Wednesday, 8 October 2014

EISCAT_3D Measurement Methods Handbook

Professor Markku Lehtinen
A significant output of the EISCAT_3D preparatory phase project, the "EISCAT_3D Measurement Methods Handbook" by Professor Markku Lehtinen is now online here.

Here is an extract of the Introduction Chapter:


Introduction

The purpose of this handbook is to define the guidelines for the EISCAT_3D radar development project. Incoherent scatter radar experiment design and data analysis is in the process of being transformed from a collection of engineering recipes to an exact mathematical problem in experiment comparison and statistical inversion theories. Also, the development of the solid-state UHF power transmitter technology has lead to a replacement of high-power transmitters and large disc antennas by arrays of several thousands or tens of thousands of simple, relatively low-power transmitters and receivers with phase control for beamforming in both directions.

Our goal is to show how the new mathematical principles of radar experiment design and data analysis can be used to design a modern radar representing the true state-of-the-art in both theoretical developments in radar experiment design and modern electronics. We also include the phased-array principle as a new chapter in rigorous radar experiment design, so that the large antenna arrays can be optimised to provide the best possible performance with the least possible cost. 


The main principle here is to introduce rigorous mathematical principles to replace numerical simulation comparisons wherever possible. This is very useful, because the number of combinations of different alternatives is so large that finding the best ways to operate is practically impossible through simulation comparisons (the search space of all alternatives is simply much too large). This is of course not possible in every respect, but we have succeeded in many sub-problems so that we are very close to the situation of being able to choose the best possible experiments and radar hardware configuration through systematic reasoning – with radically reduced assistance of computer searches optimising different alternatives.

In the traditional radars, the (multi)megawatt transmitter systems with discs of several tens of metres of diameter, the cost of signal processing is typically a rather trivial small fraction of the total cost of the system. In phased-array systems with tens of thousands of sampled data streams and beamforming by digital computation instead of the analog summation inherent in the very basic principle of operation of the parabolic disc antennas, the cost of signal processing becomes significant. The most obvious cost is that of the hardware of tens of thousands of sampling systems and the related first phases of signal processing, including IQ detection and beamforming. The cost of just cabling connecting the huge number of antennas to a central processing point is significant in recent similar systems (Such as recent developments in astronomy like LOFAR or other precursors to SKA).

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