硬件與軟件權衡。第2部分：峰值檢測器

　　編者按：這是一個典型的架構決策：它的功能是在硬件中實現，以及在軟件中實現。這兩部分系列的第1部分著眼于使用比較器作為設計的考慮和權衡。在第2部分中，我們將使用峰值檢測器作為示例。

　　正如本系列文章的第1部分所述，人們常常認為軟件是實現核心功能的簡單方法，盡管基于硬件的解決方案通常是更好的方法。

　　在給定的情況下，達到“最佳”答案需要設計者考慮許多設計因素和性能目標之間的權衡。本文將從峰值檢測器的角度探討硬件與軟件決策，同時提供一些示例。

　　Defining the peak detector function

　　Like comparators， peak detectors are a basic circuit building block for many real-world signal processing applications. Peak detection determines that a signal has passed its peak value and signals the system to indicate this occurrence. They can be used to mark the presence of valid pulses within a continuous stream， capture radar signal returns， monitor heart pulses， or to indicate a new maximum such as in data from oscillations （buildings swaying due to an earthquake）。

　　Before designing a peak detector， it’s important to be very clear about the objectives of the project， as there is some overlap and ambiguity in terminology. First， there’s a maximum signal detector， which captures the maximum value of a signal indefinitely， until a new maximum occurs （Figure 1）。

　　An example might be a sensor that is tracking the maximum shock to which a package in transit is subjected. The lesser shocks are not of interest; only that maximum is of concern.