ultra high frequency electronics and near-thz ......indoor wireless communication. application:...
TRANSCRIPT
Ultra High Frequency Electronics and Near-THz Semiconductor Devices:
Emerging TechnologiesApplications, Propagation Properties,
Mark RodwellUniversity of California, Santa Barbara [email protected]
Applications for 100-500 GHz ElectronicsOptical Fiber Transmission
40 Gb/s:InP and SiGe both feasible ICs commercially available; market has vanished
80 & 160 Gb/s may come in timenow clearly feasible with InP integrated circuitslimits: detector & modulator bandwidth, fiber dispersion
Electronic adaptive equalization: increases range, needs ADCs operating at the bit rate
0.0 0.2 0.4 0.6 0.8 1.01E-6
1E-5
1E-4
1E-3
0.01
0.1
11 kmSea level
Log
Tran
smis
sion
Frequency, THz
Radio-wave Transmission / Radar / Imaging65-80 GHz, 120-160 GHz, 220-300 GHz, ... ?Low atmospheric attenuation (weather permitting).High antenna gains (short wavelengths)
sciencespectroscopy, radio astronomy
Mixed-Signal ICs for Military Radar/Comms
direct digital frequency synthesis, ADCs, DACshigh resolution at very high bandwidths sought
applications
Applications: Optical fiber transmission
clockPLL
AD DMUX
O/E, E/O interfaces
MUX
Gtran 40 Gb/s InP HBT fiber chip set
40 Gb/s chip sets demonstrated in SiGe and InPNext: 80, 100, 160 Gb/s ?100 + GHz photodiodes demonstrated: practical limit is fiber alignment~100 GHz modulators demonstrated (Thylén group, KTH Stockholm)Major challenge: limit to range by fiber dispersion → nonlinear adaptive feedbackMajor challenge: cost of TDM vs. WDM system using low-cost CMOS electronics
Applications: Military Mixed-Signal Electronics
adder-accumulator
Sine ROM ADC
digitalbeamformer
DAC FFT
Signals are digital generated & detected at baseband, then converted IF→ RF
GHz bandwidths sought, dynamic ranges might be 60-90 dB
Moderate-resolution to high-resolution analog-digital conversion.
→ requires transistor bandwidth well beyond signal bandwidth
& requires precise and predictable DC characteristics (Vbr, leakage, beta, matching)
Applications for 100-500 GHz Radio Propagation
Limitations
Rain attenuation is very highlimits rate/range feasible with high quality of service
Bandwidth may not yet be needed bands near 70-80 GHz becoming available
Implications / Potential Applications
Gigabit-rate highly-directional communications. many channels of Gigabit-rate communicationscoexistence of many wideband services (imaging, radar, comms)beam-like propagation using phased arrays
mm-wave, sub-mm-wave imaging for surveillancehigh resolution images with reasonable aperture sizepenetration of clothing → concealed weapons detection
mm-wave, sub-mm-wave imaging for aviationaviation in fog and rain--high resolution vision over ~1 km range. high resolution images with reasonable aperture size
Properties
200-300 GHz useful bandwidth available
Short wavelengthscompact yet very directional antennas
cm-scale penetration of dielectric objects
moderate Rayleigh scatteringworse than microwave, much better than optical
moderately low attenuation when absorbtion lines, rain & fog are avoided.
0 .0 0.2 0.4 0.6 0.8 1.01E-6
1E-5
1E-4
1E-3
0.01
0.1
11 kmSea level
Log
Tran
smis
sion
F requency, TH z
Atmospheric Attenuation in Bad Weather: Summary
Absorbtion lines rule out specific bands
Very heavy rain is 50 mm/hr (0.01% of time, or less): 20 dB/km, 30-1000 GHz
Extreme Rain is 150 mm/hr (<<0.01% of time): 50 dB/km, 30-1000 GHz
Clouds, heavy fog: ~(25 dB/km)x(frequency/500 GHz)
very heavy fog
0.0 0.2 0.4 0.6 0.8 1.01E-6
1E-5
1E-4
1E-3
0.01
0.1
11 kmSea level
Log
Tran
smis
sion
Frequency, THz
good weather
rain
heavy raintropical deluge
Array (phased- or focal-plane) beamsteering is necessary
2
22
receiver FWHM,
02
er transmittFWHM,
0
225757
RRAA
PP transmitreceive
transmit
received λθθλ
==
[ ] 020
90over steerable beam array with phased 120elementsarray phasedNumber ±
≅
FWHMθ
[ ] array steerable-partially elementsarray phasedNumber 2
≅
FWHM
steerable
θθ
High Frequencies (short wavelengths) can be an advantage or a problemreducing wavelength improves performance if antenna sizes are fixedreducing wavelength reduces performance if beam widths (directivities) are fixed→ 100-500 GHz systems will use narrow beams
High Frequency systems require passive beamsteeringhighly directional antennas have narrow beamwidths
→ mobile links electronic adaptive beamsteering to compensate for motion→ fixed links need small-angle adaptive beamsteering to compensate for refraction
narrow beamwidth arrays need large number of elements
Outdoor Mobile Communication: high-rate but short-range
100
1000
104
0.1 1 10 100
rang
e, m
rain rate mm/hr
30 GHz
300 GHz
10 cm antenna diameters1 W transmit power10 Gb/s data rate5 dB noise figure5 dB system margin10-9 error rateQPSK modulation
<0.01% probability<1% probability
10 Gb/s over 1 km
rateerror 10for 36 where
)exp(
)exp(16
9-)4(
22
2
2
2
kTFBP
RRAA
RR
DDPP
QPSKreceived
receivetransmit
rt
dtransmitte
received
⋅=
−×
=
−×
=
αλ
αλπ
300 GHz compared to 30 GHz:better gain D for a given size antenna, but poorer clear-weather atmospheric attenuation α slightly poorer attenuation in fog (but fog causes less attenuation than rain), similar attenuation in rain. more spectral bandwidth available ( ~20 vs. ~200 GHz) 100-500 GHz communication is most suitable for > 10 Gb rates at few-km-range. Lower data rates benefit from lower carrier frequencies.
X-band has much lower attenuation (longer range) in bad weather, but its available bandwidth limits maximum data rates to ~1 Gb/s
Less Favorable Applications for 100-500 GHz RadioAircraft to satellite communications: No rain attenuation. Beneficial only if high bandwidthor small antennas needed.
Ground to satellite communications: Difficulty is rain attenuation. Higher at 300 GHz than at 30 GHz.Must sacrifice quality of service.
clouds& rain
sea level
Short-range high-resolution radar: high resolution can be obtained from small aperturelimited detection range in bad weather is a severe limitation
100-500 GHz for imaging: Foul-weather aviation
h wavelengtfrom ceindependen thenote ; )2exp(4
/area target resolvable theis section cross target theimaging,for but
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2antenna
antenna22
target
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rA
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Ar
RkTFBP
rA
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trans
trans
απ
λσ
αλπ
σ
−×=→
=
−×= 22
)(000,41/4 o
FWHMeffAD
θλπ ≅=
System Performance,300 GHz, 1.3 W transmit power0.2 degree angular resolution with 30 cm radar aperture
→ 4 meters image-plane resolution at 1 km range10 dB SNR at 1 km range in 25.4 mm/hr rain (12 dB/km rain attenuation)
Application:vision: flying helicopters or driving vehicles in smoke/fog/dust/rain, landing a plane on a a runway or on an aircraft carrier in heavy rain or fog
Why 300 GHz ? Short wavelength → high resolution with reasonable antenna size.Attenuation in rain/fog at 300 GHz is not substantially different from that at 30 GHz. Attenuation (hence range of vision) is much better than in the visible or infrared.
