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- Committer: Bazaar Package Importer
- Author(s): Joop Stakenborg
- Date: 2005-08-22 20:20:13 UTC
- Revision ID: james.westby@ubuntu.com-20050822202013-mhhxp4xirdxrdfx1
Tags: upstream-1.19
Import upstream version 1.19
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- man/man5
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man/man1/optimise.1
1
.TH OPTIMISE 1 "24 October 2000" "version 1.16"
2
.de BP
3
.sp
4
.ns
5
.ti -.2i
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\(**
7
..
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.SH NAME
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optimise \- Yagi-Uda project antenna optimiser
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.SH SYNOPSIS
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.B optimise
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[
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.B \-dhvwO
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]
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[
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.BI \-a angular_stepsize
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]
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[
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.BI \-b boom_extension
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]
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[
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.BI \-c cleanliness_of_pattern
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]
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[
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.BI \-e elements
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]
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[
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.BI \-f FBratio
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]
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[
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.BI \-g GA_optimisation_method
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]
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.BI \-l percent
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]
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[
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.BI \-m min_offset_from_peak
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]
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[
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.BI \-o optimisation_criteria
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]
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[
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.BI \-p population
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]
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[
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.BI \-r resistance
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]
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[
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.BI \-s swr
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]
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[
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.BI \-t length_tolerance
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]
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[
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.BI \-x reactance
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]
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[
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.BI \-A Auto_gain
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]
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[
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.BI \-C Currents_similar
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]
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[
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.BI \-F weight_FB
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]
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[
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.BI \-G weight_gain
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]
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[
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.BI \-K keep_for_tries
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]
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[
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.BI \-P weight_pattern_cleanliness
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]
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[
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.BI \-R weight_resistance
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]
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[
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.BI \-S weight_swr
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]
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[
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.BI \-T position_tolerance
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]
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[
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.BI \-W Weighted_algorithm
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]
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[
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.BI \-X weight_reactance
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[
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.BI -Z Zo
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]
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filename iterations
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.SH DESCRIPTION
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The program
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.B optimise
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is one of a number of executable programs that forms part of a set of
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programs, collectively known as the
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.I Yagi-Uda project
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, which were designed for analysis and optimisation of Yagi-Uda antennas.
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.I optimise
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attempts to optimise the performance of a Yagi antenna for one or more
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parameters that are considered important, such as gain, F/B ratio, VSWR
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etc. It does this by randomly changing the lengths and positions, of one
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or more elements, then comparing the performance before and after the change.
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Any improvements are written to a new file called
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.I filename.bes
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where
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filename is the name of the antenna description file created by
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.I input
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or
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.I first
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.LP
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When Yagi's are designed on paper, or using this program, its possible that they will be almost
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impossible to build, if their performance depends too critically on the
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dimensions. To determine if this is the case with a design, we run optimise with just the options 't' and 'T'. These specify the tolerance with which you can build the antenna, expressed as a standard deviation in mm. In this case, instead
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of trying to optimise a poor design, optimise will calculate the minimum gain, maximum VSWR,
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and minimum FB ratio of a number of designs, all slightly different from the input file. 99.7% of the components
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lie within 3 SD of the mean, so if you think you can cut elements to with 1 mm 99.7% of the time,
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specify t0.33. If you can put them in the boom to within 3 mm 99.7% of the time, specify T1.
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.LP
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If while
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.I optimise
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is running using the methods that require weights to be attached to the gain,
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FB, SWR etc, it becomes apparent, the weights are not optimum, its possible to
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pause the program and re-adjust the weights. If a file with the name of
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.I changes
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is created, the program will pause, then request new weights are entered at
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the keyboard.
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.SH AVAILABILITY
129
.SH OPTIONS
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.TP
131
.B \-d
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Print the default values of all the configureable parameters to stdout. Typing this option with any
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option that changes a parameter (see below) will display the new value of the parameter, rather
134
than the default.
135
.TP
136
.B \-h
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Print a help message.
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.TP
139
.B \-v
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Print verbose status information.
141
.TP
142
.B \-w
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Instead of optimising at one fixed frequency (the design frequency), this directs the program to
144
optimise at 3 separate frequencies (lowest, design and highest) then to average data at all 3. This
145
option is better for wideband antenna. Note that the input impedance printed is at the design
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frequency, *not* averaged over 3 frequencies. Averaging an impedance, is likely to give a very
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misleading impression. The impedance averaged over 3 frequencies can be 50+i0 Ohms, even
148
if the VSWR is very poor over all 3 frequencies, as the following 3 pieces of data show.
