[Help] Microstrip Filters
I have to make a simulation and then the fabrication of a microstrip filter (at 1, 1.5 or 2GHz). I have decided to make an edge coupled bandpass filter(it may be something else) by using Ansoft Designer SV. However, my substrate is not in the Designer. So, I first make a filter by using the filter tool and then I change the permitivity. However, I cannot add the loss tangent when I am inside the filter tool. When I add it afterwards, the response does not look as before(as usual). This time I try to optimize it by changing the dimensions by myself (because I think SV does'nt have tuning property), but I end up with 400-500MHZ bandwidth and 2.5dB loss at the center freq. Is this so unsual at this frequency or am I able to cope it by another way. Any decision?
Thanks...
Parallel coupled line could also be a nice way to create microstip filter, following the thebyshev or butterworth theories.
Hi, in Designer is possible deffine your concrete substrate and sumulate your concrete fiter on this material.
This procedure is explaned in manual.
Hi E.
"2.5dB loss" is a common specification for microstrip filters.
If you want to have good insertion loss, you need use other types of microwave filters with high-Q resonators: combline, interdigital, helical ....
you can select a high Q resonator,
hi, in my opinon an interdigital filter and a hairpin filter can have better performance at those frequencies.
bye
hi
I think 2.5 dB is unusual.
the main loss in combline filter is reffered to lump capacitances and dielectric loss have a little effect in this filter.
but I must know that what is your substrate and I think you use ideal capacitances, so if your loss tangent is less than .003 (such as RF4003) then your answer is wrong or your design is not true.
I wrote software for this type of filter and if you want I can check it with my program.
send me your dimensions (If you want)
best regards
fredy
Ha,how about cavity filter
On my experience, the main loss in combline filters is resistive loss in lines and box walls and jointings. A chip capacitors not good for this filter type due to high parameters dispersion; topological caps more good.
Thank you all,
I gave up making a filter with this material. (Electric Permittivity = 4.7, Loss Tangent = 0.019, Thickness = 1mm). I have made a branch-line coupler instead.