A Novel Detector for Adaptive Detection of Weak and Small Ships in Compact Polarimetric SAR

Compact polarimetric (CP) synthetic aperture radar (SAR) is now widely used for ship detection due to its excellent balance of data acquisition and resource allocation. In this article, a novel ship detector for weak and small targets is constructed using the CP SAR data of circular transmit linear receive mode. First, based on the X-Bragg model and circular anisotropy, a new feature
$DB$
is proposed to characterize the intensity of double-bounce scattering. Then, a new detector
$DBHw$
combining double-bounce scattering intensity
$DB$
and entropy
$H_{w}$
is constructed to characterize the difference in scattering mechanism and scattering randomness between ship targets and the sea clutter background. An adaptive constant false alarm rate (CFAR) detection method is implemented based on this novel detector and the generalized Gamma distribution (
$\text{G}\mathrm {\Gamma }\text{D}$
). Finally, experiments were conducted using CP SAR data simulated from L-band UAVSAR full polarimetric data. The signal–clutter ratio (SCR) values for strong backscattering and weak backscattering ships of
$DBHw$
are 9.4613 and 9.6705, respectively, and of
$g_{0}$
are 16.7497 and 2.2358, respectively, demonstrating the stability and superiority of
$DBHw$
regardless of the span of targets. The detection result of
$DBHw$
is 30 out of 32, and of
$DB$
,
$Hw$
, and
$g_{0}$
is 19, 20, and 11 out of 32, respectively, demonstrating the significant improvement of
$DBHw$
based on
$DB$
and
$Hw$
, and the superiority of power-independent detector
$DBHw$
compared with
$g_{0}$
in detecting weak and small ship targets.