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Large-Scale Terahertz Active Arrays in Silicon Using Highly-Versatile
Electromagnetic Structures(Invited Paper)
Cheng Wang, Zhi Hu, Guo Zhang,Jack Holloway and Ruonan Han
Dept. of Electrical Engineering and Computer ScienceMicrosystem Technology LaboratoriesMassachusetts Institute of Technology
Enabling
Technology
Applications
(Demos)
Today
The Dawn of a New Terahertz Era
2
The Dawn of a New Terahertz Era
3
Cost &
Size
System
Complexity
The Next THz Era
Enabling
Technology
Applications
(Demos)
Today
The Dawn of a New Terahertz Era
4
Cost &
Size
System
Complexity
The Next THz Era
Enabling
Technology
Applications
(Demos)
Today
Recent Progress and New Challenges
5
2006 2008 2010 2012 2014 20161E-5
1E-4
1E-3
0.01
0.1
1
10
DC
to
TH
z R
ad
iati
on
Eff
icie
nc
y (
%)
Year
0.2 0.3 0.4 0.5-15
-10
-5
0
5
10
Po
ut (
dB
m)
fout
(THz)
[IMS 2013][ISSCC 2013]
[ISSCC 2012]
[ESSIRC 2013]
[ISSCC 2014]
[T-MTT 2014]
[ISSCC 2014]
10-2
1
10-4
[ISSCC 2008]
[ISSCC 2011]
[VLSI 2011]
[ISSCC 2012]
[ESSIRC 2012][ISSCC 2013]
[ISSCC 2014]
[IMS 2013]
Our Work
Our Work
Our Work
[ISSCC 2015]
Our Work
[ISSCC 2015]
[R. Han, etc., IEDM 2016]
Recent Progress and New Challenges
6
2006 2008 2010 2012 2014 20161E-5
1E-4
1E-3
0.01
0.1
1
10
DC
to
TH
z R
ad
iati
on
Eff
icie
nc
y (
%)
Year
0.2 0.3 0.4 0.5-15
-10
-5
0
5
10
Po
ut (
dB
m)
fout
(THz)
[IMS 2013][ISSCC 2013]
[ISSCC 2012]
[ESSIRC 2013]
[ISSCC 2014]
[T-MTT 2014]
[ISSCC 2014]
10-2
1
10-4
[ISSCC 2008]
[ISSCC 2011]
[VLSI 2011]
[ISSCC 2012]
[ESSIRC 2012][ISSCC 2013]
[ISSCC 2014]
[IMS 2013]
Our Work
Our Work
Our Work
[ISSCC 2015]
Our Work
[ISSCC 2015]
[R. Han, etc., IEDM 2016]
What are the true advantages of using silicon IC for THz hardware (besides low cost, baseband integration…)?
Large-Scale Terahertz Active Array
7
Integration Capability of Silicon Chips
Homogeneous Array• Power combining• Beam collimation• Beam steering• …
Heterogeneous Array• Broadband sensing• Parallel signal processing• Waveform generation• …
Outline
Background
Homogeneous Array: 1-THz Radiation SourceMulti-Functional Mesh Structure
Chip Prototype in SiGe and Measurement Results
Heterogeneous Array: 220-to-320GHz Frequency-Comb SpectrometerHigh-Parallelism Architecture and THz Molecular Probing Module
Chip Prototype in CMOS and Measurement Results
Gas-Sensing Demonstration
Conclusion8
Outline
Background
Homogeneous Array: 1-THz Radiation SourceMulti-Functional Mesh Structure
Chip Prototype in SiGe and Measurement Results
Heterogeneous Array: 220-to-320GHz Frequency-Comb SpectrometerHigh-Parallelism Architecture and THz Molecular Probing Module
Chip Prototype in CMOS and Measurement Results
Gas-Sensing Demonstration
Conclusion9
Beam Collimation in a Radiator Array
10
-90 900-60 -30 30 60Angle (degree)
No
rma
lize
d P
ow
er
(dB
)
-30
-20
-10
0
-90 900-60 -30 30 60Angle (degree)
No
rma
lize
d P
ow
er
(dB
)
-30
-20
-10
0
-90 900-60 -30 30 60Angle (degree)
No
rma
lize
d P
ow
er
(dB
)
-30
-20
-10
0
D=λ/4 D=λ/2 D=λ
D
θ
Array of N coherent radiation sources enables: Power combining from a large number of solid-state devices
Beam collimation through wave interference
The far-field radiation intensity increases by N2
Optimum Element Pitch: λ/2
High-Density, Large-Scale Active Array on Chip
