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