Frequency shift in simulated S-Parameters in HFSS
I just started working with HFSS a while ago, so i′m still not totally aware of all relevant settings in my simulations.
The following problem is nagging me right now:
I am designing patch antennas that should work for a frequency range from 76-81GHz and transmit into a WR12 Waveguide. I got a few promising designs out of it and did some prototype boards based on my simulations.
The good news: So basically the S-parameters measured with the VNWA look quite like how they should, according to my simulations.
The bad news: Compared to my simulations, all measured parameters are shifted by 1.5GHz to the right hand side.
I used a solution frequency of 83GHz, since i was told i should choose a solution frequency a little higher than my frequency of interest. I′m not sure if this was the best hint...
Maximum number of passes 15 at a maximum Delta S of 0.03.
Mixed order solution and direct solver method.
I also am using the Huray surface roughness model, because otherwise i can′t simulate the losses correctly.
Any sugestions at where i am doing something wrong?
BR
Which direction is "the right hand side"? Upwards in frequency?
What dielectric are you using?
Are you simulating and measuring the antenna and waveguide together?
Yes, by right hand side i mean upwards in frequency. So i have to shift my simulated S-parameters 1.5GHz to a higher frequency to make them fit my measurements.
As dielectric i am using Rogers 3003.
I am simulating a short microstripline that feeds my antenna, the antenna itself and the waveguidetransition, that connects the PCB and the waveguide to eachother.
So basically i am simulating everything that i am then measuring on the VNWA.
Try a convergence of delta s = 0.01 (-20dB). As well, you might want to do some more adaptive passes after convergence to make sure nothing changes.