Automatically optimizes the
antenna giving consideration to various parameters. Select the
Optimization in the view menu or push the Optimizationbutton
in the calculation window to open the optimization window. The goals
of the optimization are:
- Minimize the jX (get the antenna resonant)
- Minimize the SWR
- Maximize the gain
- Maximize the F/B ration
- Minimize the elevation of the beam
- Matching circuit
- Maximize or minimize the current
In most cases, these parameters are in
the 'trade-off' condition. You can select the parameters that you focus
on using the slide bars in the top of the window. As you slide the bar
to right, the selected target is prioritized. As you slide the bar to
the left end, the target is ignored.
If you check the No goal set box, MMANA-GAL
simply sweeps the parameters regardless of the state of the slide bars.
MMANA-GALincrements the parameter from the current value to the Max value.
This is useful to observe the antenna behavior from the viewpoint of
the height or frequency.
Push the Advanced button to set the target
at length. Assume that you are happy if the antenna has 20 dB F/B ratio.
Put 20 in the F/B ratio box. MMANA-GALattempts to optimize the other parameters
if the antenna already has 20 or more F/B ratio.
Push the Band setting button to get the dialog
box, with which you can specify the band frequency and the source. This
is useful for optimizing a multi-band antenna. In default, MMANA-GALtries
only one band and source as specified.
Matching circuit is one of the hairpin match,
capacitance match, and any Z. The hairpin match has minus jX (capacitive)
and the capacitance match has plus jX (inductive).
Current optimization attempts to maximize or minimize
the specified pulse point.
The antenna parameters that MMANA-GAL changes during
the optimization procedure are:
- Wire coordinate and radius
- Wire length, azimuth, and zenith (in polar coordinates)
- Element width, perimeter, and radius
- Parameters of lumped-constant load
- Antenna height
- Frequency
- Voltage and phase of the source
- Stack space
You can set the parameters above as up to 128 variables.
Hit return key or click on the type field to display the type selection
pop-up menu. Hit return key on the what field to pop the menu up. Input
a value manually to other fields.
Wire coordinate and radius
These are most basic variables. You can
change the X1, X2, Y1, Z1, Y2, Z2, and R of the wire. If the specified
wire changes its coordinates, the connected wires also changes together
to keep them connected. This method should be useful for the fine-tuning.
Unit is always meter. Pos. is the element number.
Wire length, azimuth, and zenith (in polar
coordinates)
You can change the wire length and angle with respect to the
reference point in the polar coordinates. This is useful for optimizing the
length or the angle of the inverted V and V beam. It should be noted that you
must not set the element position or space as the variable if you change the
X-axis. MMANA-GALdoes not prevent it but may not update the optimized results.
When the coordinate of the wire is changed, the connected wire moves together
with it. Pos. is the wire number. The step unit is meter or degree.
Element
The parameters that define the element can
be set as the variable in the optimization. For a yagi antenna, for
example, they are the element space, position, and width. For a loop
antenna, they are space, positio, perimeter, etc. Pos. is the element
number. Unit is always meter.
Lumped-constant load
LC or R+jX can be set as the variable. If
you want to change two loads in both ends of the element (e.g., loading
DP or trapped yagi), you can use 'association function.' .
If both L and C are specified in the definition, MMANA-GALtreats them as
a trap and keeps the resonance frequency unchanged. For example, if
L is increased, MMANA-GALautomatically decreases C. Pos. is the
number of lumped-constant loads. Unit of L is uH. Unit if C is pF. Unit
of R is Ohm.
Antenna height
Unit of the variable is meter.
Frequency
Unit is MHz. If your target antenna is a multi-bander, do not
use the frequency as the variable.
Source
MMANA-GAL changes the phase and voltage of the sources.
Pos. is the
number of source. Unit of the phase is degree. Unit of the voltage is V.
Stack space
Unit is meter. If you set space in the what
box, the vertical
and horizontal spaces are changed at the same time.