• If the λ/2 pitch is achieved:‒ >10/mm2 radiators at
300 GHz can be built
‒ Dopt is ~300μm(with εr,eff≈3)
• High effective isotropicallyradiated power (EIRP) may be maintained in the mid-THz range
‒ Long transmission distance
11
0.01 0.1 1 10 100 10000.01
0.1
1
10
100
Be
am
Wid
th (
de
gre
e)
Frequency (THz)
100
101
102
103
104
105
106
107
108
# o
f Co
here
nt R
ad
iato
rs
1 Antenna
(JSSC 2002)
2 m
m
2.2 mm
4 Antennas
(ISSCC 2013)Optical Antenna Array
Note: Calculations Based on a 10mm2 Active Area
High-Density, Large-Scale Active Array on Chip
12
0.01 0.1 1 10 100 10000.01
0.1
1
10
100
Be
am
Wid
th (
de
gre
e)
Frequency (THz)
100
101
102
103
104
105
106
107
108
# o
f Co
here
nt R
ad
iato
rs
1 Antenna
(JSSC 2002)
2 m
m
2.2 mm
4 Antennas
(ISSCC 2013)
1 mm
16 Antennas
(ISSCC 2015)Optical Antenna Array
Our Work
Note: Calculations Based on a 10mm2 Active Area
1.3
mm
1.6mm
Radiators
VC
Os
+B
uff
ers
Other PLL Blocks
1.895 1.9 1.905 1.91 1.915-100
-90
-80
-70
-60
-50
Frequency (GHz)
Po
we
r (d
Bm
)
Frequency Locked
Free Running
Frequency (Hz)
PN
(d
Bc/H
z)
-67.4dBc/Hz @ 100KHz
-87.2dBc/Hz @ 10MHz
Phase Noise After Locking
10K 100K 1M 10M 100M-100
-90
-80
-70
-60
-50
• 320-GHz Array w/ PLL in SiGe BiCMOS
• 4x4 elements in 1-mm2 area
• 3.3mW total radiated power (EIRP: 24mW)
[R. Han, ISSCC 2015]
High-Density, Large-Scale Active Array on Chip
• ~100/mm2 radiator density should be possible
‒ Only 3° of beamwidth using 10-mm2 chip area(~1000 coherent radiators)
• Large challenges‒ Signal generation at 1 THz
‒ Available radiator area:100×100μm2
‒ Highly scalable array architecture
13
0.01 0.1 1 10 100 10000.01
0.1
1
10
100
Be
am
Wid
th (
de
gre
e)
Frequency (THz)
100
101
102
103
104
105
106
107
108
# o
f Co
here
nt R
ad
iato
rs
1 Antenna
(JSSC 2002)
2 m
m
2.2 mm
4 Antennas
(ISSCC 2013)
1 mm
16 Antennas
(ISSCC 2015)Optical Antenna Array
Our Work
??
Note: Calculations Based on a 10mm2 Active Area
Implementation Challenges
14
0
100
200
300
400
500
0 40 80 120 160 200 240 280
Me
as
ure
d f
ma
x (
GH
z)
(In
terc
on
ne
ct
Inc
lud
ed
)
Technology Node (nm)
CMOSSiGe
[R. Shmid, et al., IEEE Trans. Electron Devices 2015]
Cutoff Frequency of
Silicon Devices
f0 x 42. Frequency Quadrupler
1. Fundamental (f0) Oscillator
4. Filters for Unwanted Harmonics f0 2f0 3f0 4f0
λf0/4=λ4f0
3. Antenna at 4f0 λ4f0/2
λ4f0/2
Available Area
High-Order Harmonic Radiation
f0=250GHz, fout=4f0=1THz
Low device speed requires high-order harmonic generation‒ Optimal device conditions at all harmonic frequencies should be met
The available area is too small for all these necessary functions
Enabling Technology: Versatile EM Designs
• A multi-functional electromagnetic structure around the transistors to simultaneously perform all the above tasks
‒ Orthogonality of various EM wave modes
‒ Multi-order standing-wave interference in the near field 15
λ4f0/2
Multi-Functional Structure
3. Antenna at 4f0 λ4f0/2
1. Fundamental (f0) Oscillator
λf0/4=λ4f0
4. Filters for Unwanted Harmonics f0 2f0 3f0 4f0
f0 x 42. Frequency Quadrupler
High-Density, Large-Scale Active Array on Chip
16
0.01 0.1 1 10 100 10000.01
0.1
1
10
100
Be
am
Wid
th (
de
gre
e)
Frequency (THz)
100
101
102
103
104
105
106
107
108
# o
f Co
here
nt R
ad
iato
rs
1 Antenna
(JSSC 2002)