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.br
150
Z=147 + j 300 SWR= 15.46:1
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.br
152
Z=2 + j 100 SWR= 125:1
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.br
154
Z=1 - j 400 SWR= 3250:1
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.br
156
note in the above three cases, the average impedance is 50 + j 0, but
157
average SWR is 1130:1.
158
.TP
159
.B \-O
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Over-optimisation allowed. By default, the program does not over-optimise a parameter. For example, an SWR of 1.01 is usually considered good enough and
161
any change, as long as the SWR stayed good, typically below 1.1:1, would
162
be allowed, even if the SWR rose. By default, FB's of 27 dB, VSWR's of 1.1 are
163
acceptable. However, by using the
164
.B \-O
165
option, you can insist the program always improves things, no matter how good they are.
166
.TP
167
.TP
168
.BI \-a Angular_stepsize
169
When optimimising by trying to get a clean pattern, specifies the step size to
170
use when looking for features in the pattern. If its set too small, the program runs slow. If its set too large, the program may miss features in the pattern, such as a sidelobe. Then the resulting antenna will have poor sidelobe performance, even though you think it will be good. The program attempts to calculate
171
a sensible value, based on 1/10th the approximate 3 dB beamwidth, if you don't
172
set.
173
.TP
174
.BI \-b boom_extension
175
Generally speaking, the gain of a Yagi increases with boom length. Hence the optimiser would
176
often give you a Yagi with a much longer boom than the input file. This may not be what you
177
desire due to space restrictions. These long antennas often have high gain, but are very narrow in bandwidth. The default limits the antenna to 10x the original length, which
178
means effectively there is no boom length limitation.
179
You can adjust the percentage by setting
180
.I boom_extension
181
to whatever you wish.
182
.I -b30
183
will limit the boom to no more than 30% more than the original length.
184
.TP
185
.BI \-c cleanliness_of_pattern
186
Specify the number of dB down on the peak gain to aim to get the pattern. Any
187
antenna pattern cleaner than this will not effect the fitness, nor will it
188
be considered any better when comparing to antenna designs. 20 dB seems reasonable, so the default is 20, but this may of course change if it's deceided too. Check the source code to be certain (see REASONABLE_SIDELOBE in yagi.h).
189
.TP
190
.BI \-e elements
191
is an integer which specifies the type of elements that are changed in the optimisation cycle.
192
Possible values are:
193
.br
194
.in +1.5
195
1 - alter only the driven element(s) length (useful to bring to resonance)
196
.br
197
2 - alter only the driven element position. Don't change its length.
198
.br
199
4 - alter only the reflector length. The position is always at x=0.
200
.br
201
8 - alter only the director lengths. Don't change positions.
202
.br
203
16 - alter only the director positions. Don't change lengths.
204
.br
205
32 - randomly adjust one element length, then makes all other the same. Don't change the positions.
206
.br
207
64 - apply a linear taper to the lengths.
208
.br
209
128 - Set the driven element to a resonate length. It may/may-not be altered after the first run, depending on the whether or not '1' is invoked too. Eg -e128
210
will make it resonate and keep it there forever. However '-e129' will bring to
211
resonance, then alter to maximuse performance.
212
.in -1.5
213
The elements altered is made from a logical AND of the above, so for example to alter everything, except the driven element length, use -e30, since 2+4+8+16=30.
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The default is equivalent to
215
.I -e31
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, which changes everything possible. Note the
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reflector position is *never* changed. It's always at x=0.
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.TP
219
.TP
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.BI \-f FBratio
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When optimising an antenna, consider any FB ratio greater than
222
.I FBratio
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dB to be equal to
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.I FBratio
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dB. This avoids optimising to a very high FB ratio, which is impracticable, as the bandwidth over
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which this FB ratio will be maintained is very small and mechanical considerations will prevent
227
you from constructing it with such a high FB ratio anyway. If this was not prevented, you might
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just happen to get an antenna with 100 dB FB ratio, but poor gain and swr. Since by default all
229
parameters must improve, the optimisation routine will most likely never being able to improve
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on the 100 dB FB ratio, so no improvement will result. Most people would prefer to get a few extra dB of gain,
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even if the FB ratio dropped to 30 dB.
