create_bmp...irc_in_circ(1)

📦 version 4.6.1, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

💖 create_bmp_for_circ_in_circ — bestie edition 💖

okay so. this is create_bmp_for_circ_in_circ, and it lives in section 1 of the General Commands Manual (the classic "General Commands Manual" energy, we love her). she's part of the atlc family, and she's here to make you a bitmap of a circular conductor sitting inside another circular conductor. no cap. let's get into it 🫶

✨ NAME ✨

create_bmp_for_circ_in_circ — bitmap generator for circular conductor inside circular conductor (part of atlc)

✨ SYNOPSIS ✨

create_bmp_for_circ_in_circ [options... ] D d O Er filename.bmp

🚨 WARNING 🚨

bestie, listen. this man page is not a complete set of documentation. the atlc project is so complex that man pages just aren't the ideal way to document it — but out of completeness, man pages get produced anyway. iconic of them honestly.

the best documentation that was current at the time the version was produced should be found on your hard drive, usually at:

/usr/local/share/atlc/docs/html-docs/index.html

although it might be elsewhere if your system administrator chose to install the package somewhere else. (sysadmins stay doing their own thing 💅)

sometimes errors get corrected in the documentation and dropped at http://atlc.sourceforge.net/ before a new release of atlc comes out. so please — if you notice a problem with the documentation, even spelling errors and typos — please let them know. they literally asked. 🙏

🌸 DESCRIPTION 🌸

create_bmp_for_circ_in_circ is a pre-processor for atlc, the finite difference program that is used to calculate the properties of a two and three conductor electrical transmission line of arbitrary cross section.

the program create_bmp_for_circ_in_circ is used as a fast way of generating bitmaps (there is no need to use a graphics program), for a circular conductor inside a circular conductor (coaxial conductors), like this:

                           *****************
                       ****                 ****
                    ****    <-----d------>     ****
                  ***            *****            ***
                ***           ***********           ***
              ***            *************            ***
             ***            ***************            ***
            ***      ^      ***************             ***
           ***       |      ***************              ***
          ***        |       *************                ***
          **         O        ***********                  **
         ***         |            ***                      ***
         **          |                                      **
         *<------------------------D------------------------>*
         **                                                 **
         **                                                 **
         **                                                 **
         ***                                               ***
          **                                               ***
          ***                                             ***
           **                                             **
            **                                           **
             **                                         **
              ***                                     ***
               ****                                 ****
                 ****                             ****
                   *****                       *****
                      ******               ******
                          *******************
                                  ***

so the deets:

  • the parameter D is the inner dimensions of the outer conductor
  • d is the outer diameter of the inner conductor
  • the inner conductor is offset h from the centre of the outer conductor
  • the whole region is surrounded by a dielectric of relative permittivity Er

the bitmap is printed to outfile.bmp — the last command line argument.

the bitmaps produced by create_bmp_for_circ_in_circ are 24-bit bit colour bitmaps, as are required by atlc. periodt.

now, the permittivities of the dielectric Er determine the colours in the bitmap. if Er is 1.0, 1.006, 2.1, 2.2, 2.33, 2.5, 3.3, 3.335, 3,7, 4.8, 10.2 or 100, then the colour corresponding to that permittivity will be set according to the colours defined in COLOURS below. 🎨

if Er is not one of those permittivities, the region of permittivity Er will be set to the colour 0xCAFF00. the program atlc does not know what this permittivity is, so atlc must be told with the command line option -d, as in example 4 below. (yes we're getting to the examples, patience bestie 😭)

💅 OPTIONS 💅

  • -b bitmapsize — sets the size of the bitmap, and so the accuracy to which atlc is able to calculate the transmission line's properties. the default value for bitmapsize is normally 4, although this is set at compile time. the value can be set anywhere from 1 to 15, but more than 8 is probably not sensible.
  • -f outfile — set the output filename. by default, the bitmap is sent to stdout, but it must be sent to a file, with this option, or as described above.
  • -v — causes create_bmp_for_circ_in_circ to print some data to stderr. note: nothing extra goes to standard output, because that's expected to be redirected to a bitmap file. (keep your streams separate, queen 👑)

🌈 COLOURS 🌈

the 24-bit bitmaps that atlc expects 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 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 — like pink, turquoise, sandy, brown, gray etc — may mean slightly different things to different people. this is not so with atlc, because 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 recognised by atlc, or you must define it with a command line option (see OPTIONS and example 5 below). 💀

the following conductors are recognised by atlc:

