20. microwave engineering - graz university of...
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Institute of Solid State PhysicsTechnische Universität Graz
20. Microwave Engineering
Dec. 12, 2019
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Microwave engineering
Microwave frequencies are a few GHz
The wavelength is smaller than the circuit
Losses in metals increase with increasing frequency
Losses in dielectrics increase with increasing frequency
There is a characteristic length scale called the skin depth which tells us how far into a metal fields penetrate before they are reflected out.
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Skin depth << 1
0B J
Ohm's law0J E
Take the curl0
1 dBJ Edt
0 0
1 dBBdt
Ampere's law
Faraday's law
2B B B
Vector identity0
2
0 0
1 dBBdt
02 2
11
ine ne
<< 1
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Skin depth
0 0
2
2
0 0
1 dBBdt
2
0 0
k i
Assume harmonic dependence 0
i kx tB e
0 0 0 00 0 2 2
k i i
Exponential decaySkin depth
Light p is reflected out of a metal. The waves penetrate a length .
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Skin depth
//0 ˆi x txB B e e z
//0
0 0
(1 )1 ˆi x txB iJ B B e e y
/ / 4/0
0 0 0
2 ˆi x txBJE e e y
/ / 4/0
0
2 ˆi x txBJ e e y
/ 41 2 ii e
The electric field lags behind the magnetic field by 45 degrees.
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Surface resistance
0
Rw
wfor
0
1sR
Complex signal processing at high frequencies > 1 GHz is difficult because the losses increase with frequency.
Usually you mix down to a lower frequency as soon as possible.
At low frequencies: 0
Rwt wt
When < t :
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Superconducting filter
Complex signal processing at high frequencies > 1 GHz is difficult because the losses increase with frequency.
Simulation
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simultaneously ferroelectric and ferromagnetic
Multiferroics
BiFeO3
If two magnetic sublattices have different charge, changing the magnetic field can change the polarization and changing the electric field can change the magnetization.
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Phase change material Electron diffraction in a TEM of a GeSbTe alloy.
http://web.stanford.edu/group/cui_group/research.htm
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Laser‐cutting/engraving
VLS 2.30 Universal Laser System• laser source: 30 W CO2 (wavelength 10.6 μm)• equipped with: 2.0” lens (beam size at focus 120 µm)
High Power Density Focusing Optics (beam size at focus 30 µm)• cutting table dimensions: 406 x 305 mm
CUTTING AND/OR ENGRAVING of Plastic, Elastomers, Glass, Paper, Bio-derived materials, Metals, etc.
Patterning of conductive Laser Induced Graphene(photothermal process by laser scribing on polymer
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laser-induced pyrolysis of polymers
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laser-induced pyrolysis of polymers
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laser-induced pyrolysis of polymers