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Cryogenic PAF DevelopmentProgress Report
PAF WorkshopMay 3-5, 2010
Provo, UTRoger Norrod
Cryogenic PAF
PAF Workshop Provo, UT May 2010 2
• BYU/NRAO targeting noise and efficiency competitive with best single-beam receivers. i.e. 18K, 70% at L-band.
• At Green Bank, construction of cryostat for
19 element L-band PAF underway.
PAF Cryostat
PAF Workshop Provo, UT May 3-5 2010
3
With blank-off covers for leak checkApril 27
Model Drawing24 X 21 X 8 in.61 X 53 X 20 cm.
Dual LNA and Thermal Transition
PAF Workshop Provo, UT May 3-5, 2010 4
Pair of two-channel LNAs with integrated low-loss coaxial lines for transition from 15 to 300K, vacuum seal, and antenna base interface.
LNA based on: S. Weinreb, J. Bardin, H. Mani, G. Jones, “Matched wideband low-noise amplifiers for radio astronomy”, Rev. of Sci. Instr., vol. 80, 044702, 2009.
NXP SiGe transistors.Surface mount components.Thin-wall SS tubular coax.Quartz beads for vacuum seal and center conductor heat sink.
Est. input coax heat load 150 mW / chan.Bias power 17 mW / chan.
14 of 20 assembled, 8 tested cold.
LNA Measured Performance
PAF Workshop Provo, UT May 3-5, 2010 5
1300 1400 1500 1600 1700 18005
7
9
11
13
15
Dual LNA Noise8 Amps, 16 Channels Shown
Frequency (MHz)
Trx
(K
)
1000 1200 1400 1600 1800 200035
37
39
41
43
45
Dual LNA Gain8 Amps, 16 Channels Shown
Frequency (MHz)
S2
1 (
dB
)
Noise Y-factor measured with LN2 cold load at room temperature SMA connector.
LNA Measured Performance
PAF Workshop Provo, UT May 3-5, 2010 6
1000 1200 1400 1600 1800 2000-20
-15
-10
-5
0
Dual LNA S118 Amps, 16 Channels Shown
Frequency (MHz)
S1
1 (
dB
)
LNA Measured Performance
PAF Workshop Provo, UT May 3-5, 2010 7
1300 1400 1500 1600 1700 18000
10
20
30
40
50
60
70
80
90
100
SN6-Y Noise vs. Physical Temperature
15K 31K 41K 51K 61K71K 81K 91K 108K 194K302K
Frequency (MHz)
Trx
(K
)
0 100 200 3000
10
20
30
40
50
60
70
80
90
SN6-Y Noise vs. Physical TempAt 1660 MHz
LNA Body Temperature (K)
Trx
(K
)
Dipole Ohmic Losses
PAF Workshop Provo, UT May 3-5, 2010 8
Sky noise tests Nov-Dec 2009 to determine dipole noise contribution. Measured on Ciao room-temp amps (~35K).
Dipole Ohmic Losses
PAF Workshop Provo, UT May 3-5, 2010 9
1. Measured LNA/Rx with coaxial hot/cold load.
2. Attached dipole and measured using ambient load and sky.
3. Corrected for scatter, galactic plane, etc. (Tsky = 7.5K)
1300 1400 1500 1600 1700 1800-5
-4
-3
-2
-1
0
1
2
3
4
5
Fat Dipole Noise Contribution17 Dec 09
Tdipole on SN102 Tdipole on SN124
Frequency (MHz)
Td
ipo
le
(K)
Achievable Tsys?
PAF Workshop Provo, UT May 3-5, 2010 10
Contributor Noise
Receiver 9
Dipole Losses 2
Mutual Coupling 2
Spillover 5
CMB and Atm 4
Total 22 K
Next
PAF Workshop Provo, UT May 3-5, 2010 11
• Install LNA/TT assemblies.• Cooldown, measure cooling capacity.• Mount in FEB.• Sky noise tests.• Antenna (20m) tests.