Integration of planar circuits to non-planar ones has been recently considered as a credible technique for low-cost mass production of microwave and millimeter-wave circuits andsystems. This paper regards these concepts that provide for a complete integration of planar circuits andw aveguide filters synthesizedon a single substrate by means of metalizedp ost (via-hole) arrays. A method of designing a waveguide filter derived from a synthesis technique using dual array of inductive posts is presented. An experimental five-pole Chebyshev filter which has 2.5 dB insertion loss and return loss better than 10 dB is demonstrated. Such a technique of integration of planar andnon-planar circuits on the same substrate shows a significant reduction in size, weight and cost.
An interference excision algorithm in direct-sequence spread spectrum (DS-SS) communication systems is introduced. The proposed excision algorithm is developed for linear frequency modulated (LFM) signals that have broadband frequency characteristics. It is based on the time-frequency analysis of received signals employing short-time Fourier transformation (STFT). To analyze the interference, STFT of the received signal block is evaluated and thresholded. The interference detection is followed by an inverse-STFT computation to estimate the high-power jamming signal. The estimated jammer is then mitigated before demodulation. Simulations present adequate interference estimation results with mean estimation errors less than 0.01%. Various scenarios with different jammer-to-signal ratios (JSRs) and signal-to-noise ratios (SNRs) vs. bit error rates (BERs) are presented for single and multi-component LFM signals. Interference excision algorithms improve the system performance more than an order of magnitude.
A series of N identical periods of pairs of isotropic and biisotropic layers with defect in j-th basic element is investigated. The universal method that simultaneously allows to taking into account different types of defects in the structure is proposed. The problem is solved using the circuit theory and the transfer matrix methods. The analysis of the dynamic of electromagnetic properties of the investigated structure was carried out for different types of defects.
Electromagnetic fields and media can be compactly represented by applying the four-dimensional differential-form formalism. In particular, classes of linear (bi-anisotropic) media can be defined in terms of the medium dyadic mapping between the electromagnetic two-forms. As a continuation to the process started by medium dyadics satisfying linear and quadratic algebraic equations, the class of biquadratic (BQ) media is defined by requiring that the medium dyadics satisfy the bi-quadratic algebraic equation. It is shown that the corresponding four three-dimensional medium dyadics are required to satisfy only two dyadic conditions. After studying general properties of BQ media, a special case is analyzed in detail as an example.
The electromagnetic scattering problem of a short-pulse plane wave by a perfectly-conducting circular cylinder, buried in a dielectric half-space, is solved by means of a cylindrical-wave approach (CWA). The incident plane wave may have a rather general shape in the time domain. The technique is applicable for arbitrary polarization, or any cylinder size and burial depth, and it gives results both in the near- and in the far-field regions. In this work, an application of the technique to a basic but practical detection problem is presented, showing good results.
We designed two type binary 2D subwavelength (wavelength was λ = 10mm) focus diffractive photonic crystal lens and calculated the diffraction of plane TE-wave by use FDTD-method (our program in C++). It has been shown that diffractive photonic crystal lens designs have not an unique solution. Diameter lens was in 5 times more than her width and full width half maximum diameter of focal spot was 0.48λ.
In the analysis, an open-ended rectangular waveguide in an infinite ground plane is used as a near-field probe and the two-element waveguide array in an infinite ground plane is used as a radiator. Moment method analysis is used to find the reflection coefficient of the array element and probe voltage. The reflection coefficient of the array element, which is also an open-end of a rectangular waveguide, is computed and compared with the reflection coefficients, when the probe is at different positions in the near-field. The computations have also been carried out to find the induced probe voltage, when the probe scan in transverse plane (planar scanning) at a distance z_{1} from the radiator. Good agreement is obtained between measured and MOM results.
The far field behavior of a small wave size cylindrical microstrip antenna (CMA) has been originally analyzed for a small elevation angle, where a pronounced maximum has been found. Also it has been found that a similar maximum takes place in the far field of an electric dipole taken instead of the patch. It has been shown that the phenomenon originates to the far field behavior of the annular electric current given in the form of n = 1 azimuthally traveling wave harmonic held in the series representation of the electric dipole field. Approximate analytical expressions have been obtained describing the far-field components for two different polarizations. Also, the CMA radiation pattern is shown to bear similarities to the pattern of an electric dipole placed on a dielectric substrate surrounding a circular metal cylinder.
In this paper, we design the zero-dispersion wavelength shifted fiber based on the WII-type triple clad single mode optical fiber and consider the transmission parameters fluctuations owing to environmental conditions such as temperature variations on dispersion behavior of fiber. In order to estimate the thermal coefficients, the model introduced by Ghosh [1] is applied. Our calculation show that the thermal coefficient extracted for the chromatic dispersion, its slope, and the zero dispersion wavelength swing are -1.21×10^{-3} ps/km/nm/^{o}C, +2.96×10^{-3} ps/km/nm^{2}/^{o}C, and +3.33× 10^{-2} nm/^{o}C at 1.55 μm respectively. It is shown that in optical fiber design especially for dense wavelength division multiplexing (DWDM) systems, effect of temperature on channel displacement is critical and should be considered carefully.
