Perfect pulse compression codes and other advances in radar experiment theory

Lehtinen, M.

Sodankylš Geophysical Observatory, Sodankylš, Finland

Incoherent scatter radar was the main application in the early development of statistical inverse problems research in Finland. This resulted in important advances in radar methods, including alternating codes, proper statistical analysis with the GUISDAP software and radically improved experiment optimization. These early developments were mainly relevant in the case of a low SNR and also somewhat suffered from the need to be compatible with legacy type of data reduction by correlation calculations.

In connection with the Finnish Centre of Excellence in Inverse

Problems Research 2006-2011, some significant breakthroughs have recently been made, including complete charaterization of comparison radar experiments of time-coherent distributed targets for any SNR, formulation of proper signal sampling and invention of pulse compression codes with exactly zero sidelobes.

We discuss these new developments, putting emphasis on their technical consequences, including the need for arbitrarily chosen phases in phase codes - and in some cases even amplitudes, and necessity of acces to raw, uncorrelated radar echoes for proper analysis. We also discuss the ways to approximate the best codes by more practical ones (like binary phase codes) and ways to compare these to the perfect codes.

We discuss a stepwise plan to implement these new methods as practically applicable software systems for data analysis. We also shortly introduce efforts towards computer searches for the new kinds of experiments and show some first results of new types of codes with actual data. These particular experiments are designed to replace alternating codes with a significantly simpler code sets, typically using only a sequence of 2 or maybe 4 codes instead of the rather long alternating code cycle. This part is meant to serve as an introduction to a few other talks with more detailed presentation of the various new techniques.

Finally, we discuss the plans of future development of these theoretical developments. This mainly concerns generalizations of the results to the non-time-coherent case and also new planned analysis methods making full use of signal statistics by moving the inversion step from lag profiles to echo amplitudes.