232
.TP
233
.BI \-g GA_optimisation_method
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Use a genetic algorithm. With the genetic algorithm, the program does
235
not take any account any of the initial lengths/positions of elements
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specified in the input file. Rather it works by initialising a
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number of different antenna, then computing a 'fitness' value for each.
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The fitness value can depend on the gain, FB, real part of the input impedance, reactive part of the input impedance, VSWR or the level of the sidelobes. The
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integer after the g tells the optimiser what to consider.
240
-g1 Use gain
241
.br
242
-g2 Use FB
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.br
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-g4 Use R
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.br
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-g8 Use X
247
.br
248
-g16 Use the SWR
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.br
250
-g32 Use the level of the sidelobes.
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.br
252
253
You can use a logical AND of these, so for example -g49 will use a genetic algorithm, optimising for gain, swr and sidelobe level, since 1(gain)+16(SWR)+32(sidelobe level)=49.
254
.TP
255
.BI \-l percent
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is a parameter (floating point number) which specifies the maximum percentage
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change in the positions or lengths of an elements at each iteration. If the
258
option is not used, it will be set internally at 10% for the first 25% of the
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iterations, 1% for the next 25%, 0.1% for the third 25% of the iterations and
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0.01% for the last 25% of the iterations. If set to a positive number x (eg optimise -l 0.3 145e10) then the percentage will be set at x% for 25% of iterations, x/10 for the next 25%, x/100 for the next 25 and x/1000 for the last 25%. If set to a negative number y (eg optimise -l -0.5 145e10) then the paramters will stay fixed at y% (in this example 0.5%) all the time.
261
.TP
262
.BI \-m min_offset-from_peak
263
Sets the minimum angle in degrees offset from theta=90 degrees, where the
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side lobes start and the main lobe finishes. The higher the gain, the smaller
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it should be. It is set internally if not set on the command line.
266
.TP
267
.BI \-o optimisation_criteria
268
.br
269
.in +1.5
270
1 - Assume better if the gain has increased.
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.br
272
2 - Assume better if the front to back ratio has improved.
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.br
274
4 - Assume better if the real part of the input impedance is closer to the
275
value that the program was compiled for, or set using the '-Z' option.
276
This will usually be 50 Ohms, but you may wish to set this to 12.5 Ohms if
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you use a 4:1 balun. Generally you can get higher gain from a Yagi if you
278
allow the input impedance to fall, but of course feeding it becomes more
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difficult.
280
.br
281
8 - Assume better if the magnitude of the reactive component of the input impedance is lower
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(ie. the antenna is nearer resonance).
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.br
284
16 - Assume better if the VSWR is lower.
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.br
286
32 - Assume better if the level of all sidelobes is lower.
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.in -1.5
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The
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.I optimisation_criteria
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may be formed from a logical AND of these numbers, so for example choosing
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.I -o19
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will only consider a revised antenna better than the previous, if the SWR,
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gain and F/B ratio have all simultaneously improved.
294
.br
295
296
Clearly an antenna which originally had 12 dB gain and 1.01:1 VSWR but then
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changes to 20 dB gain @ 1.02:1 VSWR, would to most people be better, even
298
though the VSWR has increased. By default,
299
.I optimise
300
only optimises to sensible maximums, so to not let the optimisation stall prematurely. By running
301
.I optimise
302
with no arguments, the program will list the limits of acceptability.
303
These might be typically F/B ratio > 27 dB, VSWR < 1.1:1, magnitude of input
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reactance less than 5 Ohms and the real part of the input impedance within
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5 Ohms of Zo. Choosing
306
.I -o19
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(1+2+16=19) will optimise for gain (since G=1), FB (since FB=2) and SWR (Since SWR=16), but would consider a higher gain and FB ratio antenna better than a
308
previous one, even if the SWR rose, as long as it stayed
309
below 1.1:1 (or as was set during compilation). The default behaviour (no options) is equivalent
310
to
311
.I -o37
312
which optimiseas for gain(1), the real part of the input impedance(4) and sidelobes(32)
313
but this may be changed at any time, so type
314
.I optimise -d
315
to check the current settings. If you insist on the program optimisang for the
316
very best of all selected parameters, use the -O option too, but be warned the
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optimisation will probely stick once it gets one parameter really good.
