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 Special Topics in Optical Engineering II(15/1)
Trend of wireless communications • Number of wireless network user ↑ Higher • consuming data package ↑ Data rate • Mobile traffic ↑ Current wireless communication • Operating at microwave frequency • Improved technique • Limited by bandwidth TeraHertz wave needed • Yunsu Sung Special Topics in Optical Engineering II(15/1)
Terahertz wave • Located between millimeter waves and infrared – 100GHz~10THz • Femtosecond laser & photoconductive antennas made terahertz communication possible Yunsu Sung Special Topics in Optical Engineering II(15/1)
Atmospheric Attenuation • H 2 O and air gases absorption – Doesn’t matter at indoor application Yunsu Sung Special Topics in Optical Engineering II(15/1)
Link Budget • Output power λ = + + + − α ⋅ − c P P G G 20log { ( f ) d } L π r t t r a c ex 4 d • P t : Input power of transmitting antenna • G t ,G r : Transmitting, Receiving antenna gain • λ ,d: Wavelength, distance • α : Atmospheric attenuation • L ex : Excess loss Yunsu Sung Special Topics in Optical Engineering II(15/1)
Link Budget • SNR ( ) = − + + + SNR P ( N 10log B NF M ) dB r 0 • N 0 : noise power spectral density • B: system noise bandwidth • NF: Noise figure of receiver • M: system margin Yunsu Sung Special Topics in Optical Engineering II(15/1)
Budget Calculation • Parameter Yunsu Sung Special Topics in Optical Engineering II(15/1)
Link Budget • Data rate vs gain • Tx and Rx should be line of sight to operate Yunsu Sung Special Topics in Optical Engineering II(15/1)
Application • WLAN/WPAN – Wireless display – Rapid downloading/uploading data – HDTV Yunsu Sung Special Topics in Optical Engineering II(15/1)
Present Terahertz Communication • Channel modeling • Device technologies for front end • Demonstrations over 100GHz Yunsu Sung Special Topics in Optical Engineering II(15/1)
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 Yunsu Sung Special Topics in Optical Engineering II(15/1)
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 Yunsu Sung Special Topics in Optical Engineering II(15/1)
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 Yunsu Sung Special Topics in Optical Engineering II(15/1)
Demonstration over 100GHz Yunsu Sung Special Topics in Optical Engineering II(15/1)
Future of Terahertz Communications • Frequency conflict with astronomy applications – Terahertz used for radio astronomy • Technical Barriers – Beam steering – Packaging Yunsu Sung Special Topics in Optical Engineering II(15/1)
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. Yunsu Sung Special Topics in Optical Engineering II(15/1)
Recommend
More recommend