Why 300 GHz ? Short wavelength → high resolution with reasonable antenna size.Attenuation in rain/fog at 300 GHz is not substantially different from that at 30 GHz. Attenuation (hence range of vision) is much better than in the visible or infrared.
300 GHz carrier, 3 dB noise figure, 30 cm diameter antenna, 25 Hz image refresh rate, 25 MHz receiver bandwidth, 215 degree field of view, 1 million pixels, 10 dB SNR for image discrimination
Outdoor Fixed Wireless Communication: 100 Gb/s over 1 km
Link calculation: 100 Gb/s radio at 1 km range in 50 mm/hr rain.275 GHz carrier, QPSK modulation, 50 mm/hr rain (24 dB/km)5 dB receiver noise figure, 5 dB operating margin10 cm diameter antennas (Directivity = 105), 400 mW transmitter power
key point: fixed wireless uses more directional antennas than mobile wireless→ more range
To serve as metropolitan internet backbone requires better than 99.99% reliability.Link may need to be designed for even 150 mm/hr rain .
Indoor Wireless Communication
Application:Wireless connection of home entertainment.Devices equipped with small phased-array radioswith adaptive beam steering.
System link calculation: 4 Gb/s radio at 10 m range with 20 dB margin100 GHz carrier, QPSK modulation5 dB receiver noise figure, 20 dB operating margin6 x 6 element antenna arrays (Directivity = 140), 20 mW transmitter power
Small Monolithic Phased Arrays will be inexpensive
∆φ
∆φ
∆φ
∆φ
subarray
subarray
∆φ
∆φ
data
substrate lens
array ICcase 1: 100 GHz array in silicon VLSIassume e.g. IBM 90 nm SOI CMOS VLSIprocess has 200 GHz fmax, good for 100 GHzhigh resistivity substrate→ on-wafer antennas ?wavelength=3 mm, but 0.86 mm in dielectric20 x 20 -element array: 9 mm x 9 mm die
similar die size, hence cost, as microprocessor6 degree beamwidth, 30 dB aperture gain
case 2: 300 GHz array in InP HBTkey issue to be addressed: obtaining low IC costsemi-insulating substrate→ on-wafer antennaswavelength=1 mm, but 0.3 mm in dielectric20 x 20 -element array: 3 mm x 3 mm die
~6 degree beamwidth, 30 dB aperture gain66 x 66 -element array: 1 cm x 1 cm die
~2 degree beamwidth, 40 dB aperture gain
substrate lenses index-matchedto the semiconductor substrate 1) prevent substrate moding2) reduce array size in proportion
to their refractive index
enabling technologies
infrared and mm-waves, THz Frequencies
109 1010 1011 1012 1013 1014 1015
Frequency (Hz)
microwave3-30 GHz
mm-wave30-300 GHz
far-IR(sub-mm)0.3-3THz
mid-IR3-30 THz
near-IR30-450 THz
optical450-900 TH
z
electronics well-developed to ~200 GHz optics well developed >30 THz
mid-IR, far-IR technologies not well developedBWO & cancinotron tubes, CO2 lasers
Far-IR and Mid-IR technologies are poorly-developedBWOs (tubes), carcinotrons (tubes), CO2 lasers. Big. Inefficient. Fragile.compact & efficient solid-state sources are desirable
THz quantum cascade laserslow mW power, pulsed, cryogenic. improving rapidlyspectral linewidths (phase noise) will be vastly poorer than phase-locked electronicsMHz, not GHz/THz modulation (information) bandwidths
Desirable: solid state ELECTRONIC signal sources for 150-1000 GHz compact. very narrow spectrum (low phase noise). low noise @ 10-100 x kTGHz/THz modulation (information bandwidths)
Frequency Limitsand Scaling Laws of (almost all) Electron Devices
bottomsR ,
topsR ,
1:4 increases ,/)( limited charge-space
1:4by increase/1
/ /
/ )/1ln(~ :contact flared use
0 :Schottky use1:4by reduce
/ /
/
1:4by reduce/ /1
/1:2by reduce/metransit ti
bandwidth double toconstant timeparameters ngcontributi
2max
,
,,
,,
DvVJJ
JJD
IDWLCRqIkTR
DWLCWLR
DCRWLR
DWLC
WDWCRLR
DWLCDvD
electron
junction
junction
ctops
contact
contact
contacttopscontacttops
bottomsbottoms
electron
φ
ρρ
ρρ
ρ
τ
+∝∝
∝∝
∝
=∝∝
∝
∝∝
∝∝
diode as example
R/C/τ Limits the Bandwidth of (most) Electron Devices
capacitanceresistance transit time
device bandwidth
applies to:bipolar transistors, field-effect transistors, Schottky diodesRTDs, photomixers, photodiodes
Applies whenever AC signals are removed though Ohmic contacts
Effective THz devices must minimize, eliminate, or circumventcontact resistance, capacitance, & transit time
Why aren't semiconductor lasers R/C/τ limited ?
+V (DC)
N+
N-
I
P-
P+
metal
metal
opticalmode
-V (DC)
AC outputfield
high εr
dielectric waveguide mode confines AC field away from resistive bulk and contact regions.
AC signal is not coupled through electrical contacts
dielectric mode confinement is harder at lower frequencies
What do I think are the best approaches ?
10-nm-scale electron drift devices:
~100 nm-generation InP DHBTssignal generation with power to ~500 GHz
<30 nm-generation InP HEMTs30 nm devices now get ~600 GHz ft→ low noise figure at 300 GHz
<50 nm-generation InP or GaAs Schottky mixer diodesmany THz RC and transit time frequencies
And Silicon VLSI for applications below ~150 GHz !
transistors: InP HBT
Why transistors for 100-1000 GHz Electronics ? Integrated Circuits !
