Synthetic Instruments: A New Horizon

Fig. 1 An SI generic network analyzer block diagram.

Modular test components have been with us for many years in many forms. Going back to the early ’70s I can remember HP BWO oscillator/sweeper mainframes with their plug-in modules to address the various extremely high frequencies above 1 GHz. While this modularity in test equipment exists today, a significant new aspect is now sweeping across the landscape — the ability to configure modular components to emulate the complete functions of traditional box instruments and in many cases that of complete test systems. The purpose of this article is to further explore what we mean when we talk of these synthetic instruments, where we might want to apply them and what some of the significant trade-offs are.

Before we can begin to explore what we can do, why we would do it and what the advantages are, we should start with some definitions of terms. Appropriate to the way we work today, an appropriate definition from Wikipedia reads like this: “It describes a functional mode or personality component of a synthetic measurement system that performs a specific synthesis or analysis function on a device under test (DUT) using specific software running on generic, non-specific physical hardware. Typically the generic hardware is a dual cascade of three subsystems: digital processing and control, A/D or D/A conversion (codec) and signal conditioning. One cascade is for stimulus, one for response. Sandwiched between them is the device under test (DUT) that is being measured.” How we achieve this synthetic instrument (SI) or synthetic measurement system (SMS) will be further explored here.