What is a spectrum analyzer ? You will never encounter this product in everyday life, this is a rather specific device, and quite expensive. In this article we will consider the general purpose and application of such devices. In a nutshell, a spectrum analyzer is a device that can be described as a frequency-selective voltmeter that responds to amplitude, it is configured to display the rms value of a sine 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 sine wave and the resistance value, then you can configure the device to display the power value. Thanks to the development of digital technology, modern spectrum analyzers have truly broad capabilities.
To understand the purpose of this device, it is necessary to consider what is measured by a 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 sinusoidal waves that, with certain combinations, can give the signal in question in the context of the time domain. In the ideal case, the signal has the form of a single classical sinusoid. In practice, in the frequency domain, using a spectrum analyzer, you can see that the signal spectrum consists of two or more waves, the second harmonic can be contained in it, etc. In the time domain, it is easy to measure the duration of the pulse front and its decay, as well as the spikes and signal . Measurements of signals by a spectrum analyzer in the frequency domain are simply necessary when designing wireless communication schemes. Only with this device can out-of-band and spurious radiation be detected and subsequently eliminated. As described above, the device allows you to identify additional harmonics of the signal, and this parameter in radio transmitting equipment is of great importance, because additional harmonics can fall on the occupied frequencies and thereby create interference.
Also, this device acts as a sound spectrum analyzer. What does it mean? Sometimes it is necessary to measure noise, like 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 an overall indicator of the system.
Summing up, let’s say that radio designers just need a spectrum analyzer to check and debug the designed equipment. The price of such a device is quite substantial and varies in a wide range. For example, one of the simplest devices (Rigol DSA815) will cost about 50-60 thousand rubles, but for a professional spectrum analyzer (Agilent Technologies) you will have to pay 750-800 thousand rubles. A radio amateur is unlikely to buy such an instrument for his home workshop, but it is simply necessary for firms or laboratories of enterprises involved in the development of electronic equipment.