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.

中文翻译：

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模拟与数字空间变换：吞吐量、功率和面积比较

处理多个并行模拟信号以简化下游信号处理的空间线性变换广泛用于多天线通信系统、机器学习推理、数据压缩、音频和超声应用等。过去，已经提出了范围广泛的混合信号和数字空间变换电路——然而，模拟或数字变换在吞吐量、功率和面积方面是否优越是一个长期存在的问题。在本文中，我们专注于 Hadamard 变换，并对采用相同 65nm CMOS 技术实现空间变换的最先进模拟和数字电路进行系统比较。我们分析了吞吐量、功率和面积之间的权衡，我们确定了混合信号或数字哈达玛变换更可取的机制。我们的比较表明 (i) 没有明显的赢家，并且 (ii) 模数转换通常主导面积和能源效率——而不是空间转换。