Updated to 2.08 13 May 2008 - lowered minimum bandwidth down to
.1 Hz so that "1/PI" can be used for the bandwidth. This allows "normalized"
(one ohm impedance level, one radian/second bandwidth) values to be obtained.
Updated to 1.07 5 December 2007 - extensive Design page formatting
revisions
Updated to 1.06 1 July 2007 - improved plot capabilities
Updated to 1.05 21 October 2006 - extensive max/min value limits,
updates to error traps and screen headers
Updated to 1.04 8 September 2006 - add schematic with ideal parts values
to the top of the design page, Bessel family, time display to cursor on plot
Updated to 1.03 30 August 2006 - add Cauer 30 dB stopband depth
option, tuning buttons, cursor-controlled data readout, Bessel and Tonne families
Updated to 1.02 5 August 2006 - add hardcopy output and Elsie filewriter
Released as 1.01 1 August 2006
SVCfilter™ is a program designed to expedite the design
and analysis of lowpass (and highpass) filters with nearest 5%
component values.
Here are some pertinent features:
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SVCfilter is 32-bit Windows® electrical filter design
software nicely written to help the radio amateur, technician or engineer
design and analyze lumped-element lowpass and highpass filters.
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Order, topology and family are all entered by clicking
on buttons.
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If the Chebycheff or Cauer family is chosen
then three options for passband ripple (.01, .044 and .200) are available.
-
If the Cauer family is chosen
then four options for stopband depth (30, 40, 50 and 60 dB) are available.
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Cutoff frequency is entered in the usual text box
and can be from audio through UHF.
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Cutoff frequency can be as low as 0.1 Hz, allowing the
value of .159155 [ i.e., 1/(2*PI) ] to be used. This, in
conjunction with a termination value of one ohm, yields parts
values for the textbook classic "normalized" design.
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System impedance by default is 50 ohms but a textbox
allows entry of any value of your choice, for example
600 ohms for audio.
-
Inductor Q values are set by default to a value of one million.
A textbox allows entry of any value of your choice in the
range of 10 minimum to one million maximum.
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The graphic output draws the schematic of the filter
you have designed, and also plots the responses of that filter (both
transmission and reflection).
It selects the nearest 5% values for the capacitors and shows
those values as well as the exact values and overlays the response plots
for the nearest values on top of the original exact-value plot.
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Tuning buttons allow stepping the cutoff frequency up or down in 1% steps and
immediately seeing the new performance of the redesigned filter on the plot.
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Place the cursor anywhere on the plot and see the transmission, reflection,
VSWR and envelope delay values for that frequency.
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Inductors are retuned as necessary to maintain the response of
Cauer filters after nearest capacitors are chosen.
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To maintain the high level of quality of the graphic output, the
outputs to the printer are not "screen dumps" but instead are from
a set of dedicated routines which write directly to the printer.
The quality of the graphics as delivered by the printer will be
limited only by that printer, commonly several hundred pixels per inch.
The printer output on one sheet contains the schematic with parts values
along with the set of responses.
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Click on the "Write Elsie File" button to write a file to drive
Elsie the filter design and analysis program for followup filter
examination in even greater detail.
-
This program was written to simplify the sometimes difficult task
of lumped-element lowpass (and highpass) filter design by automating
or setting as default some of the more frequently-encountered options.
But it also includes analysis, uncommon for such an application.
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