Elsie the filter program

The Windows ® program
for electrical filter design
and ladder network analysis






Current revision is 2.72; revision history is at the bottom of this page

Elsie™ is an uncommon commercial-grade lumped-element ("L-C") electrical filter design and network analysis program, directed toward the engineer, technician or hobbyist involved in that line of work.

  • The free Student Edition of Elsie is quite adequate for student use or for use by small manufacturing operations. But with the key it operates in the much more capable Professional Edition.

  • The principal difference between the Student Edition and the Professional Edition of Elsie lies in the Student Editions's limit of seven stages (dipoles) of network size. This equates to a seven-pole lowpass or geometrically-symmetrical bandpass. In addition the editing library of manually-entered components is restricted somewhat in the Student Edition to inductors, capacitors, resistors, and series and shunt jX entries. No lines, stubs, transformers or coupled inductors are allowed. The Professional Edition allows those components and others to be entered.

  • Elsie is 32-bit Windows® electrical filter design software nicely written to help engineers design and analyze lumped-element filters in the audio through microwave range. Thanks to the standard interface, all of the various aspects of program operation are quite easy to use. Most options are selected by clicking on buttons. No scripts. Not a DOS lookalike. Schematics are drawn correctly, not using text characters.

  • This filter design program designs and then analyzes filters with a wide variety of topologies and families and with specified orders, bandwidths, impedances and the like. The usual filter familes of Butterworth, Chebyshev, Cauer (including the zig-zag transform), Bessel, Gaussian, Constant-K and M-derived are covered.

  • The quality of the screen graphics is very high (dependent on your monitor), and include transmission (S21), return loss (S11), transmission with its angle, group (envelope) delay, VSWR, input impedance and its angle and more (selected pairs of these items).

  • To maintain this level of quality, the outputs to the printer are not "screen dumps" but instead are from a separate 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 and the number of test frequency steps used (up to 2048 steps).

  • The graphics items automatically adjust themselves to various resolution screens. As an example, the size of the plot on monitors of 800x600, 1024x768 or 1280x1024 is the same in terms of centimeters or inches. Aspect ratio of the screen display can be adjusted so Smith Charts look circular on any monitor width-to-height ratio.

  • Markers can be placed on the plots. These reveal the data for that plot at the markers' frequencies. Up to eight markers can be defined. The data for each frequency is shown in tabular form beneath the plot.

  • Limits areas can also be placed on the plots. These mark the "out of bounds" area and are useful as a tool to assist in a manual tuning operation. Up to ten limits areas can be placed on each plot. They are used as part of the optimization routine to generate an error value.

  • It has a Monte Carlo routine and an extension of that forms the optimizer.

  • You can tune the width and/or center of a filter Elsie designed. Those items are adjusted using the mouse; the filter is immediately redesigned, reswept and replotted. Unique and fast - milliseconds per step.

  • You can select an item and adjust its value - "tune" it - by clicking on buttons. Because the filter design and analysis routines are very closely coupled, the results are seen immediately on the screen. There is no need to go to another program or routine to see the effects of finite inductor Q, as an example.

  • The tuning modes in conjunction with the optimizer and limits areas allow you to easily see the effect of adjusting a particular part, or to achieve a response shape meeting some unusual requirement.

  • It stores up to ten plots which can be recalled for comparison. Develop a filter, store the data plots for it, make changes to the filter, and then recall any of those old plots. The data is stored on the hard drive and so is available in future sessions, not just while the program is currently running. They'll be overlaid on top of your current graph for quick visual comparison. This facilitates a very fast visual comparison of different families; as an example of this we can instantly compare filters of different families (Butterworth vs Cauer, as an example), or we can overlay 3rd, 4th, 5th, 6th and 7th-order filters and see the changes/differences. See the "overlay example" graphic below.

  • When a plot is showing, put the cursor on the plot and press the mouse button to see a line of data at the bottom of the screen showing all of the information for the frequency corresponding to the cursor position. See the corresponding data (all of the data) at the bottom of the screen. Move the cursor and the data line reveals the data for that new frequency. Of course that data is also available in tabular form.

  • It has a very flexible routine for installing the nearest 5% values (all parts, inductors only, capacitors only or one of those while maintaining resonant frequencies of L-C pairs). This latter feature is especially helpful in the design of Cauer filters.

  • It has a library of components (including transmission lines and stubs, transformers, arbitrarily-coupled inductors, and resistors, as well as unique-to-Elsie parts) which can be added onto or inserted into the schematic manually so you can see the result. For example you can add a piece of coax (specify the impedance and length) to the filter and see what changes result.

