Abstract
This application note discusses the measurement of amplitude and frequency modulated signals using a spectrum analyzer. The basic theory behind AM and FM modulation including time and frequency domain representations is presented. For AM signals, various techniques for measuring the degree of modulation, such as fast Fourier transforms, are described. For FM signals, techniques for calculating and measuring the frequency bandwidth are also outlined. In an appendix, a detailed mathematical treatment of modulation is presented along with a phasor description of AM and FM modulated signals. This application note contains more than 60 online pages, more than 60 analyzer screen-captures, zoomable illustrations, photographs, and four QuickTime™ signal animations.

Online Materials
This application note in Adobe Acrobat format is bundled with QuickTime animations and is available for download for all major computing environments. There are also two interactive Java™ signal models allowing the exploration and experience of basic concepts underlying AM and FM modulation. Links to the interactive models are found below and also from inside the application note Acrobat file. The standalone application note file also contains web-links to the complete library of Agilent Test & Measurement application notes, datasheets, and a general reference web-link back to the T&M directory on Agilent's world wide website.