Notes
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