  • red = 255,000,000 or 0xff0000 is the live conductor.
  • green = 000,255,000 or 0x00ff00 is the grounded conductor.
  • blue = 000,000,000 or 0x000000 is the negative conductor

all bitmaps must have the live (red) and grounded (green) conductor. the blue conductor is not currently supported, but it will be used to indicate a negative conductor, which will be needed if/when the program gets extended to analyse directional couplers. (future plans, we're manifesting ✨)

the following dielectrics are recognised by atlc and so are produced by create_bmp_for_circ_in_circ:

white     255,255,255 or 0xFFFFFF as Er=1.0   (vacuum)
pink      255,202,202 or 0xFFCACA as Er=1.0006 (air)
blue      000,000,255 or 0x0000FF 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)
Turquoise 026,239,179 or 0x1AEFB3 as Er=4.8   (glass PCB)
Dark gray 142,142,142 or ox696969 as Er=6.15  (duroid 6006)
L. gray   240,240,240 or 0xDCDCDC as Er=10.2  (duroid 6010)

📝 NOTE 📝

even though create_bmp_for_circ_in_circ is used for circular inner and outer conductors, the outside of the outer conductor is drawn as a square. this is for convenience and makes no difference to the calculations. the inside of the outer conductor is drawn as a circle. (square outside, circle inside, it's giving "geometry but make it fashion" 🦋)

🎀 EXAMPLES 🎀

here are a few examples of the use of create_bmp_for_circ_in_circ. again, see the html documentation in atlc-X.Y.Z/docs/html-docs/index.html for more examples.

1) in the first example, the outer conductor has an inside diameter of 12 units (inches, mm, feet etc.), the inner has an outside diameter of 3.9 units. the inner is placed centrally (h=0) and the dielectric is vacuum (Er=1.0).

% create_bmp_for_circ_in_circ 12 3.9 0 1.0 coaxial_1.bmp
% atlc coaxial_1.bmp

atlc will indicate the correct value of impedance to be 67.3667 Ohms, whereas an exact analysis will show the true value to be 67.4358 Ohms, so atlc has an error of 0.102%.

2) in this second example, the conductor sizes are the same as in example 1, but the inner is located 3.5 units off-centre and the dielectric has a relative permittivity of 2.1 (Er of PTFE). the output is sent to a file not_in_centre.bmp which is then processed by atlc

% create_bmp_for_circ_in_circ 12 3.9 3.5 2.1 not_in_centre.bmp
% atlc not_in_centre.bmp

the impedance of this is theoretically 24.315342 Ohms, as create_bmp_for_circ_in_circ will calculate for you. atlc's estimate is 24.2493 Ohms, an error of only -0.271 %.

3) in the third example the bitmap is made larger, to increase accuracy, but otherwise this is identical to the previous one.

% create_bmp_for_circ_in_circ -b8 12 3.9 3.5 2.1
bigger_not_in_centre.bmp
% atlc bigger_not_in_centre.bmp

this time atlc will take much longer to calculate Zo, since the bitmap is larger and so it needs to do more calculations. however, the final result should be more accurate. in this case, the result reported is 24.2461 Ohms, an error that's marginally smaller than before at 0.285 %. it is possible there may be something to be gained by decreasing the cutoff at larger grids, so this is being investigated. however, errors almost always below 0.25 %, no matter what is being analysed. (she's accurate AND she's humble 💜)

4) in the fourth example, a material with a relative permittivity 7.89 is used. there is no change in how to use create_bmp_for_circ_in_circ, but since this permittivity is not one of the pre-defined values (see COLOURS), we must tell atlc what it is. the colour will be set an olive green one, with a hexadecimal representation of red=0xCA, blue=OxFF and green = 0x00. this just happens to be the default colour used when the permittivity is unknown. so atlc must be given this information, like this:

% create_bmp_for_circ_in_circ 23 9 0 7.89 an_odd_er.bmp
% atlc -d CAFF00=7.89 an_odd_er.bmp

this has a theoretical impedance of 20.041970 Ohms, but atlc version 3.0.1 will calculate it to be 20.0300, an error of -0.058 % !!! if you look at the file an_odd_er.bmp with a graphics package, you will see there are 3 colours in it — the red inner conductor, the green outer and an olive-green dielectric. 🌈

🫶 SEE ALSO 🫶

and the links, for your bookmarking pleasure:

http://atlc.sourceforge.net                - Home page
http://sourceforge.net/projects/atlc       - 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

and that's the whole page, bestie!! 💖 this one was written by Dr. David Kirkby, and it's from version atlc-4.4.2, dated the 10th Sept 2003. so iconic, so vintage, so slay. now go make yourself a coaxial bitmap and let atlc cook 🍓✨

📦 where this page comes from