Page 1 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Recent Japanese Developmentson Terahertz Communications
Graduate School of Engineering ScienceOsaka University
Tadao Nagatsuma
2nd Towards THz Communications Workshop
http://discoverlosangeles.com/getting-around/air/things-to-do-near-lax-los-angeles-airport.html
Page 2 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Overview of latest challenges and results in
THz communications technologies in Japan
1) Photonics-based: 600 GHz, new sources
2) Electronic diode-based: RTD, FMB diode
3) Si-CMOS-based challenges
Outline
Page 3 Brussels, 7 March 2019Towards Terahertz Communications Workshop
100 Gbit/s Wireless: Coming Soon!
Ethernet
FTTx
FTTH
ISDN
ADSL LTE
USB2.0USB3.0
802.11b
WiMAX2
802.11a802.11g Bluetooth
802.11ad802.11ac
WiGig
100 G
10 G
1 G
100 M UWB802.11n
LTE-A
10 M
1 M
1990 2000 2010 2020
Wired
Wireless
Dat
a R
ate
(bit/
s)
MMWTHz Wireless
Page 4 Brussels, 7 March 2019Towards Terahertz Communications Workshop
THz Communications Projects (JPN)2014 2016 20202018
300 GHz InP-based MMICs (2011-2016)
300 GHz CMOS-based MMICs
300 GHz Vacuum-tube amplifier
300 GHz Photonics-based (since 2013-2016)
NTTFujitsu/NICT
Kyushu U.+Osaka U.
Hiroshima U.Panasonic, NEC/NICT
MIC(SCOPE)
MIC
MIC
JST (CREST)300 GHz~ 1 THz Resonant Tunneling Diodes
Osaka U.RohmTokyoTech.
JST (THz)300 GHz~ 1 THz Photodiodes/PIC
Kyushu U.(+NTT, etc.)
JST: Japan Science Tech.Agency
MIC: MinistryInternal Affair& Commun.
Horizon 2020, NICT/ThoR
Page 5 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Overview of latest challenges and results in
THz communications technologies in Japan
1) Photonics-based: 600 GHz, new sources
2) Electronic diode-based: RTD, FMB diode
3) Si-CMOS-based challenges
Page 6 Brussels, 7 March 2019Towards Terahertz Communications Workshop
100 200 300 400 500 600 700
100
10
2
200
Carrier frequency (GHz)
Dat
a ra
te (G
bit/s
)
Electronics (DSP)
Photonics (DSP)Photonics (real time)
Electronics (real time)
Research Updated@2019
(6 ch.)
(8 ch.)
Page 7 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Photonics-based Approaches
Ultra-broadband signal generation and detection
Ultra-low loss signal distribution by optical fibersand waveguides
Ease of availability of components from telecom industry
Use of science & technologies established for lightwaves
Page 8 Brussels, 7 March 2019Towards Terahertz Communications Workshop
100 200 300 400 500 600 700 800 900 1000
Atte
nuat
ion
(dB
/km
)
Frequency (GHz)
10-2
101
104
105
10-1
100
102
103
100-GHz Atmospheric Windows
1dB/km
1dB/10m
325 GHz
275 GHz
600-GHz band: Next Target for Telecom
Page 9 Brussels, 7 March 2019Towards Terahertz Communications Workshop
WG
Backshort
MetalInP Quartz (100 µm) Out
Radiator
WG
UTC-PD
MSLCPW
Ribbon wire
Metal
OutputOpticalinput
Coupler
Opticalinput
Top view
Side view
CPW: coplanar waveguideMSL: microstrip line
Conventional Structures
Page 10 Brussels, 7 March 2019Towards Terahertz Communications Workshop
InP ~100 µm thick
Au
Quartz (𝜀𝜀r: 4.0)
UTC-PD Ribbon wire
CPW MSLDielectric loss smaller ε
Substrate effect thinner (~10 µm)
Propagation loss shorter
Connection loss eliminate
Top view
Side view
Problems of Coupler at High Frequencies
Page 11 Brussels, 7 March 2019Towards Terahertz Communications Workshop
UTC-PD
Microstrip line
Polymer substrate
InP substrate
Radiator
Ground metallization
(𝜀𝜀r: 2.5)
6 µm
Solution: Integrated Coupler
T. Kurokawa, T. Ishibashi, M. Shimizu, K. Kato, and T. Nagatsuma, “Over 300 GHz bandwidth UTC-PD module with 600-GHz band rectangular-waveguide output,” Electron. Lett., 54, pp. 705-706 (2018).