  • It allows manual entry of any of the library components or changing them once the filter has been entered. Any of those library components can be installed or their values changed.

  • It allows changing some elements to their distributed (coax) equivalents. Easily change a series inductor to a high-impedance line, for example. Or a shunt capacitor to a low-impedance line.

  • You can save all of the data presented as a set of files in two-column (frequency, data) for analysis by another program, for example an FFT routine to see a waveform spectrum. There are neither headers nor footers on those files to confuse the issue. Up to nine such sets of files may be saved; these are the same files used to present the overlays.

  • It does time-domain analysis as well as analysis in the frequency domain. You can observe the expected output from a network when it has been excited with a square wave or a tone-burst, and even see the envelope of a burst. See the "tone-burst" graphics below. (The envelope of the tone-burst is perhaps easier to comprehend visually. This is believed to be unique with Elsie in the filter design program field.)

  • The context-sensitive Help system is graphics-intensive (200+ graphics) and has a walkthrough, a design example, full-text search capability (100+ topics).

  • The normalized-values for a design are available, along with the option to send them to the printer; see graphic below.

  • It writes schematic files for LTspice (from Linear Technology Corp.).
    [Note: Tonne Software has no connection with Linear Technology Corp.]

  • This program is designed to approach the capabilities of the complex do-everything programs while retaining the ease of use of lesser programs.

  • The program requires a monitor with a resolution of 800x600 or better. Graphics are autoscaled to accommodate higher monitor resolutions (which are recommended).

  • The program does NOT function with computers using Japanese or Chinese-language operating systems.

