Alberto Asensio-Lopez

Statistical Analysis of a High-Resolution Sea-Clutter Database

This paper presents the statistical analysis of an experimental high-resolution sea-clutter database, collected with a high-resolution Ka-band radar at the south coast of Spain. The main motivation of this paper has been to check the validity of the available theoretical models for high-resolution sea-clutter against data corresponding to a range resolution of centimeters. The overall amplitude probability density function (pdf), the compatibility with a compound representation, and the average spectral behavior of the data are analyzed in detail. Results clearly show the suitability of the compound Gaussian model and, more precisely, that the empirical pdf is well modeled by the generalized K distribution with log-normal texture. A close agreement has also been found between the estimated clutter spectral density and a power-law model.

Traffic Surveillance System Based on a High-Resolution Radar

Traffic surveillance is an important civilian application of radars. The current high-resolution radars give new opportunities so that the traffic application may be redefined. In this paper, a traffic scenario with a high-resolution radar is presented. A range-bin alignment method, the Global Range Alignment, which comes from the focusing techniques in inverse synthetic aperture radar, is applied to obtain further capabilities than the usual velocity measurement: distinction between vehicle types via length estimation and adequate management in situations with simultaneous targets. Preliminary results from a real scenario using a high-resolution linear frequency-modulated continuous-wave millimeter-wave radar are shown.

Motion compensation for ISAR based on the shift-and-convolution algorithm

ISAR (inverse synthetic aperture radar) is a coherent technique that obtains images of targets by processing the echoes returned during the dwell time. A higher angular resolution than the antenna beamwidth may be obtained. In this paper we report high resolution ISAR images, which have been obtained from data captured by a millimeter-wave LFMCW (linear frequency modulated continuous wave) radar. The target translational motion compensation is achieved by means of a new parametric algorithm, which makes use of the shift-and-convolution technique. This image autofocusing algorithm is compared with prominent point processing (PPP) and phase gradient autofocus (PGA). Simulated and real data from the millimeter-wave LFMCW radar are used to verify the proposed technique, although the method is also applicable to any kind of coherent radar.

Experimental Performance Analysis of Distributed Target Coherent Radar Detectors

In this paper a performance analysis on recorded live data of some detectors for range-spread targets is developed. To this end, real target and sea-clutter data collected by a fully coherent Ka-band radar system, featuring submeter range resolution, are used. The study is of particular interest for homeland security radar applications where a careful coastal control is necessary to prevent the arrival of nonauthorized small boats. The performance of both rank-one and subspace range-spread target detection strategies is analyzed, both in terms of constant false alarm rate (CFAR) behavior and in terms of detection capabilities. With reference to the former issue, clutter-only datafiles are used whereas, concerning the latter data containing both real target and clutter are used. The targets returns come from typical small boats (such as inflatable, wooden, and patrol boats) appearing range distributed at the resolution of the exploited radar system. Range-time detection maps are shown, assessing the capability of the analyzed processors to detect the aforementioned targets of great interest for homeland coastal security. Finally, the performance improvements achievable by over-resolving the target is quantified.

Instrumental CWLFM High-Range Resolution Radar in Millimeter Waveband for ISAR Imaging

This paper shows a High-Range Resolution (HRR) Radar prototype development, transmitting in millimeter-wave band. The waveform selected to be used is the continuous-wave linear frequency modulation (CWLFM), which allows, at the same time, good range resolution, moderate unambiguous doppler range and reasonable operational range taking into account that high-frequency band is used. The radar prototype looks for High-Range Resolution (HRR) characteristics as well as flexibility, in order to obtain the best Inverse Synthetic Aperture Radar (ISAR) images possible depending on the applications and targets involved. That is, depending on the speed and targets trajectories, some radar features, such as transmitted bandwidth, modulator frequency or sampling frequency, play a key role in obtaining the best possible results while using lowest electrical requirements.

A coherent Radon transform for small target detection

The Radon transform can be used to implement grid based “track-before-detect” processors. The approach can be described as a range alignment step followed by non-coherent integration. In this paper, a modification of the conventional direct Radon transform is proposed to coherently integrate the energy of the target. In this way, the noise and clutter contributions to each projection angle can be minimized and the overall performance of the system will improve.

Scan rate selection for coherent high-resolution maritime surveillance radar: An experimental study

Scan rate selection has a crucial impact on the performance of maritime surveillance systems. In this work, a sea clutter database has been used to obtain experimental insight on the trade-off between within-scan and scan-to-scan integration. This paper extends the previous empirical studies to the case of sub-meter range resolution Ka-band coherent sea-clutter data. Results show a clear performance improvement for faster scan rates provided that the number of coherently integrated samples is high enough.

Low Cost Millimeter Wave Transmitter Based on SMT Techniques

The aim of this paper is to present a millimeter wave transmitter (Ka band) designed to be manufactured using low cost, surface mountable millimeter wave components onto soft PTFE based substrates. The system employs recently developed millimeter wave monolithic integrated circuits (MMICs) packaged in surface mountable Ball Grid Arrays (BGA) for the low power subsystems and surface mountable Land Grid Arrays (LM packages) for the driving power stages, mainly the power amplifiers. Tailored active bias servos are also employed to improve efficiency and reliability and to reduce adjustments and manufacturing costs also. Output power compression point of P1dB = 26dBm and Power Added Efficiency PAE=18 % have been measured at 31 GHz.

High resolution sea clutter and maritime target data: Experimental performance of distributed target coherent detectors

High resolution Ka-band radar data corresponding to small maritime targets and target-free sea-clutter acquisitions are used to evaluate the experimental performance of range distributed target coherent detectors. The statistical analysis of the sub-meter range resolution clutter data shows strong fluctuations of both the spectral shape and power between adjacent range cells. The assessment of the impact of this highly heterogeneous disturbance in the CFAR behavior of distributed target detectors is a key aim of this work. Additionally, the availability of coherent target data at a range resolution of 0.08m, 0.16m and 0.8m has been exploited to analyze the detection performance of both subspace and rank one detection approaches.

Small-target detection in sea clutter based on the Radon Transform

Small target detection in sea clutter is a challenging problem. This paper presents a novel and heuristic approach based on the application of the Radon Transform to a set of consecutive range profiles. The performance of the detection technique has been tested with real sea clutter data, acquired with a high resolution CWLFM (continuous wave linear frequency modulated) millimetre-wave radar demonstrator. Results show that performing the detection on the Radon domain makes the detection of very small targets possible while keeping the false alarm rate controlled.