Analog vs. Digital Spatial Transforms: A Throughput, Power, and Area Comparison

TL;DR

This paper systematically compares analog and digital Hadamard spatial transforms in 65nm CMOS, analyzing throughput, power, and area to identify regimes where each approach is preferable, revealing no clear overall winner.

Contribution

It provides a comprehensive comparison of analog and digital spatial transform circuits, highlighting the trade-offs and regimes where each approach excels.

Findings

Analog transforms often dominate in throughput and power efficiency.

Analog-to-digital conversion significantly impacts area and energy consumption.

No clear overall winner between analog and digital transforms in the studied regimes.

Abstract

Spatial linear transforms that process multiple parallel analog signals to simplify downstream signal processing find widespread use in multi-antenna communication systems, machine learning inference, data compression, audio and ultrasound applications, among many others. In the past, a wide range of mixed-signal as well as digital spatial transform circuits have been proposed---it is, however, a longstanding question whether analog or digital transforms are superior in terms of throughput, power, and area. In this paper, we focus on Hadamard transforms and perform a systematic comparison of state-of-the-art analog and digital circuits implementing spatial transforms in the same 65\,nm CMOS technology. We analyze the trade-offs between throughput, power, and area, and we identify regimes in which mixed-signal or digital Hadamard transforms are preferable. Our comparison reveals that (i) there is no clear winner and (ii) analog-to-digital conversion is often dominating area and energy efficiency---and not the spatial transform.