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Bessel Filter

nashat1985

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Dears,
I am looking for Bessel Filter(linear phase)
Bandpass filter with center frequency 1374 MHz and Bandwith 250 MHz OR Low pass filter with cutoff frequency 1500 MHz .
So would you please advise where can find a supplier or seller for such products?
Thank you in advance
 

KlausST

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Hi,

You posted in the "elementary electronics" sections.
Then I'd build it on my own.

But your frequency range is rather high (not may frequency range)
Maybe it should be moved to the HF section.


Klaus
 

SunnySkyguy

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You must spec passband and stopband width both in dB with must have limits or tolerances. Your 4 significant figure fo suggests you need something like an 8th order LC filter or a SAW filter.
Some of this can also be done with stripline with practice.

1E9098F4-AE34-4A74-B94B-7519576DC564.jpeg
 

BigBoss

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At that frequency, SMD components' values may be a little bit absurd or non-realizable at all. In addition to, the manufacturing tolerances will play very important role on filter response and therefore a desired response might not be obtained at all.The filter will- definitely- be very sensitive against components' values tolerances.
I recommend you to realize this filter with distributed elements such as Microstrip Lines if you have sufficient space. But you have to have a certain experience on such filters and EM simulator is a must.
 

nashat1985

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Dears,
I am looking for Bessel Filter(linear phase) with constant group delay ..
my desired Bessel Filters as following
  1. Bandpass filter with center frequency 1374 MHz and Bandwith 250 MHz
  2. Low pass filter with cutoff frequency 1500 MHz.
So would you please advise where can find a supplier or seller for such products?
Thank you in advance
 

G4BCH

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Search for custom RF filters
I have used BSC filters now part of Dover group https://dovermpg.com/ in the past.
You will need a more detailed specification, number of poles or stop band rejection and phase linearity tolerance. It won't be cheap as has been said Bessel filters at that frequency are not easy.
 

BigBoss

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May I ask you why Bessel approximation ?? Bessel approx. will not be very efficient at that frequency and this type of filter is generally used in Audio or relatively Low Frequencies to get Constant Group Delay.
Obtaining Constant Group Delay is really tough at RF Frequencies.

I have done a quick-design..
1374MHz_BP.png

1374MHz_BP_s-parameters.png

1374MHz_BP_group-delay.png
 
Last edited:

G4BCH

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Bessel filters are used quite often at RF, have done so many times in VHF IF strips that have to handle fast pulses and maintain pulse fidelity. The filters do have a very poor frequency response though.
A search for 1374MHz comes up with Parkes pulsar survey, if this is the application then accurate linear phase is definitely needed.
 

nashat1985

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May I ask you why Bessel approximation ?? Bessel approx. will not be very efficient at that frequency and this type of filter is generally used in Audio or relatively Low Frequencies to get Constant Group Delay.
Obtaining Constant Group Delay is really tough at RF Frequencies.

I have done a quick-design..
View attachment 171957
View attachment 171958
View attachment 171959
Thank you so much
--- Updated ---

Thank you so much
Dear BigBoss,
thank you again for help, on fact I plan to use the filter in the feedback system ( a bunch by bunch feedback), and maintaining the phase for correction signal is crucial for implementing feedback. this filter will be installed after 3*RF mixer to extract signal sideband from DSB
 
Last edited:

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