4 <!-- Manpage converted by man2html 3.0.1 -->
8 <B>design_coupler</B> - for designing directional couplers (part of
9 the <B>atlc</B> package)
13 <H2>SYNOPSIS</H2><PRE>
14 <B>design_coupler</B> <B>[-C][-d][-e][-H</B> <B>height][-L</B> <B>length][-q]</B>
15 <B>[s</B> <B>fstep][-Z</B> <B>Zo]</B> <B>CF</B> <B>fmin</B> <B>fmax</B>
20 This man page is not a complete set of documentation - the
21 complexity of the atlc project makes man pages not an ideal
22 way to document it, although out of completeness, man pages
23 are produced. The best documentation that was current at the
24 time this version was produced should be found on your hard
26 /usr/local/share/atlc/docs/html-docs/index.html
27 although it might be elsewhere if your system administrator
28 chose to install the package elsewhere. Sometimes, errors
29 are corrected in the documentation and placed at
30 http://atlc.sourceforge.net/ before a new release of atlc is
31 released. Please, if you notice a problem with the documen-
32 tation - even spelling errors and typos, please let me know.
37 <H2>DESCRIPTION</H2><PRE>
38 <B>design_coupler</B> is used to design directional couplers. It it
39 <B>not</B> used to analyse couplers for which you know the dimen-
40 sions. Instead, it is used but when you require a coupler to
41 have specific properties, but don't know the required odd
42 and even mode impedances or the required physical dimensions
43 that will achieve those required properties.
45 As a minimum the user must specify the coupling factor CF in
46 dB, the minimum frequency fmin in MHz and the maximum fre-
47 quency fmax in MHz. With this information, the
48 <B>design_coupler</B> will
49 a) Tell you the required odd and even mode impedances Zodd
50 and Zeven assuming the coupler is for 50 Ohms and assuming
51 the coupler is is a quarter wave long, which might be an
52 impractical length. There a numerous ways of making a
53 coupler having those impedances and <B>design_coupler</B> does not
54 (without the addition of options mentioned later), tell you
55 how to make such a coupler. b) Given you the frequency
56 response of the coupler, making the assumptions about the 50
57 Ohm impedance and quarter-wave length. The frequency
58 response is calculated at 5 points in the range specified by
61 By use of the -Z 'Zo' and -L 'length' and -f 'fstep' options
62 it it posible to specify different a different characteris-
63 tic impedance, length and different frequency steps to
64 display the frequency response.
65 The computed values of Zodd and Zeven required are valid no
66 matter how the coupler is design physically. So no matter
67 whether it's implemented on a PCB, air spaced or whatever,
68 the above impedances are correct and the frequency response
71 The -d option causes <B>design_coupler</B> to not only report the
72 required odd and even modem impedances but also the physical
73 dimensions of a coupler that achieves these properties!
74 <B>Currently</B>, the only stucture for which it is possible to
75 compute the physical dimentions is two wide edge-coupled
76 striplines between two wide plates like this:
79 ----------------------------------------------------- ^
83 | ----------- ----------- | H
84 | <----w----><--s--><----w----> | |
88 ----------------------------------------------------- v
89 <-------------------------W------------------------->
91 The width W must be much greater than the height of the
92 coupler and generally it is assumed that this width will at
93 least 2*w+s*5*H, otherwise the calculations will be
94 incorrect. In order to calculate these dimenisions an
95 analytical method is used, which is only valid if the width
96 W is infinity, but should be resonably good assuming W is at
99 It is later intended to enable design coupler to use other
100 structures, which migth be more suitable for construction,
101 such as microstrip couplers on PCBs, but for now at least,
102 it is only possible to compute the physical dimensions of
103 the coupler using the above stucture. For strong coupling
104 (less than 20 dB or so), the dimenions calculated might be
105 impractical, as the spacing s will be so small. However, for
106 weak coupling, the physcical dimensions are practical.
110 <H2>OPTIONS</H2><PRE>
112 print copyright, licensing and copying information.
114 Design a coupler, using two edgle-coupled stiplines inside a
115 wide 4-sided rectangular enclosure.
118 Priont an example of how to use <B>design_coupler</B>
119 <B>-H</B> <B>height</B>
120 Specify the height of the enclosure in some convenient unit.
121 By default, a height of 1 unit is assumed, but by use of
122 this option it is possible to specify any height you want.
123 Since its the ratio of dimensions that is important, not the
124 absolute values, this just scales all the other dimensions
125 by the specified height. It is just a conveneince for the
127 <B>-L</B> <B>length</B>
128 Specifies the coupler length in metres. By default the
129 coupler is assumed to be a quarter-wave, but this allow any
130 length you want. Don't chose a length that is a multiple of
131 a half-wave though, as this will make it impossible to cou-
132 ple any power out. <B>-q</B>
133 This is the 'quite' switch and causes <B>design_coupler</B> to
134 print out less information. One can use -qq to cause the
136 <B>-s</B> <B>fstep</B> Causes <B>design_couler</B> to print out the frequency
137 response at different steps from the default 5 values. fstep
138 must be in MHz. The default value of fstep is obviously
141 Causes <B>design_coupler</B> to compute properties of an impedance
142 Zo (shecified in Ohms). The default value for Zo is 50 Ohms.
147 <H2>EXAMPLES</H2><PRE>
148 Run <B>design_coupler</B> gives examples of its use. However, here
149 are those same examples.
