recent japanese developments on terahertz communications · 2019. 5. 15. · overview of latest...

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


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


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


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


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.)


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


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


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


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


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).


UTC-PD

Coupler Radiator

100 µm

Fabricated UTC-PD Chip


WR-1.5 waveguide

Optical fiber cableDC bias cables

191×381 µm

Fully Packaged Module


- 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


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


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.


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


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


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


Frequency Stability @ 300 GHzY. Li, A. Rolland, K. Iwamoto, N. Kuse, M. Fermann, and T. Nagatsuma, Opt.Lett., vol. 44, pp. 359-362, 2019.


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.


300-GHz QPSK Transmission Experiments

L. Yi et al., EuMC 2019, submitted.


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


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?


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


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


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.


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.


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.


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


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


Coupling structure

Photonic crystal waveguide

Air hole

Efficient Coupling Structure


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.


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


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.


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)


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.


RTD-RTD Transmission via THz Fiber


4K Video Transmission


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


FMB Diode

TransimpedanceAmplifier (11 GHz)

FMBDiode

100 µm

Baseband SignalOutput

DC Bias

Packaged FMB Diode Module


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.


Loss of Metallic Lines

M. Fujishima et al., IEICE Trans. Electron., vol. E98-C, 1091 (2015).

GHz

GHz


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)


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


IEEE Std 802.15.3d: Channels

252~325 GHz


300-GHz CMOS IC TransceiverISSCC 2019, Hiroshima U., Panasonic and NICT

80 Gbit/s with 16QAM by 40-nm CMOS


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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recent japanese developments on terahertz communications · 2019. 5. 15. · overview of latest...

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