80-160 Gb/s Optical Fiber Transceivers
clockPLL
AD DMUX
O/E, E/O interfaces
MUX
Radio communications links
600 GHz10 mW
300 GHzpush-pushVCO
Gilbert-cellharmonic mixer
15 GHzreference
150 GHz
300 GHz poweramplifier50 mW output
HBTactivefrequencydoubler
MIMIC
Frequencydoubler
Frequencydoubler
83 GHz333 GHz100 mW
167 GHz100 mW
Phased Arrays and Adaptive Beamsteering
∆φ
∆φ
∆φ
∆φ
subarray
subarray
∆φ
∆φ
data
Transistors are general-purpose, will support complex high-frequency functions
Zach Griffith, Mattias Dahlstrom
InP HBTs for 100-500 GHz Applications
InP HBTs: transmitter power transistors, frequency synthesizers, signal processing
Today's InP HBTs are sufficient for 300 GHz MMICs production processes now 300 GHz fmax → good for 200 GHz MMICs research processes now 500 GHz fmax → good for 300 GHz MMICs
InP HBTs are improving quickly: leveraged by DARPA TFAST programemitter sidewall processes: high yield at 250 nm scaling → path to 600 GHz fmaxcollector pedestal process increases fmax and breakdown
→EmaxVsat=2E13 V/s , 600 GHz ft feasible at 5 V breakdownEmitter regrowth may allow further sub 100 nm scaling
→ Feasibility of 750 GHz-800 GHz transistor bandwidth, DC-400 GHz Monolithic ICs
0
5
10
15
20
25
30
35
109 1010 1011 1012
Gai
ns (d
B)
Frequency (Hz)
ft = 391 GHz, f
max = 505 GHz
U
H21
Ajbe
= 0.6 x 4.25 um2
Je = 5.17 mA/um2, V
cb= 0.6 V
Bipolar Transistor Scaling Laws & Scaling RoadmapsScaling Laws:design changes required to double transistor bandwidth
InP Technology Roadmap 40 / 80 / 160 Gb/s digital clock rate
key figures of merit
for logic speed
unchangedbase contact resistivity(if contacts do not lie above collector junction)
decrease 4:1base contact resistivity(if contacts lie above collector junction)
increase 4:1current density
decrease 4:1emitter resistance per unit emitter area
decrease 4:1collector junction width
decrease 4:1emitter junction width
decrease 1.414:1base thickness
decrease 2:1collector depletion layer thickness
required changekey device parameter
WE
WBC
WEB
∆x
L E
base
emitter
base
collector
WC
Key scaling challengesemitter & base contact resistivitycurrent density→ device heating
Zach Griffith, Mattias Dahlstrom
Sub-mm-wave Indium Phosphide HBTs
0
5
10
15
20
25
30
35
109 1010 1011 1012
Gai
ns (d
B)
Frequency (Hz)
ft = 391 GHz, f
max = 505 GHz
U
21
Ajbe
= 0.6 x 4.25 um2
Je = 5.17 mA/um2, V
cb= 0.6 V
Ccb/Ic =0.26-0.75 ps/V
H
Late-2003 600-nm-generation mesa HBTs power amplifiers feasible to 250 GHzdigital ICs (static divider benchmark) feasible to 180 GHz
0
2
4
6
8
10
12
14
0 1 2 3 4 5 6 7 8
J e (m
A/µ
m2 )
Vce
(V)
Ajbe
=0.6 x 7 µm2 Ib step
= 0.4 mA0.5 um X 7 um emitter junction0.5 um base contact width
~6.8 V low-currentBVCEO
Miguel Urteaga
Deep Submicron Bipolar Transistors for 140-220 GHz Amplification
0
10
20
30
40
10 100 1000
Tran
sist
or G
ains
, dB
Frequency, GHz
U
UMSG/MAG
H21
unbounded U
raw 0.3 µm transistor: high power gain @ 200 GHz
-4
-2
0
2
4
6
8
140 150 160 170 180 190 200 210 220
S21
, dB
Frequency, GHz
1-transistor amplifier: 6.3dB @ 175 GHz
-30
-20
-10
0
10
140 150 160 170 180 190 200 210 220
gain
, dB
Frequency (GHz)
3-transistor amplifier: 8 dB @ 195 GHz
M. Urteaga
V. Paidi, Z. Griffith, M. Dahlström
Mesa DHBT Power Amplifiers for 100-200 GHz Communications
7 dB gain measured @ 175 GHz
7 dB small-signal gain at 175 GHz, 7.5 mW output power
175 GHz Power Amplifier Demonstrated in a 300 GHz fmax process460 GHz fmax DHBTs available now, 600 GHz should be feasible soon
→ feasibility of power amplifiers to 350 GHz→ Ultra high frequency communications
2 fingers x 0.8 um x 12 um, ~250 GHz fτ, 300 GHz fmax , Vbr ~ 7V, ~ 3 mA/um2 current densityV. Paidi, Z. Griffith, M. Dahlström
V. Paidi, Z. Griffith, M. Dahlström
172 GHz Common-base Power Amplifier
RLVin Vout
Input Matching Network Output Loadline Match
8.3 dBm saturated output power 4.5-dB associated power gain at 172 GHz DC bias: Ic=47 mA, Vcb=2.1V.
-10
-5
0
5
10
15
0
1
2
3
4
5
-15 -10 -5 0 5
Gai
n, d
B, O
utpu
t Pow
er, d
Bm
PAE (%
)
Input Power, dBm
Gain
Output Power
PAE
-10
-5
0
5
10
140 150 160 170 180 190
S 21,S
11,S
22, d
B
Frequency, GHz
S11
S22
S21
V. Paidi, Z. Griffith, M. Dahlström
176 GHz Two-stage amplifier
7-dB gain at 176 GHz8.1 dBm output power, 6.3 dB power gain at 176 GHz9.1 dBm saturated output power at 176 GHz
0
2
4
6
8
10
0
1
2
3
4
5
-6 -4 -2 0 2 4 6 8 10
Gai
n, d
B, O
utpu
t Pow
er ,
dBm
PAE (%
)
Input Power, dBm
PAEGain
Output Power
RLVoutVin
50 Ohms 50 Ohms
InputMatchingNetwork
OutputLoadlineMatchingNetwork
InputMatchingNetwork
OutputLoadlineMatchingNetwork
λ/4 at f0
λ/4 at f0
Veb,bias
Vcb,bias
-10
-5
0
5
10
15
140 150 160 170 180 190 200
S 21, S
11, S
22 d
B
Frequency, GHz
S21
S11
S22
V. Paidi, Z. Griffith, M. Dahlström
100 mW at 200 GHz should be feasible
Simulations....fabricated IC was mis-tuned2 x 2 x 0.8 µm x 12 µm, AE=40 µm2
-10
-5
0
5
10
15
150 160 170 180 190 200 210 220
S21
, S11
, S22
dB
frequency, GHz
S21
S11
S22
0
5
10
15
20
0 2 4 6 8 10 12 14
Out
put P
ower
, dBm
, Gai
n, d
B
Input Power, dBm
Pout
Gain8.7-dB gain at 180 GHz
45 GHz 3-dB bandwidth
6 fingers 0.8 µm × 12 µm
19.5-dBm Saturated output power
HBT design for low gate delay
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highat low for low very bemust 22
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withcorrelated not well Delay delay; totalof 25%-10y typicall)(
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resistance base the throughcharge stored
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resistance base the throughcharging ecapacitanc on Depleti
swing logic the throughcharging ecapacitanc on Depleti
:by ermined Delay DetGate
bb
depletion,bb
depletion,
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clock clock clock clock
inin
out
out
Why isn't base+collector transit time so important for logic?
