Antenna Modeling for Radio Amateurs

74 Pages·2008·4.36 MB·English

by  Steve Stearns

Antenna Modeling for Radio Amateurs
Steve Stearns, K6OIK
Northrop Grumman
Electromagnetic Systems Laboratory
San Jose, California
[email protected]
[email protected]
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Outline
(cid:131) History of electromagnetics
(cid:131) Computational electromagnetics
(cid:190) Method of Moments (MoM)
(cid:190) BRACT, WIRA, AMP, NEC 1-4, IE3D, WIPL-D, FEKO
(cid:131) Four main programs for amateurs
(cid:190) EZNEC
(cid:190) 4nec2
(cid:190) WIPL-D Lite
(cid:190) FEKO LITE
(cid:131) Advanced applications
(cid:190) Terrain analysis by MoM
(cid:131) References, books, and software
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Question for 2008
(cid:131) Is the current the same everywhere along a wire?
I I
in out
?
I = I
in out
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Answer: It Depends
(cid:131) “Yes” for steady-state d-c current
(cid:131) “Almost yes” for low-frequency a-c current or short wires
(cid:131) But “no” for high-frequency a-c current because electrons can
bunch up
(cid:131) J.C. Maxwell found a way to make the answer yes
∂D
I ∇×H = J + I
in out
∂t
⎛ ∂D⎞
0 = ∫∫⎜J + ⎟•dS
∂t
⎝ ⎠
S
∂
I −I = ∫∫D dS
in out n
∂t
S
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
History
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Who Does Not Belong in this Picture?
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Answer: Leonardo Da Vinci and Isaac Newton
Leonardo Da Vinci Andre-Marie Ampere Michael Faraday
1452-1519 1775-1836 1791-1867
James Clerk Maxwell
1831-1879
Isaac Newton Carl Friedrich Gauss Georg Simon Ohm
1642-1727 1777-1855 1789-1854
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
The Maxwellians
George Francis FitzGerald Oliver Heaviside Oliver Joseph Lodge
1851-1901 1850-1925 1851-1940
Heinrich Rudolph Hertz John Henry Poynting
1857-1894 1851-1914
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Heaviside’s Vector Equations for Maxwell’s Theory
∂B
∇ × E = −M −
∂t
∂D
∇ × H = J +
∂t
⋅
∇ D = ρ
e
⋅
∇ B = ρ
m
D = εE J =σ E
e
B = μH M =σ H
m
“And God said, Let there be light; and there was light.” Genesis 1:3
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008
Key Dates in Antennas
1842 Discovery of radiation – J. Henry
1873 Treatise on electrodynamics – J.C. Maxwell
1875-87 Early radiation demonstrations: Edison 1875;
A.E. Dolbear 1882; H. Hertz 1887
1889-06 Phased arrays – S.G. Brown, J.E. Murray, Artom
1895-01 Radio communication, fan dipole, polar plots
– G. Marconi
1897 Biconical dipole, loading coil, tunable LC matching
network, counterpoise, “impedance” – O.J. Lodge
1907 Goniometer, electrical steerable array, radio direction-
finding – Bellini & Tosi
1907 Ground losses, ground waves – Zenneck
1923 Wave-tilt antenna – H.H. Beverage
1928 Endfire array with parasitic elements – Yagi & Uda
1947 Polyrod antenna – G.E. Mueller and W.L. Tyrell
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 17-19, 2008