What can be measured by a spectrum analyzer

What is a spectrum analyzer? With this product, you will never encounter in everyday life, it is quite a specific device, and quite expensive. In this article we will consider the general purpose and application of such devices. If in a nutshell, the spectrum analyzer is a device that can be characterized as a frequency-selective voltmeter that responds to the amplitude, it is tuned in such a way as to display the rms value of the sinusoidal wave. And this is only in a nutshell, in fact everything is much more complicated and interesting.

It is important to understand that this device is not a power meter, even though the spectrum analyzer can directly display the value of this parameter. If we know the average or peak value of the sinusoidal wave and the magnitude of the resistance, we can set the device to display the power value. Thanks to the development of digital technologies, modern spectrum analyzers have truly wide capabilities.

To understand the purpose of this device, it is necessary to consider what is measured by the spectrum analyzer. From the name of the device you can understand that it serves to measure the spectrum. And what is this characteristic? The spectrum is a set of waves of sinusoidal form, which, under certain combinations, can give the signal under consideration in the context of the time domain. Ideally, the signal looks like a single classical sinusoid. In practice, in the frequency domain with the help of a spectrum analyzer, one can see that the signal spectrum consists of two waves and more, it can contain a second harmonic, etc. In the time domain, it is easy to measure the pulse front and its decline, as well as the emissions and beats of the signal . The measurement of signals by a spectrum analyzer in the frequency domain is simply necessary in the design of wireless communication circuits. Only with the help of this device, out-of-band and parasitic radiation can be detected and subsequently eliminated. As it was written above, the device allows to reveal additional harmonics of the signal, and this parameter in radio transmitting equipment is of great importance, because additional harmonics can fall on occupied frequencies and thereby create interference.

Also this device acts as an analyzer of the sound spectrum. What does it mean? Sometimes it is necessary to measure the noise as an ordinary signal. Any device or active circuit generates noise. Measurements of the coefficient of such noise and the signal-to-noise ratio are important characteristics of the device and a general indicator of the system.

Summarizing, let's say that a spectrum analyzer is simply needed for the radio designers to check and debug the projected equipment. The price of such a device is quite substantial and fluctuates in a wide range. For example, one of the simplest devices (Rigol DSA815) will cost about 50-60 thousand rubles, but for professional spectrum analyzer (Agilent Technologies) will have to pay 750-800 thousand rubles. A radio amateur for his home studio is unlikely to buy such a device, but it is simply necessary for firms or laboratories of enterprises engaged in the development of radio electronic equipment.