1:10~ is which ,/
of ratioby reduced ecapacitancdiffusion signal-Large
)(
)(Q :Operation Signal-LargeUnder
swing. voltage/over only ...active
/)(
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base
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+=
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+=
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LOGIC
LOGICLOGIC
dccb
Ccb
beCcb
bebe
Ccb
Ccb
ττττ
δττ
δττ
δττδ
Vin
Vout
Vin(t)
t
t
Vout(t)
diffusion+ depletioncapacitance
only depletioncapacitance
Depletion capacitances present over full voltage swing, no large-signal reduction
Scaling Laws, Collector Current Density, Ccb charging time
InGaAs base GaAsSb base
Collector Depletion Layer Collapse
Collector Field Collapse (Kirk Effect))2/)(/( 2 εφ cdsatcb TqNvJV −+>+
)2/)(( 2min, εφ cTqNV dcb +>+
0 mA/µm2
10 mA/µm2
0 mA/µm2
10 mA/µm22
min,max /)2(2 ccbcbsat TVVvJ φε ++=⇒
cecbbe VVV ≅+≅ )( hence , that Note φφ
( )( ) ( )
+
∆=∆=∆
sat
C
CECE
LOGICCLOGICcCLOGICcb v
TAA
VVVIVTAIVC
2/
emitter
collector
min,collectorε
Collector capacitance charging time scales linearly with collector thickness if J = Jmax
Key HBT Scaling Limit Emitter Resistance
.1 where; 2max,
emitter
logiccollectorlogicce
eCCcb /TJ
AJV
TεA
IV
C ∝∆
=∆
Io
RL
Rex
Noise margin
2kT/q+IoRex
Vin
Vout
∆Vlogic=IoRL
∆Vlogic
Largest delay is charging Ccb
Je ≅ 10 mA/µm2 needed for 200 GHz clock rate
Voltage drop of emitter resistance becomes excessiveRexIc = ρexJe = (15 Ω⋅µm2) ⋅ (10 mA/µm2) = 150 mV
considerable fraction of ∆Vlogic ≅ 300 mVDegrades logic noise margin
ECL delay not well correlated with fτ or fmax
ρex ≤ 7 Ω⋅µm2 needed for 200 GHz clock rate
UCSB / RSC / GCS 152 GHz Static Frequency Dividers
-40
-30
-20
-10
0
10
20
0 20 40 60 80 100 120 140 160
Min
imum
inpu
t pow
er (d
Bm
)
frequency (GHz)
0.860.740.990.59psec / VCcb/Ic
3583010.6
4.40.5 x 4.5
clock current steering
GHzGHz
V
mA/µm2
µm2
units
280268358fmax
280260301fτ
1.700.6Vcb
4.44.46.9currentdensity
0.5 x 5.50.5 x 4.50.5 x 3.5size
clock emitter
followers
data emitter
followers
data current steering
IC design: Zach Griffith, UCSBHBT design: RSC / UCSB / GCSIC Process / Fabrication: GCSTest: UCSB / RSC / Mayo
UCSB 142 GHz Master-Slave Latches (Static Frequency Dividers)Z. Griffith, M. Dahlström
Static 2:1 divider:Standard digital benchmark.Master-slave latch with inverting feedback.Performance comparison between digital technologies
UCSB technology 2004:InP mesa HBT technology12-mask process600 nm emitter width142 GHz maximum clock.
Implications:160 Gb/s fiber ICs
100 + Gb/s serial links
Target is 260 GHz clock rate at 300 nm scaling generation
-90
-80
-70
-60
-50
-40
-30
-20
-10
0.0 15.0 30.0 45.0 60.0 75.0
Out
put P
ower
(dB
m)
frequency (GHz)
+V +V +V
0V
kz
Microstrip mode
+V
0VCPW mode
0V 0V
CPW has parasitic modes, coupling from poor ground plane integrity
-V 0V +V
0VSlot modeSubstrate modes
ground straps suppress slot mode, but multiple ground breaks in complex ICs produce ground return inductanceground vias suppress microstrip mode, wafer thinning suppresses substrate modes
kz
Microstrip has high via inductance, has mode coupling unless substrate is thin.
We prefer (credit to NTT) thin-film microstrip wiring, inverted is best for complex ICs
M. Urteaga, Z. Griffith, S. Krishnan
Parasitic Reduction for Improved InP HBT Bandwidth
SiO2 SiO2
P base
N+ subcollector
N-
wide emitter contact: low resistancenarrow emitter junction: scaling (low Rbb/Ae)
At a given scaling generation, intelligent choice of device geometry reduces extrinsic parasitics
thick extrinsic base : low resistancethin intrinsic base: low transit time
wide base contacts: low resistancenarrow collector junction: low capacitance
⋅=
Wr
LR bulk
bulk2ln2
πρ
LrR c
contact πρ2
=
extrinsicbase
extrinsicemitter
N+ subcollector
extrinsicbase
+=
bulk
contactbulk
WLR
ρρ
πρ ln34.12
mintotal,
Much more fully developed in Si…
These are planar approximations toradial contacts:
→ greatly reduced access resistance
Low Parasitic, Scalable HBT processes
Polycrystalline InAs extrinsicemitter regrowth
Collector pedestal implant
Emitter dielectricsidewall process
N- collector
N+ subcollector
S.I. substrate
collectorpedestal
high-yield (10,000 transistor)alternative to emitter-base definition by mesa etch
RSC/GCS/UCSBVitesse similar to earlier Japanese GaAs processes
SiGe-like emitter-base processpolycrystalline InAs regrowthwide emitter contact → low resistancethick extrinsic base → low resistance
Independent control of base contact & collector junction widths → reduced capacitance
15
20
25
30
35
0 1 2 3 4 5 6 7 8C
cb (f
F)J
e (mA/µm2)
Aje = 0.5 x 7 µm2
Vcb
= 0.3 V2.1 µm collector pedestal
1.2 µm collector pedestal
1.0 µm collector pedestal
0
5
10
15
20
25
30
1 10 100 1000
IC=9.72 mA
VCE
=1.2 V
U, M
SG/M
AG
, h21
(dB)
, K
Frequency (GHz)
U
h21MAG/MSG
K
fT=280 GHzf
MAX=148GHz
Emitter junction area: 0.3 x 4 µm2
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
0.00 0.50 1.00 1.50 2.00 2.50
Vce (V)
Ic (m
A)
Yingda Dong, Navin PartharasaryRSC, GCS, UCSB teams Dennis Scott, Yun Wei
Early (2003) S3 HBT: RF Performance Urteaga, Rodwell , Pierson, Rowell , Brar, Nguyen, Nguyen: UCSB, RSC, GCS
