THz Communication Scenarios, Future Antenna Systems

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)


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


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


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


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

http://antwrp.gsfc.nasa.gov/apod/image/0610/ngc1931ic417_cannistra_f.jpg


• 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


250 μm

500 μm

127 μm

μ-strip slab

Air gap

Slots widthεr =3.3

Dielectric Lens

UWB Leaky Lens Antenna at Microwaves


Measured Matching

-25

-20

-15

-10

-5

0

10 20 30 40 50 60 70Freq (GHz)

S11

(dB)


Measured Patterns


Pulse Preservation: Amplitude

2fGGPP rt

tr ∝

)()( fPfP tr ∝

Spectral Amplitude is fully preservedfrom 20 GHz on


-25

-20

-15

-10

-5

0

10 20 30 40 50 60 70Freq (GHz)

S12

(dB

)

Link Characterization


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


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


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)


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

http://www.irmmw-thz2008.org/home/index.html


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


Cross Polarization

Same level of the State of the Art in X-pol. (Eleven antenna from 1 to 4 GHz))


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


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

THz Communication Scenarios, Future Antenna Systems

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