Bandpass Filter simulation ADS keysight

[guytoub]

I simulated a bandpass filter between 1.5-1.6 GHz @3dB with the ADS keysight passive circuit guide design. I used a coupled line filter with FR4 as substrate.
during the S21 simulation, I have frequency rises at frequencies 2Fc, 3Fc etc, a bit like harmonics of a fundamental. What is this due to? how to avoid this?
Thank you for your help.

 

[albbg]

Microstrip filters are periodic in frequency. In order to remove spectral regrowth you can put a lowpss filter in series with bandpass

 

[guytoub]

Microstrip filters are periodic in frequency. In order to remove spectral regrowth you can put a lowpss filter in series with bandpass

thanks , i'll try .