# Spectrum and vector analyzers

#### Vilius_Zalenas

Joined Jul 24, 2022
156
Not exactly sure if this is the right forum section, but this one is the best I could find for such a question...

Hi,

I am an electronics engineering university student. I am just starting my journey with all the measurement equipment. I gained a reasonable knowledge about digital oscilloscopes and know I am starting to learn the fundamental principles of spectrum and vector analyzers...

As I know so far, a spectrum analyzer is an instrument that shows the spectrum content of a signal. It depicts the amplitude of the signal in dBm (most often) and the frequency span on the X axis. No problems so far...

But spectrum analyzers very often come with an integrated tracking generator. As I understand, the generator generates signal in the defined frequency range and passes that signal through a system. Then the spectrum analyzer measures only the frequency response of a mentioned system.

On the other hand, there is also an instrument called a vector analyzer. As far as I know (again), vector analyzers measure S parameters by measuring the transmitted and reflected power levels. They provide one with a graph having dBm on the Y axis and frequency on the X axis (same as the spectrum analyzer.)

In the past I was thinking that the only difference between a frequency response measurement using a spectrum analyzers with TG and measurement with a vector analyzer is that spectrum analyzer measures the voltage of a signal, and the vector analyzer measures the power level, but recently one of my professors mentioned that in the RF tech field, a ,,dBm" is almost always referring to power (dBm is a power unit with respect to the 1 mW.)

So my question is:
Is there any difference between a spectrum analyzer with TG and a vector analyzer, because they both measure system`s frequency response? Can you use one instead of another? If anything that I wrote does not make any sense, please let me know, I was basing it on my knowledge, but like I said, I am only a beginner and I would love to hear any professional observations. Thank you in advance.

#### Janis59

Joined Aug 21, 2017
1,783
Spectrum analyzer is used for spectrum scanning and nothing else, vector analyzer is used for antenna adjusting, for transport function measuring, for extra small capacitors and coils measurement as well it parasitic parameter measurement, the amplifiers input and output impedance and it component measuring, for impedance passing etc etc etc. There are every imaginable wish corresponding instruments at Rode&Scwartz, just take few million pounds and everything will happen true. But when Your budget is just the salary alone, there are some rather nice modern-day alternatives what are just just weaker but ten-thousand fold cheaper. That are:
1) El-Mag component strength measurer GQ-EMF-390. Measures E field and M-field as well the power of field between 1 Hz and 6 GHz and part of this range is covered by automatic spectrograph, telling what frequencies have what signals and those partial signal strengths. The very up-wise range is uncovered over 1.5 GHz and very low range is without spectra, in less than MHz. Cost about 100 USD. P.S. Surprize, in years it price had been doubled....