318
.TP
319
.BI \-p population
320
This determines the initial population used with the genetic
321
algorithm.
322
.TP
323
.BI \-r resistance
324
When optimising an antenna, consider any input resistance closer to Zo (usually 50 Ohms) than
325
.I resistance
326
Ohms to be acceptable. This avoids optimising to an input resistance too close to Zo, which is
327
impracticable, as the bandwidth over which the input resistance could be maintained is very small
328
and mechanical considerations will prevent you from constructing the antenna with such an ideal
329
input resistance. If this was not prevented, you might just happen to get an antenna with an input
330
resistance of 50.000001 Ohms, but poor gain, FB and possibly even a poor swr, if the
331
antenna is well away from resonance. Since by default all parameters must improve, the
332
optimisation routine will get most likely never being able to improve on the antenna, whereas
333
we might be happier with a few more dB gain, if the input resistance went to 50.1 Ohms. It
334
should be noted that the default optimisation routine never uses the input resistance directly (only
335
VSWR), so this option cant be used without the '-o' option to optimise for other than the default
336
parameters (gain, VSWR and FB ratio).
337
.TP
338
.BI \-s swr
339
When optimising an antenna, consider any SWR less than
340
.I swr
341
to be equal to
342
.I swr
343
This avoids optimising to a very low swr, which is impracticable, as the bandwidth over which
344
such a low swr could be maintained would be very small and mechanical considerations will
345
prevent you from constructing such an antenna anyway. If this is was not prevented, you might
346
just happen to get an antenna with an swr of 1.000000000001:1, but poor gain, FB ratio. Since
347
by default all parameters must improve, the optimisation routine will most likely never being able
348
to improve on the antenna, even though in practice you would like to get a few extra dB of gain
349
if the SWR would rise to 1.02:1. The default was equivalent to
350
.I -s1.1
351
but run
352
.I optimise -d
353
to display this and any other defaults.
354
.TP
355
.BI \-t length_tolerance
356
.I length_tolerance
357
is the standard deviation in mm of the accuracy with which you can cut elements. Since 99.7%
358
of elements will be with 3 standard deviations of the mean length (stats theory says this), set
359
-t0.2 if virtually all (well 99.7%) of elements are within 3x0.2=0.6 mm of the correct length. This
360
option *must* be used with the '-T' option and can't be used with any other options apart from
361
'-Z', '-v' and '-d'.
362
.TP
363
.BI \-x reactance
364
When optimising an antenna, consider any input reactance of less than
365
.I reactance
366
to be
367
.I reactance.
368
This avoids over optimising the reactance, at the expense of something else.
369
.TP
370
.BI \-A auto_gain
371
When the
372
.I auto_gain
373
option is used. the program maximes the gain of the antenna (ignoring all other
374
parameters such as SWR, FB ratio etc) by adjusting the length (not position)
375
of one element only. -A-1 will maximuse the gain, by adjusting the length of
376
the reflector, -A0 will maximise the gain by adjusting the length of the driven
377
element. Its generally *not* a good idea to maximise the gain by adjusting the
378
driven element, but the program lets you do it, but using the option -A0. Using
379
-A1 will maximise gain by adjusting the length of the first director, -A2 the second director and so on, up to the last director. You must check carefully that the input impedance in particular does not fall to silly values if you use this option. On a yagi with many elements (> 10 or so), you can pretty safely maximise the 8th or more director, but doing it on the reflector, driven element or
380
early directors often leads to silly input impedances - so beware!
381
Note, no matter how many iterations you specify, this process is only done once.Its unlikely you will be able to do it again, without things going out of hand, but if you must do it, you must re-run 'optimise' again.
382
.TP
383
.BI \-C currents_similar
384
If this option is used, where
385
.I currents_similar
386
is an integer, the program looks to make the
387
currents in the last
388
.I currents_similar
389
elements as similar as possible. It computes the sum of the squares of the deviations of the absolute values of the element currents from the mean. If this falls, and the criteria specified with the -W option is also satisfied, the antenna is considered better. If
390
.I
391
currents_similar
392
is three less than the number of directors, it tries to make the currents in the the directors (but ignoringing the first 3) all similar. If
393
.I currents_similar
394
is equal to the number of directors, it tries to make all the directors have similar currents. If
395
.I currents_similar
396
is one more than the number of directors, it tries to make all the directors and the reflector have similar currents. If
397
.I currents_similar
398
is equal to the total number of elements, then it fails with an error message.
