I have a measurement set-up as depicted in the figure below.

enter image description here

The measurement settings are as following:

  • Both Generator 1 were having carrier frequency 1 GHz and output power 0 dBm. No modulation as well.
  • A power meter was set to 1 averaging factor and center frequency as 1 GHz.
  • Two settings of spectrum analyser:
  • (set a) Center freq is 2 GHz and Span 3 GHz
  • (set b) Center freq is 1 GHz and Span 1 MHz


  1. If Gen1 is ON and Gen2 is OFF with spectrum analyser settings according to "(set a)", then do we expect any reflections? and would the power meter Readings be unstable?

  2. If Gen1 is ON and Gen2 is still OFF, but now the spectrum analyser settings are according to "(set b)". Do we still expect reflections? higher or lower than the above case? And how about the power meter readings stable or unstable?

  3. If Gen2 is additionaly ON in Question 2 settings, do we expect no, higher, or lower reflections?

  • 3
    \$\begingroup\$ These questions are impossible to answer as it is unclear how the equipment behaves when it is off. Reflections occur when there is an impedance mismatch. You supply no information about the matching at all. \$\endgroup\$ – Bimpelrekkie Oct 21 '18 at 11:07
  • \$\begingroup\$ This looks a lot like a homework question. Please give us a starting point on where you got on your own, such that we can help you find what you're missing. \$\endgroup\$ – Sven B Oct 21 '18 at 17:00
  • \$\begingroup\$ yes, it's a kind of a homework (lab exercise). I have done the experiments but the results are inconclusive for me (thinking that my experiments might be wrong). So, I was thinking you experts who have spent a lot of time with these Tools may know why reflections occur (if any). But as I gather from the comments, this is not possible just looking at the schematic. \$\endgroup\$ – learning Oct 22 '18 at 4:24
  • \$\begingroup\$ Yes, I believe I can see what they're trying to demonstrate with the exercise, but without specific equipment details its a bit of a guessing game. Given that this is a "real-world test" we can assume that all of the active devices have accuracy tolerances on frequency and power in the case of the signal generators, mixer port isolation on the spectrum analyzer, and frequency response on the power meter assuming a bolometer detector. So the question is how do these interact with each other? The passive devices have the equivalent issues with port isolation, mismatch, etc. but assuming they' \$\endgroup\$ – isdi Oct 22 '18 at 5:20
  • 1
    \$\begingroup\$ are equally good (or bad) on each port, we can null their contributions out. Chapter 2 in 5952-0292EN.pdf can give some clues too. \$\endgroup\$ – isdi Oct 22 '18 at 5:22

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