151 Here are a examples of how to use <B>design_coupler</B> In the
152 examples, the % sign is used in front of anything you must
153 type which is what you will probably see when using the csh
154 or tcsh as a shell. It would probably be a $ sign if using
155 the sh or bash shell.
157 To find the odd and even mode impedances and frequency
158 response of a 50 Ohm coupler, covering 130 to 170 MHz, with
159 a coupling coefficient of 30 dB:
161 % design_coupler 30 130 170
163 Note the frequency response is symmetrical about the centre
164 frequency at 0.192 dB below that wanted. You may wish to
165 redesign this for a coupling coefficient of about 29.9 dB,
166 so the maximum deviation from the ideal 30.0 dB never
167 exceeds 0.1 dB Note the length suggested is 0.5 m (nearly
168 20") is a quarter wave at the centre frequency of 150 MHz.
169 You might find this a bit too long, so let's specify a
173 % design_coupler -L 0.25 30 130 170
175 What you may notice is that while the coupling to the cou-
176 pled port is exactly 30 dB below the input power at the cen-
177 tre frequency (150 MHz) it is no longer symmetrical about
178 the centre frequency. Also, deviations from the ideal 30 dB
179 are now much larger, with a maximum error of 1.012 dB Unlike
180 the case when the length is the default quarter wave, there
181 is not much you can do about this, since the deviations
182 occur in both directions.
184 Now assume you are reasonably happy with the response when
185 the length is 250 mm but would like to see the response at
186 every 2.5 MHz. This can be done using the -s option to
189 % design_coupler -L 0.25 -s 2.5 30 130 170
191 Assuming the performance is acceptable, the dimensions of
192 the coupler can be determined by adding the -d option. This
193 will design a coupler that must look like the structure
194 below. The two inner conductors, which are spaced equally
195 between the top and bottom edges of the outer conductor,
196 must be very thin. These are placed along the length of a
197 box of width W, height H and of a length L determined by the
198 user, which in this case is 250 mm.
200 ----------------------------------------------------- ^
204 | ----------- ----------- | H
205 | <----w----><--s--><----w----> | |
209 ----------------------------------------------------- v
210 <-------------------------W------------------------->
212 The program reports: H = 1.0, ; w = 1.44 ; s = 0.44 The
213 height of the box H must be small compared to the length L,
214 (perhaps no more than 7% of the length), or 17.5 mm in this
215 case, with a length of 250 mm, otherwise fringing effects
216 will be significant. The width of the structure W should be
217 as large as possible. The program suggests making this
218 5*H+2*w+s. The 7% and 5*H+2*w+s are educated guesses, rather
219 than exact figures. There is no problem in making the width
220 larger than 5*H+2*w+s. The length L must be kept at 250 mm.
221 The RATIO of the dimensions H, w and s (but not L or W must
222 be kept constant. W just needs to be sufficiently large - it
225 If you happened to have some 15 mm square brass available,
226 then using that for the side-walls would require that H
227 becomes 15*1.0 = 15 mm, w = 15*1.44 = 21.6 mm and s =
230 There is no need to compute the above scaling with a calcu-
231 lator, as using The -H option allows one to specify the
232 height H. The program then reports the exact dimensions for
233 the length L, height H, w, s and suggests a minimum width
237 30 dB coupler +1.02 dB / -0.78 dB for 130 to 170 MHz
238 Length L = 250 mm, height H = 15 mm, stripline spacing s
240 stripline width w = 21.6 mm enclosure width W >= 124 mm
242 By default, design_coupler prints a lot of information to
243 the screen. This can be reduced by the -q option or reduced
244 to only one line with -qq Other options include -Z to change
245 the impedance from the default 50 Ohms and -C to see the
246 fully copyright, Licensing and distribution information
251 No files are created at all.
255 <H2>SEE ALSO</H2><PRE>
257 <B>create_bmp_for_circ_in_circ(1)</B>
258 <B>create_bmp_for_circ_in_rect(1)</B>
259 <B>create_bmp_for_microstrip_coupler(1)</B>
260 <B>create_bmp_for_rect_cen_in_rect(1)</B>
261 <B>create_bmp_for_rect_cen_in_rect_coupler(1)</B>
262 <B>create_bmp_for_rect_in_circ(1)</B>
263 <B>create_bmp_for_rect_in_rect(1)</B>
264 <B>create_bmp_for_stripline_coupler(1)</B>
265 <B>create_bmp_for_symmetrical_stripline(1)</B>
266 <B>find_optimal_dimensions_for_microstrip_coupler(1)</B>
269 http://atlc.sourceforge.net - Home page
270 http://sourceforge.net/projects/atlc - Download area
271 atlc-X.Y.Z/docs/html-docs/index.html - HTML docs
272 atlc-X.Y.Z/docs/qex-december-1996/design_coupler.pdf -
274 atlc-X.Y.Z/examples - examples
284 Man(1) output converted with
285 <a href="http://www.oac.uci.edu/indiv/ehood/man2html.html">man2html</a>