Superheterodyne Spectrum Analyzer

General Instructions

This spectral simulation is an interactive Java applet. You can change parameters by clicking on the vertical arrow keys. The five control buttons at the lower right are used to start (triangle) and pause (square) the simulation, to skip forward or back one section at a time (double triangles), and to change speed (+ and -).

After the simulation is complete, the start button takes you back to the beginning of the simulation. You may experience a delay at this point.

A spectrum analyzer is an extremely useful measurement tool that can show, in the frequency domain, information not readily recognizable with a time domain instrument such as an oscilloscope. For example, the frequency content of a signal (e.g. a fundamental sinusoid and one or more harmonic components) is readily identified with a spectrum analyzer, something difficult to identify from an oscilloscope display.

The most common type of spectrum analyzer, especially at high radio frequency and microwave frequencies is the Superheterodyne Spectrum Analyzer, shown in the simplified block diagram below. It operates in a fashion similar to a superheterodyne AM radio receiver, with the output in this case going to a CRT display rather than a speaker.