Hi everyone, I am recently starting a new project on designing a 2.4GHz microstrip bandpass filter, but there are so many ways doing this, which method is better for microstrip? hairpin-filter? interdigital filter? or combline filter?
Is there any website or material anyone can recommend which relate to this topic? Thank you!
I built all of those filters. I found that some sort of tuning is required to optimize its response. Therefore the interdigital filters I did were most successful. I obtained an average insertion loss of 0.5 dB.
Microstip filters are very nice too but you can't tune them. The problem with those is the traces have to be etched very precisely and symmetrically for a good response. If you are off a bit, then you are increasing the insertion loss by a lot. If something is uneven, a pole can be outside your bandwidth. So unless you can print out the traces and transfer them on a PCB, then this route would be fun to explore. Hairpin types are difficult to design without a CAD. The easiest are coupled-lines, in most cases half or a quarter wavelength is all it takes.
http://www.lpkf.com/applications/rapid-pcb-prototyping/design-articles/design-article2.htm
There is a third type of cheap filters to construct using copper pipe caps. These work very well too with a very high Q if you polish the inside.
