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       design_coupler  -  for designing directional couplers (part of the atlc


       design_coupler [-C][-d][-e][-H height][-L length][-q]
       [s fstep][-Z Zo] CF fmin fmax


       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 this version was produced
       should be found on your hard drive, usually at
       although it might be elsewhere if your system  administrator  chose  to
       install  the  package elsewhere. 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.


       design_coupler is used to design directional couplers. It it  not  used
       to  analyse  couplers for which you know the dimensions. Instead, it is
       used but when you require a coupler to have  specific  properties,  but
       don’t  know  the  required odd and even mode impedances or the required
       physical dimensions that will achieve those required properties.

       As a minimum the user must specify the coupling factor CF  in  dB,  the
       minimum  frequency  fmin  in MHz and the maximum frequency fmax in MHz.
       With this information, the design_coupler will
       a) Tell you the required odd and even mode impedances  Zodd  and  Zeven
       assuming  the  coupler  is for 50 Ohms and assuming the coupler is is a
       quarter wave long, which  might  be  an  impractical  length.  There  a
       numerous   ways  of  making  a  coupler  having  those  impedances  and
       design_coupler does not (without  the  addition  of  options  mentioned
       later),  tell  you  how  to  make  such  a  coupler.   b) Given you the
       frequency response of the coupler, making the assumptions about the  50
       Ohm  impedance  and  quarter-wave  length.  The  frequency  response is
       calculated at 5 points in the range specified by fmin and fmax.

       By use of the -Z ’Zo’ and -L ’length’ and  -f  ’fstep’  options  it  it
       posible  to  specify  different  a  different characteristic impedance,
       length and different frequency steps to display the frequency response.

       The computed  values of Zodd and Zeven required are valid no matter how
       the coupler is design physically. So no matter whether it’s implemented
       on  a PCB, air spaced or whatever, the above impedances are correct and
       the frequency response is correct.

       The -d option causes design_coupler to not only report the required odd
       and even modem impedances but also the physical dimensions of a coupler
       that achieves these properties! Currently, the only stucture for  which
       it  is  possible  to  compute the physical dimentions is two wide edge-
       coupled striplines between two wide plates like this:

       -----------------------------------------------------  ^
       |                                                   |  |
       |                  Er                               |  |
       |                                                   |  |
       |            -----------       -----------          |  H
       |            <----w----><--s--><----w---->          |  |
       |                                                   |  |
       |                                                   |  |
       |                                                   |  |
       -----------------------------------------------------  v

       The width W must be much greater than the height  of  the  coupler  and
       generally  it  is  assumed  that  this  width  will at least 2*w+s*5*H,
       otherwise the calculations will be incorrect.  In  order  to  calculate
       these  dimenisions an analytical method is used, which is only valid if
       the width W is infinity, but should be resonably good assuming W is  at
       least 2*w+s+5*H.

       It  is later intended to enable design coupler to use other structures,
       which migth be more  suitable  for  construction,  such  as  microstrip
       couplers  on PCBs, but for now at least, it is only possible to compute
       the physical dimensions of the coupler using the  above  stucture.  For
       strong coupling (less than 20 dB or so), the dimenions calculated might
       be impractical, as the spacing s will be so small.  However,  for  weak
       coupling, the physcical dimensions are practical.


       print copyright, licensing and copying information.
       Design  a  coupler,  using  two  edgle-coupled  stiplines inside a wide
       4-sided rectangular enclosure.

       Priont an example of how to use design_coupler
       -H height
       Specify the height  of  the  enclosure  in  some  convenient  unit.  By
       default, a height of 1 unit is assumed, but by use of this option it is
       possible to specify any  height  you  want.  Since  its  the  ratio  of
       dimensions that is important, not the absolute values, this just scales
       all the other  dimensions  by  the  specified  height.  It  is  just  a
       conveneince for the user.
       -L length
       Specifies  the  coupler  length  in  metres.  By default the coupler is
       assumed to be a quarter-wave, but this allow any length you want. Don’t
       chose  a  length that is a multiple of a half-wave though, as this will
       make it impossible to couple any power out.  -q
       This is the ’quite’ switch and causes design_coupler to print out  less
       information. One can use -qq to cause the even less output.
       -s  fstep  Causes  design_couler to print out the frequency response at
       different steps from the default 5 values. fstep must be  in  MHz.  The
       default value of fstep is obviously (fmax-fman)/5.
       Z Zo
       Causes   design_coupler  to  compute  properties  of  an  impedance  Zo
       (shecified in Ohms). The default value for Zo is 50 Ohms.


