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TRABEM
Guest
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 Posted:
Sun Sep 11, 2005 4:35 pm Post subject:
Butterworth bandpass filter question |
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I am trying to scale an existing front end receiver (butterworth
bandpass) filter to a different frequency range. Unfortunately, it has
a transformer in the original design, so I'm stuck. I also don't know
how to handle the load presented by the active front end component
other than it's probably not significantly reactive.
The existing filter is for a 7 Mhz receiver, I'd like to have a
similar filter design for 50 to 200 Khz.
The filter components and transformer winding details are in the
document at:
http://www.amqrp.org/kits/softrock40/SoftRock40%20Assy%20v1.pdf
The input chip is an FST3126, spec sheet is at:
http://www.fairchildsemi.com/ds/FS/FST3126.pdf
The spec for the T30-2 transformer core is at:
http://partsandkits.com/T30-2.htm
I have aade filter design software, but it isn't allowing me to plug
in the transformer into the design page of the software....so, I need
to know it's equivalent circuit I think.
The transformer winding details are on page 4 of the document and the
schematic of the front end is page 9. Ultimately, I need new values
for L1, L2, C20, C21 and C22.
If someone can give me a reasonable guess as to the equivalent circuit
of the transformer and the IC (U5), I can do the rest of the job
myself using the aade filter software.
Thanks,
T
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maxfoo
Guest
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| Posted:
Sun Sep 11, 2005 10:09 pm Post subject:
Re: Butterworth bandpass filter question |
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On Sun, 11 Sep 2005 12:14:11 -0400, TRABEM <> wrote:
Get the free software program call RFsim99 lets you design buttrworth filters. |
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Reg Edwards
Guest
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| Posted:
Mon Sep 12, 2005 6:07 am Post subject:
Re: Butterworth bandpass filter question |
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| Quote: | I am trying to scale an existing front end receiver (butterworth
bandpass) filter to a different frequency range.
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=====================================
How do you know it is a Butterworth as distinct from other types?
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TRABEM
Guest
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| Posted:
Mon Sep 12, 2005 4:35 pm Post subject:
Re: Butterworth bandpass filter question |
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A butterworth is a butterworth............in any discussion of the
butterworth filter, you will see this schematic.
Asking how I know it's a butterworth is a little like asking how I
know a car is a car.
However, I don't know it all.........perhaps it's closely related to a
butterworth, but called something else???
Let me know if I've made an error please.
T
On Mon, 12 Sep 2005 06:07:31 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:
| Quote: | I am trying to scale an existing front end receiver (butterworth
bandpass) filter to a different frequency range.
=====================================
How do you know it is a Butterworth as distinct from other types?
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Helmut Sennewald
Guest
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| Posted:
Mon Sep 12, 2005 9:49 pm Post subject:
Re: Butterworth bandpass filter question |
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<TRABEM> schrieb im Newsbeitrag
news:peabi1hcgh2ql1t5nvn5vp6thisopqkju7@4ax.com...
| Quote: | A butterworth is a butterworth............in any discussion of the
butterworth filter, you will see this schematic.
Asking how I know it's a butterworth is a little like asking how I
know a car is a car.
However, I don't know it all.........perhaps it's closely related to a
butterworth, but called something else???
Let me know if I've made an error please.
T
|
Hello T,
a Bessel filter would have the same structure. The value of
the components define what filter type it is.
Bessel: max. flat group delay
Butterworth: max flat frequency response
You can also make a filter with this structure which is anything
between both types.
Best regards,
Helmut |
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TRABEM
Guest
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| Posted:
Tue Sep 13, 2005 12:35 am Post subject:
Re: Butterworth bandpass filter question |
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| Quote: |
a Bessel filter would have the same structure. The value of
the components define what filter type it is.
Bessel: max. flat group delay
Butterworth: max flat frequency response
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Cool, didn't know that.
At VLF, the inductances are becoming quite large, requiring a toroid
core for even a simple inductor.
What are the advantages/disadvantages of each type relative to
inductor size requirements?
Maybe I should be looking at a bessel instead of a butterworth.......
GL to all.
T |
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maxfoo
Guest
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| Posted:
Tue Sep 13, 2005 8:35 am Post subject:
Re: Butterworth bandpass filter question |
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On Mon, 12 Sep 2005 12:18:52 -0400, TRABEM <> wrote:
| Quote: | A butterworth is a butterworth............in any discussion of the
butterworth filter, you will see this schematic.
Asking how I know it's a butterworth is a little like asking how I
know a car is a car.
However, I don't know it all.........perhaps it's closely related to a
butterworth, but called something else???
Let me know if I've made an error please.
T
On Mon, 12 Sep 2005 06:07:31 +0000 (UTC), "Reg Edwards"
g4fgq.regp@ZZZbtinternet.com> wrote:
I am trying to scale an existing front end receiver (butterworth
bandpass) filter to a different frequency range.
=====================================
How do you know it is a Butterworth as distinct from other types?
|
A Butterworth filter is a Chebyshev filter with No ripple in the passband. |
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