In this chapter we have seen how the relatively simple theoretical ideas underlying the K distribution model of sea clutter that were discussed in Chapters 6 and 7 can be extended, both in terms of their physical content and of the mathematical techniques used in their analysis. The simple isotropic random walk model of scattering that formed the foundation of the modelling of strong scattering observed in backscattered clutter returns can be relaxed by imposing either a bias or offset to the random walk; in the absence of number fluctuation effects, both these models yield the familiar Rice distribution model, which in turn has formed the basis for more elementary discussions of weak scattering. The impacts of negative binomial number fluctuations on the offset and biased random walk models are different; in the former case the homodyned K distribution model (which also underpins the radar performance modelling in Chapter 12) emerges and has proved to be a useful model for weak scattering. This model has recently found application in the analysis of medical ultrasound imagery. The biased random walk model preserves the infinite divisibility characteristic of the K distribution (this is not the case for the HK model) and yields an analytically tractable PDF; these pleasing formal attributes are rendered rather superfluous by the model's inability to produce a sensible very weak scattering limiting behaviour. This seemingly parlous state of affairs is redeemed, however, by the rather unexpected applicability of the GK model to the analysis of the performance of an interferometric SAR system.

Chapter Contents:

• 8.1 Introduction
• 8.2 The homodyned and generalised K models
• 8.3 Populations on coupled sites and their continuous limit
• 8.4 Some applications
• 8.5 Conclusions
• References

Inspec keywords: marine radar; radar interferometry; synthetic aperture radar; random processes; radar clutter; backscatter; statistical distributions

Other keywords: Rice distribution model; scattering limiting behaviour; sea clutter; GK model; mathematical technique; radar performance modelling; interferometric SAR system; medical ultrasound imagery; offset random walk model; backscattered clutter; homodyned K distribution model; negative binomial number fluctuation; isotropic random walk model; biased random walk model; weak scattering; fluctuation effect

Subjects: Other topics in statistics; Radar equipment, systems and applications; Electromagnetic wave propagation