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