New Results on Antenna Impedance Models and Matching

113 Pages·2007·6.22 MB·English

by  Steve Stearns

New Results on Antenna Impedance
Models and Matching
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 19-21, 2007
Electromagnetic Cloaking
(cid:131) Idea introduced in the Star Trek television series, episode 9,
on December 15, 1966, which featured a Romulan Bird Of Prey
(cid:131) Practical technique presented at Pacificon Antenna Seminar,
October 13, 2006
(cid:131) Laboratory proof announced by Duke University on October
17, 2006
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Outline
(cid:131) Antenna impedance models
(cid:131) SWR basics
(cid:131) Why not conjugate match?
(cid:131) Impedance matching networks
(cid:190) Multi-band match networks
(cid:190) Networks that give extremely broad match bandwidths
(cid:131) Interesting antennas
(cid:131) Terrain effects by computational electromagnetics
(cid:190) Meshing Silicon Valley
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Antenna Impedance Models
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Sidney Darlington, 1906-1997
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Darlington Forms (1939)
(cid:131) Every immittance function can be realized as a lossless two-
port terminated by a resistor
(cid:131) Every antenna impedance function has an equivalent circuit in
Darlington form
Reactance
Lossless
2-Port
This…… Not This!
(cid:131) The Darlington form is the starting point for interesting results
in network and matching theory
(cid:190) The Fano (1947) and Carlin-LaRosa (1952) bounds on impedance
matching
(cid:190) Constant resistance reflectionless impedance matching networks
(cid:190) Non-Foster active impedance matching networks
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Impedance Models for Electrically-Small Dipoles &
Monopoles
K6OIK 3-Element
Tang, Tieng, Gunn 4-Element
Series RLC
K6OIK 4-Element K6OIK 5-Element
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Broadband Models of Dipole Impedance
That Span Multiple Resonances
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Schelkunoff’s Universal Antenna Impedance Models
(cid:131) Schelkunoff (1941) gave universal impedance models for
a two broad classes of antennas
(cid:131) Cascaded transmission lines terminated by a TE or
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TM mode impedance (e.g. loops or dipoles)
10
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007
Foster’s 1st Canonical Form with Small Losses Added
C0 = 43.9 pF C1 = 22.9 pF C2 = 30.3 pF C3 = 57.1 pF
L∞ = 4.49 mH L1 = 12.5 μH L2 = 2.26 μH L3 = 522 nH
R1 = 4,970 Ω R2 = 3,338 Ω R3 = 2,702 Ω
(cid:131) Ramo, Whinnery, and Van Duzer, Fields and Waves in
Communication Electronics, Wiley, 1965, Section 11.13
(cid:131) Was applied to antennas by Tang-Tieng-Gunn (1993),
Hamid-Hamid (1997), Rambabu-Ramesh-Kalghatgi (1999)
(cid:131) Fits dipole impedance best near antiresonances
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S.D. Stearns, K6OIK ARRL PacificonAntenna Seminar, San Ramon, CA October 19-21, 2007