microstrip low pass filter design
Just wonder beside step impedance and elliptic, is there any topology that is compact enough to design microstrip low pass filter, i trying to make the length of the filter to be less than 15mm.
I had attempt to use Alumina (10 mil thick) as substrate, to do a low pass filter at which the bandpass is up to frequency 4.5GHz, but then the problem is that the inductance line of this kind of filter is very long, and i had try to bend the inductance line in order to make it compact. Beside that i trying to hit a rejection of -50dB at 5.1GHz, in order to do so, i have to increase order, but then these will cause the filter to be very big. I also try to design a bandstop filter in order to meet the rejection, but is too big to be used, so i give up on that idea.
Anyone can advise me how to make the microstrip filter as compact as possible and yet meet the rejection? Thanks.