2 m
m
2.2 mm
4 Antennas
(ISSCC 2013)
1 mm
16 Antennas
(ISSCC 2015)
1 mm
91 Antennas
(RFIC 2017)Optical Antenna Array
Our Work
Note: Calculations Based on a 10mm2 Active Area
1 mm
• 1-THz Array in 130-nm IHP SiGe BiCMOS
• 91 coherent radiator in 1-mm2 area
• 0.1-mW total radiated power(EIRP: 20mW)
[Z. Hu and R. Han, IEEE RFIC, Jun. 2017
(Best Student Paper Award-2nd Place)]
Fundamental Oscillation at f0=250GHz
• At f0, each square slot line behaves as a pair of λ/4 standing-wave resonators
17
Q≈20 @ 250GHzCap
Cap
ABCD B
C D
AB
C D
B
C
@ f0
λf0/8
λf0/8 AC Short
λf0/4
Optimal Fundamental Oscillation
Multi-Order Standing Wave Interference
• Unwanted harmonics (@ f0, 2f0, 3f0) are canceled by near-field interference
18
Cap
Cap
Cap
Cap
ABCD B
C D
AB
C D
B
C
AB
C D
B
C
AB
C D
B
C
AB
C D
B
C
ABCD B
C D ABCD B
C D ABCD B C D
@ f0
Cap
Cap
Cap
Cap
250-GHz Oscillation
Radiation Suppression and Energy Recycling of Harmonics 1-THz Radiation
λ/4
@ 2f0
λ/2
@ 3f0
3λ/4
@ 4f0
λ
No Separate Filter is Needed
High-Density Radiation at 1 THz
• The 1-THz standing waves in all horizontal slots are in phase‒ Effective backside radiation (ηrad,sim=63%)
‒ On average, each oscillator (4x7 in total) drives 2 slot dipole antennas
19
AB
C D
B
C
ABCD B C D
@ 4f0=1THz
Cap
Cap
λ/2 @
1THz
Slot Dipole
Antenna
91 Coherent Antennas (D≈λ/2)
Measurement Results: Frequency and Spectrum
• Oscillation frequency is determined by a sub-harmonic SBD mixer‒ Weak radiation leakage at f0
‒ Measured fundamental frequency: 252.5 to 254.1 GHz
‒ 4f0 output: 1.01 to 1.016 THz 20
Power Supplies
VB
GNDVCC
Spectrum Analyzer
(Tektronix RSA3303A)
WR-3.4
AntennaWR-3.4
Mixer
IF
Amplifier
Chain
Signal Generator (Keysight E8257D)
LO=15.8GHz
1.0 1.1 1.2 1.3252
253
254
Me
as
ure
d fOSC,fund (
GH
z)
VB (V)
f0 = 16fLO + foffset
Measurement Results: Radiated Power
• The radiated power is measured by a calibrated WR-1.0 zero-biased diode detector
‒ Measured total radiated power: 80 μW
‒ Measured beam directivity: 24 dBi (θ-3dB=11°)
‒ Measured EIRP: 20 mW21
Simulation
Measurement
H-Plane
-90 -60 -30 0 30 60 90
-40
-30
-20
-10
0
Phi (degree)No
rmalized
Re
ce
ive
d P
ow
er
(dB
)
E-PlaneSimulation
Measurement
-90 -60 -30 0 30 60 90
-40
-30
-20
-10
0
Theta (degree)No
rmalized
Re
ce
ive
d P
ow
er
(dB
)
Measurement Results: Radiated Power
• The measured radiated power is further verified by a photo-acoustic (TK) power meter with large aperture
22
Power
Supply
Function
Generator
VB
GND VCC
Trigger
TK Processing Unit
Signal
Heater PC
TK Powermeter
(30Hz)
Comparison with the State-of-the-Arts in Silicon
• The achieved radiated power is 10x higher than prior silicon-based radiation sources in the mid-THz range
‒ 100x higher EIRP than prior arts
• Even larger scale with higher power should be possible
23
[RFIC 2017]
Outline
Background
Homogeneous Array: 1-THz Radiation SourceMulti-Functional Mesh Structure
Chip Prototype in SiGe and Measurement Results
Heterogeneous Array: 220-to-320GHz Frequency-Comb SpectrometerHigh-Parallelism Architecture and THz Molecular Probing Module
Chip Prototype in CMOS and Measurement Results
Gas-Sensing Demonstration
Conclusion24
Wave-Matter Interactions for Material Sensing
25
THz Spectrometer for Gas Sensing
26
MoleculeFrequency
(GHz)Toxic? Flammable?
