P. Ilavarasan

Performance of an automated radar target discrimination scheme using E pulses and S pulses

Previous studies have demonstrated the viability of natural resonance based target discrimination using extinction pulses (E pulses) and single-mode pulses (S pulses). These studies qualitatively demonstrated the principles of resonance annihilation by forcing the interrogating pulse to have zeros at the complex natural resonance frequencies of the target. Here a quantitative scheme for evaluating discrimination using the E pulse and the S pulse is given. The performance of an automated E-pulse and S-pulse discrimination scheme is evaluated using numerically derived scattering data with varying amounts of noise. >

Radar target identification using a combined early-time/late-time E-pulse technique

The E-pulse technique has been applied in the past to both the early- and the late-time components of a transient radar response. While the late-time E-pulse technique uses aspect-independent waveforms, the early-time E-pulse technique requires a separate waveform for each target aspect angle and thus significantly more storage and processing time. This paper discusses a combination of the two techniques that employs the early-time technique to remove ambiguities generated from application of the late-time method. By narrowing the possible range of aspect angles of the potential targets, the early-time technique can be employed more efficiently.

A general E-pulse scheme arising from the dual early-time/late-time behavior of radar scatterers

A duality between the temporal late-time response and the spectral early-time response of a radar target is used to form the basis for a general E-pulse technique. Examples, using the ultrawide-band measurements of an aircraft model, reveal that E-pulse cancellation is possible both in the time domain for the late-time component and in the frequency domain for the early-time component. Applications to radar target discrimination and clutter cancellation are described, and the aspect dependence of early-time discrimination is investigated. >

Natural resonance extraction from multiple data sets using a genetic algorithm

The paper presents a scheme to extract the natural frequencies of a radar target from multiple data sets using a genetic algorithm technique (GAT). This technique prevents the extracted damping coefficients from being positive, as often happens with low signal-to-noise ratio data, by restricting the search parameters of the damping coefficients to be negative values. The GAT does not require an initial guess, unlike the constrained E-pulse technique (CET). The results from the GAT compare well with the CET (with much less effort required) and also with such established techniques as the pencil-of-functions method and the nonlinear least-squares technique. >

Natural resonance extraction from multiple data sets using physical constraints

This paper presents a scheme to extract natural frequencies from multiple data sets using an E pulse technique. Physical constraints are placed on the amplitudes of the E pulse basis functions to prevent the extracted damping coefficients from being positive, as often happens with low signal-to-noise ratio (snr) data. The constrained technique is compared to the usual E pulse extraction technique to show the improvement in the estimated natural frequencies.

Transient scattering of a short pulse from a conducting sinusoidal surface

A study on the transient scattering of a short EM pulse from a conducting sinusoidal surface which simulates a sea surface has been conducted. Theoretical analyses were performed for an infinite sinusoidal surface as well as a finite sinusoidal surface for both TE and TM polarized illuminations. A series of experiments was also conducted on a finite sinusoidal surface model to verify the theory. There are some interesting observations due to cut-off and band-pass phenomena of the Floquet modes excited in the periodic surface. It is shown theoretically and experimentally that the backscattered response of a short EM pulse from a conducting sinusoidal surface is a series of periodic peaks representing the reflections of the pulse from the crests of the surface.

Radar Identification and Detection Using Ultra-Wideband/Short-Pulse Radars

An ultra-wideband/short-pulse (UWB/SP) radar has promising potential for target identification due to its ultra-high resolution capability and for target detection due to its clutter-suppression capability. This paper describes various research topics studied at Michigan State University on target identification and detection using a UWB/SP radar.

Natural resonance extraction from: multiple data sets using a genetic algorithm

Identification of radar targets based on their late-time, natural-resonance signature requires the accurate knowledge of target natural frequencies. Realistically, these frequencies must be determined from measurements of actual or scale model targets. Many approaches have been studied to extract the natural frequencies from measurement, including the E-pulse technique, several variants of Pronys method, and the pencil-of-functions method. Perhaps the most straight-forward are those based on nonlinear least squares algorithms. Difficulty arises with least-squares techniques, however, because of their dependence on initial guesses for the natural frequencies and their tendency to get trapped in local minima. Also, constraints must often be placed on the ranges of the parameters as dictated by the measurement process and the principle of energy conservation. A genetic algorithm provides a natural minimization procedure for implementing constraints and avoiding initial guesses. Early studies have shown that a genetic algorithm provides results equivalent to the constrained E-pulse technique, with much less computer effort.<<ETX>>

Radar Target Identification and Detection Using Short EM Pulses and the E-Pulse Technique

The E-pulse radar target discrimination scheme, a resonance cancellation technique based on the late-time behavior of the transient scattered field, has been successfully demonstrated1,2,3,4 in the laboratory on a variety of occasions. The technique is based on the target natural frequencies and is inherently aspect-independent. Unfortunately, this approach ignores the early-time scattered field component, which is dominated by specular reflections from target scattering centers.

Transient radar for target identification and detection

Summary form only given. A radar system using narrow interrogating EM (electromagnetic) pulses can provide target identification and detection capabilities. When a target is illuminated by a narrow EM pulse, the scattered response from the target consists of an early-time response and a late-time response. The late-time response has been utilized to discriminate and identify the target based on the E-pulse (extinction-pulse) and the S-pulse (single-mode extraction pulse) techniques. These techniques are aspect-independent and their basic principles have been developed at Michigan State University. The present effort on these techniques is to study their effectiveness in the presence of sea clutter and noise.<<ETX>>