An experimental comparison of optimum and sub-optimum filters' effectiveness in the generalized correlator

Contact Localization and Motion Analysis in the Ocean Environment: A Perspective

“…Even for ideal channels with additive Gaussian noise, the distribution of time delay estimates becomes non-symmetric as a function of decreasing signal spectra to noise spectra ratio [20,21]. The resulting skewed distribution of errors is undesirable, and has given impetus to the use of windowing and gating techniques to remedy the situation.…”

“…Where the clue is identified as having sufficient signal power over noise power, a time delay gate is centered at the corresponding output region, and clue estimation is executed over the gate output for each observation interval. The characteristics of the gate may be provided by a Kalman filter operating on the raw time delay estimates [20]. Such gating enhances the robustness of the processor against signal fades and limits the clue search to the most probable region in the processor output.…”

“…To effect this minimization, different windows are added to the basic time delays estimators with varying effectiveness [20,28,35,[59][60][61][62][63][64][65][66][67][68][69][70][71][72][73]• Such a ranging approach presumes stationary contact and sensor positions, as well as stationary signal and noise statistics.…”

“…The order K is not known a-priori since it is a function of the relative range and the number of observation intervals. Over a limited number of observation intervals, however, T(t) is likely to vary in a linear or parabolic fashion and parameter estimation may be carried out with a short-memory filter [20,36,78]. This filter has other benefits, since it can aid in the estimation of time delays through the design of a gating mechanism [20] or through a peak search in the correlator output.…”

“…Over a limited number of observation intervals, however, T(t) is likely to vary in a linear or parabolic fashion and parameter estimation may be carried out with a short-memory filter [20,36,78]. This filter has other benefits, since it can aid in the estimation of time delays through the design of a gating mechanism [20] or through a peak search in the correlator output. In addition, the resulting decrease in time delay variance allows an extended region of operation away from a given array before the need arises to precede the triangulation scheme by spatial gating.…”