Base contact: 0.5 µm on each side of emitterfmax limited by high base contact resistance (since addressed)High current operation and low Ccb
0.401332666.90.6 x 6 µm2
0.501272446.70.6 x 3 µm2
0.661462576.80.4 x 6 µm2
0.821422396.00.4 x 3 µm2
Ccb/IEps/V
Fmax
GHzFt
GHzJE
mA/µm2
Emitter Junction
Dimensions
Process, now fully at RSC and GCS, now produces 300 GHz ft/fmax transistors at 500 nm & 250 nm scaling
Collector Pedestal Implant for InP HBTs Y. Dong
Pedestal can be integrated into: sidewall or mesa emitter processes, emitter regrowth process
0 1 2 3 4 5 6 7 815
20
25
30
35
AE=0.7 x 8 um2
1.0 um pedestal
1.2um pedestal
2.1um pedestal
CC
B (fF
)
JE (mA / um2)
Good DC characteristics, high power density,increased breakdown: 5.4 V with a 90 nm thick collector
N++ InP subcollector
Collector contact
N+ pedestalBase contact
Emitter contact
SI substrate
N- collector UID InP
0
2
4
6
8
10
0 1 2 3 4 5 6
J e (mA
/µm
2 )
Vce
(V)
Aje = 0.4 x 7 µm2
Ib step = 500 µA
HBT with pedestalHBT without pedestal
20 mW/µm2 device failure
large collector capacitance reductionsignificant increase in breakdown2(1013) V-sec Johnson Figure-of-Merit transistors have low leakage, good DC characteristics
~2:1 reduction in collector base capacitance
Monocrystalline Emitter Regrowth Christoph Kadow
InGaAs extrinsic baseetch stop layer
InGaAs intrinsic baseBC gradecollector
N+ sub collector
S.I. InP substrate
pedestal
InAlAs current-block layerInP anti-oxidation layer
regrown emitter
emitter contact
base contact
cTPW
b,contW
eW
Tp
ebWe,contW
swW
underW
Regrown base-emitter junction
Emitter width defined by emitter window
Large-area, low-resistance emitter contact
Low-resistance extrinsic base
200 nm Scaling Generation: Target 230 GHz clock rate
InGaAs extrinsic baseetch stop layer
InGaAs intrinsic baseBC gradecollector
N+ sub collector
S.I. InP substrate
pedestal
InAlAs current-block layerInP anti-oxidation layer
regrown emitter
emitter contact
base contact
cTPW
b,contW
eW
Tp
ebWe,contW
swW
underW
300 nm50 nm
600 nm
100nm400nm
100nm300nm
200 nm
/square) (145 base extrinsic cm/10 nm, 001base intrinsic cm/102 nm, 30
320
319
Ω
⋅
buscollector ondelay wiringps 3.0mmA/ 5.9
m- 20
m- 5.7
m- 15
2
2,
2
2,
µ
µρ
µ
µρ
=
Ω=
Ω=⇒
Ω=
e
basec
Eex
emitterc
J
AR
V 4GHz 606 GHz 495
GHz 232
,
max
(divider)clock
≅==
≅
ceobrVff
f
τ
transistors: InP HEMT
Sub-mm-wave Transistors
InP HEMTs: receiver low noise amplifiers
Today's InP HEMTs are nearly ready for sensitive 300 GHz receiverstechnology demonstration devices have 600 GHz ft → potential for low 4.5 dB noise figure to 300 GHzsome improvement in fmax is desirable for the highest-ft devices
InP HEMTs are ready for improvement20-30 nm gate lengths. Thinner gate-channel barriers. Pd-based contact technologygoal: 800 GHz ft and fmax for low noise and high gain up to 400 GHz
→ Feasibility of sensitive receivers to 400 GHz
0.1 1 10 100 10000
10
20
30
40
50
60
MSG
|h21|2
Ug
fmax = 500 GHz
fT = 395 GHzLg = 60 nm
Gai
n (d
B)
Frequency (GHz)
Keisuke ShinoharaCRL, Japan
30 nm footprint
Gate
HEMT Noise Figure
sR
skTR4
)(4 ig RRkT +
ig RR +
gsC
gqI2
gsmVg
mgkT /4 Γ
dsG
sfrequencielow at degrades noise,input 2 induces leakage Gate
/1)( that ensure 1/g becuase low for bias , increased
through Improve
)(2)(1
:negligible iscurrent leakage gate If
min
m
min
2
min
FqI
gRRRf
FffRRRg
ffRRRgF
g
mgsi
igsmigsm
<+≈Γ
⋅Γ+++
⋅Γ+++≈
τ
ττ
HEMT Noise Figure
20 40 60 80 100 120 140 160 1800 200
1
2
3
4
5
6
7
0
8
Frequency, GHz
Min
imu
m N
ois
e F
igu
re, d
B
GHz 500=τf
GHz 200=τf
A ~2.5:1 fτ /fsignal ratio is sufficient for 3 dB noise figure.
Low-noise 100-300 GHz preamplification is a key application for 1-THz-fτ HEMTs
10 20 30 40 50 60 70 80 900 100
0.5
1.0
1.5
2.0
2.5
3.0
0.0
3.5
Frequency, GHz
Min
imum
Noi
se F
igur
e, d
B
GHz 300=τf
leakage gateA 10...4,2,0 µ
transistors: Silicon !
Si / SiGe Bipolar & BiCMOS processes
high digital speed process
high fτ processhigh digital speed process
high fτ process
IBM has reported a 96 GHz static divider in their 130 nm processthis version had 210 GHz fτ , 270 GHz fmax
Device & IC results will undoubtedly continue to progress
SOI CMOS is a mm-wave technology
IBM 120 nm SOI CMOS has 150 GHz fmax
IBM TWA result indicates that MOSFET MAG/MSG is > 8 dB at 90 GHz
A 4-91 GHz distributed amplifier in a standard 0.12 um SOI CMOS microprocessor technologyPlouchart, J.-O.; Jonghae Kim; Zamdmer, N.; Liang-Hung Lu; Sherony, M.; Yue Tan; Groves, R.; Trzcinski, R.; Talbi, M.; Ray, A.; Wagner, L.;Custom Integrated Circuits Conference, 21-24 Sept. 2003
A 4-91 GHz distributed amplifier in a standard 0.12 um SOI CMOS microprocessor technologyPlouchart, J.-O.; Jonghae Kim; Zamdmer, N.; Liang-Hung Lu; Sherony, M.; Yue Tan; Groves, R.; Trzcinski, R.; Talbi, M.; Ray, A.; Wagner, L.;Custom Integrated Circuits Conference, 21-24 Sept. 2003
IBM 90 nm SOI CMOS has 200 GHz fmax
...the process used for the MAC G5 CPU
mm-wave systems to 150 GHz will be very inexpensive...
Schottky diodes
Scaled Schottky mixer diodes
Schottky mixer diodes:transit time, RC limits
This device:JPL / UCSB (late 90's)100 nm x 0.5 um T-gate150 Å depletion depth~15 THz RC & transit timecutoff frequencies