399
.TP
400
.BI \-F weight_FB
401
is the floating point number (default 1.0) specifying the weight to attach to
402
the FB ratio of the antenna when using the '-W' option, which calculates a fitness for the antenna based on one or more parameters (FB, gain, input resistance, input reactance, SWR, cleanliness of antenna pattern). The '-F' option is
403
similar to the options -G, -P, -R, -S, -X (which specify weights for gain, pattern cleanliness, input resistance, SWR and input reactance).
404
When using the -W option the exact algorithm used to compute the fitness (and hence the effect of this parameter) is best checked by looking at the source code (see perform.c). This is one area of constant program improvement/changes/development, so its difficult to say exactly the effect the parameter has. However, increasing the weight of a parameter (using the -F, -G, -R, -S or -X options) will make the associated parameter have a greater effect on the fitness.
405
However, unless you optimise for a high FB ratio with the -W option, then setting the -F option will have no effect. For example, setting the options -F2.5 -W1 is a complete waste of time. There you have used the -W1 option to optimise only for gain (see -W option section of man page) but have changed the weight of the FB ratio from its default 1.0 to 2.5. If you are not optimising for FB ratio, the weight you attach to it is irrelavent.
406
.TP
407
.BI \-G weight_gain
408
is the floating point number (default 1.0) specifying the weight to attach to
409
the gain of the antenna when using the '-W' option, which calculates a fitness for the antenna based on one or more parameters (FB, gain, input resistance, input reactance, SWR, cleanliness of antenna pattern). The '-G' option is
410
similar to the options -F, -P, -R, -S, -X (which specify weights for FB ratio, pattern cleanliness, input resistance, SWR and input reactance).
411
When using the -W option the exact algorithm used to compute the fitness (and hence the effect of this parameter) is best checked by looking at the source code (see perform.c). This is one area of constant program improvement/changes/development, so its difficult to say exactly the effect the parameter has. However, increasing the weight of a parameter (using the -F, -G, -R, -S or -X options) will make the associated parameter have a greater effect on the fitness.
412
However, unless you optimise for gain with the -W option, then setting the -G option will have no effect. For example, setting the options -G2.5 -W2 is a complete waste of time. There you have used the -W2 option to optimise only for FB ratio (see -W option section of man page) but have changed the weight of the gain from its default 1.0 to 2.5. If you are not optimising for gain, the weight you attach to it is irrelavent.
413
.TP
414
.BI \-K keep_for_tries
415
.br
416
.I keep_for_tries
417
is the number of tries for the optimise to persist using the original data
418
file as the starting point for optimisation. By default it is 1, which means the
419
program immediately looks from a new position once a better one is found. It
420
is theeoretically possible that this might result in a quick, but poor local maximum. If however,
421
.I keep_for_tries
422
is 1000, it will
423
stay at a position for 1000 iterations after finding the last best result,
424
before considering this to be a global optimum. Then it starts for the new
425
position. In practice, I have found this option to make matters worst in most cases. It was added to avoid the local-minimum problem, but it appears the optimisation surface is pretty smooth, so it just slows the program, without gaining much. Anyway, it can stay as an option, but check the results with/without carefully before using extensively.
426
.TP
427
.BI \-P pattern_cleanlyiness
428
is the floating point number (default 1.0) specifying the weight to attach to
429
the cleanness of the antenna pattern when using the '-W' option, which calculates a fitness for the antenna based on one or more parameters (FB, gain, input resistance, input reactance, SWR, cleanliness of antenna pattern). The '-P' option is similar to the options -F, -G, -R, -S, -X (which specify weights for FB ratio, gain, input resistance, SWR and input reactance).
430
When using the -W option the exact algorithm used to compute the fitness (and hence the effect of this parameter) is best checked by looking at the source code (see perform.c). This is one area of constant program improvement/changes/development, so its difficult to say exactly the effect the parameter has. However, increasing the weight of a parameter (using the -F, -G, -R, -S or -X options) will make the associated parameter have a greater effect on the fitness.
431
However, unless you optimise for a clean antenna pattern with the -W option, then setting the -P option will have no effect. For example, setting the options -P2.5 -W1 is a complete waste of time. There you have used the -W1 option to optimise only for gain (see -W option section of man page) but have changed the weight of the pattern cleanliness from its default 1.0 to 2.5. If you are not optimising for a clean radiation pattern, the weight you attach to it is irrelavent.
