CHAPTER 4 – Response

This chapter discusses the concepts and design issues related to the response side of a synthetic measurement system. The goal of the response subsystem is to measure some aspect of the DUT in a measurement context. A secondary goal is to measure the output of the stimulus system for calibration purposes. The response signal conditioner is the signal processing interface between the DUT and the response codec. It is as simple as an amplifier with anti-alias filtering, or complex as a down-converter. In a response conditioner, there are two fundamentally different approaches to implementing a linear system and it can be known as high-gain and low-gain response processing strategy. The response digital processor section performs various sorts of functions, ranging from simple measurement and analysis tasks, to full-blown digital demodulation. The signal conditioner, like any analog system, can have offset, drift, noise, distortion, or spurious signals that corrupt the desired signal. The codec itself, with one foot firmly in the analog world, can also be plagued by these analog troubles. Therefore, focusing only on the bits in the codec distracts attention from the performance of the whole system. It is necessary to analyze signal flow, noise, and distortion through the whole system in order to draw any conclusions about accuracy and fidelity.