thz communication scenarios, future antenna systems
TRANSCRIPT
February 23, 2010
Vermelding onderdeel organisatie
1
THz Communication Scenarios, Future Antenna Systems
Hermes
IRCTR, Faculty of Electrical Engineering, Mathematics and Computer Science
Andrea Neto
February 23, 2010 2
The quest for BW: first scenario Wireless communications
• Wireless communications are exploding• BW demanding Multimedia Applications • Extrapolating the growth …in 10 years 20 GHz of
Wireless BW required
• Conference application scenarios
• Fiber Optics high data rates: 40/100 Gbits per channel:will have to be wireless extended
February 23, 2010 3
•All bands up to 100 GHz are completely full
•1-5 GHz different WLAN, 3-10 UWB, 57-65 GHz
Wireless communications
? …
but still it is 7 GHz only
•Only available BW is above 100 GHz (0.1 THz-10 THz):
•Infrared Communication is understood to be no option a bit of humidity and there is no more signal
10 years from now !
February 23, 2010 4
High Losses
Spreading Loss (?) much larger than in μ-waves
Atmospheric losses much larger than in μ-waves line-of-sight connection
High-gain antennascompletely new concepts and ideas
Only Indoor
Wireless THz Scenario
Secure communications
February 23, 2010 5
The quest for BW: second scenario the Space Segment
• Up and Down Links now use 1 GHz max
• Constellations (like Galileo) need to communicateand at low freq. antennas are heavy(here IR also possible)
On ground optical fibers with 15 Tbits centered at 200 THz are available ….
February 23, 2010 6
(ITU) International Telecommunication Union
All bands up to 100 GHz are completely full
All bands from 100 to 250 GHz are allocated either for satellite Communication or radio-astronomy
By the way, THz links are very directive links
Disturbances much less likely
………..
All bands from 250 GHz on are completely free
Earth-satellite Indoor short links
Inter satellite
None is actually used
February 23, 2010 7
THz start at 0.1 THz (1)Up to 100 GHz components off the shelf
Power Generation(Compact sourses)
No strong natural sources
R. Piesiewicz et al. IEEE Antennas and Propagation Magazine Vol. 49, No. 6 Dec. 2007 “Short Range Ultra Broad Band THz comm….
Peter H. Siegel Terahertz Technology IEEE Transactions on Microwave Theory and Techniquews, Vol. 50, No. 3, March 2002
100 GHz and Multipliers Up
Commercially based -band (75–110 GHz) InP MMICpower-amplifier chips (20 mW)
At 100 GHz, power levels from waveguide-combined amplifiers of 500 mW
Photo mixers down
narrow-band, tunable over the full terahertz band frequency of one of the two lasers 1μw at 1 THz
UWB, time domain pulsed sensing<5μw at 0.1-2 THz pulse
QCL The new thing (3-10 THz narrow band)
February 23, 2010 8
Cryogenically Cooled detectors
Equivalent noise Temperature rise fast with frequency
Best HEB Mixer 200-800 GHz: 500-1500 K
THz start at 0.1 THz (1)
LNA before mixers up to 250 GHz exist (20 Keuro at 94 GHz)
February 23, 2010 9
Communication Using Photomixers
f11 f1N
Could be entire THz range (0.1-10 THz)
Entirely integrated source and detectors
Exactly the same scheme to generateand receive the signal
February 23, 2010 10
Technology Jump
(2009)
February 23, 2010 11
Antennas in THz System Designs
Guided Losses are enormous:
All T/R architectures include T/R modules attached to antennas
3 λ -10 dB
The future isof antenna specialists
February 23, 2010 12
Integrated antenna technology for THz Applications
•Two-dimensional arrays for multibeam applications
• Tolerances + high capacity indicate Wide band antennas
•Substrate modes losses
Integrated Architecturesa few trends
Waveguide based architectures
Too expensive
February 23, 2010 13
Integrated Lens Antennas
Short Dipoles or slotsIn focus
• Frequency Domain Spectrometers
• Time Domain Sensing
THz waves
Narrow band Future Broad Band (?)
