In ground-based L-band radar sea clutter, Bragg scattering caused by short gravity waves on the sea surface frequently exhibits azimuthal dependence, with higher order Bragg-scattering spectra clearly visible alongside the first-order spectrum. Recent measurements from an L-band airborne moving target detection (MTD) radar, operating in side-looking mode with HH polarization at medium incident angles (30°–60°), near the Zhoushan Fishing Ground in Ningbo, China, also reveal azimuth-dependent and multipeak characteristics, that pose challenges for target detection within the endo-clutter region. To better understand the clutter characteristics in L-band airborne MTD radar, this article investigates the modeling of sea clutter Doppler spectra under medium incident angles ranging from 30° to 60°. Using the small slope approximation (SSA) incorporating a time-varying rough sea surface with spikes, a systemic expression for the Doppler spectrum, accounting for the sea clutter space-time coupling, is derived. Specifically, the Doppler spectrum related to the sea surface is expressed as an azimuth-dependent underlying spectrum weighted by the antenna beam (i.e., the spatial spectrum), while the spectrum due to spikes is represented as a convolution of the spatial spectrum with an azimuth-independent underlying spectrum. Each individual spectrum is characterized with Gaussian profiles, forming the basis of a comprehensive spectrum model that can successfully capture an azimuth-independent peak and approximately 2–7 or more azimuth-dependent peaks in the real-world sea-clutter Doppler spectra. Note that the proposed model is directed against sea echoes with azimuth-dependent scattering properties from the main lobe of the two-way antenna pattern, and thus, suitably characterizes the corresponding sea-clutter Doppler features.

Multiaspect synthetic aperture radar (SAR) observations of complex targets often exhibits distinct anisotropic feature, which also contains rich information about target structural complexity. In practical scenarios, SAR images at certain aspects may be unsampled or may not be available, in such case, interpolation of SAR images from other sampled or available aspects, known as multiaspect interpolation, is needed. This article conducts a preliminary study on the quantitative description of anisotropic scattering variation (ASV) and the relationship between ASV and multiaspect interpolation based on typical aircraft target airborne multiaspect SAR dataset. The aim is to clarify when it is more meaningful to perform multiaspect interpolation and propose ASV operator to describe the variation of anisotropic scattering, which, to some extent, can also express target structural complexity. In the exploration process, it was found that certain expression of anisotropic feature can reflect the structural and textural feature of targets, which can represent changes of anisotropic scattering. Therefore, these expressions are incorporated into ASV operator, which makes the operator effective. Experimental results show that the proposed ASV operator can accurately describe changes of anisotropic scattering based on aircraft target data. Moreover, it can predict the effectiveness of interpolated SAR images based on the value of ASV operator. Consequently, multiaspect interpolation of SAR images at required aspects can be performed based on prior predictions using sampled SAR images.

This paper presents the design methodology and implementation of reconfigurable coordinate rotation digital computer (CORDIC) architecture that can be configured to operate in different modes and rotations to achieve singleprecision floating point division, multiplication and square-root operations. Through introducing pre- and post-processing, the float-point operations can be integrated into a unified CORDIC iteration procedure. According to the characteristics of different operations, we propose a pipeline-parallel mixed architecture to optimize the area-delay-efficiency. Finally, the prototype based on Xilinx XC7VX690T has been established to test the performance of the proposed design. The result shows the related error with arithmetic computation is less than 10−6, and the resource-consumption of the proposed design is less than the sum of existing IP cores.