PARSAX An Informal Look at Radar Technology and Applications within TU Delft

2Mar/101

Software Defined Radar

The ElectroScience Laboratory in Ohio State University recently announced their new development - a software defined radar (SDR) platform that can adaptively switch between different modes of operation by modifying both transmit waveforms and receive signal-processing tasks on the fly.  High-speed analog-to-digital and digital-to-analog converters along with modern FPGAs and fast digital signal processors Software Defined Radar Architectureallow for maximum flexibility in algorithm design. Until this point their concept and development is very similar to our PARSAX radar. But if in the PARSAX radar the parallel coherent transmit and receive channels enable the exploration of simultaneous polarimetric information about radar objects, the multi-channel radar from Ohio has a few modes such as multiple-input multiple-output (MIMO) radar and polarimetric radar.  As for our group, the target phenomenology is one of research topics. Another area of study which will also be explored with SDR system is the urban propagation environment for radar.

The ESL Software defined radar features:

  • 500 MHz or greater waveform bandwidth
  • RF Frontend tunable from 1-18 GHz
  • High-speed Xilinx FPGAs and Texas Instruments 32-bit DSPs for implementing real-time signal processing
  • Information driven active sensing layer based on a game theoretic approach to sensor management implements competitive sensor tasking to control the selection of the current radar operating mode

 Sundance press release in PDF file

25Feb/100

Scanning Radar – Interpretation of the Doppler Velocity Patterns

Occasionally found quite old, but very clever presentation "Interpreting Doppler Velocity Patterns" (2000) by Dr. Ronald E. Rinehart from University of North Dakota, which is based on even older (1983, 1987) reports of Rodger A. Brown and Vincent T. Wood from the National Severe Storms Laboratory, NOAA, Norman, Oklahoma. The best way to view this on-line slide show, created in the beginning of this century, is still to use Internet Explorer. But the presentation explains to you, for example, what spatial structure of wind field is responsible for this unusual pattern and what type of meteorological phenomena can produce such wind-field.

 Misterious Pattern of Doppler Velocity

Brief explanation for those who still did not understand experimental setup. The radar with narrow antenna pattern (pen-like) rotates in horizontal plane and measure Doppler velocity. It is assumed that full interval of observation is homogeneously filled with some kind of reflectors (e.g. rain drops), which are moving by wind. The wind (or, more precisely, its amplitude and direction) is a function of height and position on azimuthal plane. The problem to solve is: to sketch the pattern of wind directions and the vertical profile of wind amplitude using presented measured Doppler pattern.

On practice such mysterious pattern, probably, not often can be observed using middle range radars like PARSAX and IDRA, but... Anyhow, the study and analysis of such patterns can be a good practice in understanding and interpretation of radar observations.

Image source

10Feb/100

Information Geometry in Radar Signal Processing

"Applications of Information Geometry to Radar Signal Processing" by Frédéric BarbarescoQuite interesting lecture "Applications of Information Geometry to Radar Signal Processing" by Frédéric Barbaresco from THALES AIR DEFENCE, Radar Development Unit, Algorithms & Functional Studies Department is available on-line. It includes video and slides of presentation.

Abstract. Main issue of High Resolution Doppler Imagery is related to robust statistical estimation of Toeplitz Hermitian positive definite covariance matrices of sensor data time series (e.g. in Doppler Echography, in Underwater acoustic, in Electromagnetic Radar, in Pulsed Lidar). We consider this problem jointly in the framework of Riemannian symmetric spaces and the framework of Information Geometry. Both approaches lead to the same metric, that has been initially considered in other mathematical domains (study of Bruhat-Tiits complete metric Space (see also) & Upper-half Siegel Space in Symplectic Geometry). Based on Frechet-Karcher barycenter definition (see ref and ref) & geodesics in Bruhat-Tiits space, we address problem of N Covariance matrices Mean estimation. Our main contribution lies in the development of this theory for Complex Autoregressive models (maximum entropy solution of Doppler Spectral Analysis).

Specific Blocks structure of the Toeplitz Hermitian covariance matrix is used to define an iterative & parallel algorithm for Siegel metric computation. Based on Affine Information Geometry theory, we introduce for Complex Autoregressive Model, Kohler metric on reflection coefficients based on Kohler potential function given by Doppler signal Entropy. The metric is closely related to Kohler-Einstein manifold and complex Monge-Ampere Equation. Finally, we study geodesics in space of Kohler potentials and action of Calabi & Kohler-Ricci Geometric Flows for this Complex Autoregressive Metric.

We conclude with different results obtained on real Doppler Radar Data in HF & X bands : X-band radar monitoring of wake vortex turbulences, detection for Coastal X-band & HF Surface Wave Radars.

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