Features of spatial power spectrum (SPS) of scattered radiation in a randomly inhomogeneous medium with strongly prolated anisotropic inhomogeneities of dielectric permittivity are investigated. In single scattering approximation, it has been shown that a pronounced gap along a direction of prolate inhomogeneities appears in SPS. Features of SPS of multiple scattered waves at oblique illumination of a boundary of randomly-inhomogeneous medium with prolate irregularities have been analytically studied using smooth perturbation method taking into account diffraction effects. Numerical calculations have shown that with an increase of a distance passing by the wave in random media, SPS has a double-peaked shape and a gap substantially increases. Its maximum is slightly changed and the width is broadening. The results have been obtained analytically for the first time and could find extensive practical application in optics and be useful in development of principles of remote sensing of random media.
This paper focuses on a tutorial overview of defected ground structure (DGS). The basic conceptions and transmission characteristics of DGS are introduced and the equivalent circuit models of varieties of DGS units are also presented. Finally, the main applications of DGS in microwave technology field are summarized and the evolution trend of DGS is given.
In our earlier work we introduce a numerical analysis to investigate the excess noise and performance factor of double carrier multiplication homojunction avalanche photodiodes (APDs) considering the nonlocal nature of the ionization process. In this paper we investigate the gain,breakdo wn voltage and carrier injection breakdown probability of homojunction avalanche photodiode in the wide range of multiplication region width. Also in our calculations the effects of dead space has been considered. Our analyses based on the history dependent multiplication theory (HDMT) and width independent ionization coefficient.
Employing Lorentz reciprocity and the Stratton-Chu formalism it is shown that the Poincare-Steklov or admittance operator can be interpreted as a complex symmetric operator mapping the tangential electric field (instead of the equivalent magnetic current) onto the equivalent electric current. We show that the pertinent block Calder´on projectors can be reformulated as operators with a block Hamiltonian structure. This leads to an explicitly complex symmetric Schur complement expression for both the interior and exterior admittance operators.
It is well known that under certain conditions, one dimensional photonic crystal (1D-PC) displays total omni-directional reflection (ODR) band gaps. The enhancement of total omnidirectional reflection band gap in 1D-PC is calculated theoretically. Using Transfer Matrix Method (TMM) and Bloch theorem, the reflectivity of one dimensional periodic structure for TEand TM-modes at different angles of incidence has been calculated.
An expression for the eddy current loss in solid rectangular cores is obtained using linear electromagnetic field analysis. Wherefrom text book formula for eddy current loss is derived highlighting various assumptions involved. To get an insight into the current interruption phenomena, electromagnetic fields in a composite rectangular core are analyzed. It is concluded that the reduction in eddy current loss in a laminated cores is basically due to the insertion of distributed capacitors in eddy current paths. Presence of these capacitors increases the impedance of the eddy current path, reducing eddy currents and eddy current loss.
In this paper, a compact waveguide bandpass filter is proposed. The proposed structure consists of some inductive diaphragms in a rectangular waveguide and the regions between them have been filled fully by dielectrics. The relations between the physical and electrical parameters of the existed asymmetrical impedance invertors are obtained. The usefulness of the proposed structure and its performance are verified by designing and simulating an equal-ripple X-band bandpass filter.
In this paper, optimum code rates for a number of channel codes which are used in the coded direct-sequence spread-spectrum (DS-SS) and coded code-division multiple-access (CDMA) communication systems operating in the presence of narrow-band interference (NBI) are investigated. The criteria in obtaining the optimum code rates is based on maximum tolerable NBI power to signal power ratio. First, we consider Optimum Codes, Super Orthogonal Codes (SOC), and Repetition Codes for a single-user DS-SS system and then, the optimum rates for the Optimum Codes in CDMA system using single-user and multi-user detection methods are obtained. In the latter case, we will consider evaluating the optimum code rate for two different multi-user detection schemes, namely, a detection method using joint coding/decoding and a detection method using successive interference cancellation.
The performance of capacitive interdigital sensors involved with anisotropic and inhomogeneous nematic liquid crystal (LC) film is investigated. These sensors have potential applications in chemical and biological systems. The theory for modeling the permittivity tensor of the LC film as a function of the molecular orientation is presented. The LC film is handled as inhomogeneous material where molecules are assumed to have different orientations with respect to the frame axes. Under these conditions, fringing field capacitances as functions of the molecular deformations are calculated. Examples of modeled capacitive interdigital sensors in the present of different inhomogeneous distributions of LC films will be studied and discussed.
The three-dimensional Gaussian beam scattering from the bounded periodic sequence of one-to-one composed isotropic magnetodielectric and bi-isotropic layers are investigated. The beam field is represented by an angular continuous spectrum of plane wave. The problem of the partial plane wave diffraction on the structure is solved using the circuit theory and the transfer matrix methods. It is found that after reflection from the structure, the circular Gaussian beam becomes, in general, an elliptical Gaussian beam, in addition to a displacement of the beam axis from the position predicted by ray optics.
This paper presents some new techniques for high resolution (HR) image processing and compares between them. The paper focuses on two main topics, image interpolation and image superresolution. By image interpolation, we mean extracting an HR image from a single Degraded low resolution (LR) image. Polynomial based image interpolation is reviewed. Some new techniques for adaptive image interpolation and inverse image interpolation are presented. The other topic treated in this paper is image super-resolution. By image super resolution, we mean extracting a single HR image either from multiple observations or multiple frames. The paper focuses on the problem of image super resolution using wavelet fusion and presents several super resolution reconstruction algorithms based on the idea of wavelet fusion.
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.