Carbon Monoxide (CO) 230.538001 Y Y
Sulfur Dioxide (SO2) 251.199668
Hydrogen Cyanide (HCN) 265.886441 Y
Hydrogen Sulfide (H2S) 300.511959 Y
Nitric Oxide (NO) 250.436966 Y
Nitrogen Dioxide (NO2) 292.987169 Y
Nitric Acid (HNO3) 256.657731 Y
Ammonia (NH3) 208.145904 Y
Carbonyl Sulfide (OCS) 231.060989 Y Y
Ethylene Oxide (C2H4O) 263.292515 Y
Acrolein (C3H4O) 267.279359 Y
Methyl Mercaptan (CH3SH) 227.564672 Y
Methyl Isocyanate (CH3NCO)
269.788609 Y
Methyl Chloride (CH3Cl) 239.187523 Y Y
Methanol (CH3OH) 250.507156 Y Y
Acetone (CH3COCH3) 259.6184 Y Y
Acrylonitrile (C2H3CN) 265.935603 Y Y
[Source: HITRAN.org]
0 0.3 0.6 0.9 1.2
40
60
80
100
Tra
ns
mit
tan
ce
(%
)
16O
12C
32S
Frequency (THz)
𝜸 =𝟐𝑱 + 𝟏 𝒉𝑩𝒆−𝒉𝑩𝑱(𝑱+𝟏)/𝒌𝑻
𝒌𝑻Absorption Intensity:
Quantum Number
J≈40
J=1
-5 50
Frequency Offset From
231.060983GHz (MHz)
100%
85%
70%
Wide Detection Range High Sensitivity High Selectivity
Dual-THz-Comb Spectrometer
27
IF
f (GHz)220 320
Transmitter
f (GHz)220
Receiver
320
• Conventional single-tone sensing scheme– Bandwidth-efficiency tradeoff
– Long scanning time(~3 hours for 100-GHz bandwidth)
IFB,-n
~IFB,n-1 f (GHz)220 320 f (GHz)220 320
IFA,-n
~IFA,n-1
THz Comb A
Spectrum of Comb A Spectrum of Comb B
fIF
THz Comb B• Our scheme using bilateral THz
frequency combs– Each circuit block maintains peak
performance in a narrow band
– Simultaneous scanning using 20 comb lines(>20x increased speed)
220-to-320GHz Comb-Based CMOS Spectrometer
28
Hemispheric
silicon lens
CMOS chip
[C. Wang and R. Han, IEEE ISSCC, Feb. 2017]
• 10 molecular-probing THz transceivers‒ Key technology: multi-function, energy-efficient electromagnetic structures
• Seamless coverage of the 220 to 320 GHz band with kHz resolution
Operation of the Transceiver Unit Core
29
• Optimum device conditions created via a multi-functional EM structure‒ Slot 1: resonator at f0 and antenna at 2f0
‒ Slot 2: power recycle path at f0 and leakage blocker at 2f0
• Simultaneous transmit/receive function
[C. Wang and R. Han, IEEE JSSC, Dec. 2017]
High-Parallelism Broadband Architecture
• The relaxed tunability requirement allows the introduction of device positive feedback and higher device gain
‒ 43% simulated doubler conversion efficiency
• The total spectral scanning time is reduced by more than 20x, leading to high energy efficiency
30
η=18%, w/o
feedback
η=43%, with DTL
feedback
η (%)
Gmax
Original Transistor (W/L=12µ/60n)
Transistor with
DTL Feedback
fmin fmax
Tim
e P
er
Sa
mp
le
fmin fmax
Ave
rag
e T
ime
Pe
r
Sa
mp
le
20x
Single-Tone Spectrometer Dual-Comb Spectrometer
CH
1
CH
2
CH
3
CH
4
CH
17
CH
18
CH
19
CH
20
CMOS Chip Prototype
• TSMC 65nm bulk CMOS process (fmax=250GHz)‒ Chip area: 2×3mm2
• 10 transceivers (doubler+receiver+antenna), 9 mixers, 40 amplifiers, operating at 0.1~0.3 THz
‒ DC power: 1.7 W 31
3 mm
2m
m
Testing Board
WR-3 Even-Harmonic Mixer
Setup for Radiation Spectrum and Pattern Testing
Experimental Results
32
Span=10kHz
RBW=10Hz
Antenna Pattern of One Line (265GHz)Average Phase Noise: -102dBc/Hz @ 1MHz
