Atacama Large Millimeter/submillimeter Array

Karl G. Jansky Very Large ArrayRobert C. Byrd Green Bank Telescope

Very Long Baseline Array

NRAO Receivers

Richard Prestage(Marian W. Pospieszalski, Steve White, Steve Durand)

ALMA Workshop, March 21-22, 2011 2

Noise Temperature Summary of Cryogenic HEMTs

NRAO Cryogenic Amplifiers 3

Mmin Prediction (1991) and State of the Art (2009)

0

5

10

15

20

25

0 10 20 30 40 50

Frequency (GHz)

Nosi

e M

easu

re (K

)

Noise measure at 12.5 K Best Amps.

NRAO Cryogenic Amplifiers 4

VLA/EVLATRx versus Frequency

TRx = m·F + b ; m = 0.5ºK/ GHz ; b = 8ºK

EVLA Project Book - TRx Requirements (Band Center)

Band L S C X Ku K Ka Q

TRx 14 15 16 20 25 34 40 48

0 5 10 15 20 25 30 35 40 45 500

5

10

15

20

25

30

35

40

45

50Simple Noise Model

L-Band 1-2 GHz (Interim)

S-Band 2-4 GHz (N/A)

C-Band 4-8 GHz

X-Band 8-12 GHz (VLA)

Ku-Band 12-18 GHz (N/A)

K-Band 18-26.5 GHz

Ka-Band 26-40 GHz

Q-Band 40-50 GHz

Frequency (GHz)

Rec

eive

r Tem

pera

ture

(K)

L#32(i)

C#20

X#01(t)

K#28

A#07

Q#18

S#01

R. HaywardNRAO, Socorro, NM

The RF Signal Path

• The Feedhorn:– Compact

corrugated horn.

The RF Signal Path

• A top view of the 15K cold plate and RF signal path:– The input to the

cryostat.– The charcoal trap, the

heaters and the thermostat.

The RF Signal Path(cont.)

• The thermal gap and OMT assemblies:– Foam window.– Gap set to 5mils.– The full assembly

forms the circular-to-square transition, the square to quad-ridge taper and the quad-ridge to coaxial sections.

The RF Signal Path(cont.)

• The RF Tree:– Thermal gap/RF choke.– Ortho-mode transducer.– 90°Quadrature hybrid

coupler.– Cryo-isolator and

calibration coupler.– Three stage NRAO Cryo-

3 InP HFET low noise amplifier.

10

Receiver Characterization

K Band Focal Plane Array(Shanghai)

Steven D. White*, Matt Morgan, Felix J. Lockman,

Eric Bryerton, Glen Langston, Roger Norrod, Bob Simon,Galen Watts,

Sivasankaran Srikanth, Gary Anderson

System Baseline Specifications

Specification Requirement

Frequency Band 18-26.5 GHz (complete K-Band coverage)Can tune up to 27.5 GHz

Instantaneous RF Bandwidth 1.8 GHz (front-end) as built

Number of Beams 7

TRX (each beam, not including sky) <25K (75% of band)<35K (entire band)

Aperture Efficiency >55% (any pixel)

Polarization dual, circular (axial ratio <= 1dB)

Polarization Isolation >25 dB

Pixel-to-Pixel Isolation >30 dB

Headroom >30 dB (to 1 dB compression point)

12

Bandwidth Limitations

Sub-Assembly Total Potential Bandwidth Comments

cold-electronics(feed, OMT, LNAs...)

>8.5 GHz degrades outside of 18-26.5 GHz

warm analog electronics DC – 7.7 GHz (up to 8 dual-polarized beams)

Type II IntegratedDownconverter Module

13

Green Bank, West Virginia, January 11, 2009 14

0.00

5.00

10.00

15.00

20.00

25.00

18.00 20.00 22.00 24.00 26.00

Frequency (GHz)

Nois

e Te

mpe

ratu

re (K

)

043 117 118 125 126 127 128 129 130

131 132 133

GBT K-Band Array Amplifiers at 19 K

Feedhorn Arrangement

• GBT:• 36” mounting ring on the

receiver turret would support about 60 K-Band feedhorns.

• 3.45” spacing (~2.5 HPBW)

• Shanghai:• Feed Design.• Efficiency ?• Spacing?• Mechanical Impact.

15

Compact Corrugated Feedhorns

3.4” O.D. Feedhorns22 GHz Telescope Beams

16

Thermal Gap

17

• 0.543" circular waveguide• 0.010" gap with choke

groove• upper half at 300 K, lower

at 15 K• hollow, shaped G10

supports• optimized for weight,

strength, and thermal isolation

• Cuming Microwave PS-102 foam for vacuum seal

• Cuming Eccobond 45 epoxy

• 3-mil Kapton vapor seal

Quadrature Phase Shifter and OMT

18

Noise Calibration Source Integrated With Coupler

19

KFPA Uses Existing EVLA Low-Noise Amplifier Design

20

Gapped WR42 Sliding Waveguide Output Transition

• 0.360” maximum travel• ∆ length on cool-down:

~0.144”• Stable at final temperature• Chomerics 1285 conductive

elastomer• Ecco-foam PS102 with 3 mil

Kapton

21

Sliding Waveguide/Thermal Gap Assembly

Thermal Gap and 20 cm SS waveguide: 1.7 Watts 1st Stage Load.30 cm SS coax: 0.54 Watts 1st Stage Load.Total: 1st Stage 18 W; 2nd Stage 3 W.

Contraction from 300K to 15K is ~ 4.1 mm of total 6.35 mm.

Downconverter Size Dominated by DC Control FunctionsPCB Side MMIC Side

23

Snakes of Star Formation

26

The Galaxy is rich in Snakes of star forming clouds:

Finn and Jackson, in preparation.

KFPA NH3 (1,1) contours on Spitzer Glimpse Image

Langston, Batistti, Jones 2011, in preparationAlso see posters by Batistti et al and Jones et al

28

The National Radio Astronomy Observatory is a facility of the National Science Foundation

operated under cooperative agreement by Associated Universities, Inc.

www.nrao.edu • science.nrao.edu