An approximate logarithmic squaring circuit with error compensation for DSP applications

摘要

The squaring function is one of the frequently used arithmetic functions in DSP, so an approximation of the squaring function is acceptable as long as this approximation corrupts the bits that are already corrupted by noise, and does not degrade application's performance significantly. Approximation of the squaring function can lead to significant savings in hardware and processing time. Previously proposed approximations of the squaring function include LUT-based solutions, linear interpolation of the squaring function and minimization of combinational logic. This paper proposes approximation based on a simple logarithmic interpolation of a squaring function with a simple logic block, which can be reused for the error compensation. The proposed block performs approximation of the squaring function with a shift operation and a carry-free subtraction. The proposed approximate squarer with one compensation block achieves the average relative error below 1.5% for any bit length, while maintaining a low power consumption. In order to evaluate the device utilization, the propagation delay and power consumption and to compare it with the existing solutions, we have synthesized the proposed squarer and the existing solutions for the standard cell library and 0.25 urn CMOS process parameters.