Help with band-pass filter for UWB

Hi, I'm designing a BPF in range 3.1-3.8 GHz (700MHz bandwith at -10dB). I'm using ADS's Filter Design Guide. But it is only allowable to design filter with luped components, so I'm using Passive Circuit Design Guide to design microstrip coupled-line filter. I want my filter be with constant group delay, this is most critical thing to design. Seems like Gaussian or Bessel filters are most suitable, but I can't see these options when I'm using Passive Circuit Design Guide, there are only Chebychev or Maximally flat responses available.
Any help with this?

You may find something in @ds' help!
You can exchangge lumped components to microstrip too

sorry, i didn'f find any information how to automatically convert the filter to microstrip lines filter...