A Scaling-Less Newton–Raphson Pipelined Implementation for a Fixed-Point Reciprocal Operator

The reciprocal is a widespread operation in digital signal processing architectures. A usual method consists in using the Newton-Raphson algorithm or its derivatives, either in floating or in fixed-point formats. With the former format, the standardized format of the mantissa makes the implementation easier, but for the fixed-point format there are many possibilities. This forces a design with scaling of the input in order to respect a predetermined work range. Having the input in a known range makes it possible to compute a first approximation with coefficients stored in memory blocks. With this method, it is hard to propose a “ready to use” IP for all the fixed-point formats. In this letter, a novel architecture, which does not require scaling, is proposed. This design is totally pipelined, ROM-less and can be directly used in any architecture. The implementation was optimized to reach a maximum clock frequency of 740 MHz on a Virtex-7 Field-Programmable Gate Array (FPGA).