ALMA BAND 2 EVALUATION RECEIVER AT THE 12 m TELESCOPE
David Forbes, Thomas Folkers, Robert Freund, Eugene Lauria, Martin McColl, Mark Metcalfe, George Reiland, Lucy Ziurys
Arizona Radio Observatory
Tucson, AZ
ARO 12m Antenna
Objective
• Evaluate the performance of the latest cryogenic MIC/MMIC amplifier technology as compared to the well established SIS technology for the 4mm band
• Provide a direct comparison of each of the technologies with observational data• Done by constructing an insert for each type of amplifier
(MIC/MMIC) and installing each opposite of an insert using an SIS mixer• These mixers have been used at the 12 m over the past 20 yrs.
• Deep integrations done at the J = 1→0 H2CO line at 72.8 GHz
Receiver Architecture
SIS
SIS
MMIC
MIC
Receiver Architecture
Amplifier
SIS Mixer IF Amplifier
1.5 GHz IF to Backends
E-band downconverter
Dewar Boundary
4-8 GHz 1st IF
1.5 GHz 2nd IF downconverter
1.5 GHz IF to Backends
LSB
USB
SISLO
SB selector switch
• SIS mixer channel operates in single-sideband mode
• Amplifier channel utilizes sideband-separating mode
LO
Needed for MMIC
Legacy 68 - 90 GHz 12 m Insert
• SIS mixer• Uses (2) backshorts to provide SSB
operation• 1.5 GHz IF
RF Amplifier-Based Inserts
E-band Downconverter Architecture
WR-12 Quadrature
hybrid couplerMillitech
MCA-12-120187
MillitechMCA-12-120187
MAC Tech.C7256 4-12 GHz quad.
hybrid coupler
USB
LSB
Front end signal from amplifier
WR-12 Y junction power splitter
LO
4 – 8 GHz IF
Test Bench Setup
Image Rejection Performance for Each Mixer Pair
60 65 70 75 80 85 90 950
5
10
15
20
25
30
35
IF = 6 GHz
19-1/19-3, LSB19-1/19-3, USB19-1/20-2, LSB19-1/20-2, USB19-1/20-4, LSB19-1/20-4, USB19-3/20-4, LSB19-3/20-4, USB20-2/19-3, LSB20-2/19-3, USB20-2/20-4, LSB20-2/20-4, USB
RF (GHz)
IR (d
B)
Millitech MCA-12-120187 Bal-anced Mixers
Pairs Used on Inserts
60 65 70 75 80 85 90 950
5
10
15
20
25
30
35
IF = 6 GHz
19-1/19-3, LSB19-1/19-3, USB20-2/20-4, LSB20-2/20-4, USB
RF (GHz)
IR (d
B) } MMIC
} MIC
Complete E-band Downconverter Assy.
Receiver Testing in Lab
Receiver Temperatures at the Telescope*
SIS (1) MIC SIS(2) MMIC
64 56 64 78
68 (USB) 60 (USB)
Frequency: 72.8 GHz, LSB, 1st IF = 5 GHz
*Noise temperature measured with Y-factor method, using hot / cold loads at the window of each receiver.
Observations: SIS / MICSIS MIC
Object: IRC+10216Frequency: 72.8 GHzIntegration time: 10hrs, 42minTsys: 403 K (SIS), 303 (MIC), Trec = 64 K (SIS), 56 K (MIC)
Observations: SIS / MMICMMIC
Object: IRC+10216Frequency: 72.8 GHzIntegration time: 10hrs, 42minTsys: 264 K (SIS), 333 (MIC), Trec: 64 K (SIS), 78 (MMIC)
SIS
Conclusions
• Amplifier technology has shown comparable noise performance as compared to SIS mixer technology which has been the benchmark for the state-of-the-art over the past 20+ years.
• Use of cooled amplifiers reduces the number of cooled components and complexity of the receiver dewar.• Increase reliability• Moves image separating mixer outside the dewar
• 1/f stability may still be an issue:• Increases with the number of stages in an amplifier• Typically worse in amplifiers, especially when gate widths become shorter• Important for continuum observations but may not be as much as an issue for
spectral line work since a narrower bandwidth is utilized
• E-band downconverter needs improvement to meet the ALMA spec. of better than 10 dB of IR, further improvement is needed for single-dish observations.
Top Related