Page 12 Brussels, 7 March 2019Towards Terahertz Communications Workshop
UTC-PD
Coupler Radiator
100 µm
Fabricated UTC-PD Chip
Page 13 Brussels, 7 March 2019Towards Terahertz Communications Workshop
WR-1.5 waveguide
Optical fiber cableDC bias cables
191×381 µm
Fully Packaged Module
Page 14 Brussels, 7 March 2019Towards Terahertz Communications Workshop
- 18.96 dBm (12.7 µW)
-40
-35
-30
-25
-20
-15
900850800750700650600550500450400Frequency (GHz)
IPD= 9 mAIPD= 6 mA
340 GHz
Out
put p
ower
(dBm
)Evaluated Results
Page 15 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Data signal
Optical signal
generatorPD
moduleOptical
amplifierHorn
antenna
Opticalintensity
modulator
Driveramplifier
Laser
PM
PM
Wavelength λ Opticalfilter
&combiner
18 x f0
λ
(30~43 GHz)f0
f0
Sub-harmonic mixer
LO signal
Basebandinstruments
(oscilloscope/bit error rate tester)
Horn antenna
Transmitter
Receiver
Basebandamplifier
PM: Optical phase modulator
600-GHz-band Communications
Page 16 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Error-free OOK 10 Gbit/s @670 GHz
10-1210-1110-1010-910-810-710-610-510-410-3
3.002.752.502.252.001.751.501.251.000.750.50Photocurrent (mA)
10 Gbit/s6 Gbit/s
Bit e
rror r
ate
T. Nagatsuma et al., IMS 2018, Th1E-1.
Page 17 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Frequency
0 +6-6 ・ ・ ・ ・ ・・ ・ ・ ・ ・
25 GHz ×12 = 300 GHz
25 GHz
Multiplicationnumber
Phase noise
PM
Synthesizer (𝑓𝑓s) Optical filter
Laser (𝑓𝑓0)Frequency 𝑓𝑓
𝑓𝑓0𝑓𝑓s
… …
Frequency 𝑓𝑓
UTC-PD
Phase Noise Issue: Optical Frequency Comb
Page 18 Brussels, 7 March 2019Towards Terahertz Communications Workshop
I
Q
Effect of Phase Noise
Offset frequency (Hz)
SSB
Phas
e N
oise
(dBc
/Hz)
0
20 log10(𝑁𝑁)
log10(𝑓𝑓)
Multiplied
Fundamental
𝑁𝑁 = 1221.6 dB
Change in constellation: QPSK
Page 19 Brussels, 7 March 2019Towards Terahertz Communications Workshop
19
1
Piezo
EDFA 23
PD
PID
PID
Laser
Mixer
UTC-PD
PID
PID
SHM SG
SG
Temp. Stab.
Mixer
For experiment
Brillouin cavity
PM
PM
SG
UTC-PD:Uni-Travelling Carrier PhotoDiodeSHM:Sub-Harmonic Mixer
Solution: Brillouin-based Fiber Lasers
Page 20 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Frequency Stability @ 300 GHzY. Li, A. Rolland, K. Iwamoto, N. Kuse, M. Fermann, and T. Nagatsuma, Opt.Lett., vol. 44, pp. 359-362, 2019.
Page 21 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Offset Frequency (Hz)
SSB
Phas
e N
oise
(dBc
/Hz)
Brillouin-based Source
Optical Frequency Comb
Measurement Noise Floor
SSB:Single Side Band
Phase Noise @ 300 GHzY. Li, A. Rolland, K. Iwamoto, N. Kuse, M. Fermann, and T. Nagatsuma, Opt.Lett., vol. 44, pp. 359-362, 2019.
Page 22 Brussels, 7 March 2019Towards Terahertz Communications Workshop
300-GHz QPSK Transmission Experiments
L. Yi et al., EuMC 2019, submitted.
Page 23 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Our Recent Progress with RTD
New operation regime: injection-locked receiver32-Gbit/s error-free at 300 GHz
Frequency stabilizatin with photonic crystal cavity
Combination with THz fiber and transmission
Page 24 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Compact (~mm2) Low power consumption (~10 mW) High-frequency oscillation at room temperature (1.98 THz*) Operating as both a transmitter and receiver
I
VC
urre
nt
Voltage
NDR region
NDR : Negative differential resistance
ReceiverTransmitter
*R. Izumi et al.IRMMW-THz (2017)
Why Resonant Tunneling Diodes?
