This application note is intended to explain the fundamentals of swept-tuned,
superheterodyne spectrum analyzers and discuss the latest advances in
spectrum analyzer capabilities.
At the most basic level, the spectrum analyzer can be described as a
frequency-selective, peak-responding voltmeter calibrated to display the
rms value of a sine wave. It is important to understand that the spectrum
analyzer is not a power meter, even though it can be used to display power
directly. As long as we know some value of a sine wave (for example, peak
or average) and know the resistance across which we measure this value,
we can calibrate our voltmeter to indicate power. With the advent of digital
technology, modern spectrum analyzers have been given many more
capabilities. In this note, we shall describe the basic spectrum analyzer
as well as the many additional capabilities made possible using digital
technology and digital signal processing.