An efficient structure of variable fractional-delay filter for digital time-delay beamformer

In this paper, an efficient structure of online adjustable variable fractional-delay filter (VFDF) for digital time-delay beamformer (DTDBF) is presented. The proposed structure is based on the decomposition of sine function. The efficiency improvement is achieved by decomposing the VFDF into two sub-VFDFs with lower polynomial order and a complex phase shift which can be easily realized by CORDIC algorithm. A high precision programmable delay element for DTDBF is designed with an FPGA as an example, and the implementation results show that the proposed structure can save over 6% of the logic elements (LEs) compared with the existing structures.