Page 25 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Side viewTop view
Si lens
Baseband circuit
Schematic diagram of RTD chip
1 cm 1 cm
RTD chip
Connector
RTD
Bowtie antenna
MIM
50 μm
CPS
Shunt resistor Signal line
RTD
Signal line
MIMShuntresistor
Packaged RTD Transmitter and Receiver
Page 26 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Principle of Coherent Homodyne Receiver
RTD
Signal line
I
V
Bias withinthe NDR region
Self-oscillating mixer
RTD oscillation
f
Injection locking phenomenon
f
f
Received signal
f
Data signal
Page 27 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Experimental Setup with Photonics Transmitter
Wavelength-tunable laser #1
Coupler
EOM
Wavelength-tunable laser #2
EDFA
UTC-PD
Horn antenna RTD chipSi lens
DC bias
2 cm
Bias-tee
𝑓𝑓THz
AC+DC
DC
Error detector
AC
LNA
DEMUX
Tx Rx
Pulse Pattern Generator
05
10152025
0 800
Cur
rent
[mA]
Voltage [mV]
N. Nishigami et al., “Resonant Tunneling Diode Receiver for Coherent Terahertz Wireless Communication,” Tech. Dig. 2018 Asia-Pacific Microwave Conference (APMC), 2018.
Page 28 Brussels, 7 March 2019Towards Terahertz Communications Workshop
1.00E-12
1.00E-10
1.00E-08
1.00E-06
1.00E-04
1.00E-02
1.00E+00
10 20 30 40 50
100
10-2
10-4
10-6
10-8
10-10
10-12
Bit
erro
r rat
e
Data rate [Gbit/s]
Coherent detectionDirect detection
Error free
Error-free transmission (BER < 10-11) was achieved at 32 Gbit/s.FEC-limited data rate reached ~50 Gbit/s.
Error free @32 Gbit/s400 mV
0 120 ps
@32 Gbit/s40 mV
0 120 ps
Tx output power : 48 μW
Record Data Rate with RTD ReceiverN. Nishigami et al., APMC 2018.
Page 29 Brussels, 7 March 2019Towards Terahertz Communications Workshop
X: 10 ps/div Y: 50 mV/div
Record Performance with RTD Tx/Rx
“Error-free” >26 Gbit/s (BER < 10-12)
Record performance among all electronic semiconductor devices including InP, GaAs, SiGe, Si-CMOS.
It is best to make things simple!!N. Nishigami et al., The 2018 IEICE General Conference, C14-7, Mar. 2019.
Page 30 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Ultra-low propagating loss(< 0.1 dB/cm@300 GHz)
K. Tsuruda et al. Opt Express, 23 (2015)
300 μm
200 μm
1 cm
Si
Confinement by photonic bandgap
Confinement by total internal reflection
THz Photonic Crystal Waveguide
Page 31 Brussels, 7 March 2019Towards Terahertz Communications Workshop
1 mm
Q > 10000@ 300 GHzK. Okamoto et al. Journal of Infrared, Millimeter,and Terahertz Waves, 49 (2017).
2 mmPort 2
Port 4Port 3
Port 1
THz Photonic Crystal Cavity
Page 32 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Coupling structure
Photonic crystal waveguide
Air hole
Efficient Coupling Structure
Page 33 Brussels, 7 March 2019Towards Terahertz Communications Workshop
E-field distribution Integrated device
The measured coupling efficiency between RTD and PC waveguide is ~80%.
The measured Q value and oscillation frequency of the PC cavity is ~500 and 335.4 GHz, respectively.
Cavity-coupled RTDX. Yu et al., “Highly Stable Terahertz Resonant Tunneling Diode Oscillator Coupled to Photonic-Crystal Cavity,” Tech. Dig. 2018 Asia-Pacific Microwave Conference (APMC), 114-116, 2018.
Page 34 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Free running
The RTD oscillation frequency is locked strongly by PC cavity. The locked frequency is the same as the resonant frequency
of PC cavity.
335.4 GHz
X. Yu et al., APMC 2018.
Dependence of Frequency on DC Voltages
Page 35 Brussels, 7 March 2019Towards Terahertz Communications Workshop
The linewidth of RTD oscillator is decreased significantly from 8 MHz to 8 kHz .
ConditionRBW(kHz): 10 kHzVBW(kHz): 10 kHz
Average: 5
Linewidth ReductionX. Yu et al., APMC 2018.
