Yunsu Sung Yunsu Sung Special Topics in Optical Engineering - - PowerPoint PPT Presentation

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Yunsu Sung Yunsu Sung Special Topics in Optical Engineering - - PowerPoint PPT Presentation

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Apr 23 2015 Yunsu Sung Yunsu Sung Special Topics in Optical Engineering II(15/1) Contents Introduction Terahertz wave for wireless communication Present Terahertz communication Future Terahertz communication Yunsu Sung

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Yunsu Sung

Apr 23 2015

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Contents

  • Introduction
  • Terahertz wave for wireless communication
  • Present Terahertz communication
  • Future Terahertz communication
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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Trend of wireless communications

  • Number of wireless network user ↑
  • consuming data package ↑
  • Mobile traffic ↑
  • Operating at microwave frequency
  • Improved technique
  • Limited by bandwidth
  • TeraHertz wave needed

Higher Data rate

Current wireless communication

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Terahertz wave

  • Located between millimeter waves and infrared

– 100GHz~10THz

  • Femtosecond laser & photoconductive antennas

made terahertz communication possible

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Atmospheric Attenuation

  • H2O and air gases absorption

– Doesn’t matter at indoor application

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Link Budget

20log { ( ) } 4

c r t t r a c ex

P P G G f d L d λ α π   = + + + − ⋅ −    

  • Pt: Input power of transmitting antenna
  • Gt,Gr: Transmitting, Receiving antenna gain
  • λ,d: Wavelength, distance
  • α: Atmospheric attenuation
  • Lex: Excess loss
  • Output power
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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Link Budget

  • SNR
  • N0: noise power spectral density
  • B: system noise bandwidth
  • NF: Noise figure of receiver
  • M: system margin

( )

( 10log )

dB r

SNR P N B NF M = − + + +

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Budget Calculation

  • Parameter
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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Link Budget

  • Data rate vs gain
  • Tx and Rx should be line of sight to operate
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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Application

  • WLAN/WPAN

– Wireless display – Rapid downloading/uploading data – HDTV

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Present Terahertz Communication

  • Channel modeling
  • Device technologies for front end
  • Demonstrations over 100GHz
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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Channel Modeling

  • Only few report on channel measurement
  • Priebe at al

– 300GHz based on ray tracing techniques – Consider building material and reflection from rough surface

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Device for Front End

  • 1. InP HEMT
  • Cutoff frequency >1THz
  • 10Gbps QPSK modulator demonstrated
  • 2. Si based semiconductor
  • High loss base material, cost effective
  • >100Gbps reported
  • 3. Resonant tunneling diodes(RTDs)
  • LC oscillation
  • 1.04THz at room T
  • 4. Schottky barrier diodes(SBDs)
  • Detecting, mixing
  • 1THz at GaAs, 100GHz at Si
  • 5. UTC PD
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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Demonstration over 100GHz

  • 120GHz transmission system by NTT

– To Improve mobility, photonic component replaced with InP HEMT MMICs – Fuji Television Network use terahertz system to broadcast Beijing Olympics Game

  • 300GHz transmission system by NTT

– 16Gbps over 0.5m distance ASK modulation

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Demonstration over 100GHz

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Future of Terahertz Communications

  • Frequency conflict with astronomy applications

– Terahertz used for radio astronomy

  • Technical Barriers

– Beam steering – Packaging

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Special Topics in Optical Engineering II(15/1) Yunsu Sung

Conclusion

  • Terahertz communications can be future wireless

communication systems

  • High bandwidth will offer lots of potential
  • Radio astronomy issue and technical barrier issue have to

solved.