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Spectrum analyzer and vector network analyzer are the common instruments in the measurements of high frequency for electronic component. I think two of the most important issue in the high-frequency measurement probably is the impedance and S-parameters.

I have the following questions:

  1. Why don't we use the impedance analyzer to do so?
  2. Can we use a impedance analyzer to measure impedance or S-parameters?
  3. If we can't, what's the problem when we use the impedance analyzer?
  4. Can impedance analyzer be replaced by spectrum analyzer or vector network analyzer? Why or why not?

Original question:
Impedance analyzer, spectrum analyzer and vector network analyzer are the common instruments in the measurements of electric circuits at high frequency. I want to wonder what's the difference among these instruments? What's their major functions, advantages and disadvantages?

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  • \$\begingroup\$ Welcome to EE.SE. Please note that the scope of this question is too broad to get concise answers as it is desired on this Q&A site. Please read some resources like wikipedia first and bring up more specific questions then. \$\endgroup\$
    – Ariser
    Commented Jun 22, 2016 at 4:48
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    \$\begingroup\$ I edited the question to be a bit less broad. It seems like it should be possible to give a reasonably concise high-level overview. \$\endgroup\$
    – Adam Haun
    Commented Jun 22, 2016 at 5:12

1 Answer 1

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An impedance analyzer is for measuring impedances, which you could call AC resistance as inductors and capacitors act like resistors with phase shifts at AC. They can be handy for testing filters and finding the ESR and ESL of all kinds of components. Many impedance analysers are used for frequencies much lower than VNAs, but will usually give you more fidelity in the measurements. You'd need a pretty expensive VNA to give you impedance information a few Hz to a few kHz, but this range is easy for an impedance analyser. A good impedance analyser will probably also give you twice as many significant digits worth of precision. It's a different tool for different applications.

A spectrum analyser is a tool for graphically displaying the frequencies in a signal, it's exactly like the graphic equalizer displays found on some HiFi systems except it operates into the GHz regions. It shows frequency content, if you fed it a 1GHz and a 2GHz signal, you'd get two peaks at 1 & 2GHz. A spectrum analyser on it's own won't give you any impedance or S-parameter information, you need both a phase sensitive spectrum analyser (not all of them can measure phase) and suitable tracking generator to create the test frequencies, at which point you've got yourself a VNA anyway.

A VNA is a combination of the two (which makes it far more useful than either one alone), it can not only display frequency content but plot how impedance and phase change with frequency. VNAs usually have a slew of other more advanced functions for doing all kinds of sophisticated RF magic.

N.B. A VNA should not be confused with a straight "Network Analyser" which is a tool for analysing computer networks - Although sometimes people refer to VNAs as just 'network analysers', only the VNAs will have coaxial connectors on their front panels.

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  • \$\begingroup\$ Straight "Network Analyzer" might also refer to a Scalar Network Analyzer (SNA). \$\endgroup\$
    – Roger C.
    Commented Jun 22, 2016 at 6:37
  • \$\begingroup\$ That's a great point, I s'pose I kind of glazed over the distinctions a bit \$\endgroup\$
    – Sam
    Commented Jun 23, 2016 at 4:46

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