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Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is widely used in integrated radar and communication systems (IRCSs). Moreover, index modulation (IM) is a reliable OFDM transmission scheme in the field of communication, which transmits information by arranging several distinguishable constellations. In this paper, we propose a sparse reconstruction-based joint signal processing scheme for integrated MIMO-OFDM-IM systems. Combining the advantages of MIMO and OFDM-IM technologies, the integrated MIMO-OFDM-IM signal design is realized through the reasonable allocation of bits and subcarriers, resulting in better intercarrier interference (ICI) resistance and a higher transmission efficiency. Taking advantage of the sparseness of OFDM-IM, an improved target parameter estimation method based on sparse signal reconstruction is explored to eliminate the influence of empty subcarriers on the matched filtering at the receiver side. In addition, an improved sequential Monte Carlo signal detection method is introduced to realize the efficient detection of communication signals. The simulation results show that the proposed integrated system is 5 dB lower in the peak sidelobe ratio (PSLR) and 1.5 × 10 5 lower in the number of complex multiplications than the latest MIMO-OFDM system and can achieve almost the same parameter estimation performance. With the same spectral efficiency, it has a lower bit error rate (BER) than existing methods. [ABSTRACT FROM AUTHOR]

Most of the existing methods for the analysis of meanderline polarizer assume that the embedded metallic grids are infinitely thin. A modal procedure is presented here for treating meanderline grids with finite thicknesses. The space between the metallic grids in a unit cell is considered as a meanderline wavegnide with a stepped cross-section and length given by the grid thickness. The modes of this guide are obtained using the transverse resonance technique. A generalized scattering matrix characterization of the grid is obtained by field matching of the modes of the meanderline guide and the free space Floquet guide. The accuracy of this approach is verified by the very good agreement obtained between predicted and measured transmission phases of polarizer grids. Index Terms--Circular polarization, generalized scattering matrix, mode matching methods, printed circuits.

The performance of high-frequency surface wave radar (HFSWR) is known to suffer from external environmental interference and noise, such as cochannel radio-frequency interference from other radiating source, ionospheric clutter, lightning impulsive noise, etc. This paper experimentally evaluates the interference cancellation performance of various adaptive beamforming schemes with respect to the aforementioned three types of interferences in an attempt to find the most promising adaptive cancellation scheme in practical HFSWR environment. Index Terms--Adaptive beamforming, high-frequency surface wave radar (HFSWR), interference cancellation.

In this paper, a 3-D inverse synthetic aperture radar (ISAR) imaging method based on an antenna array configuration is proposed. The performance of conventional interferometric ISAR imaging system using three antennas is poor, as the positions of scatterers, which have the same range-Doppler value and projected onto the ISAR plane as a synthesis scatterer, cannot be correctly estimated. However, by using two antenna arrays perpendicular to each other, the system's ability to separate these scatterers can be improved. The criterion for the selection of a range unit that contains an isolated scatterer in the 2-D array domain for doing motion compensation is discussed. If there is no range unit which contains only an isolated scatterer, then radial and cross-range motion compensation has to be carried out by motion parameter estimation. Two cross-range motion parameters measurement algorithms, one based on array processing of the range profile and another based on correlation of ISAR images of different antennas, are proposed. The coordinates registration problem for the scatterers of a synthesis scatterer is also discussed. Simulation results have shown the effectiveness of the proposed methods. Index Terms--Antenna array, cross-range motion compensation, inverse synthetic aperture radar (ISAR), 3-D imaging.

The rotation of structures in a target introduces additional frequency modulations on the returned signals and also generates sidebands about the center Doppler frequency of the target. In other words, the body image will be contaminated due to the interference from the rotating parts. In this paper, an imaging method for moving targets with rotating parts is presented. The method is simple to implement and is based on the Hough transform (HT), which is widely used in image processing. Using the standard HT and an extended HT, we put forward a separation method by detecting the straight lines and the sinusoids on the spectrogram, respectively. A computer simulation is given to illustrate the effectiveness of the proposed method. Index Terms--Hough transform (HT), micro-Doppler, moving targets, rotating parts, spectrogram.

