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

Here are pertinent features of the Professional edition of Elsie:

• 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.
  
  
• 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, Chebycheff, Cauer (including the zig-zag transform), Bessel and Gaussian 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 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.
  
  
• 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.
  
  
• Markers can be placed on the plots. These reveal the magnitude of the plot at that frequency. 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. 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 filesets 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).
  
  
• It writes schematic files for LTspice (a product of Linear Technologies). And it writes fairly generic Spice netlists. They can be imported into a variety of nodal analysis programs. (Note: Tonne Software has no connection with Linear Technologies.)
  
  
• 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.
  
  
• The program does NOT function with computers using Japanese or Chinese-language operating systems.