What is a spectrum analyzer?
A spectrum analyzer is a measuring instrument for electrical or electronic devices that provides the set of combined waves, called the spectra, of electrical signals at different frequencies. This information is shown in a graph through a logarithmic scheme.
This measurement tool makes it possible to verify communications circuits, transmissions, electromagnetic interference measurement receivers, radio signals, and more. It can even recognize frequencies that would be very difficult to identify without it.
What are waves and the electromagnetic spectrum?
Electromagnetic waves are a form of energy that has different particularities and applications according to their frequency. The range of all its frequencies is known as the electromagnetic spectrum.
The electromagnetic spectrum is represented between the axes of spectral content (ordinate axis) and frequency (abscissa axis). The spectrum meter measures the size and frequency (number of times something repeats in a given time) of the electromagnetic waves.
What is a spectrum analyzer for?
One of the applications of a spectrum analyzer is, for instance, in music production. The frequency of sound is constantly measured in this field both to identify the values of the voice and to recognize ambient noises. In this case, the signal being analyzed has a useful frequency range and another range where low-frequency noises that may affect the base sound are captured.
In the graph, the intrusive sound is shown as a curve that has a lower frequency than the rest.
How does a spectrum analyzer work?
Every spectrum analyzer divides the spectrum into different frequency groups, regardless of the type of wave, and then applies the mathematical process called the Fast Fourier Transformation (FFT). This algorithm transforms the signal from the frequency domain to the time domain, and vice versa.
In practice, when using a spectrum analyzer, what you will see are lines moving as the frequency changes and amplitude level peaks at different frequencies.
What types of spectrum analyzers are there?
Spectrum analyzers can be classified according to their type, which are:
- Analog spectrum analyzer: shows how the spectrum of a wave is composed, regardless of its type (acoustic, optical, electrical, etc.), and determines its structure within a frequency range. To measure, the analog analyzer uses a filter that divides the signal into specific frequencies, showing some ranges and blocking others; this filter is called a band-pass filter.
- Digital spectrum analyzer: unlike the analog spectrum analyzer, this kind doesn’t use a filter but a mathematical process to measure the frequency spectrum: the Fast Fourier Transformation (FFT).
What is the difference between a spectrum analyzer and an oscilloscope?
- Every signal can be measured in two ways: one in the time domain and one in the frequency domain. The first is done by an oscilloscope and the second by a spectrum analyzer. Therein lies the main difference between the two measuring tools.
- The oscilloscope provides information on the value of a signal at a certain time to show how long it takes to rise, fall, or repeat; the spectrum analyzer offers information on the frequency domain to show how much energy is in each frequency.
What are the limitations of a spectrum analyzer?
This measuring device cannot provide the values of the magnetic or electric field. However, there are settings that make it possible to obtain these values simply and immediately.
Currently, the vector signal analyzer is displacing the spectrum analyzer in its functions. The vector analyzer can make all the same measurements as the spectrum analyzer, but it also has many other digital demodulation functions.