Like the oscilloscope, the spectrum analyser is a piece of test equipment that produces a picture of an electrical signal. The picture on the oscilloscope will show you how the signal varies over time, but this might not tell you all you need to know about the signal.
This is where the spectrum analyser steps in. The spectrum analyser looks at how the signal varies according to frequency, rather than time. If you’re looking at a complex signal made up of more than one frequency, the spectrum analyser separates the signal into its different frequency components and displays the level at each frequency. The spectrum analyser can display information about the signal including voltage, power and frequency.
Spectrum analysers have many applications in the design, manufacture and repair of electrical devices and systems. Their job is to analyse the signals being either transmitted by the equipment or passing through the equipment. By analysing the signals you can see if your equipment is working correctly or if it has a fault. You could also use a spectrum analyser to identify the frequency of any sources of interference to your equipment, for example, harmonic distortion.
There are many different models of spectrum analyser available covering a range of different frequencies such as the FSV3 from Rohde & Schwarz which covers up to 6 GHz . At the other end of the scale you have the FSW67, also from Rohde & Schwarz, with a frequency range of 2 Hz to 67 GHz.
Benchtop spectrum analysers are designed to be used in a fixed setting whereas handheld devices like the 9103 from Aeroflex are, you guessed it, lightweight analysers which you can carry round with you in the field.