Association
If you put 0 to the association box, the parameter
changes freely as an independent variable. If you put a plus number,
it is assumed to have the same variable that the number points to. If
you put a minus number, it is assumed to have the same variable negated
that the number points to. You can put a simple equation, too. The operators
supported here are +, -, *, and /. It works like a primary spreadsheet.
[Examples of association]
0 Not associated (independent variable)
1 Associated with variable 1 (the same value of variable_1
is put there)
-5 Associated with negated variable 5 (- variable_5)
1*1.05 Associated with variable_1•1.05 (variable_1 • 1.05)
2-1.5 Associated with variable2_-1.5 (variable_2 - 1.5)
-3+1.2 Associated with 1.2 - variable-3
If you optimize the positions of the traps of a multi-band
dipole, you should want to move two traps proportionally to the center
of the antenna. You define two variables, Y1 and Y2, which specify the
trap positions. The center of the dipole must be Y = 0. Define Y1 as
an independent variable (association of Y1 = 0), and Y2 as Y1's negated
value (association of Y2 = -1). You can make use of the automatic
association by right click at the variable box. MMANA-GAL makes a guess
what should be the target of the association. This method can
be used to move the center wire of hentenna or tri-hat antenna.
Pitch specifies the minimum step of variable change in
either an absolute value or a percentage. Large pitch makes the convergence
fast but will not reach the best result.
Min and Max defines the range of the variable.
The variable does not become smaller than Min or larger than Max. You
could specify other variable with # followed by the variable number.
If you put #1 in the Max box for example, the Max value is set
the value of variable 1.
If you do not put Max value to the element space of Uda-Yagi
antenna, MMANA-GAL might give you much larger space than you expected.
If you do not put Min to the width or perimeter, MMANA-GAL might
shrink one of five elements of Uda-Yagi antenna and configure a four-element
Uda-Yagi antenna as a result. It is a good idea to see how the antenna
dimension is being changed in the antenna view window during the optimization.
Push the Delete button to delete the variable where
the cursor resides.
Push the All element button to make MMANA-GAL add
all the parameters to the optimization variable list. If the space check
box is checked, the element space is used. If not, the absolute position
of the element is used.
Push the Element edit button to start an element
selection view. Move the cursor to the variable that you want to vary
in the optimization procedure, and push the OK button. MMANA-GAL
registers the variable for the optimization. The variable marked with
* is already registered. If you want to do this with the 3-D view, select
the wire selection tab. Click the wire you want to add as a variable.
Push the OK button. The wire already registered as a variable
is shown in red.
Step in absolute values: if checked, put an absolute
value to the pitch. If not checked, put a percentage value.
Resolution 2 degrees: MMANA-GAL calculates the beam
pattern every 2 degrees. It shortens the calculation time, but degrades
the accuracy particularly for the high-frequency antenna with a ground.
Display log: the intermediate states of the optimization
procedure are displayed in the log window.
Push the Start button to start the optimization.
Even during the optimization, you can see the wire definition, the antenna
view, or the far field pattern in real time. Note that the MMANA-GAL
is dedicated to the optimization; the response of the mouse should be
very slow.
Needless to say, MMANA-GAL works on the Windows operating
system, so you can do another job even during the optimization. You
could execute two MMANA-GAL at the same time. You can run the optimization
in one window and design an antenna in the other window.
Optimization log
The optimization routine would not always judge
the result, which one thinks the best, is the best. This might be due
to the fact that the rate of evaluation is different from that the designer
expects. You can read the optimization log by pushing the Optimization
log button at the bottom of the Optimization window. It shows up
to 128 latest steps of the optimization. You can select one of the steps
and get it back to the optimization window so that you can manually
pick out the optimization result you think best
Tips on the optimization
I have tried various optimization
algorithms. I have figured out that the algorithm similar to the practical
antenna adjustment, that is, changing one parameter at a time to maximize
the target value and repeating it for other parameters as well, gives
fast convergence and good results.
This procedure, however, would not always give the real optimized
solution that the one-by-one method gives. It could terminate the optimization
just after finding a local minimum. If you are not satisfied with the
result, change the parameter manually and retry the optimization.