Measured Down-converted IF Spectra of all Comb Lines Spectrum of a Comb Line at 265GHz
Experimental Results
33
• Total radiated power of the 10 comb lines: 5.2 mW– Highest in silicon
• Minimum detectable signal: 0.1 fW (-130 dBm) @ τ=1 ms
Effective Isotopically-Radiated PowerNoise Figure of Each Channel
(SSB, Antenna Loss Included) This work
TST
2016
On-wafer measured with an
assumed 50% radiation efficiency Radiated
RFIC
2016
RFIC
2015
ISSCC
2015
ISSCC
20161
PBW
JSSC
2013
TST
2015MTT
2012
CSICS
2012 ISSCC
2016
ISSCC
2015
This work
TST
2016
On-wafer measured with an
assumed 50% radiation efficiency Radiated
RFIC
2016
RFIC
2015
ISSCC
2015
ISSCC
20161
PBW
JSSC
2013
TST
2015MTT
2012
CSICS
2012 ISSCC
2016
ISSCC
2015
This work
TST
2016
On-wafer measured with an
assumed 50% radiation efficiency Radiated
RFIC
2016
RFIC
2015
ISSCC
2015
ISSCC
20161
PBW
JSSC
2013
TST
2015MTT
2012
CSICS
2012 ISSCC
2016
ISSCC
2015
Spectroscopy Demonstration
• Low pressure is applied to eliminate the spectral broadening due to the inter-molecular collisions
• Wavelength modulation is used to reduce the impacts of the standing wave inside the gas chamber 34
Comb A Comb BGas Chamber
fIF
fm 2fm
LNABPFDetector
IFi
L=70 cm, Pressure =3 Pa
WM input
fref+Δf/6·sin(2πfmt)
Signal SourceSignal Source
Lock-in amplifier
fref – fIF/6
GPIB
GPIB
fm
Laptop
fm
Output
Spectral
line
Freq
Am
pli
tud
e
Time
Time
Acetonitrile (CH3CN)
Spectroscopy Results
• Sensitivity: 11 ppm for OCS, 14 ppm for CH3CN, 3 ppm for HCN…
‒ 10-100 ppt with standard gas pre-concentration
• Any polar molecule heavier than HCN can be detected
• Spectral linewidth is ~1MHz, leading to absolute specificity
O C S
CH3CN
CH3CN
OCS
SNR Pressure
BW=78Hz
279.6825 279.6840 279.6855 279.6870
-4
-2
0
2
4
1st-
Ord
er
De
riv
ati
ve o
f T
ran
sm
iss
ion
(a
.u.)
Frequency (GHz)
-45
0
45
90
135
180
225
Ph
as
e S
hift (D
eg
ree)
Conclusions• Using CMOS/BiCMOS device technologies not only enables “THz
frontend + analog/digital baseband” integration, but may also directly enhance the THz-circuit performance
‒ Homogeneous arrays: high-density coherent wave interference Large total radiated power
Ultra-narrow beam generation
‒ Heterogeneous arrays: high-parallelism EM spectral sensing Broadband coverage
Optimal energy efficiency
• Key technology: versatile THz circuits with multi-functional structures
36
A unified design framework:device, circuit, electromagnetism and architecture, all rolled into one
Acknowledgement
• Other Group Members:M. Kim, M. Ibrahim, M. I. Khan,
X. Yi, J. Mawdesley, J. Maclver, Z. Wang
• Collaborators:B. Perkins (MIT Lincoln Lab), S. Coy (MIT),
Q. Hu (MIT), M. Kaynak (IHP)
37
• Sponsors:
Large-Scale Terahertz Active Arrays in Silicon Using Highly-Versatile
Electromagnetic StructuresCheng Wang, Zhi Hu, Guo Zhang,Jack Holloway and Ruonan Han
Dept. of Electrical Engineering and Computer ScienceMicrosystem Technology LaboratoriesMassachusetts Institute of Technology