This paper suggests parameter estimation and error reduction scheme in a multicarrier transmission system. A multicarrier orthogonal frequency division multiplexing (OFDM) signal by using a time-domain spreading (TDS) coupled with a cyclic time shift enables a pilot-less synchronization. Exploiting the modified OFDM signal endowed with the TDS, the proposed synchronization receiver can accurately estimate the carrier-frequency offset as well as the timing offset of OFDM signals without the use of training symbol.

After a short presentation of the boundary layer method extended to strongly elongated objects by Andronov and Bouche [1], the author develops some techniques for deriving explicit formulas for the asymptotic currents on a strongly elongated object of revolution excited by an electromagnetic plane wave propagating in the paraxial direction. The performance of the different techniques are demonstrated by comparing numerical results obtained for the asymptotic currents on an elongated prolate ellipsoid with those obtained by solving the EFIE.

Ray tracing algorithms rely on two dimensional or three dimensional database. They use ray optical techniques referred to as the uniform theory of diffraction (UTD) using building database given as polygons. Building geometries can also be modelled as having non-planar geometries, and this would be important in modeling of shadowing loss due to curved structures in urban radio propagation. To demonstrate modelling of buildings as non-polygonal geometries, a particular building composition involving 3D cruved geometries is chosen, and shadowing loss for this building composition is studied via UTD ray tracing. Building structure considered in this study involves main canonical shapes of non-planar geometries including cone, cylinder and sphere. Single and multiple interaction of surface diffractions, effect of creeping waves are taken into consideration in the analysis.

It is well known in B-scan ground penetrating radar (GPR) imagery that the underground scatterers generally exhibit defocused, hyperbolic characteristics. This is mainly due to the data collection scheme and the finite beam width of the main lobe of the GPR antenna. To invert this undesirable effect and obtain focused images, various migration or focusing algorithms have been developed. In this paper, we survey the performance of our recent focusing algorithms, namely; hyperbolic summation (HS) and frequency-wavenumber (w-k) based synthetic aperture radar (SAR) focusing. The practical usage of these focusing methods were tested and examined on both simulated and measured GPR data of various buried targets. The simulation data set is obtained by a physical optics shooting and bouncing ray (PO-SBR) technique code. Measurements were taken by a stepped frequency continuous wave (SFCW) radar set-up. Scattered C-band field data were measured from a laboratory sand box and from outdoor soil environment. The proposed focusing methods were then applied to the B-scan GPR images to enhance the resolution quality within these images. The resultant GPR images obtained with the proposed algorithms demonstrate enhanced lateral resolutions.

In this work a new method based on the adaptive neuro-fuzzy inference system (ANFIS) was successfully introduced to determine the characteristic parameters, effective permittivities and characteristic impedances, of conventional coplanar waveguides. The ANFIS has the advantages of expert knowledge of fuzzy inference system and learning capability of neural networks. A hybrid-learning algorithm, which combines least-square method and backpropagation algorithm, is used to identify the parameters of ANFIS. There are very good agreement between the results of ANFIS models, experimental works, conformal mapping technique, spectral domain approach and a commercial electromagnetic simulator, MMICTL.

The scattering of electromagnetic waves from a Frequency Selective Surfaces (FSSs) composed of a new one- and two-turn square spiral shaped periodic structures are investigated by using modal expansion method for a linearly polarized transverse electric (TE) and transverse magnetic (TM) incident waves. The Moment Method (MM) of Galerkin type is employed by expressing the current induced on the metallic surfaces in terms of Piecewise Sinusoidal (PWS) basis functions to determine the FSS structure reflection and transmission coefficients.

Tunable frequency selective surfaces (FSSs) based on split ring resonators (SRRs) are presented. Tuning performance is achieved by means of several on/off switches placed between the rings of each SRR element. The band-stop FSS response is dynamically tuned to different frequency bands at different switching states. In addition, loadings placed at the corners of outer ring elements, forming a fan-like shape, with additional switches are shown to offer rather fine-tuning capability. A dual-layer FSS is also introduced to demonstrate a filter response over a larger frequency band, and also offers tunable dualband operation via switching. By using complementary SRR elements, a tunable band-pass response instead can be obtained using a similar switching configuration. Practical switch modeling is also examined in the paper along with the scanning performance of the SRR-FSS. The numerical analysis of the FSS designs is accomplished using a fast periodic array simulator, and the measurements demonstrate preliminary validation of the proposed switching configuration.

