Provided by: gsmc_1.2.1-1_amd64 bug

NAME

       gsmc - A GTK Smith Chart Calculator for RF impedance matching

SYNOPSIS

       gsmc

DESCRIPTION

       gsmc  is  a  GTK  application  that allows one to do all the calculation usually done on a
       Smith Chart.  It permits one  to  make  calculation  for  network  composed  by  resistor,
       capacitor,  inductance, and transmission line (also as stub).  Network topology is limited
       to series, parallel and as trasmissive for transmission line.  No  series  connection  are
       allowed  in  parallel  branch, neither parallel connection in series branch.  Transmission
       line can be placed as quadrupole or as a parallel or series stub, either opened or shorted
       at the other end.

       Calculation  procedure  starts  with  setting  the  initial  impedance to be matched, next
       network elements are added and tuned to obtain the desidered impedance value.

       The network so obtained can be saved in spice format for other analysis; current work  can
       be saved for successive retrieve.

       The  initial (start) impedance is thought as "the load" so when adding a transmission line
       placed as a quadrupole rotation is  clockwise,  going  "toward  generator";  generator  is
       placed after the last network element, as can be seen from spice output.

OPTIONS

       None

INTERACTIVE COMMANDS

       gsmc  is a menu based GTK application with as much as possible accelerators and mnemonics.
       Nearly all the command can to be issued as a single keystroke or keystroke with modifiers.
       This  is,  in the author's opinion, the preferable way for very specialistic programs that
       has to be used extensively.

       Ctrl+q Quit the program.

       Ctrl+1 Toggle visualization of impedance (Z) circle

       Ctrl+2 Toggle visualization of admittance (Y) circle

       Ctrl+3 Toggle visualization of reflection coefficient (RHO) circle

       Ctrl+4 Toggle visualization of constant Q circle

       s      Set start point: can be entered as impedance, admittance or reflection coefficient

       Ctrl+0 (zero)
              Set characteristic impedance z0

       f      Set frequency (f0)

       r      Add a resistor

       l      Add an inductor

       c      Add a capacitor

       t      Add a transmission line or stub

       Shift+r
              Insert a resistor before the highlighted element

       Shift+l
              Insert an inductor before the highlighted element

       Shift+c
              Insert a capacitor before the highlighted element

       Shift+t
              Insert a transmission line or stub before the highlighted element

       d      Delete the currently highlighted element

       Shift+Curs Up
              Highlight previous element

       Shift+Curs Down
              Highlight next element

       Shift+Curs Left
              Decrease the first field of currently highlighted element

       Shift+Curs Right
              Increase the first field of currently highlighted element

       Mod+Curs Left
              Decrease the second field of currently highlighted element

       Mod+Curs Right
              Increase the second field of currently highlighted element

       Mod+Curs Up
              Increase the tuning step

       Mod+Curs Down
              Decrease the tuning step

       Ctrl+w Write network file in spice format

       Ctrl+n Restart for a new calculation with a clean chart

       =      Change first field of currently highlighted element

       Mod+=  Change second field of currently highlighted element

       Ctrl+a Start autotune procedure (tune goal is characteristic impedance)

       Ctrl+x Toggle lock flag in autotune procedure

       Ctrl+p Write an EPS or PS file

       Ctrl+l Load a previously saved .B gsmc job

       Ctrl+l Save a .B gsmc job

       Ctrl+f Increase frequency

       Shift+Ctrl+f
              Decrease frequency

       Check online keystroke for an updated list of commands.

       DIALOG WIN

       For operation that requires data entry a widget is created; it  is  composed  by  an  text
       entry field and optionally some radio button to chose the format of data entry.

       The  format  for data entry can be a single number, or a more complex string. First of all
       every number can be supplied using standard prefix for unit of measure i.e.:

              a      (atto) 1e-18

              f      (femto) 1e-15

              p      (pico) 1e-12

              n      (nano) 1e-9

              u      (micro) 1e-6

              m      (milli) 1e-3

              k      (kilo) 1e3

              M      (mega) 1e6

              G      (giga) 1e9

              T      (tera) 1e12
       Note that for spice output format mega is written as  MEG  instead  of  M,  that  will  be
       otherwise recognized by spice as milli.  Unit of measure are not allowed to be in the text
       entered.

       Where a complex number  is  required  both  the  rectangular  and  the  polar  format  are
       recognized: the former can be supplied as '12.3-j456m' while the latter can be supplied as
       '34.2 145' meaning a modulus of 34.2 with a phase of 145 degrees. If the complex number is
       purely  imaginary  only  something  like 'j82' can be supplied, while if imaginary part is
       zero a single number can be given. Imaginary operator can be issued as 'i' as well as 'j'.

DATA PRESENTATION

       The single window of gsmc is divided in four parts:

       -      The Smith chart itself in the upper left portion, where arcs  and  constant  circle
              are drawn.

       -      The  vertical  bar on the right of the Smith chart, where initial, final and cursor
              impedance are presented together general data.

       -      The horizontal bar on the bottom of Smith  chart  where  the  network  element  are
              listed.

       -      The portion in the lower right portion, for future use...

EXAMPLE OF USE

       Let's  try  a  simple  example  to  understand  how  gsmc  work. Suppose to have a load of
       10-j35ohm to be matched to 50+j0ohm at an operating frequency of 15.5MHz and  we  can  use
       only concentrated reactive elements, i.e. inductances and capacitors.

