Notes

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Outline

Electromagnetic Field Animations
Introduction
| Exploring Electromagnetic Fields in and around antennas
| Animate the fields to help visualize
| Small feed antennas – simpler fields
| Complement to explanations in Appendix 6C
Antenna - Electromagnetic Fields
Field Relationship
Example:
| Open Rectangular Waveguide
| Simple, well known
Calculate field inside waveguide
Calculate full aperture field
WR-90
WR-90 E&H
WR-90 open
WR-90 rim
Near Field ß Fourier à Far Field
E x H
Coffee can
Coffee rim
Interference from multiple sources
Feed with two sources
Penny
Reduce sidelobes from edge currents
| Choke rings
| VE4MA
| Chaparral
| Dual-mode feeds
| W2IMU
| Clavin ’74
| Diagonal Feeds
VE4MA
VE4MA rim
Chaparral stock
Chaparral flush
W2IMU
W2IMU dual-mode feed - very small edge current
G3PHO
Bad IMU
Clavin 74
Diagonal Horns
| No Flare – 0.73 wavelengths sq.
| 1.4 wavelengths square
| 14 degree flare
| 30 degree flare
| 60 degree flare
| 1.85 wavelengths square
| 30 degree flare
| 60 degree flare
No flare
1.4, 14
1.4, 30
1.4, 60
Diagonal rim
1.85, 30
1.85, 60
Flared horns
| Conical
| 1.88 wavelength diameter
| Rectangular
| Small, for DSS dish
| Surplus, only E-plane flare
Conical
Conical rim
DSS
AT-68/U
Reverse feeds
| G4ALN Penny feed
| RSGB “Professional” Penny
| DC3QS Bent penny
| DK2RV Small disk 30 mm
| DK2RV Large disk 60 mm
| DK2RV Large disk with rim
| RSGB waveguide dipole
| Clavin 1954 feed
Penny
Pro
DC3QS
30 mm
diffraction
60 mm
Rim
Phase error
Waveguide dipole
Clavin ‘54
Other feeds
| Primestar
| Vertical polarization
| Horizontal polarization
| Sectoral horn
| E-plane corrugations
| H-plane corrugations
Primestar vertical
Primestar horizontal
E-plane
H-plane
corrugations
Multiband feeds
| W5ZN 10 and 24 GHz
| W5ZN with choke
| Some multiband experiments
| 2 and 5 GHz (like W5ZN)
| 3 and 10 GHz (dual-mode style)
W5ZN at 10
W5ZN at 24
W5ZN choke 10
W5ZN choke 24
2 and 5 experiment
3 and 10 experiment at 3456
3 and 10 experiment at 10 GHz
SUMMARY
| Near Field Animations
| Visualize antenna operation
| Highlight strange behavior
| Help explain performance
Slide 68
Slide 69
W1GHZ favorite feeds
| Prime focus dish
| VE4MA
| Chaparral
| W2IMU
| Offset dish
| Rectangular horn
| large W2IMU