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    750 MHz Band Attenuation Filter

    Approximate band attenuation 20 dB from 735 MHz to 765 MHz. Is microstrip pcb and lumped components a possible method to create this filter? In simplest form, a series paralleled inductor and capacitor.

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    Re: 750 MHz Band Attenuation Filter

    Lumped Components serve well here..No need Microstrip structures..
    The Simplest Form is a Parallel LC in series or a Series LC in Parallel or combination of those.But better solution is to use N-stage LC filter approximations ( Butterworth or Chebychev etc. ) then apply Bandstop Transformation.The best method is to use a Filter Design Program..



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    Re: 750 MHz Band Attenuation Filter

    You need the complete pass- and stop band specification to determine the filter effort, e.g. minimal order.



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    Re: 750 MHz Band Attenuation Filter

    Lumped Components is a good method. No need Microstrip structures.



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    Re: 750 MHz Band Attenuation Filter

    Any lumped component Band Pass Filter with central frequency greater than about 500MHz would be very sensitive to component tolerances, to PCB layout, and especially to temperature variations.
    May need more space for a 750 MHz microstrip filter, but for sure you will have much less headache designing and manufacturing it.



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    Re: 750 MHz Band Attenuation Filter

    Actually, I like to combine both discrete and line elements at these frequencies. But as FvM mentioned, without full specs it's not possible to estimate anything.



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    Re: 750 MHz Band Attenuation Filter

    Series LC usually has some amount of neighboring resistance also in series. It reduces Q.

    LC tank has maximum Q due to slight R. It's easier to achieve narrow bandwidth.

    Bandwidth is affected by the L:C ratio. These 3 layouts are identical except for having different LC ratios.

    Click image for larger version. 

Name:	band-stop LC tank reson f 750 MHz ident 3 layouts exc diff LC ratios sine sweep.png 
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    To choose a value, 50 ohms is assumed for input and output resistance.



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    Re: 750 MHz Band Attenuation Filter

    Quote Originally Posted by BradtheRad View Post
    These 3 layouts are identical except for having different LC ratios.
    Your inductors have different Q factor.



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