Low-Cost Approximate Constant Coefficient Hybrid Binary-Unary Multiplier for DSP Applications

Multipliers are used in virtually all Digital Signal Processing (DSP) applications, such as image and video processing. Multiplier efficiency has a direct impact on the overall performance of such applications, especially when real-time processing is needed, as in 4K video processing, or where hardware resources are limited, as in mobile and IoT devices. We propose a novel, low-cost, low energy and high-speed approximate constant coefficient multiplier (CCM) using a hybrid binary-unary encoding method. The proposed method implements a CCM using simple routing networks with no logic gates in the unary domain, which results in more efficient multipliers compared to Xilinx LogiCORE IP CCMs and table-based KCM CCMs on average. We evaluate the proposed multipliers on 2-D discrete cosine transform and fast Fourier transform algorithms as two common DSP modules. Post-routing FPGA results show that the proposed multipliers can improve the {area × delay cost, and energy consumption per sample} of 8-bit fixed-point 2-D discrete cosine transform on average by {33%, 36%}. The improvement for 128-point 16-bit fixed-point fast Fourier transform on these metrics is {45%, 54%}. Moreover, the throughput of the proposed 2-D discrete cosine transform and 128-point fast Fourier transform architectures are on average 1.04× and 1.76× of the throughput of the binary architectures implemented using Xilinx LogiCORE IP CCMs, respectively.