       So start with setting operating frequency: press 'f' and a dialog win will appear. Type in
       the string '15.5M' and then press enter. Now in the vertical bar the frequency entered  is
       displayed.

       Next  set the start point impedance: press 's' and a dialog win will appear with the title
       "Start Point"; select the format for start point either clicking the "Z" radio  button  or
       using  the  mnemonic  via  Mod+Z.  Now the impedance can be entered as the string '10-j35'
       followed by enter. The starting point is now displayed as a small circle.

       The network has now to be constructed: let start with a series  inductance  of  800nH,  so
       press  'l'  and  next introduce the value as '800n', be sure that "Series" radio button is
       selected before pressing enter. TAB and Shift+TAB is useful to move across items in dialog
       win  without  leave  hands  from keyboard.  This value is really too large, use Shift+Left
       cursor to reduce a bit. Up to where? Let's help you  displaying  the  admittance  constant
       circles pressing "Ctrl+2", the arc should arrive to the G=1 circle (also called the mirror
       circle), it's around 546nH.

       Now add a capacitor in parallel connection, saying of 200pF:  press  'c'  and  insert  the
       string  '200p'  and  select Parallel either with mouse or with "Mod+p". Now the admittance
       circles may confuse, remove it by pressing "Ctrl+2" again.  The  value  of  200pF  is  too
       small,  enlarge  it  by  pressing  Shift+Left  cursor  up to get the end point near to the
       chart's center. The point reached with 429pF has nearly zero imaginary  but  is  43ohm  of
       real part instead of 50ohm.

       So  back  to  the  inductance and try to modify it, with Shift+Cursor up move to the first
       component and then try to change the inductance value by pressing cursor left  and  right.
       The  changes are too large and 50+j0 cannot be reached. So press "Mod+Cursor down" and the
       "tunestep" value shown in the vertical bar is reduced from 10% to 5%,  try  again  to  use
       Shift+Cursors  left and right. It feel better. Now do the same on the capacitor, moving to
       it by pressing cursor down and than adjusting value as for the inductance.

       Final values should be around 568nH and 408pF. Now you want to see what happen  using  the
       closest  standard  commercial  values,  that  is 560nH and 390pF in the E12 series. Select
       (with Shift+Cursor Up), if needed, the inductance and then press '=',  the  dialog  window
       appear  (middle line is unused) and the string '560n s' has to be introduced. Next move to
       capacitor (Shift+Curs Down) and pressing '=' here insert '390p p'. The final result is  of
       SWR=1.14, if it's enough for you...

       Moving  the  mouse  to the point where the two arcs ends you can see that the point has an
       impedance of about 10+j20ohm.

       Transmission line and resistor can be used similarly  refer  to  the  section  INTERACTIVE
       COMMANDS  for knowing how they can be placed.  The major difference with transmission line
       is that they have two parameter, the electrical length and the  characteristic  impedance:
       the  former  can  be adjusted with Shift+Cursor left/right as for resistor, inductance and
       capacitor; the latter can be adjusted with Mod+cursor left/right.

       Now the network can be saved either in a gsmc format (.gdt extension) by  pressing  Ctrl+s
       or  in  spice  format  pressing  Ctrl+w:  The file so generated can be now analyzed with a
       spice simulator or gnucap or ngspice ; maybe you are interested in simulating it  sweeping
       around 15.5MHz, so modify the line

            .ac lin 1  15.50MEG  15.50MEG

       in

            .ac lin 51  10MEG  30MEG

       and run spice or gnucap

       This example should be included in gsmc package an can be retrieved by pressing Ctrl+l and
       selecting example1.gdt.

       Autotune algorithm is very primitive and may not reach what is very simple to do by  hand,
       do not ask to much from it, work in progress...

       Charts so drawn can be printed to a Postscript or Encapsulated Postscript file; in printed
       file some information are added on the chart drawing as well as  Circuit  Description  and
       some  of  the Current Value are transcripted.  Automatic recognition of filename extension
       .eps or .ps allows one to specify if the file has to be in encapsulated format or not.

FILES

       gsmc don't use special configuration file, a gtkrc file is supplied and can  be  tuned  to
       user preferences; if present it must be in /root/.gsmc/gtkrc.  File describing the network
       currently analyzed can be generated, it's only needed that a minimum  file  permission  is
       allowed, if not the program will work but data could not be saved.

       Data  file  (.gdt)  contain  a  copy of internal data structures in a quite human readable
       format; by inspection one can recognize and modify some parts using  a  text  editor.  For
       more details compare a .gdt file with smcdata struct defined in source file main.h.

LIMITATIONS

       Porting  can  be  very very difficult, since all is based on X windows programming and GTK
       library, but for other platform a plenty of similar program are available, free  and  good
       one too.

BUGS

       Help me to find.

TODO

       · Improve autotune algorithm

       · Target setting (not always one want to match to z0) for autotune.

       · Auxiliary window for error reporting instead of stderr.

COPYING

       This program is free software; you can redistribute it and/or modify it under the terms of
       the GNU General Public License as  published  by  the  Free  Software  Foundation;  either
       version 3 of the License, or (at your option) any later version.

AUTHOR

        Lapo Pieri  (IK5NAX)

        Home address: via delle Ortensie, 22  I-50142 Firenze Italy
        Phone: +39 055 706881
        e-mail: ik5nax@radioteknos.it
        website: www.qsl.net/ik5nax ; www.radioteknos.it

SEE ALSO

       spice3(?), gnucap(1), ngspice(1), qucs(1)