Scroll to navigation

atlc(1) General Commands Manual atlc(1)


atlc - an Arbitrary Transmission Line Calculator


atlc [-C] [-s] [-S] [-v] [-c cutoff] [-d rrggbb=Er] [-i factor] [-i prefix] [-t threads] [-r rate_multiplier] bitmapfile


This man page is not a complete set of documentation - the complexity of the atlc project makes man pages not an ideal way to document it, although out of completeness, man pages are produced. The best documentation that was current at the time the version was produced may be found in
Sometimes, errors are corrected in the documentation and placed at before a new release of atlc is released. Please, if you notice a problem with the documentation - even spelling errors and typos, please let me know.


atlc is a finite difference program that is used to calculate the properties of a two-conductor electrical transmission line of arbitrary cross section. It is used whenever there are no analytical formula known, yet you still require an answer. It can calculate:
The impedance Zo (in Ohms)
The capacitance per unit length (pF/m)
The inductance per unit length (nF/m)
The velocity of propagation v (m/s)
The velocity factor, v/c, which is dimensionless.

A bitmap file (usually with the extension .bmp or .BMP) is drawn in a graphics package such as Gimp available from The bitmap file must be saved as a 24-bit (16,777,216 colour) uncompqessed file. The colours used in the bitmap indicate whether the region is a conductor (pure red, pure green or pure blue) or a dielectric (anything else). Pure white is assumed to be a vacuum dielectric, but other colours have different meanings. See COLOURS below for precise definitions of the colours.


print copyright, licensing and copying information.
Skip writing the Ex, Ey, E, V, U and Er bitmap (.bmp) files -S
Skip writing the Ex, Ey, E, V, U and Er binary (.bin) files
makes the output more verbose/talkative.
-c cutoff
Sets the convergence criteria of the finite difference program. The default is 0.0001, meaning two separate iterations must be within 01% for the program to stop iterating. Setting to a smaller positive number gives more accuracy, but takes longer.

-d rrggbb=Er
is used to indicate the colour 0xrrggbb in the bitmap is used to represent a material with permittivity Er. See also COLOURS below

-i factor
is used to lighten or darken the .bmp electric field profile images produced by atlc. Set factor > 2 to lighten or between 1 and 2 to darken.

-r ratemultiplier
Sets the parameter 'r' used internally when computing the voltage at a point w,h. The default, which is (as of version 3.0.0) 1.95, results in what is believed to be optimal results. Setting to 1.0 will avoid the use of the fast convergence method, which is generally not a good idea.

-p prefix
Adds 'prefix', which is usually a directory name, in front of the output files.


The 24-bitmaps that atlc uses have 8 bits assigned to represent the amount of red, 8 for blue and 8 for green. Hence there are 256 levels of red, green and blue, making a total of 256*256*256=16777216 colours. Every one of the possible 16777216 colours can be defined precisely by the stating the exact amount of red, green and blue, as in:

red = 255,000,000 or 0xff0000
green = 000,255,000 or 0x00ff00
blue = 000,000,255 or 0x0000ff
black = 000,000,000 or 0x000000
white = 255,255,255 or 0xffffff
Brown = 255,000,255 or 0xff00ff
gray = 142,142,142 or 0x8e8e8e

Some colours, such as pink, turquiose, sandy, brown, gray etc may mean slightly different things to different people. This is not so with atlc, as the program expects the colours below to be exactly defined as given. Whether you feel the colour is sandy or yellow is up to you, but if you use it in your bitmap, then it either needs to be a colour reconised by atlc, or you must define it with a command line option (see OPTIONS).
red = 255,000,000 or 0xFF0000 is the live conductor.
green = 000,255,000 or 0x00FF00 is the grounded conductor.
blue = 000,000,255 or 0x0000FF is the negative conductor

All bitmaps must have the live (red) and grounded (green) conductor. The blue conductor is used to indicate a negative conductor, is needed when the program is used to analyse directional couplers.

