Fundamentals of Real-Time Spectrum Analysis

This document describes how the Real time Spectrum Analyzers (RSA) work and provides a basic understanding of how it can be used to solve many measurement problems associated with modern RF signals.

As RF signals have become ubiquitous in the modern world, so too have problems with interference between the devices that generate them. Products such as mobile phones that operate in licensed spectrum must be designed not to transmit RF power into adjacent frequency channels and cause interference. This is especially challenging for complex multi-standard devices that switch between different modes of transmission and maintain simultaneous links to different network elements. Devices that operate in unlicensed frequency bands must be designed to function properly in the presence of interfering signals, and are legally required to transmit in short bursts at low power levels. These new digital RF technologies that involve the combination of computers and RF include wireless LANs, cellular phones, digital TV, RFID and others. These, combined with new advances in Software Defined Radio (SDR) and Cognitive Radio (CR) provide a new path forward and will fundamentally change spectrum allocation methodologies resulting in increased efficiency in the way that the RF spectrum, one of the scarcest commodities, is utilized.

To overcome these evolving challenges, it is crucial for today’s engineers and scientists to be able to reliably detect and characterize RF signals that change over time, something not easily done with traditional measurement tools. To address these problems, Tektronix has designed the Real-Time Spectrum Analyzer (RSA), an instrument that can discover elusive effects in RF signals, trigger on those effects, seamlessly capture them into memory, and analyze them in the frequency, time, modulation, statistical and code domains.