A comparative study of the electromagnetic field excited by a vertical electric dipole on the earth is presented. Four sets of formulas for both the planar earth model and the spherical earth model (of large radius) are compared to find out their valid ranges. Numerical computations are also carried out specifically for a three-layered earth model. For the planar earth model, when both the source and observation points are on the surface, and the planar earth covered with a thick-enough dielectric layer, the method by Zhang is more accurate; while for the fields above the surface and the thin-enough dielectric layer, the method by King and Sandier is more accurate. However, the hybrid of the trapped surface wave and the lateral wave were exhibited in the curves in, but they were not shown in the curves. Numerical calculation also shows that the amplitude of the trapped surface wave attenuates as [[rho].sup.-1/2] in the [rho] direction as expected. However, the lateral wave given by does not exhibit [[rho].sup.-2] decay in the [rho] direction. For the layered spherical earth model, the exact series summation, which serves as an exact solution to the classic problem, is computed and compared with the residue series. Numerical results show that the residue series gives a good approximation to the field, but the smooth curve illustrates that the hybrid effect due to the trapped surface wave and the lateral wave was ignored in literature. The field strength of the trapped surface wave decreases with the dielectric layer thickness and is affected by the curvature of the earth. The exact series shows the oscillation of the field caused by the hybrid effects, which can be considered as the dielectric resonance between the upper and lower dielectric interfaces when it is guided to propagate, but none of the other three approximations can depict the effects. Index Terms--Dipole radiation, earth, planar waveguides, radio propagation, surface waves.

When deriving dyadic Green's functions for the spherical structures with gyrotropic or bianisotropic materials, an integral whose integrand function consists of two spherical Bessel functions and a power function needs to be evaluated. Therefore, this paper revisits thoroughly the evaluation of the integral of [I,sub,l,l']([kappa], [kappa]). Starting from pointing out an error, it provides the correct solution to the integral in spherical coordinates in terms of distribution, in particular, step functions and delta functions. The formulation is further extended to a more generalized integral [H.sup.[lambda].sub.l,l'],([kappa],[kappa]'); and it is newly found that the solution to the generalized integral varies differently in the cases of even and odd values of l-l'. The mistakes that we found in the previous literature can also be proved easily by some of our intermediate solutions. Index Terms--Bessel function, bianisotropic metamaterials, dyadic Green's functions (DGFs), electromagnetic field.

A fast solution to the combined field volume integral equation (CFVIE) for electromagnetic scattering by large three-dimensional dielectric bodies of arbitrary permittivity and permeability is presented. The CFVIE is formulated in the region of the scatterers by expressing the total fields as the sum of the incident wave and the radiated wave due to both the electric and magnetic polarization currents. The resultant integral equation is solved using the method of moments (MoM). Then the pre-corrected fast Fourier transform (P-FFT) method is applied to reduce the memory requirement and accelerate the matrix-vector multiplication in the MoM solution. In the implementation of the P-FFT method, two sets of projection operators are constructed respectively for the projections of the electric sources and magnetic sources. In addition, two sets of interpolation operators are also applied respectively for the computation of the vector/scalar potentials and the curl of the vector potentials in the support of the testing functions. The resultant method has a memory requirement of O(N) and a computational complexity of O(N log N) respectively, where N denotes the number of unknowns. Index Terms--Combined field volume integral equation (CFVIE), electromagnetic scattering, magnetic material, method of moments (MoM), precorrected-FFT (P-FFT) method.

A method based on the volume-surface-wire integral equation and precorrected-fast Fourier transform (FFT) method is presented for accurate analysis of probe-fed microstrip antennas on arbitrarily-shaped, finite-sized ground plane and substrate. The method of moments (MoM) is used to solve the integral equation. Three triangular-type basis functions are used to represent the unknown currents in the substrates, on the conducting surfaces, and probes respectively. The connection of a vertical probe feed to the patch is rigorously modeled by an attachment mode at the junction. The precorrected-FFT method is applied to reduce the memory requirement and computational cost of the traditional MoM to facilitate analysis of large antenna arrays. Index Terms--Finite ground plane, method of moments (MoM), precorrected-fast Fourier transform (FFT) method, probe-fed conformal microstrip antennas.