The following dielectrics are reconised by atlc:

white 255,255,255 or 0xFFFFFF as Er=1.0 (vacuum)
pink 255,202,202 or 0xFFCACA as Er=1.0006 (air)
L. blue 130,052,255 or 0x8235EF as Er=2.1 (PTFE)
Mid gray 142,242,142 or 0x8E8E8E as Er=2.2 (duroid 5880)
mauve 255.000,255 or 0xFF00FF as Er=2.33 (polyethylene)
yellow 255,255,000 or 0xFFFF00 as Er=2.5 (polystyrene)
sandy 239,203,027 or 0xEFCC1A as Er=3.3 (PVC)
brown 188,127,096 or 0xBC7F60 as Er=3.335 (epoxy resin)
L. yellow 223,247,136 or 0xDFF788 as Er=3.7 (FR4 PCB)
Turquoise 026,239,179 or 0x1AEFB3 as Er=4.8 (glass PCB)
Dark gray 142,142,142 or 0x696969 as Er=6.15 (duroid 6006)
L. gray 240,240,240 or 0xDCDCDC as Er=10.2 (duroid 6010)
D. orange 213,160,067 or 0xD5A04D as Er=100.0 (mainly for test purposes)


Here are a few examples of the use of atlc. Again, see the html documentation in atlc-X.Y.Zocs the documentation on your system (normally at /usr/local/share/atlc/docs/html-docs/index.html ) or online at for examples.

ex_1 % atlc coax2.bmp
This is a simple example (ex_1), in which the geometry of a transmission line is defined in coax2.bmp. In this example, only the predefined dielectrics (Er =1.0, 1.0006, 2.1, 2.2, 2.33, 2.5, 3.3, 3.335, 3.7, 4.8, 6.15 or 10.2) could have been used in the bitmap, which would have been done with one of 13 different colours. white (0xFFFFFF) for Er=1.0, pink (0xFFCACA) for 1.0006 etc. No other colour (dielectric) could have been used, since it was not specified with the -d option.

ex_2 % atlc -d f9e77d=2.43 somefile.bmp
In ex_2, a dielectric with Er=2.43 was wanted. A colour with the RGB values of 0xF9E7&d was used. The -d option tells atlc what Er this colour refers to.

ex_3 % atlc -v coax2.bmp
In ex_3, atlc has been instructed to print the results of intermediate calculations to stdout. Normally, only the final result is printed. Using -vv even more information may be produced, but this is really of only use to the developer of the project.


Original bitmap file. Must be 24-bit colour uncompressed.
X-component of E-field as a bitmap. Red=+dV/dx, blue =-dV/dx
y-component of E-field as a bitmap. Red=+y, blue =-y
E-field, as E=sqrt(Ex^2+Ey^2).
Voltage as a bitmap, red= positive, blue =negative.
Bitmap showing the permittivity as a grayscale. Lighter is a higher

In addition to the bitmaps, the data is also saved in binary files.

All the saved binary files (.bin's) are saved as a double precision number for each of the pixels. The first double is the top left, the last the bottom right. If the original image has width W and height H, the saved binary files will be W-1 by H-1.

All the saved bitmap files are 24-bit uncompressed, just like the input files.


atlc(1) create_bmp_for_circ_in_circ(1) create_bmp_for_circ_in_rect(1) create_bmp_for_microstrip_coupler(1) create_bmp_for_rect_cen_in_rect(1) create_bmp_for_rect_cen_in_rect_coupler(1) create_bmp_for_rect_in_circ(1) create_bmp_for_rect_in_rect(1) create_bmp_for_stripline_coupler(1) create_bmp_for_symmetrical_stripline(1) design_coupler(1) find_optimal_dimensions_for_microstrip_coupler(1) readbin(1) - Home page - Download area
atlc-X.Y.Z/docs/html-docs/index.html - HTML docs
atlc-X.Y.Z/docs/qex-december-1996/atlc.pdf - theory paper
atlc-X.Y.Z/examples - examples

atlc-4.4.2 10th Sept 2003 Dr. David Kirkby