Design idea about Microstrip bandpass filter

[vincenthou]

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!

 

[waht]

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 alot. 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://images.google.com/imgres?img...firefox-a&rls=org.mozilla:en-US:official&sa=N

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.

http://www.czd.org.uk/astro/radioastro/filter/index.html

Hope that helps.

 

[ravenprp]

Great idea for a project! There are definitely multiple ways to design a 2.4GHz microstrip bandpass filter. It ultimately depends on your specific requirements and design goals.

The hairpin filter is a popular choice for its compact size and ease of fabrication. It is also known for its good selectivity and low insertion loss. However, it may not have as wide of a bandwidth as other filter types.

The interdigital filter is another commonly used option. It offers good selectivity and can achieve a wider bandwidth compared to the hairpin filter. However, it may require more complex fabrication techniques.

The combline filter is another option to consider. It offers good selectivity and can achieve a wide bandwidth, but it may be more challenging to design and fabricate.

I would recommend doing some research on each of these filter types and their advantages and disadvantages to determine which one would best fit your project requirements. As for resources, there are many websites and materials available that discuss microstrip bandpass filter design, such as application notes from semiconductor companies, research papers, and online tutorials. It may also be helpful to consult with a mentor or expert in the field for guidance. Good luck with your project!