IS IRONI

HIFI Mixer CDR

Band 3 and 4 Mixer UnitsRF Design and Performance

SRONB. Jackson, G. de Lange, W. Laauwen, L. de Jong

DIMES, TU DelftT. Zijlstra, M. Kroug, M. Zuidam,

N. Iosad, B. de Lange, J.R. Gao, T.M. Klapwijk

IS IRONI Outline

• requirements• historical overview• prototype mixers: design and performance

– waveguide mixer– quasi-optical mixer

• development model program– waveguide mixer re-design– measured performance

• flight model program– band 3 design– band 4 design

• conclusions and current status

IS IRONI Required Sensitivity

800 880 960 1040 1120

100

1000

Noi

se T

empe

ratu

re (

K)

Frequency (GHz)

SOAP '96 Baseline Goal

TN,DSB (mixer + IF)

IS IRONI Historical Overview

• 1998-1999– integration of Nb SIS with NbTiN tuning circuits at RUG

– pre-existing mask-set, full-height 1 THz mixer

• 1999-2000– implementation of SIS 13 (WG) and SIS 14 (QO) masks at RUG

– NbTiN/SiO2/NbTiN vs. NbTiN/SiO2/Al tuning circuits

– NbTiN/SiO2/Al → low-noise mixers up to 1 THz

• 2000-2001– redesign of WG mixer → ccn5 and SIS 19 mask designs

– re-establishment of SIS process at DIMES

• 2001-2002– implementation of SIS 19 mask at DIMES

– demonstration of broad-band, low-noise performance in band 3

• 2002– FM designs: SIS 20 (band 3) and SIS 21 (band 4)

IS IRONI WG Mixer Prototype, 1

• tunable and fixed-tuned 1 THz mixers– pre-existing full-height waveguide + diagonal horn

• single- and twin-junction designs– Nb SIS, NbTiN/SiO2/NbTiN and NbTiN/SiO2/Al tuning circuits

NbTiN/SiO2/NbTiN NbTiN/SiO2/Al

0 1 2 3 4 50

100

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400 Unpumped IF-V Hot IF-V Cold IF-V

Unpumped I-V Pumped I-V

Bias Voltage (mV)

Cur

rent

(A

)

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IF O

utput Pow

er (W)

0 1 2 3 4 50

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400 Unpumped IF-V Hot IF-V Cold IF-V

Unpumped I-V Pumped I-V

Bias Voltage (mV)

Cur

rent

(A

)

0

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IF O

utput Pow

er (W)

IS IRONI WG Mixer Prototype, 2

600 700 800 900 1000 11000.0

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1.0

Cou

plin

g (a

.u.)

Frequency (GHz)

c14 c72 a c72 b

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Cou

plin

g (a

.u.)

Frequency (GHz)

c07 a c07 b c13 c37 c71 a

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Rec

eive

r N

oise

(K

)

Frequency (GHz)

, c07, 4.5 K c13, 2.8 K, c37, 2.8 K c71, 4.5 K

NbTiN/SiO2/NbTiN NbTiN/SiO2/Al

700 750 800 850 9000

300

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900

1200

Noi

se T

empe

ratu

re (

K)

Frequency (GHz)

, c72, 14 um, c14, 14 um, c14, 49 um

IS IRONI QO Mixer Prototype

• quasi-optical lens-antenna– twin-slot, double-dipole antennas– 10 mm elliptical lens, AR-coated

• twin-junction tuning circuit– Nb SIS + NbTiN/SiO2/Al

– low receiver noise to 1 THz800 1000 1200

0.0

0.2

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1.0

Mea

sure

d C

oupl

ing

(a.u

.)

Frequency (GHz)

166 meas. 162 meas.

0 1 2 3 4 50

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Cur

rent

(A

)

Bias Voltage (mV)

unpumped I-V pumped I-V

0

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Out

put P

ower

(nW

)

unpumped IF-V cold IF-V hot IF-V

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Frequency (GHz)

Noi

se T

empe

ratu

re (

K) 166, 6 m

166, 14 m 162, 14 m 162, 49 m

IS IRONI Prototype Mixers, Conclusions

• microstrip geometry– heat-trapping, flux-trapping, and excess RF loss in NbTiN/SiO2/NbTiN

• NbTiN/SiO2/Al preferred

• NbTiN ground-plane quality– room-temp. deposition

• “low-loss” to 1 THz– improvements needed for band 4

• elevated-T or MgO substrate

• WG vs QO design– similar peak TN,mix+IF (190-230 K)