Computational aspects of EM pulse propagation along the nonuniform earth surface are considered. For ultrawide-band pulses without carrier, the exact wave equation in a narrow vicinity of the wave front is reduced to a time-domain version of the Leontovich- Fock parabolic equation. To solve it by finite differences, we introduce a time-domain analog of the impedance BC and a nonlocal BC of transparency. Numerical examples are given to demonstrate the influence of soil conductivity on the received pulse waveform. For a high-frequency modulated EM pulse, we develop an asymptotic approach based on the ray structure of the monochromatic wave field calculated at the carrier frequency. As an example, a problem of target altitude determination from overland radar data is considered.

In this paper, propagation model considers the region as a perfect conductor, covered by the two layer dielectrics, and air above. Propagation of the electromagnetic field in the presence of a four-layered region is examined in detail when a vertical electric dipole and observation point are located in the air. Similar to the three-layered case, analytical results are found for the electromagnetic field, which includes four wave modes: a direct wave,an ideal reflected wave, trapped surface waves, and lateral waves. The wave number of the trapped surface wave, which is contributed by the sums of residues of the poles, is between the wave numbers k₀ in the air and k₂ in the lower dielectric layer. The lateral wave is evaluated by the integrations along the branch cut. Analysis and computations shows that the trapped surface wave play a major role in communication at large distance when both the source point and observation point are on or close to the boundary between the air and the upper dielectric layer.

The characteristics impedance of the fundamental mode in a rectangular waveguide is computed using finite element method. The method is validated by comparison with the theoretical results. In addition to this, we have considered the problem of determining the modes of propagation of electromagnetic waves in a rectangular waveguide for the simple homogeneous dielectric case. The starting point is Maxwell's equations with an assumed exponential dependence of the fields on the Z-coordinates. From these equations we have arrived at the Helmholtz equation for the homogeneous case. Finite-element- method has been used to derive approximate values of the possible propagation constant for each frequency.

A composite right/left-handed transmission line resonator with 3 unit cells is fabricated and its radiation loss is investigated. At the zeroth order resonance state, the resonator shows radiation loss, which is dominant over other conductor and dielectric losses. This paper investigates the radiation loss of zeroth order resonators from a quality-factor point of view. With the use of a metal shield, the quality factor is considerably increased through a reduction of the radiation loss. The increase in the quality factor is explained by means of the extracted parameters of the equivalent circuit model.

This paper presents an exact performance analysis for the evaluating a mean acquisition time in a cellular code division multiple access system. New expressions for the probabilities of detection, miss, and false alarm are derived in a frequency-selective Rician fading channel. From the numerical results, it is shown that our formula gives the accurate results of the mean acquisition time in the performance analysis of the parallel acquisition system with the reference filter.

A new structure is proposed for wideband differential phase shifter. The proposed structure consists of a microstrip Nonuniform Transmission Line (NTL) and a microstrip Uniform Transmission Line (UTL). To optimally design the NTL, its strip width is expanded in a truncated Fourier series, firstly. Then, the optimum values of the coefficients of the series are obtained through an optimization approach to have low phase shift error and low reflection coefficient in desired frequency bandwidth. The usefulness of the proposed structure is studied using two examples.

Our scope in this paper is to provide a complete analysis of CFARdetection of fluctuating targets when the radar receiver incoherently integrates M returned pulses from a chi-squared fluctuating targets with two and four degrees of freedom and operates in a multitarget environment. Since the Swerling models of fluctuating targets represent a large number of such type of radar targets, we restrict our attention here to this interesting class of fluctuation models. There are four categories of such representation; namely SWI, SWII, SWIII, and SWIV. SWI and SWIII represent scan-to- scan fluctuating targets, while SWII and SWIV represent fast pulse-to-pulse fluctuation. Exact expressions are derived for the probability of detection of all of these models. A simple and an effective procedure for calculating the detection performance of both fixed-threshold and adaptive-threshold algorithms is obtained. The backbone of this procedure is the ω-domain representation of the cumulative distribution function of the test statistic of the processor under consideration. In the CFARcase, the estimation of the noise power levels from the leading and the trailing reference windows is based on the OS technique. The performance of this detector is analyzed in the case where the operating environment is ideal and where it includes some of extraneous targets along with the target under test. The primary and the secondary outlying targets are assumed to be fluctuating in accordance with the four Swerling's models cited above. The numerical results show that, for large SNR, the processor detection performance is highest in the case of SWIV model while it attains its minimum level of detection in the case of SWI model. Moreover, SWII model has higher performance than the SWIII representation of fluctuating targets. For low SNR, on the other hand, the reverse of this behavior is occurred. This observation is common either for fixed-threshold or for adaptive-threshold algorithm.

