Fixed-Point Processing of the SAR Back-Projection Algorithm on FPGA
Don Lahiru Nirmal Hettiarachchi, Eric J. Balster
Abstract
Time-domain back projection (BP) is a widely known method used in Synthetic Aperture Radar (SAR) image formation. Despite its advantages over other image formation algorithms, the BP method is hindered due to its computational complexity and its requirement of higher number of operations and processing power. Recently, Field Programmable Gate Array (FPGA) devices have been used for BP acceleration mainly due to their parallel processing capabilities, reconfigurability, scalability, and low power requirement. This paper presents a new Fixed-point based BP (FxBP) design for FPGA devices and a Floating-point based BP (FlBP) design to compare performance. Both designs are developed with N-Dimensional Range (NDR) structure and Single Work Item (SWI) structure using OpenCL. The FPGA performance is evaluated using a FPGA performance metric (FPM). It is shown that FxBP-NDR and FxBP-SWI designs generate high quality back projected images compared to FlBP designs, while saving 16.87% and 42.54% on logic resources and gaining 17.90% and 91.62% on FPGA performance in NDR and SWI, respectively. Obtained results clearly indicate that FPGA devices perform significantly better with FxBP designs compared to FlBP designs, even with hardened FPUs.