Author Topic: Simple 2.4 GHz bandpass design  (Read 498 times)

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Offline rfspezi

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Simple 2.4 GHz bandpass design
« on: June 14, 2018, 05:04:35 pm »
I am planing to build an 2.4 to 2.5 GHz bandpass filter (around 4th order) to improve out of band signal rejection for my WIFI RX preamp.
Using Rogers PCB material is no option.
FR4 is a no-go either.
So i wonder what would be the easiest implementation in your experience?

EDIT:
It should be able to handle up to 36 dBm as the TX power also goes through.
« Last Edit: June 14, 2018, 05:35:32 pm by rfspezi »
 

Offline yl3akb

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Re: Simple 2.4 GHz bandpass design
« Reply #1 on: June 14, 2018, 10:04:34 pm »
Long time ago I verified that this interdigital BPF calculator works quite well: https://www.changpuak.ch/electronics/interdigital_bandpass_filter_designer.php

I would not recommend too narrow relative bandwidths (<<10..20%) though. Here picture of my quick and dirty implementation:
 

Offline rfspezi

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Re: Simple 2.4 GHz bandpass design
« Reply #2 on: June 14, 2018, 10:43:53 pm »
Long time ago I verified that this interdigital BPF calculator works quite well:
I would not recommend too narrow relative bandwidths (<<10..20%) though. Here picture of my quick and dirty implementation:

Thanks!
This comb-line filter indeed looks fairly easy to build.
Is there a reason why you did alternate the rod-grounding instead of having all rods grounded on the same side?
Do you think threaded rods may also be used?
 

Offline yl3akb

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Re: Simple 2.4 GHz bandpass design
« Reply #3 on: June 14, 2018, 11:17:04 pm »
Actually this is interdigital filter which allows for less spacing between resonators for same relative (fractional) bandwidth in comparison to combline, in other words it is more compact.

I guess threaded rods should work okay. Low surface loss of material is very important, if low insertion loss and/or narrow BW is required. I used tinned copper pipes, which could also be easily soldered to box walls.
 

Offline yl3akb

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Re: Simple 2.4 GHz bandpass design
« Reply #4 on: June 14, 2018, 11:18:16 pm »
 

Offline CopperCone

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Re: Simple 2.4 GHz bandpass design
« Reply #5 on: June 14, 2018, 11:54:17 pm »
You can find a ton of wifi ones that work at that frq on ebay pretty cheap now with 5ghz fyi
 


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