UAz 4mm Receiver - Part 1 Technical

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.