Saul R. Dooley

Notes on the interpolation of discrete periodic signals using sinc function related approaches

Considering the sinc interpolation of discrete periodic signals, this correspondence establishes the equivalence of two recently published methods. Furthermore, the interpolation methods are equivalent to a fractional delay filter designed using the frequency sampling technique. A numerically stable and computationally attractive form of the equivalent methods is presented.

On explicit time delay estimation using the Farrow structure

Abstract This letter addresses the problem of adaptive, computationally inexpensive fractional sample delay estimation using the well-known explicit time delay estimator technique. The Farrow structure approximation for fast filter realisations is suggested which is then used to derive closed form update equations for arbitrary filter designs, with much reduced computational complexity.

Adaptive equalization in oversampled subbands

The potential presence of fractional delays, non-minimum phase parts, and a colouring of the channel output can require adaptive equalizers to adapt very long filters, which can have slow convergence for LMS-type adaptive algorithms. These problems can be addressed by a subband approach to reduce computational complexity and improve convergence speed. We discuss, why amongst other possibilities of subband processing the oversampled approach is particularly appealing to significantly reduce computational complexity and improve convergence speed. Simulation results for typical systems found in acoustics and communication channels are presented and highlight the benefit of our method.

Adaptive time delay and frequency estimation for digital signal synchronization in CDMA systems

The problem of synchronization of digital narrowband signals is presented. For non-stationary communication channels, accurate adaptive time delay and carrier frequency offset estimation is required. Modifications to a well-known time delay estimation method (the explicit time delay estimator), including a novel frequency adjustment element, are proposed which are shown through simulation to enable significantly low estimation bias, even at the very short filter lengths desirable in this application.

Subsample time delay estimation with variable step size control

Abstract Judicious selection of the step size parameter is often necessary for satisfactory performance from gradient-based adaptive algorithms for nonstationary time delay estimation. This paper provides two variable step size techniques for these algorithms which allow for fast initial adaptation. Simulations are provided which verify the useful behaviour of these methods.

Fast range and Doppler estimation for narrowband active sonar

We present a computationally simple algorithm suitable for fast, high resolution estimation of time delays and Doppler shifts (which are necessary for target localization and tracking) between narrowband signals in an active sonar system. The algorithm uses a modulated Lagrange interpolation filter and an LMS-type algorithm. The problem of delay and Doppler estimation is reduced to a linear regression problem. Convergence and performance analysis of the method is studied both analytically and through simulation. It is demonstrated that the method provides estimates close to the Cramer-Rao lower bound.