– QO: ΔFRF > 200 GHz

– WG: ΔFRF ~ 100 GHz

– WG mixer redesign needed

800 1000 1200 14000.0

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1.0

Mea

sure

d C

oupl

ing

(a.u

.)Frequency (GHz)

166 meas. 162 meas. 166, 1080 166, 970 162, 1080 162, 970

0.0

0.1

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Cal

cula

ted

Cou

plin

g

Calculated vs. MeasuredQO Mixer Response

IS IRONI DM Program, RF Design

• narrow RF bandwidth of prototype mixer due to non-optimized design• scale 650 GHz JCMT mixer design (half-height waveguide)

– RF geometry scaled to 880- and 1040-GHz

• band 3: WG = 300x75, BS = 60, channel = 75x55, substrate = 60x30

– “embedding impedance” needed for device design

• 650 GHz design modelled in HFSS by J. Kooi (CalTech)

• result scaled to 880 and 1040 GHz centre frequencies

600 800 1000 1200-100

-50

0

50

100

Impe

danc

e (

)

Frequency (GHz)

Real 1 THz Real 650 GHz Real 880 GHz Real 1040 GHz

Imag. 1 THz Imag. 650 GHz Imag. 880 GHz Imag. 1040 GHz

IS IRONI DM Program, Device Designs

• band 3– single- and twin-junctions– NbTiN/SiO2/Al tuning circuit– both designs: full RF bandwidth– twin-junction: better RF coupling

• band 4– twin-junction designs only– NbTiN/SiO2/Al tuning circuit:

• 3 designs• sensitive to NbTiN quality

– Al/SiO2/Al tuning circuit:• broad RF bandwidth• reduced coupling

880 960 1040 1120 12000.0

0.2

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1.0

Cou

plin

g

Frequency (GHz)

Fgap

= 1095 GHz F

gap = 985 GHz

Fgap

= 985 GHz all-Al tuning circuit

720 800 880 960 10400.0

0.2

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1.0

Cou

plin

g

Frequency (GHz)

twin-junction single-junction

IS IRONI DM Program, Results 1

• band 3 twin-junctions– strong, broad-band response

• RF bandwidth > 200 GHz

• Fcentre ~ 900 GHz

• Fcut-off ~ 1 THz

– DM = device c56

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Cou

plin

g (a

.u.)

Frequency (GHz)

A68 A67

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1.0

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3.0

Cou

plin

g (a

.u.)

Frequency (GHz)

A74 A73 A72

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1.0

2.0

3.0

4.0

Cou

plin

g (a

.u.)

Frequency (GHz)

C56 C65 C68

IS IRONI DM Program, Results 2

• b3 twin-junction, c56: TN,mix+IF ~ 230-250 K (IF = 4-8 GHz, Tbath = 2.5 K)

800 850 900 9500

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se T

empe

ratu

re (

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Frequency (GHz)

bs=55, meas. bs=55, corr. bs=14, meas. bs=14, corr

825 850 875 900 925 9500

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se T

empe

ratu

re (

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Frequency (GHz)

4.5, bs=15, meas. 4.5, bs=15, corr.

800 850 900 9500

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1200N

oise

Tem

pera

ture

(K

)

Frequency (GHz)

2.5, bs=12, meas. 2.5, bs=12, corr. 2.5, bs=12/55, meas. 2.5, bs=12/55, corr.

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se T

empe

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re (

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Frequency (GHz)

4.5, bs=6/55, meas. 4.5, bs=6/55, corr. 2.5, bs=6, meas. 2.5, bs=6, corr.

A68A67

C56(DM)

C65

IS IRONI

800 850 900 9500

300

600

900

1200

Noi

se T

empe

ratu

re (

K)

Frequency (GHz)

4.5 K, meas. 4.5 K, corr. 2.5 K, meas. 2.5 K, corr.

DM Program, Results 3

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0.5

1.0

1.5

Cou

plin

g (a

.u.)

Frequency (GHz)

B53 B67

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1.0C

oupl

ing

(a.u

.)

