Classical Electrodynamics Applied in Modern Technology
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Transcript of Classical Electrodynamics Applied in Modern Technology
Classical Electrodynamics Applied in Modern Technology
Günter Nimtz
Physics Department, University of Cologne
1. Properties of Nano-Metal Films2. Anechoic EMC Chambers: Pyramidal Absorber 3. Absorption by Anechoic Traps: Reflecting Curtains4. Ferrite Tile Absorber……….Hybrid Absorbers5. Rain Sensing Wipers: Frustrated Total Internal
Reflection = Tunneling
Free carrier EM interaction : Drude (1900), Hagen & Rubens (1902)
Nano metal films (gravimetrical determination !)Infrared studies on Absorption, Reflection and Transmission: A + R + T = 1 Murmann; Barnes; Czerny; Woltersdorff (1929 – 1934)
R + T + A = 1of Nano-Film ResistanceAngle of incidence =
TM = 450
EM = 450
= 900
A T R
l> d
T = {1 + Zo/(2 Z)}-2 ;
Zo vacuum impedance
Z =/d sheet resistance d film thickness
How to get a huge metal cavity behave like free space with : ZO = 377 Ω, i.e. no standing wave patterns? Install absorbers at the walls!
EM anechoic chambers
Install absorbers at the walls!Metal walls
EM Anechoic Chamber
Nano-Metal-Film, a 10 nm metal film vapor deposited on 10 µm polyethylene film
d
Sheet Resistance Z is Relevant for Wave Propagation if l » d :
Z = 1/( d)
= conductivityd = film thicknessl = wavelength Foam ≈ 10-7 Nano-Metal Film (≈ 0.1 S/m) (≈ 106 S/m)
d
International Patents: G. Nimtz and A. Enders (1998)
2.4 m
Absorbing Pyramids: Absorption with Low Reflection
E = electric field
E
Standing Waves in Front of the Metal Wall
Z = 0
Nano-film
Foam
Variation of impedance with position along the line (Smith Diagram)
Z
Z = Ω ≈ 377 Ω Shunt No Reflection
l/4
EMetal
Vacuum Impedance Z0 = 377 Ω
The variation of impedance with position along the line (Smith Diagram)
R + T + A = 1of Nano-Film ResistanceAngle of incidence =
Special Property :
For 188 Ω:
0.25 + 0.25 + 0.5 = 1
TM = 450
EM = 450
= 900
A T R
l > d
e.g. 8 Reflections: R(total) = 0.258 - 48 dB; dB = 10 lg(P1/P2)
Anechoic trap
Transmitter
nano-Metal Films
Novel Principle, Device under Test: Absorption by Multiple Reflection
Metal Wall
Nimtz and Panten, Ann. Phys. 19, 53 (2009); Pending Patents, G. Nimtz (2008)
Curtains of nano Films instead of Pyramids at one wall as shown next figure
EM AnechoicChamber
In small Chambers: Ferrite Tiles with ZF ≈ Z0 6.3 mm; 30 MHz – 300 MHz (< -20 dB, regulation) Hybrid Absorber: Pyramidal Absorber + Ferrite Tile(30 – 18 000 MHZ)
Metal Wall
ZF = Z0 µr/r = Z0 !
Reflection R: R = (n1 – n2)/(n1 + n2)
= (ZF – Z0)/ZF + Z0)
Ferrite tiles TDK (Ni-Cu-Zn) :
Rain sensing wiper: frustrated total reflection
Total Reflection if:
sin n2/n1
tot = arc sin(n2/n1)
Frustration : tot
glass n1 > n2
air
ß
The double prisms: frustrated total internal reflectionThe analog of quantum mechanical tunneling Sommerfeld (1954)
Front windshield
Prism
Rain…….
LED
Receiver
Rain Sensing Wipers:
Frustrated total reflexion
Rain represents the second prism
• Nano-Metal Film Absorbers are Broad Band Absorbers, Superior to Carbonized Foam Absorber
• Incombustible. Non-Toxic. No Hazardous Waste• Nano-Metal Film Absorbers on Duty since 1995• Ferrite Tiles, very thin but expensive (30-400 MHz)• Frustrated total internal reflection
as rain sensing car device. • Double Prisms: Newton 1700, BOSE 1900,
Sommerfeld 1954
Summing Up :