T-gate region
e-beamair-bridge
R. P. Smith, S. Martin, U. Bhattacharya
Scaling contact to ~10 nm should further increase cutoff frequencies
InGaAs/InP Schottky: further increased bandwidth or HBT/HEMT integration
Applications of Schottky Diodes
Transmitter- signal generation
Frequencydoubler
Frequencydoubler
100 GHz400 GHz50 mW ?
200 GHz100 mW
Frequencydoubler
800 GHz10 mW ?
Receiver- signal downconversion
How to integrate sub-mm-wave transistors with THz Schottky diodes
emitterbase
collector
HBT
THzSchottky Diode
substrate
InP subcollector
October 13, 2004
A Smattering of Existing Device Technologies at JPLA Smattering of Existing Device Technologies at JPL
THz Devices for new ApplicationsTHz Downconverters THz Sources
Red Blood Cell
2500 GHz Nanoconverter Diode (JPL)180 GHz MMIC Power Amplifier Chip (JPL/HRL)THz HEB Mixer Circuit (JPL)
1200 GHz Silicon MEMS Nanoklystron Cavity (JPL)200 GHz High Power Multiplier Chip (JPL)THz SIS Mixer Circuit (Caltech/JPL)
Broadband THz Photomixer Chip (JPL)2.5 THz Schottky Diode Mixer Chip (JPL) THz Transistor Prototype (JPL/UCSB)
October 13, 2004
SubmmSubmm--wave Mixers for MLS, MIRO & Cloud Icewave Mixers for MLS, MIRO & Cloud Ice
Input Horn
Input E-plane TunerWaveguide
IF Output
LO E-planeTuner
Signal Backshort
Rectangular-to-CircularWaveguide Transformer
LO Input
Diodes
DC return
Mixer
TriplerDual-Gunn
Feed Horn
PhaseLock Port
MLS 640 GHz Single Pixel Heterodyne Receiver Front End 5cm
MEASURED JPL 640 GHZ PLANAR-DIODE MIXER PERFORMANCE VS. IF FREQUENCYMLS 640 GHz Protoflight Receiver JPL Subharmonic mixer block (bottom) JPL Antiparallel-pair planar Schottky diodes
Best Fundamental Mixer Performance at 640 GHz Flight Receiver Performance: Subharmonic Mixer
2 3 4 5 7 8 9 10 11
1416
3492
16492 3
4 7 8 9 10
11
1213
1415
16
10.54
1000
2000
3000
4000
5000
1 3 5 7 9 11 13 15 17
IF Frequency (GHz)
DSB
Noi
se T
emp.
(K)
8
9
10
11
12
13
14
DSB Loss (dB)
NoiseLoss
Sponsors: NASA Code R/Y Work By: J. Oswald, R. Dengler, J. Velebir, I. Mehdi, P. Smith, S. Martin, A. Pease, H. Javadi R. LinR. Tsang, P. Siegel – JPL
EOS-MLS 640 GHz DSB Receiver Noise Performance640EM01 5/11/00 Entry #869 UM107x3 source, LO=321.45
0
2000
4000
6000
8000
10000
12000
14000
16000
6 8 10 12 14 16 18
IF Frequency (GHz)
Rec
eive
r N
oise
Te
mpe
ratu
re (K
)
-31
-30.5
-30
-29.5
-29
-28.5
-28
-27.5
-27
Conversion Loss (dB)
Receiver Noise Temperature (K) Conversion Loss (dB)
RF Freq.: 642 GHz. LO Pwr: 0.5 mW: Gunn/X2X3 multiplier RF Freq.: 642 GHz. LO Pwr: 2 mW: Gunn/X3 multiplier
October 13, 2004
Semiconductor Detectors for Atmospheric StudiesSemiconductor Detectors for Atmospheric Studies
Input Noise
S. Weinreb& UMass
Planar Schottky Mixers to 2.5 THz
Siegel et.al. JPL
12 12
11 11
10 10
9 9
8 8
7 7
6 6
5 5
Noi
se T
empe
ratu
re (x
100
0 K
, DSB
)
1.61.41.21.00.80.60.40.20.0
Diode Bias Current (mA)
JPL OH-38 mixer @ 2.5 THz4/3/00, room temperature12.8 GHz IF, - 3 mW LOminimum 6500 K, DSB
6500 K, DSB@ 2.5 THz
MMIC Arrays for 100 - 240 GHz
Samoska et.al. JPL/NGC
October 13, 2004
2.5 THz MOMED Mixer/Receiver for EOS2.5 THz MOMED Mixer/Receiver for EOS--MLSMLS
JPL 2.5 THz MOMED mixer chip in waveguide mountTwo channel receiver for 2.5 THz flight application
-30
-20
-10
0
10
20
30
Elev
atio
n, D
egre
es
-30 -20 -10 0 10 20 30Azimuth, Degrees
-5
-10
-15 -20
-25
-30
-35
Receiver performance vs. LO Power at 2.5 THzBeam pattern of 2.5 THz dual mode horn
12 12
11 11
10 10
9 9
8 8
7 7
6 6
5 5
Noi
se T
emp
(x 1
000
K, D
SB)
1.61.41.21.00.80.60.40.20.0
Current (mA)
JPL OH-38 mixer @ 2.5 THz4/3/00wafer 039E-BL, OH-2 blockR4C4, reticle 7,9150 ž xformer, 0.75 mil bshrt< 3 mW LO coupled
8.4 GHz IF 12.8 GHz IF 20.4 GHz IF
Sponsors:NASA Code R/Y
Work By:M. Gaidis, H. Pickett, D. Harding, R. Tsang,T. Crawford, P. Siegel
October 13, 2004
Multiplier Chains Driven by Power AmplifiersMultiplier Chains Driven by Power AmplifiersRecent Amp/Multiplier Performance
• Power Amps: 400mW at 94GHz; 200mW 90-105 GHz; 40mW 65-145GHz; 15mW with 85-90 GHz VCO, 20mW 145-170 GHz (HRL)
• Multipliers: >20% efficiency & 9mW from 200-400 GHz (doubler);
• 2 mW @ 800 GHz (double-doubler)• >250µW @ 1200 GHz (cooled tripler)• >80 µW @ 1600 GHz (120K chain)
• 25 µW @ 1900 GHz (tripler)!
Drop-In Substrateless 200 GHz Balanced Doubler Circuit in waveguide split-block
800 GHz balanced doubler with 1 milliwatt output power
SEM photograph of the anode area for a balanced 1500 GHz doubler chip
Work by SWAT LO Team: Imran Mehdi, Frank Maiwald, Alain Maestrini, Erich Schlecht, Goutam Chattopadhyay, Dave Pukala, Ray Tsang, John Gill, Suzi Martin, William Chun, Brad Finamore, Lorene Samoska and HRL (VCO), NGC (power amps)
ps-pulse technologies
Scaled Schottky diodes ICs for near-THz Instruments
GaAs Nonlinear Transmission Line ICs:0.5 ps pulse generators & DC-700 GHz sampling circuits
2
4
6
8
10
Cut
off F
requ
ency
, TH
z
0.5 µm design rules
1 µm design rules
2 µm design rules
underlying Semiconductor Technology:scaled THz Schottky varactor diodes
S. A
llen
00 1 2 3 4 5 6
Surface doping, N0 , x 1017/cm3
1st monolithic NLTLs: Rodwell, Madden, & Bloom, 1986Stanford, UCSB, Hewlett-Packard ~1985-1995
Instrumentation, not communication technology: harmonic conversion loss ~1/n2, noise figure of sampler (harmonic mixer) > n:1
Shock-wave Pulse Compression, Sampling ICs
THzps 4.1, •≈diodecfall fT
-4.0
-3.0
-2.0
-1.0
0.0
1.0
NLT
L ou
tput
, m
easu
red
by s
ampl
ing
circ
uit (
Vol
ts)
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
0%
100%
Time (ps)
0.68 ps measured10%-90% falltime;0.48 ps deconvolved NLTL falltime,725 GHz deconvolved sampler bandwidth
M. Case S. Allen
NLTL-Gated Sampling ICs
DC-100 GHz NLTL-samplerfrom Picosecond Pulse Labs
Instruments from Agilent
O. Wohlgemuth
NLTL-based mm-wave spectrometer system Y. Konishi, 1993
Difficulties with Time-Domain Measurements
time frequency
n)descriptio domain (time on) / timeoff (time n)descriptio domain (frequency conversion oforder harmonic
rsion DownconveSampling of figure Noise
1/Nleast at harmonic Nth toloss Conversion onics Many HarmAmong tributed Power DisSignal :tionMultiplicaFrequency
≥≥
FF
Time-domain sampling techniques offer simplified hardware but have high conversion loss and noise figure.This applies to BOTH NLTL-based sampling circuits and laser-based ps/fs optoelectronic sampling techniques (photoconductive sampling, electrooptic sampling, etc.)
