Hi, I'm curious about the advantages of getting a full 2-port VNA which can simultaneously measure S11, S21, S12, S22 compared with the economy models which just measure S11, S21 - what type of applications is the full measurement capability useful for? I'm guessing it's useful for non-passive/non-reciprocal networks, but don't have much experience with characterizing Active RF networks, so any feedback would be greatly appreciated. Many Thanks, Dave
> Hi, I'm curious about the advantages of getting a full 2-port VNA which can simultaneously measure S11, S21, S12, S22 compared with the economy models which just measure S11, S21 - what type of applications is the full measurement capability useful for? I'm guessing it's useful for non-passive/non-reciprocal networks, but don't have much experience with characterizing Active RF networks, so any feedback would be greatly appreciated. Many Thanks, Dave
I assume you are comparing network analyzers with S-parameter test sets, against those with transmission/reflection (T/R) test sets.
Most (perhaps all) VNAs can't measure all 4 S-parameters simultaneously. The source is switched between different ports - first the source is connected to port 1, then to port 2, then back to 1 etc. It is possible to get high-end VNAs with dual sources. I don't know if they can simultaneously measure S11, S21, S12 and S22.
Most passive devices have S12=S21, although there are exceptions such as isolators and circulators. But S11, will not be the same as S22, even on passive devices, so as John Miles says, you need to turn the device around. There are other advantages in having an S-parameter test set.
* You can do unknown thru calibration, which removes the effect of adapters.
* You can do TRL calibration, which is particular good if using test fixtures, or other cases where you don't have a calibration kit for the DUT.
Those calibration methods need a VNA with 4 receivers, which are not available on low-end models. None of the 8753 series have 4 receivers, it is an option on the 8720 series, and standard on the 8510 series. 4 receivers is probably standard on current Agilent/Keysight PNAs, although I'm not 100% sure of that.
Are you looking to buy a new or used VNA? If your budget is limited to used VNAs, the 8753 series is hard to beat.
Dave