Extreme BW’s
Essentially scientific missions in sub-mm
Sensitivity is the issue via efficiencyMoney is no issue
Military, Security, Medical applications
Phase dispersivity is the issue
Money is issue
February 23, 2010 14
Base line forHerschel Planck HeterodyneReceivers0.5 -1.8 THz
Antenna Coupling
• SPICA is future mission for 2018• SRON is prime for Receivers • This time array of lenses
Lens-array antenna coupled to KID
February 23, 2010 15
• Break-through radiation concept • Ten years of space science oriented development• First essentially non Dispersive, UWB, efficient Radiation link • Both SRON and JPL trying to develop it at THz frequencies• When successful will probably dominate THz broad band radiation
My Contribution to Science: UWB Leaky Lens Radiation
February 23, 2010 16
250 μm
500 μm
127 μm
μ-strip slab
Air gap
Slots widthεr =3.3
Dielectric Lens
UWB Leaky Lens Antenna at Microwaves
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Measured Matching
-25
-20
-15
-10
-5
0
10 20 30 40 50 60 70Freq (GHz)
S11
(dB)
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Measured Patterns
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Pulse Preservation: Amplitude
2fGGPP rt
tr ∝
)()( fPfP tr ∝
Spectral Amplitude is fully preservedfrom 20 GHz on
February 23, 2010 20
-25
-20
-15
-10
-5
0
10 20 30 40 50 60 70Freq (GHz)
S12
(dB
)
Link Characterization
February 23, 2010 21
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5 3time(ns)
norm
aliz
ed S
12
main response (40.4 cm in fs)
0.6
0.8
1
1.2(5-70 GHz) pulse, fidelity=0.94
Received signalIdeal delayed signal
0.013ns
0.015ns
0
0.5
0.7
1
1.33 1.34 1.35 1.36 1.37
0
0.2
0.4
1.2 1.25 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7time(ns)
norm
aliz
ed S
12
0
0.2
0.4
0.6
0.8
1
1.2
1.2 1.25 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65
(15-70 GHz) pulse, fidelity=0.97
Received signalIdeal delayed signal
time(ns)1.7
norm
aliz
ed S
12
S12 in Time Domain
Best reported comparable antenna is Vivaldi with 0.75 over a band 1-3
February 23, 2010 22
21.3 37.5 53.7 70
-0.2500.250.5
freq (GHz)
Δφc
(mm
)
5
404.0403.5403.0402.5
Δr12(m
m)
With Matching Layers
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5 3time(ns)
norm
aliz
ed S
12
main response (40.4 cm in fs)
Phase Center Stability
February 23, 2010 23
ConclusionsIndoor Wireless Links will use 0.1-1 THz for Line of Sight links:
• evolution scenarios (20 GHz BW around 100-150 GHz) can be imagined already, configuration issues
• revolutionary scenarios still with some power
Satellite Based Links will use THz for data links: • Inter-Satellite Links will will use 0.1-10 THz ranges.• Earth-Satellite-Earth will use 100 Ghz-400 GHz ranges.
The Optical photo-mixing communication link seems to be the revolutionary scheme. Among many other things it a revolutionary UWB THz radiation management
The Leaky Lens radiation concept presents unprecedented performances in• Pulse preservation (no distortion of signal)• Phase center stability (multi-beam reflectors)
February 23, 2010 24
February 23, 2010 25
THz Time Domain Sensing
PicometrixT-Rays
Measurement Systems cost about 250.000 Euros
Components about 30.000 Euros
In Optics very confused about antennas !
Microwave and Optical community merge
February 23, 2010 26
The Antennas in Use
Typical Spectra
Impedance of short dipoles is quadratic with frequency
Over a decade BW efficiency lower than 10%Picometrix claims 2 decades…… they use antennas in TX and RX.. Efficiency =1/10000
February 23, 2010 27
February 23, 2010 28
Cross Polarization
Same level of the State of the Art in X-pol. (Eleven antenna from 1 to 4 GHz))
February 23, 2010 29
Gain and Efficiency
Difference between Measured Gain and
Calculated Directivity (with ML)
February 23, 2010 30Phase Center
t1
t2
t3
t =t + /c2 1 Δ
rlow
rhigh
e-jk x0
x
Phase Dispersivity
rlow
rhigh
e-jk x0
x TEM Horns or Vivaldi Like
No real solution known yet !
Phase Center
t1
t2
t3
t =t + /c2 1 Δ
Log periodic or spiral like
February 23, 2010 31
Linear Phase Variation with Frequency
Pulse Preservation: Phase
•Real Input Impedance (70 Ohm)•Constant Phase Center•Constant Group Delay
S. Maci, A. Neto, “Green’s Function of … Part II: Space Wave- Leaky Wave Asymptotics”,IEEE Transactions on Antennas and Propagation Vol. 52, no.3 March 2004
Inside the dielectric
Also Phase Should be fully preserved