An efficient numerical algorithm based on the modified Gram--Schmidt (MGS) procedure is developed in this paper to solve the electrical-field integral equation for characterizing metamaterials. The method of moments (MoM) with rooftop basis functions is implemented in the integral-equation solver. The MGS-based algorithm is implemented into the solver for decomposing the local MoM dense matrix without prior knowledge of the matrix elements. Although each element of the metamaterials is electrically small in size, the number of elements is very large so that the number of unknowns for characterizing the metamaterials is very large. Even so, this algorithm in the MoM solver has demonstrated via examples to be efficient and accurate. Numerical results on the number N of unknowns show that the CPU time per iteration and the memory requirements are both reduced from O ([N.sup.2]) to O ([N.sup.1.5]). After implementing this algorithm in the solver, propagation characteristics are finally presented when electromagnetic waves pass through a metamaterial prism that is synthesized using square split-ring resonators and wires in free space. Index Terms--Electrical-field integral equation (EFIE), left-handed material, metamaterial, modified Gram--Schmidt (MGS) procedure.

The performance of over-the-horizon radars (OTHRs) degrades significantly due to transient interferences such as lightnings, meteor echoes, and man-made impulse bursts. The conventional techniques used to suppress these transient interferences generally follow a simple time-domain procedure which first localizes the transient, sets the corrupted time samples to zero, and follows by data reconstruction via interpolations. However, for an OTHR operation with a short coherent integration time (CIT) of a few seconds, the transient interference may corrupt a significant portion of the received data such that data interpolation can become erroneous. In this paper, a new transient interference excision technique is proposed. It utilizes the adaptive time-frequency analysis technique to parameterize the radar signal. The transient interference can then be identified and subsequently removed via their characteristic parameters. No data interpolation is needed. The performance of the proposed technique is illustrated by simulated and experimental OTHR data. Index Terms--Adaptive Gaussian basis representation (AGR), over-the-horizon radar (OTHR), transient interference.

This paper presents a fast hybrid volume-surface integral equation approach for the computation of electromagnetic scattering from objects comprising both conductors and dielectric materials. The volume electric field integral equation is applied to the material region and the surface electric field integral equation is applied on the conducting surface. The method of moments (MoM) is used to convert the integral equation into a matrix equation and the precorrected-FFT (P-FFT) method is employed to reduce the memory requirement and CPU time for the matrix solution. The present approach is sufficiently versatile in handling problems with either open or closed conductors, and dielectric materials of arbitrary inhomogeneity, due to the combination of the surface and volume electric field integral equations. The application of the precorrected-FFT method facilitates the solving of much larger problems than can be handled by the conventional MoM. Index Terms--Electromagnetic scattering, method of moments, precorrected-FFT method, volume-surface integral equation.

This paper presents a fast solution to the volume integral equation for electromagnetic scattering from three-dimensional inhomogeneous dielectric bodies by using the precorrected-fast Fourier transform (FFT) method. The object is modeled using tetrahedral volume elements and the basis functions proposed by Schaubert et al. are employed to expand the unknown electric flux density. The basis functions are then projected onto a fictitious uniform grid surrounding the nouniform mesh, enabling the FFT to be used to speed up the matrix-vector multiplies in the iterative solution of the matrix equation. The resultant method greatly reduces the memory requirement to O(N) and the computational complexity to O (N log N), where N is the number of unknowns. As a result, this method is capable of computing electromagnetic scattering from large complex dielectric objects. Index Terms--Electromagnetic scattering, method of moments (MoM), precorrected-fast Fourier transform (FFT) method, volume integral equation.