Frequency (GHz)

C31

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Noi

se T

empe

ratu

re (

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Frequency (GHz)

4.5 K, meas. 4.5 K, corr.

B67C31

Band 3 Single-Junction Band 4, NbTiN/SiO2/Al

IS IRONI DM Program, Conclusions

• waveguide mixer redesign– half-height 880 and 1040 GHz mixers based on 650 GHz JCMT mixer– 880 GHz twin-junction → low-noise performance covering band 3– band 4 performance limited by NbTiN quality

• comparison with prototype QO mixer– DM WG:

• TN,mix+IF ~ 230-250 K over 4-8 GHz IF (TN,IF ~ 10 K)– QO:

• TN,mix+IF = 190-210 K at 850-980 GHz at 1.5 GHz IF (TN,IF ~ 4 K)• extra noise for 4-8 GHz IF ~ 30-35 K (Gmix ~ - 8-9 dB)

• other– low success rate for device mounting

• very low effective device yield• need to increase device size for FM, if possible

IS IRONI FM Program, Band 3 Design

• modified DM design → enlarged substrate and substrate channel• channel = 90x60, substrate = 75x35 (vs. 60x30), BS = 50

– resulting embedding impedance shifted slightly vs. DM design

• mounting using Al2O3 carrier intrinsically suspends device– sensitivity of “embedding” to air gap reduced by intentional suspension

• channel = 90x87, substrate = 75x45, air gap = 17, BS = 25

• “embedding impedances” calculated in HFSS by J. Kooi (CalTech)– results input to device design (as for DM design)

700 800 900 1000

-50

0

50

100

Impe

danc

e (

)

Frequency (GHz)

Real "DM" Real modified Real suspended

Imag. "DM" Imag. modified Imag. suspended

IS IRONI FM Program, Band 3 Design

• twin-junctions only, Nb SIS + NbTiN/SiO2/Al tuning circuit

• two designs (“modified” and “suspended”)– “modified” design: equivalent to “DM” (small changes to transformer)

– “suspended” design: less frequency-dependent than “DM”

• predicted performance– Jc = 8 kA/cm2 → similar to DM

– Jc = 10-15 kA/cm2 → improvement possible, depending upon junction quality

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0.2

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1.0 DM, J

c=8

DM, Jc=15

modified, Jc=8

modified, Jc=15

Cou

plin

g

Frequency (GHz)720 800 880 960 1040

0.0

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c=8

DM, Jc=15

suspended, Jc=8

suspended, Jc=15

Cou

plin

g

Frequency (GHz)

IS IRONI FM Program, Band 4 Design

• improved NbTiN quality needed– NbTiN deposited at elevated temperature at JPL, devices processed at DIMES

• Tc = 15.5-16.0 K, ρn, 20K = 60 µΩ·cm

• RF design– scaled band 3 “suspended” design only (available design variation used for

NbTiN properties, production tolerances)

880 960 1040 1120 12000.0

0.2

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1.0

Cou

plin

g

Frequency (GHz)

Fg = 1175,

n = 60

Fg = 1135,

n = 77

Fg = 1095,

n = 100

Fg = 1015,

n = 110

• device design– RF properties of NbTiN uncertain

→ 3 basic designs

• Fgap = 1095 GHz, ρn = 100 µΩ·cm

• Fgap = 1135 GHz, ρn = 77 µΩ·cm

• Fgap = 1175 GHz, ρn = 60 µΩ·cm

• predicted performance– similar to band 3 design (calculated

RF coupling ~ 50 % vs. 55 %)

IS IRONI Conclusions

• prototype program– NbTiN/SiO2/NbTiN + Nb SIS → heat-trapping, RF loss above 900 GHz

– NbTiN/SiO2/Al tuning circuit → high sensitivity up to 1 THz

• TN,mix+IF ~ 190-230 K (1.5 GHz IF, TN,IF ~ 4 K)

• DM program– redesign of RF geometry yields desired RF bandwidth in Band 3

– noise performance similar to prototype mixers

• DM: TN,rec = 350 K, TN,mix+IF ~ 240 K (4-8 GHz IF, TN,IF ~ 10 K)

• FM– redesign of band 3 RF design to ease device mounting, improve yield

• increased substrate size, suspended substrate

• expected band 3 performance equal to DM (Jc = 8 kA/cm2), or better

– improved NbTiN quality needed in band 4

• NbTiN ground planes obtained from JPL, processed at DIMES

• performance comparable to band 3 DM is expected

IS IRONI Current Status

800 880 960 1040 11200

200

400

600

800

1000N

oise

Tem

pera

ture

(K

)

Frequency (GHz)

SOAP '96 Baseline Goal c57 c65

TN,DSB (mixer + IF)