Ultra High Frequency Electronics and Near-THz Semiconductor Devices:

Emerging TechnologiesApplications, Propagation Properties,

Mark RodwellUniversity of California, Santa Barbara rodwell@ece.ucsb.edu

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

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rA

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Ar

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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

/ /

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/1:2by reduce/metransit ti

bandwidth double toconstant timeparameters ngcontributi

2max

,

,,

,,

DvVJJ

JJD

IDWLCRqIkTR

DWLCWLR

DCRWLR

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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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AA

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CI

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f

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electron

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highat low for low very bemust 22

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total.of 80%-55% is

withcorrelated not well Delay delay; totalof 25%-10y typicall)(

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( )

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∆

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resistance base the throughcharge stored

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swing logic the throughcharging ecapacitanc on Depleti

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clock clock clock clock

inin

out

out

Why isn't base+collector transit time so important for logic?

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of ratioby reduced ecapacitancdiffusion signal-Large

)(

)(Q :Operation Signal-LargeUnder

swing. voltage/over only ...active

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+=

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I

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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

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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