Transcript Document

Antenna Design Tools
VE3KL
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Antenna simulation tools based on NEC Fortran Program
Eznec
4NEC2 (free) including optimizer and tuner design
• Transmission Line Utility (TLDetails, Dan Maguire, AC6LA)
• Antenna Tuner Utility (included in 4NEC2)
• Specialized C#, C++, VB programs to drive EZNEC/4NEC2
• Measurement Tools and Software :
AIM4170 vector meter + Zplots(AC6LA)
7/17/2015
David Conn VE3KL
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Outline
• My Antenna Design Process
• 4nec2 Overview..Analysis, Optimization, Utilities
• Design Example …..40/17 metre fan dipole
• Future Trends
• Demo of 4NEC2 or AIM4170 Analyzer
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Antenna System
Simulate/build/test
Antenna
Transmission Line
Zo, velocity, length
losses
Use TLDetails to select
Tuner
Discrete or
Stubs
Optional : use if SWR >1.5
Transmitter
Power and Frequency
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My Design Process
Idea ?
4nec2
Simulator
Optimizer
Transmission
Line Analysis
(TLDetails)
Tuner Design
4NEC2 Matching Utility
Build
Measure
Vector Z meter
Aim 4170 …..
File Transfer .csv
Capture Data for plotting
Zplots Software
Design Review
OK ? Start Over?
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4nec2 ArieVoors
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A free full featured antenna simulator
Uses the nec FORTRAN kernel
Several input editors
Built-in 3D graphics
Excellent help file
Many standard antennas….helix etc.
First free simulator to contain an optimizer
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Spherical Coordinate System
Z
θ
Rx Antenna
Elevation angle = 90 - θ
Tx Antenna
Y
φ
XY Horizontal Plane
Z Vertical axis
X
φ is the horizontal azimuth angle
Θ is the angle measured from vertical
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Method of Moments
• A discrete numerical method
• Divide wires into many segments
• 25 segments per wavelength
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Use built-in
editor to the
Define
Antenna
Geometry
4nec2 Simulation
Analyze
Gain,SWR…
Optimize
(Tune)
Use TL Details
to select Transmission line
Use Matching Utility to
Design Tuner if Needed
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The Big Gun (Optimization)
Optimize (Tune) a 2 metre dipole
to 6 metres Adjust reactance to zero
Vary Length
Results
L= 2.8 metres
Xin = -0.13 Ohms
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4NEC2
Far Field Traditional Plot
Several Views
• Vertical, Horizontal, Total
• Circular Polarization
RHC, LHC, Total
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3D VE3XK 50 MHz Stack
50 MHz OMNI
Source Side
Along X Axis
Right Hand Circular
Polarization
Shown
All Graphs
are dynamic
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4NEC2
3D Near Field
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4NEC2
Advanced Far Field Map
θ
High Gain
φ
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Spherical Coordinate System
Z
θ
Rx Antenna
Elevation angle = 90 - θ
Tx Antenna
Y
φ
XY Horizontal Plane
Z Vertical axis
X
φ is the horizontal azimuth angle
Θ is the angle measured from vertical
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Examples “Simple” 2m Dipole Free Space
-L/2
L/2
X Axis
Total Gain
Theta = 75 degrees
PHI = 311 degrees
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Simple 2m Dipole .. Horizontal Plane
-L/2
L/2
X Axis
Horizontal Plane
BLUE :Vertical E Field
RED: Horizontal E Field
Green: Total Field
Theta = 45 degrees
(Is it OK to say that a dipole
is Horizontally Polarized? No!)
Receives Power Line Noise
off the end (Vertically Polarized)
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4NEC2
Several Views of Frequency Response
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4NEC2
Smith Chart
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A Design Example
Two Element Fan Dipole
40/17 metres
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Wire Lengths?
Tuner needed?
Frequency Response?
Gain and direction of radiation?
Mounted between two towers (North South)
Simulate/Build/Test
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Two Element Fan Dipole
Four Wires Connected to a Transmission Line
L1 (1/4 Lambda)
40 metre top section
30 degrees
17 metre bottom section
(Inverted V)
L2 (1/4 Lambda)
Height
RG8-X Cable (Length, Losses, Zin)
Tuner
Lossy Ground
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Transmitter
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Two Element Fan Dipole
40 Metre Gain Pattern……broadside radiation
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Two Element Fan Dipole
17 Metre Gain Pattern……45 degree lobes
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Two Element Fan Dipole
Frequency Response ..SWR around 1.5
Tuner might be useful
Very High SWR ???
Good Candidate for an auto-tuner
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Two Element Fan Dipole
Frequency Response…… Impedance
Z= 28.5+j2 Ohms @ 18 MHz
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TLDetails to select the Transmission Line
Length needed = 15 Metres
Zin = 40 + j 20
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Matching (4nec2 Utility)
18 MHz
No need for Xs
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Measurements
Antenna or other DUT
Aim 4170
Vector Z Meter
Complete Data
Set Generated
.csv
Import Data to Zplots
or Excel or Data Base (SQLITE)
Plotting or Further Computing
E.g.. Calculate Cable Losses
AIM 4170 Vector Impedance Meter
Connected to Computer via Serial Port
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Fan Dipole
Measurements AIM4170 & Zplots
Measured
Simulated
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The Future
• Much more software integration needed
link measurement tools to all software
include data base output for all software
use Excel and SQLite data bases
standard data base file format
• Models, especially ground types need improvement
• Much more work on optimization
• Electrical design to mechanical drawing needed for
Microwave Antennas
2010 Antenna design tools similar to Silicon IC design in its
infancy
Summary
• Antenna/Simulation Tools are well developed
• See VE3KL’s articles in TCA for more details
• Presentation posted on ve3kl.com Web Site
VY 73 Dave VE3KL