Power-Efficient Approximate Newton-Raphson Integer Divider Applied to NLMS Adaptive Filter for High-Quality Interference Cancelling

The division datapath is undoubtedly the most complex operation in a wide range of digital signal processing applications, such as in adaptive filtering algorithms. This paper proposes an optimized and approximate integer divider hardware architecture, based on the Newton-Raphson algorithm combining both fixed-point dynamic range and truncation techniques, to speed up that operation. Adaptive filters have been much studied over time, as they comprise one of the most challenging fields in signal processing. This work presents dedicated hardware architectures based on normalized least mean square adaptive filtering algorithms for the power line harmonics interference cancelling. The hardware architectures are based on 2's complement representation and were described in VHDL and synthesized into a 65 nm CMOS dedicated ASIC. Our results show that the increased approximation level of Newton-Raphson divider approximation presents up to 223 times less power dissipation than the baseline version without our optimization and approximations, providing up to 93 times of power dissipation savings in the complete interference canceller system.