In order to generate a curve for the Return Loss, an analyzer will output a frequency sweep through its internal directional coupler and then measure the forward and reflected signals. I was curious about how this signal looked like, so I connected the measurement port of two of my instruments to the input of my Agilent E4411B.
The 2 instruments were:
- Anritsu S331E Sitemaster
- Agilent E5061B Network Analyzer
I was mindful not to overload the input to the spectrum analyzer, so an external 20dB attenuator was placed before the input to the spectrum analyzer, in addition to its internal 20db attenuation setting.
You can see the scanning spectrums here:
The S331E scanning was not as fast as the E5061B. Also there were many harmonics for the case of the S331E. It is not necessary for the spectrum to be very clean because the spectrum analyzer’s tracking receiver will ignore the out of band responses.