Here are screen dumps from the program illustrating some of the outputs to the screen. Click on them to see larger versions; use your browser's BACK button to return.
Design menuDesign menu
Analysis menuAnalysis menu
Plot showing transmission and returnPlot S21 & S11
Transmission with limits S21 with limits
Transmission with limits and markers S21, limits, markers
Transmission and delay S21, delay
Normal Smith Chart Smith Chart
Magnified Smith Chart Smith 2x, markers
Illustrating a tuning mode Tuning mode
A tone-burst Tone burst
Envelope of tone-burst Envelope of burst
How schematic is presented on-screen Schematic
Circuit editor screen Circuit editor
Tabulated output Tabulated output
A help page Help page
Monte Carlo while running Monte Carlo running
Monte Carlo stopped Monte Carlo stopped
Normalized value display Normalized values
Inductor specification Inductor specs
Overlay example - various orders Overlay - orders
Modulation response of a bandpass Modulation response
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Updated to 2.72 - Refined Design screen error trapping
Updated to 2.71 - Found and corrected error in Monte Carlo stepsize assignment
Updated to 2.70 - Complete rewrite of .CIR and .SUB file writers
Updated to 2.69 - Added SPICE subcircuit file writer and LTspice filter symbol (.ASY) writer
Updated to 2.68 - Added generic SPICE file (.CIR) writer
Updated to 2.67 - Force LTspice .ASC files to have periods for decimal places; cosmetic and minor interface upgrades
Updated to 2.66 - Increased plot X-axis divisions to 20; allowed negative jX values in editor
Updated to 2.65 - Added AutoScale button to plot and analysis pages; allowed diplexer design to go to 10 GHz
Updated to 2.64 - Corrected missing element in Manual Entry routine
Updated to 2.63 - Total rewrite and upgrade of diplexer routine
Updated to 2.62 - Found and corrected errors in page/screen sizes
Updated to 2.61 - Found and corrected error in file reader; updated editor, file writing and file reading
Updated to 2.60 - Added schematic display option to show the filter as it would be in a balanced configuration; improved erroneous-value entry handling in circuit editor
Updated to 2.59 - Clarified Cauer odd/even entry areas; polished design and editor pages
Updated to 2.58 - Added capability to change return loss reference value to editor page
Updated to 2.57 - Found and corrected error in transmission line math routine when line lengths are exactly 90 degrees; limited S11 and S21 to -120 dB
Updated to 2.56 - Found and corrected S11 and S22 phase error in Touchstone file writers (Versions 1 and 2)
Updated to 2.55 - Added bandpass filter modulation-response routine
Updated to 2.54 - Complete rewrite of transient-response routine
Updated to 2.53 - Added Entry Assistance screen; revision of Analysis screen
Updated to 2.52 - Found and corrected error in Cauer highpass design routine; other cosmetic upgrades
Updated to 2.51 - Complete rewrite of Wind Inductor routine
Updated to 2.50 - Rewrite of all subroutines for uniform appearance; limits-editing bugfix; many cosmetic upgrades
Updated to 2.49 - Complete rewrite of circuit editor and manual component-entry routines along with upgrades to schematic display and design inputs
Updated to 2.48 - Complete rewrite/update of inductor-specification routine
Updated to 2.47 - Upgraded plotting screens to show on the screen the point where the mouse-down datapoints are being taken; Smith Chart seriously upgraded
Updated to 2.46 - Upgraded Design page to prohibit problems resulting from missing bandpass/bandstop center frequency, or missing topology entry
Updated to 2.45 - Corrected file-reading and file-writing routines to ignore unused numbers in memory; corrected Cauer normalized-value readout
Updated to 2.44 - Upgrade normalized-value routine; added option to send normalized values to printer
Updated to 2.43 - Major upgrades to each of the routines on the Design page
Updated to 2.42 - Major upgrade to Smith Chart routine
Updated to 2.41 - Major upgrade to Monte Carlo routine
Updated to 2.40 - Changed overlay color scheme
Updated to 2.39 - Corrected erroneous saving of limits areas to file
Updated to 2.38 - Corrected error causing plot type to change unexpectedly
Updated to 2.37 - Corrected error in "specify inductor" routine
Updated to 2.36 - Major revision of Manual Component Entry and Editor pages, revised menu system, added aspect-ratio correction capability
Updated to 2.35 - Added toroidal-inductor turns calculator, Smith Chart aspect ratio correction capability and total re-write of menus
Updated to 2.34 - Refined LTspice file-writer
Updated to 2.33 - Changed order-entry to up/down button style; forced location of Last Session file
Updated to 2.32 - Discovered and corrected error in frequency printout for regions using comma for decimal
Updated to 2.31 - Added "Instant Help" button to the Design page to assist in Family selection
Updated to 2.30 - Added "Instant Help" buttons to the Design page to assist in Topology selection
Updated to 2.29 - Updated Help system
Updated to 2.28 - Added end-sections option to Constant-k family (this in addition to the M-derived family); updated Help system
Updated to 2.27 - Editor now disallows termination or resistor-value entries less than .01 ohms
Updated to 2.26 - Correct various plot top definition entry oddities
Updated to 2.25 - Add option to show "magnified" plot on Transmission graph to reveal detail in low-loss region.
Updated to 2.24 - Changes to design page to prevent design of families requiring passband ripple when no such entry is present.
Updated to 2.23 - Add M-derived family with up to five specifiable zeros; update Help system.
Updated to 2.22 - Eliminate ProLite option; miscellanous upgrades.
Updated to 2.21 - Rewrite of bandpass impedance-matching routine.
Updated to 2.20 - Add nominal-value plot(s) at end of Monte Carlo routine. Also allow overlays to be placed on top of Monte Carlo display.
Updated to 2.19 - Remove revision number checking, fix tuning mode error.
Updated to 2.18 - Added resistors to those elements used for the Optimization and Monte Carlo routines.
Updated to 2.17 - Added LTspice schematic-writing
Note: Tonne Software has no connection with Linear Technology Corp.
Updated to 2.16 - Total rewrite and expansion of bandpass Impedance Matching routine and associated Help system
Updated to 2.15 - Added tabulated-data file writing
Updated to 2.14 - Correct conditional errors for Optimizer maximum-allowed-time and limit-deletion
Updated to 2.13 - Correct subtle plot-color error in Monte Carlo and Optimizer routines; upgrade Exit message
Updated to 2.12 - Total rewrite of Diplexer routines and associated Help system; minor cosmetic text-size changes
Updated to 2.11 - Rewrite of Monte Carlo and Optimization routines; notice design changes and suggest saving prior to retrieving a new design; upgrade Help system.
Updated to 2.10 - Rewrite overlay plotting including simple deletion of overlay files; print all overlay files on hardcopy outputs (to duplicate screen); upgrade Help system.
Updated to 2.09 - Correct error in coupled-inductor component in the optimization routine; minor interface improvements.
Updated to 2.08 - Near-total rewrite of Plot page menu and Help graphics.
Updated to 2.07 - Printing problem resolved; nearly complete rewrite of menu and help system.
Updated to 2.06 - Cosmetic only; most text size as well as graphics now independent of screen resolution.
Updated to 2.05 - Add another error-trap to Cauer design.
Updated to 2.04 - Add error-trap to Cauer design.
Updated to 2.03 - All outputs to printer are now routed via Printer Selection windows.
Updated to 2.02 - Save-file (an internal operation) now forces use of a period for decimal delineation to allow operation in global regions which use a comma for decimal
Released as 2.01 - June 2004