The result could depend on the parameter order. MMANA-GAL
attempts the optimization by changing No. 1 parameter first and then
does No.2 parameter. It is a good idea to put the most effective parameter
in the first place of the variable parameter list.
Pursuing the gain often results in the low impedance. The
very low impedance makes the sustainable bandwidth narrow, and the wire
loss cannot be ignored. It is difficult to implement the very low impedance
antenna in the real world. Consider SWR in the optimization for obtaining
reasonable results.
If you put two or more bands, MMANA-GAL attempts the optimization
in each band and sums up the evaluation rates. Only the first feeding
information is displayed.
To keep the performance even in the band edge, put the band edge
frequency as well. However, it increases the calculation time for the
convergence. I am not sure if you could achieve good results.
In case of Uda-Yagi antenna, the moment method is weak
in the calculation speed, so I recommend you use another analyzing tool
that uses the electromotive force method.
Optimization goals
- If your goal is Z
Push Options menu, select Options and setup, click on the
Setup tab, and input R and jX in the Standard SWR pane. Set the target to the SWR minimization and start the
optimization.
Another way to this is: push Options menu, select Optimization, push
Advance button, select Goal tab, check Optional Z, and put your R and
jX. Set the target to the matching circuit and star the optimization. Do not set the target to SWR or
jX.
- If your goal is R
Push Service menu, select Optimization, push Advance
button, select Goal tab, check Optional Z, and put your R. Put * to
jX. Set the target to the matching circuit and star the optimization. Do not set the target to SWR or
jX.
- If your goal is jX
Push Service menu, select Optimization, push Advance
button, select Goal tab, check Optional Z, and put your jX. Put * to
R. Set the target to the matching circuit and star the optimization. Do not set the target to SWR or
jX.
- If your goal is to get the voltage fed antenna resonant
Push Options menu, select Optimization, push Advance button, select Goal tab, check Optional Z, and put 10000 to R. Put 0 to jX. Set the target to the matching circuit and star the optimization. You may put a little value to jX. In case of the end-fed antenna, put * to jX.
Note: If you put * in R or jX, the marked value are not taken into consideration in the
evaluation.
- If your goal is beam pattern
Push Service menu, select Optimization, push
Advance button, select Environment tab, put 180 to Azimuth, and put 90 to
Vertical. Set the slider bars of the Gain and F/B rates around the center, input your SWR, and start the optimization.
- If your goal is a broad band antenna
Set two or three frequency spots as the bands in
the Band setting window. It is recommended to minimize SWR rather than jX because R will not vary much (set SWR to the target beforehand).
- If you want to keep the boom length
Use the element position as a variable. Bear in mind that you have to keep the front-end and back-end elements fixed. In other words, you use the positions of the elements except for these two elements.
To automatically register the element position as a variable, you should uncheck the
Distance from the active element box in the Edit element window.
All elements button in the optimization
When you push the All elements button
in the optimization window, MMANA-GAL automatically uses the following
parameters as variables: Loop length, space (or position), Width, length,
X-width, space (or position).
MMANA-GAL analyzes the relative positions of the elements and assigns the variables in the order of the radiator, reflector, and directors (d1-dn).
If two or more elements have the identical X-axis value, they are assumed to be connected. MMANA-GALmakes them associated. If an element has two or more variables in the width, length, and X-width, MMANA-GALasks the user how they should be treated (a dialog box appears).
MMANA-GAL does not automatically make association between the elements
that have different X values. In such a case, right click on the optimization
window to get the pop-up menu, select the element association. You can
make association the element with the other element that have different
X value. This technique would be useful for the antennas, such as a
surface antenna, which has many elements in the same size and space.
When you push the All elements button, MMANA-GALputs a typical value to the pitch. You may change the value as you like. The pop-up menu provides a means to give the identical pitch to the all variables.
Resonance frequency of the element
It should be useful for the antenna construction
to have the resonance frequency of each element by using the antenna
simulation. Put the source to the target element. Set the
frequency as the variable and set jX to the goad. jX = 0 indicates the
resonance, so the obtained frequency is the resonance frequency.
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