Wireless technology offers new found freedom and the potential for 'anytime, anyplace' communications. Communication technology requires being sustainable in the sense of efficiency, not only to preserve the information within the quality requirements, but also to express the same contents with the minimum resources. The Code Division Multiple Access (CDMA) is an emerging technology for next generation multimedia information of real-time and non real-time traffic and various multi-source multi-traffic communication environments. Multiple inputs multiple output (MIMO) as an adaptive antenna based technology which can improves the capacity of wireless mobile communication. The combined technique has both the advantages of CDMA and MIMO systems. Below the jamming margin CDMA alone works up to satisfactory level but above jamming margin CDMA along with MIMO may be a better proposition for anytime-anywhere communication.

This article aims to provide a novel and efficient technique for pattern shaping and null steering in the environment of unwanted interferences. This paper presents a DSP based method, where at first DFT coefficients are obtained from spatial domain sampling and then operating by suitable window function gives new set of DFT coefficients. IFFT(IDFT) over these coefficients provide complex weights which adaptively introduces null in the direction interference while keeping the main beam toward desired signal.

The propagation properties of surface plasmon polaritons (SPP) modes and surface magnetoplasmon polaritons (SMP) modes in a semiconductor slit waveguide are analyzed by the effective dielectric constant approach, and the interaction of the external magnetic field with the dispersion properties and field distributions of SMP modes in the Voigt configuration are emphasized in our analysis. Both the symmetric structure and the asymmetric structure are discussed in details. In contrast to the SPP modes which have one propagation band below the plasmon frequency only, the SMP modes have both the low-frequency propagation band below the plasmon frequency and the high-frequency propagation band above the plasmon frequency. When the external magnetic field increases, the two bands of the SMP modes will separate further in frequency, and the even symmetric distribution of the fundamental mode, which usually associates with the SPP mode, will be destroyed. These results can provide some guidance for the design of the tunable semiconductor waveguide in the terahertz regime.

An efficient, electrically small prolate spheroidal antenna coated with confocal double-negative (DNG) metamaterials (MTMs) shell is presented. The radiation power of this antenna-DNG shell system excited by a delta voltage across an infinitesimally narrow gap around the antenna center is obtained using the method of separation of the spheroidal scalar wave functions. Our results show that this electrically small dipole-DNG shell system has very high radiation efficiency comparing with the normal electrically small antenna due to the inductive effect of the MTMs shell that cancel with the capacitive effect of the electrically small antenna. It is found that the spheroidal shell can achieve more compact structure and higher radiated power ratio than the corresponding spherical shell. This dipole-DNG shell systems with different sizes are analyzed and discussed.

This paper aims at finding an algorithm featuring good estimation performance and easy hardware implementation for tracking airborne target hidden in blind Doppler. Incorporating the current statistical model which is effective in dealing with the maneuvering motions that most blind Doppler issues are caused, a current statistical model particle filter (CSM-PF) is presented in this paper for tracking airborne targets hidden in blind Doppler. Simulation results demonstrate that the proposed CSM-PF shows similar performance with the interacting multiple model particle filter (IMM-PF) in terms of tracking accuracy and track continuity, but it avoids the difficulty of model selection for maneuvering targets. In addition, when hardware implementation is considered, the proposed CSM-PF has lower processing latency, fewer resource utilization and lower hardware complexity than the IMM-PF.

Broadband single carrier modulated signals experience severe multipath distortion scrambling & ISI when propagating through physical medium. Correcting the distortion with channel equalization is the foremost task of the detector. Prior information about the transmitted signals in the form of channel decoder feedback can significantly enhance equalization accuracy. An algorithm that iteratively performs channel decoding and equalization with prior information is generally denoted turbo-equalizer. Turbo-Equalizer uses prior information & the principle of interference cancellation by MMSE criterion. Here we have tested Adaptive Turbo Equalization with least Mean Square Algorithm (LMS) & modified normalized LMS algorithm & Turbo-Decoding with a Log-Map. Consequently the Mean Square Error analysis, Stability analysis and convergence analysis are provided and its shown if the system is sparse, then the system will converge faster for a given total asymptotic MSE, though the choice of initialization is important. Here all the Implementation concepts have been verified in MATLAB platform and evaluation of the proposal is presented. The measurement for the performance is displayed as bit error rates (BER) in comparison to SNR of the Channel.