple flexibleselections of open- or short-circuited and pi- or T-network topologies. For demonstration, four numerical examples with different parameters are presented.Furthermore, two microstrip couplers based on open-circuited pi- and T-network topologies were fabricated and measured.The measured results show good performance at dual 1.8/3.45 GHz bands.Thefractional bandwidthsdefined by the fluctuation of the coupling level and the phase difference less than ±0.5 dB and ±5°are up to 17% and 18%, 18% and 2% for open-circuited pi- and T-network topologies, respectively.

Failure mode characterization was applied to coplanar transmission lines by utilizing 0.5-10-GHz S-parameter measurements and post-calculated TDR (Time-Domain-Reflectometry) analysis. Coplanar waveguide transmission lines were inkjet-printed on 1.0-mm-thick flexible plastic RF substrates. Inductive, resistive, and capacitive types of failures-as the main failure modes caused by manufacturing, bending, or thermal cycling stresses-were investigated. The inkjet-printed CPW (Co-Planar Waveguide) lines were damaged by inductive shorts due to mechanical hits or resistive and capacitive failures due to bending of the substrate. By using the TDR method the type and physical location of the failure can be determined.

Difference patterns are vital for the successful function of tracking radar employing monopulse techniques to estimate target direction. Traditional monopulse antenna pattern synthesis methods require the use of two independent distributions, e.g. Taylor and Bayliss distributions, for formation of sum and difference patterns for one antenna. Hence, these approaches require a feed network of considerable complexity. In this letter, a method for forming difference pattern in linear arrays using a very simple beamforming network and two additional elements is described. The sum pattern is determined by adding signals received by original radiating elements of the array whereas the difference pattern is determined by subtracting the output of the sum pattern from signals received from two external edge elements. The proposed method used to generate these two patterns offers significant hardware and software savings over current methods.

This paper deals with the design of small-sized bio-implanted spiral circular coils (pancake) with an operating frequency of 13.56 MHz. The external and internal coils' geometric dimensions are d_out = 56 mm, d_in = 10 mm and d_out = 11.6 mm, d_in = 5 mm, respectively, in which the electrical performance is verified through the commercial field solver High Frequency Structural Simulator (HFSS 13.0), which employs the finite-element method (FEM) technique. Mathematical models for the proposed coils are developed. The simulation is performed-based on the developmental model in the air and at depths 6\,mm in a human biological tissue of dry and wet-skin. The results demonstrate that the external and internal coils have maximum near-field gains of 54.15 dB and 53.30 dB in air. The maximum gains of the external coil contacted the wet and dry skin are 49.80 dB and 48.95 dB, respectively. The maximum gains of the internal coil at depths of 6 mm in the wet and dry tissue are 41.80 dB and 41.40 dB, respectively. However, the external coil radiation efficiencies on wet- and dry-skin are 92% and 90%, respectively, compared with that on air. The internal coil radiation efficiencies on wet- and dry-skin are 78.4% and 77.6%, respectively, compared with that on air. In this study, the specific absorption rate (SAR) and radiated power results of the internal coil are investigated using SEMCAD 16.4 software. The SAR and power loss studies show that the designed implanted coil has a negligible effect on the wet and dry skin and can be ignored.

A novel hybrid approach to the synthesis of non-uniformly spaced linear arrays of printed antennas is presented and thoroughly discussed in this paper. In order to account for parasitic mutual coupling between array elements, a dedicated optimization procedure in combination with a multiport network approach is adopted. Selected examples are included in order to assess the effectiveness and versatility of the proposed technique.

In high dynamic environment, due to the rapid relative movement between receiver and transmitter, the DOA (Direction of Arrival) of signals will change even between two consecutive snapshots. Thus, covariance-based DOA estimation algorithms are ineffective. Compressive sensing algorithms, as a kind of novel DOA estimation algorithms, are still effective with only one snapshot. At the same time, it is noted that the DOA changing is limited by relative moving speed and distance between receiver and transmitter. In this paper, a DOA tracking algorithm based on weighted L₁ minimization is proposed which utilizing the DOA changing scope between two consecutive snapshots as a prior to improve the tracking performance. Different from other multiple snapshots compressive sensing algorithms which assumed fixed DOA among multiple consecutive snapshots, the proposed algorithm takes into account the DOA changing among different snapshots. The simulation results demonstrate the advantages of the proposed algorithm.

At the ultra-high frequencies (UHF) common to portable radios, the mine tunnel acts as a dielectric waveguide, directing and absorbing energy as a radio signal propagates. Understanding radio propagation behavior in a dielectric waveguide is critical for designing reliable, optimized communication systems in an underground mine. One of the major parameters used to predict the power attenuation in lossy waveguides is the attenuation constant. In this paper, we theoretically and experimentally investigate the attenuation constants for a rectangular waveguide with dielectric walls. We provide a new derivation of the attenuation constant based on the classic Fresnel reflection coefficients. The new derivation takes advantage of ray representation of plane waves and provides more insight into understanding radio attenuation in tunnels. We also investigate the impact of different parameters on the attenuation constant, including the tunnel transverse dimensions, permittivity, conductivity, frequency, and polarization, with an aim to find their theoretical optimal values that result in the minimum power loss. Additionally, measurements of the attenuation constants of the dominant mode at different frequencies (455, 915, 2450, and 5800 MHz) for a straight concrete tunnel are presented and compared to theoretical predictions. It is shown that the analytical results match the measured results very well at all four frequencies.

For the chirp rate and its change rate estimation of cubic phase signal (CPS), conventional algorithms cannot achieve a trade-off between low computational cost and high performance. In this paper, by utilizing the numerical computational method (NCM), effects of Doppler frequency shift are quantified, and the relationships of the optimal signal length with the chirp rate and change rate of chirp rate are obtained. Then a fast parameter estimation algorithm (DMNUFFT), based on dechirp method (DM) and nonuniform fast Fourier transform (NUFFT), is proposed. Compared with existing algorithms, DMNUFFT can achieve high performance with relatively low computational cost. The performance analyses and an application to inverse synthetic aperture radar (ISAR) imaging are shown to validate the effectiveness of DMNUFFT.