Butterworth bandpass filter question

T

TRABEM

Guest
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
 
On Sun, 11 Sep 2005 12:14:11 -0400, TRABEM <> wrote:
Get the free software program call RFsim99 lets you design buttrworth filters.
 
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?
Click to expand...
 
<TRABEM> schrieb im Newsbeitrag
news:peabi1hcgh2ql1t5nvn5vp6thisopqkju7@4ax.com...
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
Click to expand...
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
 
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
Click to expand...

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
 
On Mon, 12 Sep 2005 12:18:52 -0400, TRABEM <> wrote:

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?
Click to expand...
A Butterworth filter is a Chebyshev filter with No ripple in the passband.
 
"TRABEM" bravely wrote to "All" (12 Sep 05 12:18:52)
--- on the heady topic of "Re: Butterworth bandpass filter question"


I thought it was a turkey until I opened a filter cookbook...
Isn't it flat smooth response without overshoot as opposed to
Tchebychev with a little overshoot but faster risetime?
Bessel is something in between these?
Where do they find these names!!!

M*i*k*e


TR> From: TRABEM <>
TR> Subject: Re: Butterworth bandpass filter question
TR> Xref: core-easynews sci.electronics.components:101732
TR> sci.electronics.design:505281 sci.electronics.repair:341949


TR> A butterworth is a butterworth............in any discussion of the
TR> butterworth filter, you will see this schematic.

TR> Asking how I know it's a butterworth is a little like asking how I
TR> know a car is a car.

TR> However, I don't know it all.........perhaps it's closely related to a
TR> butterworth, but called something else???

TR> Let me know if I've made an error please.

TR> T


TR> On Mon, 12 Sep 2005 06:07:31 +0000 (UTC), "Reg Edwards"
TR> <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?
Click to expand...
.... If all else fails, hurl it across the room a few times!
 
I am trying to scale an existing front end receiver (butterworth
bandpass) filter to a different frequency range.
Click to expand...
=====================================

How do you know it is a Butterworth as distinct from other types?
 
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