Ringing in reflection coefficient graph

Dear all ,

1. Why is a ringing being observed in my reflection coefficient graph at the beginning frequencies? (CST MWS)

2. How can I remove it?

Note: When I increase the number of pulses in some cases it used to get removed, but not working now even after making it 200 pulses.

Please help

Thanks in advance :)

Missed to tell any useful information.

- schematic circuit or drawing of the design under test
- simulation parameters
- obtained curve

Thanks for the reply :)

Mine is a patch antenna

The reflection coefficient graph is here

Where's the designed center frequency? Linear or log frequency scale?

200 pulses? Seriously? Did your simulator come without user's manual?
Show the time domain response, and check energy decay.

It is a linear dB scale. Center Frequency is 1.52 GHz



Please see the configuration. The default value is 20.

Show the time domain response, and check energy decay.

Here is the energy decay graph
What parameter should I check for time domain response in CST?

Based on the "200 pulses" I was thinking your simulation time ends before signal has decayed. You can check time signals at the ports.

The -40dB energy isn't too bad, but the S11 > 0dB in your plot above is obviously wrong. Can you increase the simulation time and lower the energy limit? Also check the resonance estimation, I think that's called "AR filter" in CST.

@volker@muehlhaus
Thanks very much for your reply
Can you please help me with this question
https://www.edaboard.com/showthread....nna-simulation