This paper investigates the use of frequency domain equalization techniques to suppress narrowband interference and combine multiple paths in both direct sequence spread spectrum (DS-SS) and orthogonal frequency division multiplexing (OFDM) spread spectrum (OFDM-SS) systems. The similarities between the two signaling formats are highlighted and it is shown that the same receiver structures can ...

When considering low-frequency sources, the oceanic environment can act as a very dispersive waveguide, especially in shallow-water long-range sound wave propagation. One efficient tool for studying dispersion effects is based on time-frequency (TF) analysis of the received signals using a single receiver [1,2] . However, theses studies only considered two-dimensional (2-D) waveguides. In the p...

Waves with constant, nonzero linearized frequency form an interesting class of nondispersive waves whose properties differ from those of nondispersive hyperbolic waves. We propose an inviscid Burgers-Hilbert equation as a model equation for such waves, and give a dimensional argument to show that it models Hamiltonian surface waves with constant frequency. Using the method of multiple scales, w...

4 Finite Difference Frequency Domain 7 4.1 Forcing Term Expressed as Deviation from a Background . . . . . . . . . . . . . . . 7 4.2 Setting up FDFD Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.3 Electric Field FDFD Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.4 Magnetic Field FDFD Equation . . . . . . . . . . . . . . . . . . . . . . ...

With OFDM, which is a kind of multi-carrier systems, it is possible to use a diãerential coding/diãerential detection either in the time or frequency domain depending on the condition of transmission channels with the adoption of DQPSK as a method of subcarrier modulation. This paper proposes an approximate derivation method of the bit error rate (BER) in DQPSK/OFDM systems over frequency nonse...

when a direct voltage is applied under low injection conditions. In Equation (1) o is the angular frequency o= 2pf, where f is the frequency, R0=(dI/ dV)ÿ1, tp is the lifetime of the hole minority carriers, w is the length of the lower doped n bulk region, Lp is the minority carrier di€usion length for holes, with tp=Lp /Dp, where Dp is the di€usion coecient, and ®nally tw=w /Dp is a character...

We construct a numerical scheme based on the Liouville equation of geometric optics coupled with the Geometric Theory of Diffraction (GTD) to simulate the high frequency linear waves diffracted by a corner. While the reflection boundary conditions are used at the boundary, a diffraction condition, based on the GTD theory, is introduced at the vertex. These conditions are built into the numerica...

The linear governing equations of a transversely isotropic microstretch elastic solid medium are formulated and solved for surface wave solutions. The appropriate solutions satisfying the radiation conditions are applied to the required boundary conditions at the free surface of the halfspace of the medium. A frequency equation is obtained for Rayleigh surface wave in the medium. The non-dimens...

The governing equations of generalized magneto-thermoelasticity with hydrostatic initial stress are solved for surface wave solutions. The particular solutions in the half-space are applied to the boundary conditions at the free surface of the half-space to obtain the frequency equation of Rayleigh wave. The frequency equation is approximated for small thermal coupling and small reduced frequen...

In this paper the vibration of a spinning cylindrical shell made of functional graded material is investigated. After a brief introduction of FG materials, by employing higher order theory for shell deformation, constitutive relationships are derived. Next, governing differential equation of spinning cylindrical shell is obtained through utilizing energy method and Hamilton’s principle. Making ...