What is a spectrum analyzer

A spectrum analyzer is a device for measuring the magnitude of different frequencies in a signal across the frequency range of the instrument.

We use spectrum analyzers when we are interested in the spectral composition of a signal, which can be difficult to see from the waveform that an oscilloscope would display.

If we observe the complex voltage signal above, with a spectrum analyzer we would see the following:

Instead of a waveform of voltage over time, we get a display of amplitude on the Y axis and frequency on X axis. If we analyze the outputs of a spectrum analyzer we can learn about the dominant frequency, power, distortion, harmonics, bandwidth and other spectral components.

Spectrum analyzers usually come in one of four form factors:

• Benchtop spectral analyzers are used where they can be plugged into AC power and their larger size and weight are not a factor
• Portable spectral analyzers are smaller than benchtop ones and are equipped with a battery which allows for use outside the laboratory.
• Handheld spectrum analyzers are used whenever there is a need for the instrument to be lightweight and mobile.
• Networked spectrum analyzers do not include a screen and are commonly used for monitoring geographically distant locations. To allow for this, they tend to be more affordable and smaller in size.

Red Pitaya Spectrum Analyzer

Red Pitaya offers two input channels which can be used as a spectrum analyzer using a DFT (Discrete Fourier Transform) algorithm. Similar to networked spectrum analyzers, Red Pitaya does not have a screen and buttons, so all the interaction is done through a web interface and a dedicated 'Spectrum Analyzer' application.