       Run design_coupler gives examples of its use. However, here  are  those
       same examples.

       Here are a examples of how to use design_coupler In the examples, the %
       sign is used in front of anything you must type which is what you  will
       probably  see  when using the csh or tcsh as a shell. It would probably
       be a $ sign if using the sh or bash shell.

       To find the odd and even mode impedances and frequency response of a 50
       Ohm coupler, covering 130 to 170 MHz, with a coupling coefficient of 30

       % design_coupler 30 130 170

       Note the frequency response is symmetrical about the  centre  frequency
       at  0.192  dB  below  that  wanted. You may wish to redesign this for a
       coupling coefficient of about 29.9 dB, so the  maximum  deviation  from
       the ideal 30.0 dB never exceeds 0.1 dB Note the length suggested is 0.5
       m (nearly 20") is a quarter wave at the centre frequency  of  150  MHz.
       You  might  find this a bit too long, so let’s specify a length of 0.25

       % design_coupler -L 0.25 30 130 170

       What you may notice is that while the coupling to the coupled  port  is
       exactly  30  dB below the input power at the centre frequency (150 MHz)
       it  is  no  longer  symmetrical  about  the  centre  frequency.   Also,
       deviations  from  the  ideal  30 dB are now much larger, with a maximum
       error of 1.012 dB Unlike the  case  when  the  length  is  the  default
       quarter  wave,  there  is  not  much  you  can do about this, since the
       deviations occur in both directions.

       Now assume you are reasonably happy with the response when  the  length
       is 250 mm but would like to see the response at every 2.5 MHz. This can
       be done using the -s option to design_coupler.

       % design_coupler -L 0.25 -s 2.5 30 130 170

       Assuming the performance is acceptable, the dimensions of  the  coupler
       can  be  determined by adding the -d option. This will design a coupler
       that must look like the structure  below.  The  two  inner  conductors,
       which  are spaced equally between the top and bottom edges of the outer
       conductor, must be very thin.  These are placed along the length  of  a
       box  of  width  W,  height  H and of a length L determined by the user,
       which in this case is 250 mm.

       -----------------------------------------------------  ^
       |                                                   |  |
       |                  Er                               |  |
       |                                                   |  |
       |            -----------       -----------          |  H
       |            <----w----><--s--><----w---->          |  |
       |                                                   |  |
       |                                                   |  |
       |                                                   |  |
       -----------------------------------------------------  v

       The program reports: H = 1.0, ; w = 1.44 ; s = 0.44 The height  of  the
       box  H must be small compared to the length L, (perhaps no more than 7%
       of the length), or 17.5 mm in this case,  with  a  length  of  250  mm,
       otherwise  fringing  effects  will  be  significant.  The  width of the
       structure W should be as large as possible. The program suggests making
       this  5*H+2*w+s. The 7% and 5*H+2*w+s are educated guesses, rather than
       exact figures. There is no problem in making  the  width   larger  than
       5*H+2*w+s.  The  length  L  must  be  kept  at 250 mm. The RATIO of the
       dimensions H, w and s (but not L or W must be  kept  constant.  W  just
       needs to be sufficiently large - it is uncritical.

       If  you  happened to have some 15 mm square brass available, then using
       that for the side-walls would require that H becomes 15*1.0 = 15 mm,  w
       = 15*1.44 = 21.6 mm  and s = 15*0.44 = 6.6 mm

       There  is  no  need  to compute the above scaling with a calculator, as
       using The -H option allows one to specify the  height  H.  The  program
       then  reports the exact dimensions for the length L, height H, w, s and
       suggests a minimum width for W.

       In summary we have:
           30 dB coupler +1.02 dB / -0.78 dB for 130 to 170 MHz
           Length L = 250 mm, height H = 15 mm, stripline spacing s = 6.3 mm
            stripline width w = 21.6 mm enclosure width W >= 124 mm

       By default, design_coupler prints a lot of information to  the  screen.
       This  can  be reduced by the -q option or reduced to only one line with
       -qq Other options include -Z to change the impedance from  the  default
       50  Ohms  and -C to see the fully copyright, Licensing and distribution


       No files are created at all.


       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_in_circ(1)           create_bmp_for_rect_in_rect(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/design_coupler.pdf - theory paper
       atlc-X.Y.Z/examples                        - examples