432
With appropiate use of the -W option (eg -W49 for gain, SWR and a clean pattern), the computer program finds the level of the most significant sidelobe, wherever it may be outside the main bean. It then optimises to reduce this. The -P option tells it how much weight to put on reducing this sidelobe.
433
.TP
434
.BI \-R weight_resistance
435
is the floating point number (default 1.0) specifying the weight to attach to
436
the obtaining an input resistance close to Zo on the antenna when using the '-W' option, which calculates a fitness for the antenna based on one or more parameters (FB, gain, input resistance, input reactance, SWR, cleanliness of antenna pattern). The '-R' option is similar to the options -F, -G, -P, -S, -X (which specify weights for FB, gain, pattern cleanliness, SWR and input reactance).
437
When using the -W option the exact algorithm used to compute the fitness (and hence the effect of this parameter) is best checked by looking at the source code (see perform.c). This is one area of constant program improvement/changes/development, so its difficult to say exactly the effect the parameter has. However, increasing the weight of a parameter (using the -F, -G, -R, -S or -X options) will make the associated parameter have a greater effect on the fitness.
438
However, unless you optimise for an an input resistance close to Zo, with the -W option, then setting the -R option will have no effect. For example, setting the options -R2.5 -W1 is a complete waste of time. There you have used the -W1 option to optimise only for gain (see -W option section of man page) but have changed the weight of the resistance from its default 1.0 to 2.5. If you are not optimising for an input resistance close to Zo, the weight you attach to it is irrelavent.
439
.TP
440
.BI \-S weight_swr
441
is the floating point number (default 1.0) specifying the weight to attach to
442
the SWR of the antenna when using the '-W' option, which calculates a fitness for the antenna based on one or more parameters (FB, gain, input resistance, input reactance, SWR, cleanliness of antenna pattern). The '-S' option is
443
similar to the options -F, -G, -P, -R, -X (which specify weights for FB, gain, pattern cleanliness, input resistance and input reactance).
444
When using the -W option the exact algorithm used to compute the fitness (and hence the effect of this parameter) is best checked by looking at the source code (see perform.c). This is one area of constant program improvement/changes/development, so its difficult to say exactly the effect the parameter has. However, increasing the weight of a parameter (using the -F, -G, -R, -S or -X options) will make the associated parameter have a greater effect on the fitness.
445
However, unless you optimise for SWR with the -W option, then setting the -S option will have no effect. For example, setting the options -S2.5 -W1 is a complete waste of time. There you have used the -W1 option to optimise only for gain (see -W option section of man page) but have changed the weight of the SWR from its default 1.0 to 2.5. If you are not optimising for SWR, the weight you attach to it is irrelavent.
446
.TP
447
.BI \-T position_tolerance
448
.I position_tolerance
449
is the standard deviation in mm of the accuracy with which you can cut elements. Since 99.7%
450
of elements will be with 3 standard deviations of the correct position (stats theory says this), set
451
-T2 if virtually all (well 99.7%) of elements are within 3x2=6 mm of the correct position.This
452
option *must* be used with the '-t' option and can't be used with any other options apart from
453
'-Z', '-v' and '-d'.
454
.TP
455
.BI \-W Weighted_algorithm
456
Try to get an antenna which is better according to a weighted combination of
457
parameters, rather than require them all to improve. The integer specifies
458
what to consider in the weighted parameters.
459
.br
460
W1 Gain.
461
.br
462
W2 FB
463
.br
464
W4 R
465
.br
466
W8 X
467
.br
468
W16 SWR
469
.br
470
W32 SIDE_LOBE
471
.br
472
You can logically AND these together, so for example -W3 will optimise using a weighted combination of gain and FB. -W49, will use a weighted combination of gain, swr and sidelobe leve, since 32+16+1=49.
473
.TP
474
.BI \-X weight_reactance
475
is the floating point number (default 1.0) specifying the weight to attach to
476
achieving a low input reactance on the antenna when using the '-W' option, which calculates a fitness for the antenna based on one or more parameters (FB, gain, input resistance, input reactance, SWR, cleanliness of antenna pattern). The '-X' option is similar to the options -F, G, -P, -R and -S (which specify weights for FB ratio, gain, pattern cleanliness, input resistance, and SWR).
