network analyzer s parameters
I′m simulating a component that I already have it built. The problem is that the scattering parameters I got on HFSS are different that those I got with the Network Analyzer. So here goes the questions!
? With kind of solution I′d would choose (driven modal or driven terminal) to have the same answer of the network analyzer?
? When I terminate an output, does it means to put a load with matched impedance?
? Any other suggestion to solve my problem?
Thanks very much!!!
Thadeu
Hey guys, I'm really needing some help! I don't know what else to do...
Thanks again!
If ur device is a wideband device, it is normal to see the difference between HFSS and VNA. If it is an antenna, driven model should be used and driven terminal for waveguide structures. Usually, it is the case if u terminae a load with a match impedance.
Dear tjunqueira,
This is what I think I would answer to your queries:
(1) In my honest opinion, you have to choose your solution to be 'driven terminal' if you know your antenna is to be of wideband response (e.g. biconicals). 'Driven modal' is normally chosen if you know what modes that you are exciting on your antenna (e.g. patches). Of course you will never get simulated results to be 100% spot-on as practical results. Simple things that you cannot control, like for example, mechanical/building defects can effect your results. Well, this is exactly also why practical antenna engineers like me are still employed! ;) Hahaha!
(2) And yes, when you terminate an output, it means to put a load with matched impedance. As you know by now, alot of antennas are designed at 50 ohms. However, most antennas don't like 50 ohms. But that is another story. :P
Hope these helps,
Dave
Note that the s-param in HFSS are generalized S-param, which means that the wave port is always matched in any frequencies and there is no "normalization impedance" but in network analyzer S-param are normalized to some impedance (say 50 ohm)
just go to your excitation wizard in post processing tab and choose "Renormalize" to the same network normalization impedance (50 ohm) to get consistent result