A four-layered forest geometry with two anisotropic slabs representing canopy and trunk is used for the investigation of wave characteristics in forest environment. Propagation of radio waves is examined in which the transmitter is embedded inside the forest, while the receiving point is located either inside the forest or above the vegetation. Dyadic Green's functions in their eigen-function expansion forms for planarly layered anisotropic media are applied to analyze this problem. The analytical close forms of these electric fields are then obtained by using the saddle point techniques, and branch cut integrations in the complex plane and, hence, expressed in terms of quasidirect wave, multiply reflected waves, and lateral waves. Propagation mechanisms of these waves are studied and radio losses in a typical forest are calculated numerically. Index Terms--Anisotropic forest, dipole antennas, Dyadic Green's functions, inhomogeneous layered media, radio wave propagation.

In this paper, a three-dimensional (3-D) interferometric synthetic aperture radar (ISAR) imaging method for moving targets is presented. This imaging method is based on the ISAR principle and the simple observation that all scatterers on a moving target move in tandem. The angular motion parameters in the cross-range directions could be estimated using the overall range profile of the moving target. Registration of the respective complex images at the two (or more) interferometric antennas can then be achieved via compensating the respective echoes at the raw data level, thus avoiding phase-unwrapping processing and image-resampling processing as required by conventional methods. Finally, a 3-D image of the moving target can then be reconstructed from the 3-D spatial coordinates of these scatterers. Furthermore, the method works well even for a target moving in heavily cluttered environments. Index Terms--Motion parameters estimation, synthetic aperture radar (SAR), moving target imaging.

A complete eigenfunction expansion of the dyadic Green's functions (DGFs) for planar, arbitrary multilayered anisotropic media using cylindrical vector wave functions is presented. These formulations are constructed based on the principle of scattering superposition. For the scattering dyadic Green's function in each layer, the scattering coefficients of TE and TM modes are determined from the boundary conditions matched at the planar interfaces. The explicit representation of the DGFs after reduction to the isotropic case agrees well with the existing results corresponding to the isotropic media. The general DGFs for multilayered anisotropic media are then reduced to those for a four-layered forest where the trunk layer is modeled as anisotropic medium. Application is further made for radio-wave propagation through forests of a four-layered geometry, whereas it is shown how these Green dyadic formulations are used in a practical way and how the field distributions due to a dipole can be obtained. Index Terms--Dyadic Green's functions (DGFs), eigenfunction expansion, electromagnetic wave propagation, forest environment, vector wave functions.

In most interferometric inverse synthetic aperture radar (InISAR) systems, the pixels between two ISAR images derived from corresponding antennas usually do not register properly. As such, correct phase difference between two ISAR images could not be obtained. A three-dimensional (3-D) motion compensation method, or 3-D focusing, is put forward in this paper. With a multiple antenna pair configuration, the angular motion parameters both in the azimuth and pitching directions are accurately estimated without the usual phase-unwrapping processing. As such, there is no phase ambiguity in the inteferometric systems. The angle motion trajectory measurement here is based on the range profiles (or spatial spectrum) so that the 'angle scintillation' phenomenon can be effectively suppressed. The angular motion trajectory is then obtained by curve fitting of the spatial spectrum (range profile in the cross-range direction). The compensated ISAR images are registered accurately. Finally, the simulation data are used to illustrate the accuracy of the proposed method. Index Terms--Angle motion parameter, interferometric inverse synthetic aperture radar (ISAR), radar imaging, registration, three dimensions.

An accurate and efficient method that combines the precorrected fast Fourier transform (FFT) method and the discrete complex image method (DCIM) is presented to characterize the scattering and radiation properties of arbitrarily shaped microstrip patch antennas. In this method, the mixed potential integral equation (MPIE) is discretized in the spatial domain by means of the discrete complex image method. The resultant system is solved iteratively using the generalized conjugate residual method (GCR) and the precorrected-FFT technique is used to speed up the matrix-vector multiplication. The precorrected-FFT eliminates the need to generate and store the usual square impedance matrix and thus leads to a significant reduction in memory requirement and computational cost. Numerical results are presented for arbitrarily shaped microstrip antenna arrays to demonstrate the accuracy and efficiency of this technique. Index Terms--Discrete complex image method, microstrip antenna array, precorrected fast Fourier transform (FFT) method, scattering and radiation.