477
When using the -W option the exact algorithm used to compute the fitness (and hence the effect of this parameter) is best checked by looking at the source code (see perform.c). This is one area of constant program improvement/changes/development, so its difficult to say exactly the effect the parameter has. However, increasing the weight of a parameter (using the -F, -G, -R, -S or -X options) will make the associated parameter have a greater effect on the fitness.
478
However, unless you optimise for a low input reactance with the -W option, then setting the -X option will have no effect. For example, setting the options -X2.5 -W1 is a complete waste of time. There you have used the -W1 option to optimise only for gain (see -W option section of man page) but have changed the weight of the reactiance from its default 1.0 to 2.5. If you are not optimising for a low input reactance, the weight you attach to it is irrelavent.
479
.TP
480
.BI \-Z Zo
481
.br
482
.I Zo
483
is the characteristic impedance used when evaluating the VSWR, reflection coefficient and other
484
similar calculations. The optimiser usually tries to bring the input impedance of the antenna to
485
this value. It is set by default to 50 Ohms, so the default is equivalent to
486
.I -Z50
487
but may be set to any positive number. Set to 12.5 Ohms if you are going to feed the antenna
488
with a 4:1 balun. Generally speaking, the gain of a Yagi
489
can be higher for low input impedances, but of course such antennas are
490
more difficult to feed.
491
.TP
492
.I filename
493
This is the name of the file containing the antenna description. It is expected
494
to be in a format created by either
495
.I input
496
or
497
.I first
498
- two other programs in the
499
.I Yagi-Uda project.
500
This is an ASCII text file.
501
.TP
502
.I iterations
503
is an integer specifying the number of iterations for the optimiser to perform to try to get the best
504
antenna. Time will limit the number you choose. 1000 iterations of a 1ele yagi takes about 5
505
seconds, a 6ele approximately 60 seconds, an 11 element 350 seconds, a 20 element 1030
506
seconds, a 33ele 2440 seconds, a 50element 5400 seconds, 100ele 21320 seconds all on an old
507
25MHz 486 PC with no external cache.
508
When using the
509
.I -A
510
option the
511
.I iterations
512
is automatically set internally so only one attempt is
513
made.
514
When using the '-t' and '-T' options,
515
.I iterations
516
specifies the number of iterations to attempt to get a poorer design, to check the sensitivity of
517
the design to small manufacturing tolerances.
518
.SH EXAMPLES
519
Here are a number of examples of using
520
.I optimise.
521
.PP
522
1) optimise 5ele 1000
523
.PP
524
Here the file 5ele will be optimised using the default system for 1000
525
iterations. The default might typically require gain, FB and SWR to
526
all improve, but this may be changed at any time. In any case, the
527
program tells you what its optimising for. By default the program will
528
only optimise to the selected parameters are good, not over-optimising any
529
one at the detrement of the others.
530
531
2) optimise -b30 -f50 -s2 5ele 1000
532
.PP
533
This is similar to above, but the boom can not extend by more than 30%
534
from its original length, FB ratios above 50 dB are considered acceptable,
535
as are SWR's less than 2:1. The optimised resultant antenna is likely to have
536
better FB ratio, but poorer SWR than in (1) above.
537
538
3) optimise -o1 5ele 1000
539
.PP
540
This will simply optimise 5ele for maximum forward gain. The resultant
541
antenna may have a poor FB ratio and is likely to have an unacceptably
542
low input impedance and hence high VSWR. This is not a very sensible
543
method of optimisation.
544
545
4) optimise -W49 -l7 5ele 10000
546
.PP
547
This will optimise the file 5ele using for 10000 iterations. It will
548
require that the weighted performance of the antenna in three important
549
parameters (gain, sidelobe level and SWR) improves from one design to the
550
next. One or two parameters can actually get worst from one design to
551
the next, but the weighted performance is better. The positions of the elements or lengths of
552
elements will not change by more than 7% in each iteration.
553
.PP
554
5) optimise -g -S30 -G50 -F20 -p1500 5ele 10000
555
.PP
556
This will optimise the file 5ele using a genetic algorithm. 1500 antennas will be randomly
557
designed. The performance of each of these will measured using a 'fitness' function, weighted
558
30% to SWR, 50% to gain and 20% to FB ratio. The probability of breading from a pair of
559
antennas is proportional to the fitness function.
