Fundamentals of modern spectral analysis

Digital Signal Processing (DSP) has revolutionized spectral analysis. Where the swept spectrum analyzer dominated the market in the past, the Fast Fourier Transform (FFT) based spectrum analyzer is now gaining acceptance as the method of choice. This is due in part to the prevalence of high speed, high dynamic range Analog-to-Digital Converters (ADC) and high speed signal processing devices such as Field Programmable Gate Arrays (FPGA). Because the FFT-based spectrum analyzer is readily implemented with a limited set of generic hardware, it is an attractive technique for Synthetic Instruments (SI), where the goal is to form multiple measurement functions from a limited set of generic hardware modules. In this paper some of the fundamental design parameters and specifications of modern spectrum analyzers such as dynamic range, instantaneous bandwidth, and image rejection are presented. These parameters are explored with a focus on maintaining system performance without sacrificing flexibility.