Page 36 Brussels, 7 March 2019Towards Terahertz Communications Workshop
RTD with THz Fiber
Waveguide type Propagation loss Flexibility Cost
Metallic transmission line × 〇 〇
Metallic hollow waveguide 〇 △ △
Photonic-crystal waveguide 〇 △ △
Hollow fiber 〇 〇 〇
Our recent result: loss ~2 dB/m @ 300 GHzPorous PTFE (R1 = 0.25 mm, R2 = 0.14 mm)
Page 37 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Dielectric Waveguide as an InterfaceX. Yu et al., “Terahertz fibre transmission link using resonant tunnelling diodes integrated with photonic-crystal waveguides,” Electron. Lett., to be published.
Page 38 Brussels, 7 March 2019Towards Terahertz Communications Workshop
RTD-RTD Transmission via THz Fiber
Page 39 Brussels, 7 March 2019Towards Terahertz Communications Workshop
4K Video Transmission
Page 40 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Fermi-level Management Barrier Diode
・Low barrier hight: 70 meVlower differential resistance high frequency operation, lower required LO as mixers
H. Ito and T. Ishibashi, Japanese Journal of Applied Physics, Vol. 56, No. 014101, pp. 1-7, 2017.
FMB Diode: Fermi-level Management Barrier Diode
70 meV
Page 41 Brussels, 7 March 2019Towards Terahertz Communications Workshop
FMB Diode
TransimpedanceAmplifier (11 GHz)
FMBDiode
100 µm
Baseband SignalOutput
DC Bias
Packaged FMB Diode Module
Page 42 Brussels, 7 March 2019Towards Terahertz Communications Workshop
EDFAWavelength-Tunable LaserEOAM UTC-PD
EDFA
Wavelength-Tunable Laser
PPG
FMB Diode
ModuleED
Oscillo-scope
LimitingAmplifier
SBDModule
Pre-amplifier
Transmitter
Receiver
300-GHz Transmission ExperimentsTo be presented at IEEE IMS2019.
Page 43 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Overview of latest challenges and results in
THz communications technologies in Japan
1) Photonics-based: 600 GHz, new sources
2) Electronic diode-based: RTD, FMB diode
3) Si-CMOS-based challenges
Page 44 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Loss of Metallic Lines
M. Fujishima et al., IEICE Trans. Electron., vol. E98-C, 1091 (2015).
GHz
GHz
Page 45 Brussels, 7 March 2019Towards Terahertz Communications Workshop
300-GHz CMOS IC TransmitterISSCC 2016, Hiroshima U., Panasonic and NICT
IF
RF
LO
5 GHz/ch17.5 Gb/s x 6CH (105 Gb/s)40-nm CMOS (fmax=280 GHz)
32QAM (5 bit/time frame)
Page 46 Brussels, 7 March 2019Towards Terahertz Communications Workshop
300-GHz CMOS IC Transmitter
2.76 mm
1.88 m
m
[1] Song et al., TMTT, 2014. [3] Kallfass et al., IEICE Trans., 2015.[2] Boes et al., IRMMW-THz, 2014. [4] Sarmah et al., TMTT, 2016. [5] Takano et al., Electron. Lett., 2016.
Single channel
[1] [2] [3] [4] [5] This workTechnology 250nm
InP35nm GaAs 35nm GaAs 0.13µm
SiGe40nm CMOS
40nm CMOSFreq. (GHz) 300 240 300 240 300 302 289−311Modulation QPSK 8PSK QPSK 64QAM 16QAM 32QAM 128QAMPout (dBm) − −3.5 −4 7 −14.5 −5.5
Pdc (W) − − − 0.54 1.4 1.4Data rate (Gbit/s) 50 96 64 1.02 28 105 24.64 x 6
Modulation 32QAMConstellation (Equalized)
EVM 8.9%Data rate 105Gbit/s
ISSCC 2017, Hiroshima U., Panasonic and NICT
21Gbaud
Page 47 Brussels, 7 March 2019Towards Terahertz Communications Workshop
IEEE Std 802.15.3d: Channels
252~325 GHz
Page 48 Brussels, 7 March 2019Towards Terahertz Communications Workshop
300-GHz CMOS IC TransceiverISSCC 2019, Hiroshima U., Panasonic and NICT
80 Gbit/s with 16QAM by 40-nm CMOS
Page 49 Brussels, 7 March 2019Towards Terahertz Communications Workshop
Summary
Steady progress towards 100Gbit/s wireless☞ GaAs/InP/Photonics/RTD/Si-CMOS/SiGe HBT
Interconnection is a key: hollow vs. dielectric
Meeting network trend in fiber-wireless convergence☞ RF photonics integration is a key
RF Si-photonics or hybrid integration
Towards real success in market places☞ Let potential customers use THz comms
by bringing THz outside our labs!☞ International collaboration is a key
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