560
.PP
561
6) optimise -w atv_antenna 10000
562
.PP
563
This will optimise the file atv_antenna for a best average performance over a wide band. The progrram calculates the gain, FB and SWR at three frequencies, then computes an average (mean) performance of the antenna over the band. N iterations will take 3x as long to execute as N iterations on the same antenna without the '-w' option.
564
.PP
565
7) optimise -t0.1 -T1 good_design 100
566
.PP
567
This will take the file good_design and make 100 different antennas from it,
568
to simulate the effects of building tolerances. Each element is assumed to be cut so that the mean
569
error of all elements is 0 mm, but a standard deviation of 0.1 mm, so 68.4% of element lengths
570
are within 0.1 mm, 95.4% within 0.2 mm and 99.7% with in 0.3 mm. The accuracy of placing
571
elements along the boom is much lower, so here we have specified a standard deviation of
572
1.0 mm, so 68.6% of elements are placed within 1 mm of the correct position, 95.4% within 2 mm
573
of the correct position etc. The program will report the *worst* performances achieved. If the
574
performance dips too mush, then you either need to build them better, or get a design that's less critical!
575
576
.SH STOPPING
577
.I Optimise
578
will stop after the number of iterations specified in the parameter
579
.I iterations.
580
It will also stop if a file
581
.I stop
582
exits in the current directory of the executable
583
.I optimise
584
This file can of course only be created using a multi-tasking operating
585
system such as Unix. It is *not* advisable to stop the program by
586
hitting the DEL key (Unix) or CONTROL-C (DOS), as one of the files may
587
be open at the time, resulting in an empty file. Files are not open for
588
any longer than necessary (they are closed immediately after writing to
589
them), so this is not a likely occurrence, but can still occur.
590
.SH LIMITATIONS
591
I'm not aware of any limitations, apart from that filenames, including full
592
path, can't exceed 90 characters.
593
.SH FILES
594
.nf
595
filename Antenna description, created by input or first.
596
filename.up Update file, listing achievements of optimise.
597
filename.bes Best file, containing the best design to date.
598
changes File that causes the program to pause to re-adjust weights.
599
stop File that stops optimisation process.
600
.br
601
.fi
602
.SH "SEE ALSO"
603
first(1), input(1), output(1), yagi(1), first(5), input(5) output(5) and optimise(5).
604
605
.SH PLATFORMS
606
Both DOS and Unix versions have been built. The DOS version as
607
distributed requires a 386 PC with a 387 maths coprocessor.
608
609
Although I have altered the source to make it more compatible with DOS (reduced file name
610
lengths etc), my wish is to build a decent program, rather than fit the program to an outdated
611
operating system. If there is a *good* reason to use code that is incompatible with DOS, this will
612
be done.
613
.br
614
Since
615
.I optimise
616
takes a while to optimise an antenna (I've optimised one design for a week), it is obviously
617
more sensible to build this program under a multi-tasking operating system, as otherwise a PC
618
can be tied up for days.
619
.SH BUGS
620
Bugs should be reported to
621
.BR david.kirkby@onetel.net .
622
Bugs tend actually to be fixed if they can be isolated, so it is in your
623
interest to report them in such a way that they can be easily reproduced.
624
625
The program will dump core (crash) if asked to optimise a 1ele beam, without any arguments.
626
This is because a 1ele beam has no parasitic elements and by default the program only changes
627
parasitic elements.
628
629
Some of the options are not checked for sensible values, although most are
630
now checked and report if they are out of range.
631
632
If the user specifies very large manufacturing errors using the '-t' and '-T'
633
options, its possible for elements to overlap or for element lengths to
634
become negative. This will cause numerical errors. Any reasonable values
635
will not cause this.
636
637
638
On long Yagi's (50 elements) optimise can go a bit silly. It can optimise
639
say a 1296MHz Yagi to get 20 dB at 1296 MHz, but less than 0 dB at only 1 MHz
640
away. Needs some thought!
641
642
The level of the sidelobes is not computed with the GA or some other optimisation types. This will be corrected later.
643
644
All those I don't know about.
645
646
.nf
647
.SH AUTHORS
648
Dr. David Kirkby G8WRB (david.kirkby@onetel.net).
649
with help with converting to DOS from Dr. Joe Mack NA3T (mack@fcrfv2.ncifcrf.gov)
Loggerhead is a web-based interface for Breezy
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