please help in justifying these things in microwave filter

[electronicman]

Hi, I designed band pass microwave filters using Agilent ADS for my project, and the simulations were perfect, but when I did the measurements, The whole results were relativily good but not like the simulated ones so I put the following questions that appear after analyzing the results.

why there is not a good reciprocity Snn not to some extents equal to Smm?
what cause the insertion loss at my resonate frequency instead of starting from zero,it started from -5db?
what causes my bandwidth to be narrower?
what type of losses I have to take into account when dealing with filters?
(mismatch, coupling, parasitic elements)
how can I recognise these type of losses by using just only the s11,s12,s21,ans s22 data file from VNA,which for which.

thanks

 

[tyassin]

Re: please help in justifying these things in microwave filt

Hi

How is the filter realized? Harpin, Combline...etc?

Regards

 

[Grig]

Re: please help in justifying these things in microwave filt

Hi
It seems to be calibration error

 

[khouly]

also don't forget ur dielectric material , and conductor finite resistivity so it , also how accurate ur PCB realization ?

also the connectors , and soldering

u need also to be sure how accurate ur calibration of the VNA ?

khouly

 

[electronicman]

Re: please help in justifying these things in microwave filt

my microwave filters consist of four planar lumped filter and one planar distributed filter(parallel coupled filter).my substrate RT/Duroid with dielectric constant 10.2,tanD=0.0023,thikness 0.635mm, my frequency range is 6-14 GHz