Constantino Rago

Detection-tracking performance with combined waveforms

It is commonly understood that in radar or active sonar detection systems constant-frequency (CF) pulses correspond to good Doppler but poor delay resolution capability; and that linearly swept frequency (FM) pulses have the opposite behavior. Many systems are capable of both types of operation, and hence in this paper the fusion of such pulses is examined from a system point of view (i.e., tracking performance) via hybrid conditional averaging (HYCA), a new but increasingly accepted technique for evaluating tracking performance in the presence of missed detections. It is shown that tracking errors are highly dependent on the waveform used, and in many situations tracking performance using a good heterogeneous waveform is improved by an order of magnitude when compared with a scheme using a homogeneous pulse (CF or FM) with the same energy. Between the two types of FM considered (upsweep and downsweep), it is shown that the upsweep is always superior. Also investigated is an alternating-pulse system, which, while suboptimal, appears to offer robust performance.

A comparison of the JPDAF and PMHT tracking algorithms

Here we analyze the tracking characteristics of a new data-association/tracking algorithm proposed by Streit and Luginbuhl, the probabilistic multi-hypothesis tracker (PMHT). The algorithm uses a recursive method (known amongst statisticians as the expectation-maximization or EM method) to compute in an optimal way the associations between the measurements and targets. Until now, no comparative performance analysis has been done. We compare the performance of this new scheme to that of a commonly used tracking algorithm, the joint probabilistic data association filter (JPDAF).

Direct data fusion using the PMHT

We analyze the tracking characteristics of a new data-association/tracking algorithm proposed by Streit-Luginbuhl, the probabilistic multi-hypothesis tracking (PMHT) algorithm, in a multisensor environment. Given that in the formulation of the algorithm there is no constraint on the number of measurements originated per target, it is a natural candidate for direct fusion in the multi-sensor case, where a combined frame (assuming synchronicity among the sensors) may have more than one target-originated measurement. In this paper we compare the performance of this new algorithm to that of a commonly used multisensor tracking algorithm: the joint probabilistic data association filter with a centralized estimation-to-estimation fusion.

CW-FM pulse fusion schemes

It is commonly understood that in active detection system constant-frequency pulses correspond to good Doppler but poor delay resolution capability; and that linearly-swept frequency pulses have the opposite behavior. Many systems are capable of both types of operation, and hence in this paper the fusion of such pulses is examined. It is discovered that in many (but not all) situations the features complement in such a way that tracking performance using a combined CW-FM pulse is improved by an order of magnitude when compared to a scheme using only a full CW or FM pulse. Also investigated are alternating- pulse systems, and while these are suboptimal their performances appear robust.

Estimation of the direction of arrival of water waves

The direction-of-arrival (DOA) of water waves is an important design consideration for construction. The authors propose two methods to estimate the DOA from records of pressure sensors deployed on the sea bottom. These methods are based on broadband noise subspace and signal subspace multiple signal characterization. The array manifold is not the standard one due to the frequency-dependent velocity of propagation of water waves. The cross-correlated signals case is analyzed for both methods. For the same data, these two methods are compared with the standard Longuet-Higgins (1963) method for wideband DOA estimation.<<ETX>>