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
MIC
MMIC
Receiver Architecture
4-8 GHz
1st IF
USB
1.5 GHz 2nd IF
downconverter
E-band
downconverter
Needed
for MMIC
Amplifier
LSB
SB selector
switch
1.5 GHz IF to
Backends
LO
1.5 GHz IF
to Backends
SIS Mixer
SIS
LO
IF Amplifier
Dewar
Boundary
• SIS mixer channel operates in singlesideband mode
• Amplifier channel utilizes sidebandseparating mode
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 coupler
MAC Tech.
C7256 4-12 GHz quad.
hybrid coupler
Millitech
MCA-12-120187
Front end
signal
from
amplifier
USB
4–8
GHz IF
LO
LSB
Millitech
MCA-12-120187
WR-12 Y junction
power splitter
Test Bench Setup
Image Rejection Performance for Each Mixer Pair
Millitech MCA-12120187 Balanced
Mixers
IF = 6 GHz
35
30
19-1/19-3, LSB
25
19-1/19-3, USB
19-1/20-2, LSB
19-1/20-2, USB
20
IR (dB)
19-1/20-4, LSB
19-1/20-4, USB
15
19-3/20-4, LSB
19-3/20-4, USB
20-2/19-3, LSB
10
20-2/19-3, USB
20-2/20-4, LSB
5
20-2/20-4, USB
0
60
65
70
75
80
RF (GHz)
85
90
95
Pairs Used on Inserts
IF = 6 GHz
35
30
25
20
IR (dB)
19-1/19-3, LSB
19-1/19-3, USB
15
20-2/20-4, LSB
20-2/20-4, USB
10
5
0
60
65
70
75
80
RF (GHz)
85
90
95
} MMIC
} MIC
Complete E-band Downconverter Assy.
Receiver Testing in Lab
Receiver Temperatures at the Telescope*
Frequency: 72.8 GHz, LSB, 1st IF = 5 GHz
SIS (1)
MIC
SIS(2)
MMIC
64
56
64
78
68 (USB)
60 (USB)
*Noise temperature measured with Y-factor method, using hot / cold loads at
the window of each receiver.
Observations: SIS / MIC
SIS
Object: IRC+10216
Frequency: 72.8 GHz
Integration time: 10hrs, 42min
Tsys: 403 K (SIS), 303 (MIC), Trec = 64 K (SIS), 56 K (MIC)
MIC
Observations: SIS / MMIC
SIS
Object: IRC+10216
Frequency: 72.8 GHz
Integration time: 10hrs, 42min
Tsys: 264 K (SIS), 333 (MIC), Trec: 64 K (SIS), 78 (MMIC)
MMIC
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 singledish observations.