Consider the #s with Photoconductive Sampling
time frequency
Signal Generation by Photoconductive Gap0.1 ps pulse width100 MHz pulse repetition rate→ strong harmonics from 100 MHz to ~1.6 THzbut (individual harmonic power)/(total power) = 10-4
Signal Detection by Photoconductive Sampling0.1 ps pulse width100 MHz pulse repetition rateNoise figure > Toff/Ton = 10 ns/0.1 ps = 104 = 40 dBNoise temperature = 3,000,000 Kelvin
other technologies
October 13, 2004
Continuously-Tunable THz-Photomixing SourcesElliot Brown & Coworkers, UCSBTechnical Approach
• Based on combination of ultrafast photoconductors, low capacitance interdigital electrodes, and THz planar balanced antennas.
• Utilizes semiconductor laser technology to create two, tunable optical tones separated by ~1 THz
• Recent highlights: (1) ErAs:GaAs cw source with Pout = 12 µW @ 100 GHz, 1 µW @ 1 THz; (2) ErAs:InGaAs photomixer working at λpump = 1.55 µm.
• Useful Applications: (1) THz spectrometry, (2) widely tunable local oscillators, (3) scalar network analyzer
Device Structure
Six 0.2-µm wide Interdigital Electrodes
Ultrafast photomixer in THz Integrated CircuitSelf-- complementary spiral antenna
Ultrafast photomixer in THz Integrated Circuit-
0.00001
0.0001
0.001
0.01
0 500 1000 1500 2000Frequency [GHz]
Pow
er [A
rb U
nits
]
Noise floor of room temperature detector
Experiment
Model power spectrum withRC time only (= 0.11 ps)
Model power spectrum w/RC and lifetime ( = 0.38 ps)
Ave
rage
Pow
er [m
W]
Measured and Modeled THz Photomixer Power Spectrum
0.00001
0.0001
0.001
0.01
0 500 1000 1500 2000Frequency [GHz]
Pow
er [A
rb U
nits
]
Noise floor of room temperature detector
Experiment
Model power spectrum withRC time only (= 0.11 ps)
Model power spectrum w/RC and lifetime ( = 0.38 ps)
Ave
rage
Pow
er [m
W]
0.00001
0.0001
0.001
0.01
0 500 1000 1500 2000Frequency [GHz]
Pow
er [A
rb U
nits
]
Noise floor of room temperature detector
Experiment
Model power spectrum withRC time only (= 0.11 ps)
Model power spectrum w/RC and lifetime ( = 0.38 ps)
Ave
rage
Pow
er [m
W]
Measured and Modeled THz Photomixer Power Spectrum
EmbeddedErAs IslandLayers
Gold interdigital electrodes
Silicon nitride film
AlAs/AlGaAs
DielectricMirror
Semi-insulating
GaAssubstrate
1.09 µm
-
ν1
+ ν2
+ - +
h1
+ ν2
h
THz Output Beam
12repeatunits
0.31 µm
EmbeddedErAs IslandLayers
Gold interdigital electrodes
Silicon nitride film
AlAs/AlGaAs
DielectricMirror
Semi-insulating
GaAssubstrate
1.09 µm
-
ν1
+ ν2
+ - +
h1
+ ν2
h
THz Output Beam
12repeatunits
0.31 µm
Scaling Schottky-Resonant-Tunnel-Diodes for THz bandwidths
fmax ∼ (2π)−1(RnC)−1/ 4 (RsC)−1/ 4 (τqw )−1/ 2
Lqw = −τqw Rn
Rs
− Rn
C
Emitter WellSpacechargeregion
Schottkymetal
RTD Scaling:reduce contact width: 0.1 umreduce depletion depth: 300 Åincrease J: 5*105 A/cm2
use zero-resistance top Schottky contact→ estimated 2 THz maximum frequency of oscillationUCSB/JPL, 1996
M. Reddy, S. Allen
64-element Schottky-RTD oscillator at 650 GHz
M. Reddy et al (UCSB/JPL), IEEE EDL, 1997
Low power: 20 uW from 64-element 200 GHz array...extremely low efficiencyRTDs are a single-application device with limited general utility
THzTHz--regime foldedregime folded--waveguideTWTs:waveguideTWTs:sources and amplifiers above 300 GHzsources and amplifiers above 300 GHz
Current THz DevicesCurrent THz Devices
2p ba
e-beam
Folded Waveguide (FWG) TWTFolded Waveguide (FWG) TWTThe wave velocity is slowed by the FWG, enabling TWT gain. The planar structure of the FWG makes it ideal for
microfabrication at THz-regime dimensions.
DRIEDRIEA FWG trench is etched in silicon with a DRIE tool, and then gold-plated. Two bonded trenches form a FWG [close-up view compared to a 50 um diameter human hair].
SEM micrograph of a 400 GHz FWG TWT circuit mold (negative) fabricated in SU-8 using UV lithography. The serpentine wall height is ~ 250 µm and the “pitch” (distance between bends) is ~ 100 µm. This “LIGA” method does not require an xray source.
instruments
High-Frequency Measurements: Network Analysis
Circuit frequency response
No extrapolation
Acceptable errors (roughly)~ 0.25 dB in S2130 dB directivity
0
2
4
6
8
10
140 150 160 170 180 190 200S
21 (d
B)
Frequency (GHz)
Device characterization
S-parameters convertedto Yij and Zij
Frequency variation allowsdevice parameter extraction.
Calibration must be very precise
S22
S12x10S21/10
S11
Ccb,x = 7.1 fF
Rbc = 25 kΩ
Ccb,i = 2.3 fFRbb = 23 Ω
Cje
Cdiff rbeVbe
rce==250k Ω
Cpoly= 1.5 fFRex=4.23 Ω Cout=1 fF
gmVbeexp[-jω(0.23ps)]
rbe=112.5 Ω, Cje = 47.4 fFCdiff = gm τf , τf = 0.8866 ps
gm = Ic/VT= 0.239
Base
Emitter
Collector
High Frequency Instruments
Integrated circuit development requires precision Instrumentsdevice model extraction: vector network analyzers and microwave wafer probes
Classical mm-wave physics instruments are not adequatemeasure only power & wavelengthno on-wafer access
Commercial ultra-high-frequency instruments are now available Oleson microwave labs, GGB industries, Cascade Microtech
Oleson network analyzer extensions330 GHz available, higher bands in development
GGB Wafer Probes330 GHz available, 500 GHz feasible
Oleson / Agilent / GGB 140-220 GHz System at UCSB
170-180 GHz Saturated Power Measurements at JPL
Powermeter
Frequencydoubler
W-band PA
DUT
BWOPowerSource
Variableattenuator
W-bandPoweramplifier
W-bandPowermeter
SchottkyDoubler
WR-5Picoprobe
Calorimeter
Probe loss 170-180 GHz band ~ 2.6 dBWR-5Picoprobe
DUT
L. Samoska, A. Fung
100-500 GHz ElectronicsFiber Transmission: 40/80/160 Gb/s
Wireless Transmission: 100 Gb/s km-range outdoor fixed wireless10 Gb/s km-range outdoor mobile wireless1-10 Gb/s indoor wireless networks
250 GHz imaging for foul-weather aviation
Military Mixed-Signal ICs microwave ADCs/DACs for radar etc
Enabling Technology: diode and transistor integrated circuits
Schottky diodes: highest frequencies, highest cost, in astronomy & military applications
InP HEMT & HBTs: high frequencies, power amplifiers, low-noise amplifiers
Silicon: consumer and office infrastructure applications to about 150 GHz. Perhaps more
Supporting Data(not to show)
Atmospheric Attenuation Data: Variabilities
Horizontal Attenuation Depends on Altitude higher altitudes have less rain/fog/humidity, lower gas pressures
Horizontal Attenuation Depends on Weather variables are H20 concentrations
-- in gaseous phase (humidity)-- rain; weather varies with time & with location-- snow; generally not dominant-- fog & clouds
What controls worst-case propagation attenuation?absorbtion lines dominate only if frequency tuned close to major lines. heavy rain causes largest severe-weather attenuation below ~500 GHzfog causes largest severe-weather attenuation above ~500 GHz
Data should be verified, treated with cautionattenuation varies tremendously with weathersome data in papers and on applications charts is quite wrong*.
