Provided by: gsmc_1.1-1.3_amd64 bug


       gsmc - A GTK Smith Chart Calulator for RF impedance matching




       gsmc  is  a  GTK  application that allow to do all the calculation usually done on a Smith
       Chart.  It permits to make  calculation  for  network  composed  by  resistor,  capacitor,
       inductance, and trasmission line (also as stub).  Network topology is limitated to series,
       parallel and as trasmissive for trasmission line. No  series  connection  are  allowed  in
       parallel  branch,  neither  parallel connection in series branch.  Trasmission 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 analisys; current work  can
       be saved for succesive retrieve.

       The  initial  (start) impedance is thought as "the load" so when adding a trasmission 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.




       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

              Insert a resistor before the highlighted element

              Insert an inductor before the highlighted element

              Insert a capacitor before the highlighted element

              Insert a transmission line or stub before the highlighted element

       d      Delete the currently highligthed 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 Rigth
              Increase the first field of currently highlighted element

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

       Mod+Curs Rigth
              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

              Decrease frequency

       Check online keystroke for an updated list of commands.


       For operation that requires data entry a widget is created; it  is  composed  by  an  text
       entry field and optionaly 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 supplyed using standar 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

       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  immaginary  only something like 'j82' can be supplied, while if immaginary part is
       zero a single number can be given. Immaginary operator can be issued as  'i'  as  well  as


       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 rigth of the Smith chart, where initial, final  and  cursor
              impedance are presented togheter general data.

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

       -      The portion in the lower right portion, for future 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

       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 buttono or
       using the menmonic 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 enter. TAB and  Shift+TAB  is  usefull  to  move
       across  items  in  dialog win without leave hands from keyboard.  This value is really too
       large, use Shft+Left cursor to reduce a bit. Up to where? Let's  help  you  displaing  the
       admittance  constant  circles  pressing  "Ctrl+2", the arc should arrive to the G=1 circle
       (also called the mirror circle), it's arround 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+Curors  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 arround 568nH and 408pF. Now you want to see what appen  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.

       Trasmission line and resistor can be  used  similary  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 lenght and  the  caracteristic  impedance:
       the  former  can  be adjusted with Shift+Cursor left/rigth 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 analized with a
       spice simulator or gnucap or ngspice ; maybe you are interested in simulating it  sweeping
       arround 15.5MHz, so modify the line

            .ac lin 1  15.50MEG  15.50MEG


            .ac lin 51  10MEG  30MEG

       and run spice or gnucap

       This example should be included in gsmc package an can be retreived 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  drawed  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 allow to specify if the file  has  to  be  in  encapsulated
       format or not.


       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  analized  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.


       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.


       Help me to find.


       · Improve autotune algorithm

       · Target settting (not alwais one want to match to z0) for autotune.

       · Auxiliary window for error reporting instead of stderr.


       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 2 of the License, or (at your option) any later version.


        Lapo Pieri  (IK5NAX)

        Home address: via A. dei Corbizi 9  I-50127 Firenze Italy
        Phone: +39 055 410209


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