Efficient on-board quantization for interferometric and multi-channel SAR systems

Abstract

In synthetic aperture radar (SAR) applications, raw data quantization represents an aspect of primary importance, since the number of bits employed for radar signal digitization on the one hand defines the on-board memory consumption and the data volume to be transmitted to the ground, while on the other hand it affects the quality of SAR images. In this paper, we discuss a novel approach for efficient raw data quantization for interferometric and multi-channel SAR systems, which aims at optimizing the resource allocation strategy as a function of the specific interferometric acquisition requirements. Once the required performance is set (in terms e.g. of phase error or coherence loss), the resulting bitrate is defined according to the expected performance degradation. This is estimated with the help of a priori information, such as high-resolution backscatter statistics as well as coherence maps, which are available e.g. from the latest global data set provided by TanDEM-X (X-band) or Sentinel-1 (C-band). Finally, the desired non-integer compression rate is achieved by dynamically toggling the integer quantization rate of a standard block adaptive quantizer (BAQ). Hence, higher flexibility in terms of performance design and resource allocation can be achieved, without increasing the complexity and the computational load of the quantization scheme.