*Corrections to published curves for atmospheric attenuation in the 10 to 1000 GHz region: Wiltse, J.C.;Antennas and Propagation Society International Symposium, 1997. IEEE., 1997 Digest , Volume: 4 , 13-18 July 1997
Rain: How often and how hard ?
100 mm/hr (4 inch/hr) rain occurs < 0.01 % of the timein most locations in Japan
Rare events with ultra-high rain ? data: very high rain rates less probable than standard Gamma distribution→ 150 mm/hr (6"/hr) extremely unlikely
Ka-band Earth-space propagation research in JapanKarasawa, Y.; Maekawa, Y.; Proceedings of the IEEE , Volume: 85 , Issue: 6 , June 1997 Pages:821 - 84 Digital transmission characteristics on millimeter waves Manabe, T.; Yoshida, T.
;Communications, 1993. ICC 93. Geneva. Technical Program, Conference Record, IEEE International Conference on , Volume: 3 , 23-26 May 1993 Pages:1602 - 1605
Rain: what attenuation is expected ?
0.1"/hr
0.01"/hr
0.5"/hr
2"/hr
6"/hr Extreme-case attenuation is 50 dB/km any frequency from 30-1000 GHzsevere tropical deluge 150 mm/hr (6"/hr)<< 0.01 % probability in most locations
Severe-case attenuation is 20 dB/kmany frequency from 30-1000 GHzvery heavy rain (2"/hr or 50 mm/hr)occurs about 0.01% of the time
In heavy rain, >13 mm/hr (0.5"/hr): loss increases DC-30 GHzloss relatively constant 30-1000 GHz
In light rain, <2.5 mm/hr (0.1"/hr): loss increases DC-100 GHzloss relatively constant 100-1000 GHz
Plot from Olsen; data is reasonably consistent with theory and measurements from several other papers.
The aRb relation in the calculation of rain attenuationOlsen, R.; Rogers, D.; Hodge, D.; Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988] , Volume: 26 , Issue: 2 , Mar 1978 Pages:318 - 329
More than 4"/hr (100 mm/hr) rain is extremely rare
Cumulative time distribution of one-minute rainfall for Hamada (Japan), where record-breaking heavy rains hit in 1983All years except 1983
>25 mm/hr 0.1% of time>80 mm/hr 0.01% of time
1983 only>37 mm/hr 0.1% of time>120 mm/hr 0.01% of time
Ka-band Earth-space propagation research in JapanKarasawa, Y.; Maekawa, Y.; Proceedings of the IEEE , Volume: 85 , Issue: 6 , June 1997 Pages:821 - 84
Fog: what attenuation is expected ?
(heavy fog)
Categories of Foglight: 10-3 g/m3 medium: 0.05 g/m3 heavy: 1 g/m3
non-precipitating clouds: 1 g/m3
Attenuation in extreme fog less than that of rain~10 dB/km @ 200 GHz, ~26 dB/km @ 500 GHz,
mm-wave is better than optical in extreme fog fog causing ~1 dB attenuation at 245 GHzcaused > 30 dB attenuation at IR (0.85 um)
Millimeter-wave attenuation and delay rates due to frog/cloud conditionsLiebe, H.J.; Manabe, T.; Hufford, G.A.; Antennas and Propagation, IEEE Transactions on , Volume: 37 , Issue: 12 , Dec. 1989 Pages:1617 - 16
time series of recorded path attenuations in the near-infrared & at 50, 81, 140, and 245 GHz
1
Attenuation from Mountain (13,000 ft) to Sky: Very Clear Weather
No Clouds
(Mauna Kea)
Computed zenith atmospheric transmission at the CSO for 1mm precipitable H2OPlot generated using the program AT (E. Grossman 1989). From http://www.ericweisstein.com/research/thesis/node10.html
1 mm precipitable H2O, e.g. good observing conditions
Measured Terrestrial atmospheric transmission between 180 and 540 GHz From http://www.ericweisstein.com/research/thesis/node10.html
good observing conditions
relevance: radio astronomyhigh-flying aircraft to satellite
Data from Caltech Submillimeter Observatory [CSO]
Atmospheric Attenuation from Ground to Skyclear weather
additional attenuation due to rain
clouds& rain
sea level
attenuation is due to rainsignal propagates vertically through the rainattenuation depends upon cloud height (a few km) and rain rate
Final Report: A Study into the Theoretical Appraisal of the Highest Usable Frequencies. Radiocommunications Agency Contract Reference AY 4329, J. R. Norbury,C. J. Gibbins and D. N. Matheson, Radio Communications Research Unit Rutherford Appleton Laboratory Chilton, Didcot Oxfordshire OX11 0QX Tel: +44 (0) 1235 446522 Fax: +44 (0) 1235 446140 www.ofcom.org.uk/static/archive/ra/topics/ research/topics/propagation/frequency/frequency.pdf
ScintillationProbability distribution of scintillation amplitude
Scintillationrapid beam amplitude modulationarises from atmospheric refractive index fluctuationsunderlying cause is turbulent air flow
Characteristicsc.a. +/- 3 dB signal amplitude modulation (1:105 confidence)c.a. 1 Hz modulation bandwidth
Implications if no corrective action takenadds to system noisedecreases SNR and hence range
System impact minimized by receiver design1) scintillation is amplitude modulation, not additive noise2) scintillation has 1 Hz bandwidth→ equip comms receivers with fast gain correction (AGC)AGC loop bandwidth ~100 Hz→ system SNR impairment is c.a. 3 dB
Power spectral density of a strong scintillation event
Extra-high frequency line-of-sight propagation for future urban communicationsKhan, S.A.; Tawfik, A.N.; Gibbins, C.J.; Gremont, B.C.;Antennas and Propagation, IEEE Transactions on , Volume: 51 , Issue: 11 , Nov. 2003 Pages:3109 - 3121