529 Wideband Low-Noise Balanced IF Amplifiers for ALMA Band 6, with Future Application to ALMA Bands 3-10

  • Reviewer 5

Grade: 1

Wideband Low-Noise Balanced IF Amplifiers for ALMA Band 6, with Future Application to ALMA Bands 3-10

1. Alignment with NA ALMA Partnership strategic goals;

Excellent. Expanding the IF bandwidth of the IF system is a high priority ALMA strategic goal.

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the ALMA 2030 development documents.

High. This work would be almost a drop-in replacement of the IF amplifiers for bands 3-10.

3. Quality of the upgrade conceptual design;

The balanced amplifier approach provides improved matching to the SIS mixers, potentially improving the receiver sensitivity while increasing the available IF bandwidth. Relying on Low Noise Factory MMICs is a low-risk path to the most sensitive cryogenic amplifiers commercially available.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development);

This work will directly lead to a development proposal to upgrade band 6 receivers.

5. Strength of the consortium organization (if applicable);

Excellent.

6. Qualifications of the key personnel of the Study;

Excellent.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study;

Excellent. In addition to having experience developing the band 6 receivers, this team has been researching the balanced amplifier approach for many years.

8. Assessment of the level of risk inherent in the design;

Low. By using commercial sources for the MMICs the greatest risk is in the development of the superconducting hybrid. While it is acknowledged there is a high risk of needing a redesign of the hybrid, the design has previously been demonstrated (ref 4.1.1)

9. Strength of the Scientific Team supporting the Study;

N/A

10. Level of support guaranteed by the Institutes;

No additional support from NRAO. UVa is contributing the fabrication time of the hybrid.

11. Budgeted cost of the Study;

Reasonable, considering the high level of maturity of this technology.

  • Reviewer 7

Title of ALMADev Proposal: "Wideband Low-Noise Balanced IF Amplifiers for ALMA Band 6" by Tony Kerr et al.

Review Comments

The proposed study will construct and test prototype balanced IF amplifiers for 4-12 GHz. Such balanced IF amplifiers will remove the need for lossy cryogenic isolators between the SIS mixers and the IF amplifiers, and result in significantly better noise and bandwidth performance. The proposers will design and fabricate super-conducting lumped-element quadrature hybrids which will significantly reduce the size of the balanced amplifiers and make them no bigger than the current un-balanced amplifiers. Combining with an external company, Low Noise Factory, the project aims to deliver tested balanced 4-12 GHz IF LNAs that can be used in all ALMA bands.

The science case for the proposal is strong. The current 4-8 GHz IF of ALMA receivers is a significant limitation, and is not well matched with the proposed bandwidth increases for the ALMA correlator. The proposed effort for example will allow CO and its isotopologues to be well studied in one LO setting for Band 6. The lumped element superconducting hybrid is a novel design and the integrated design of hybrids, amplifier chips and bias circuits in one housing is well thought out and has options for testing individual pieces as well as the integral assembly.

The proposing team is strong and brings together a diverse team with strong competencies in their respective areas. Low-Noise Factory has a track record of producing some of the lowest noise MMIC LNAs. UVML has good facilities for producing the super-conducting hybrids and has ALMA SIS device heritage. The PI is an innovative designer who can bring effective system level design to this project.

The study is well aligned with ALMA's long term goals. Budget and work plan seems well thought out.

Review Score: 2.0

  • Reviewer 10

529 Wideband Low-Noise Balanced IF Amplifiers for ALMA Band 6, with 

Future Application to ALMA Bands 3-10 Tony Kerr

Score: 3

The goal of this proposal is to implement a 4-12 GHz balanced amplifier based upon a new superconducting quadrature hybrid and state-of-the-art MMIC low noise amplifiers, which will be obtained from Low Noise Factory. A balanced amplifier has the advantage of being insensitive to the phase of the generator reflection coefficient. As the balanced amplifier will not require an isolator (provided the SIS junctions have relatively constant reflection coefficient magnitude), there is a real possibility that, beyond the increase in bandwidth, the system noise temperature will be improved. While perhaps less ambitious than several of the other proposals, the work proposed here is logical and will have impact on multiple bands if successful.

  • Reviewer 11

Grade: 3

Title Wideband Low-Noise Balanced IF Amplifiers for ALMA Band 6, with Future Application to ALMA Bands 3-10

1. Alignment with NA ALMA Partnership strategic goals; Particularly well aligned to 1.1 and 4.2

2. Strength of the scientific case for the proposed ALMA upgrade concept; The science case presented is not very specific. The wider bandwidth and improved noise will certainly increase sensitivity and observing efficiency for continuum and spectral line measurements. Several important lines are listed. The science case would be improved by showing (or citing) an example observation where CO might be assumed to be optically thin, but 13CO observations demonstrate that it is not. Comment on the relevance to the ‘ALMA 2030’ development documents. Increasing bandwidth and increasing sensitivity are both well aligned with the ALMA 2030 vision.

3. Quality of the upgrade conceptual design; The design appears to be very sound and based on proven technologies.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development); The proposal would demonstrate that the balanced amplifier with superconducting hybrid architecture is ready to move into production. At the end of the proposed project period, it is likely that the technology would be well on its way to being ready for production

5. Strength of the consortium organization (if applicable); Collaboration between CDL and UVML is well established. It is clear from the proposal that a strong relationship also exists with LNF

6. Qualifications of the key personnel of the Study; The personnel are extremely well qualified and have all of the relevant expertise

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study; UVML has all the facilities and experience necessary for fabricating the superconducting hybrids. CDL has the facilities and technical expertise for designing, testing and integrating the amplifier modules.

8. Assessment of the level of risk inherent in the design; The risk seems quite low because it is based on proven technologies.

9. Strength of the Scientific Team supporting the Study; No concerns

10. Level of support guaranteed by the Institutes; The level of support seems sufficient

11. Budgeted cost of the Study; The budget seems to include funds for purchasing a spectrum analyzer, but no details are given in the proposal as to why this is necessary (I would assume CDL already has several spectrum analyzers). The budget relies on unspecified in-kind contribution from UVML for the hybrid fabrication.

  • Reviewer 12

Proposal 529:

- Comment:

A wideband low-noise balance IF amplifiers should be essential for simultaneous measurement of spectral lines and increase the efficiency of ALMA observations. This is aligned with the development path of "larger bandwidths". I am curious why for a strategic study, the IF bandwidth is only limited to 4-12 GHz ?

- Score: 2.5

  • Reviewer 13

Grade: 5.0 Title: Wideband Low-Noise Balanced IF Amplifiers for ALMA Band 6, with Future Application to ALMA Bands 3-10

1. Alignment with NA ALMA Partnership strategic goals; Comment: The proposal aims to improve the performance of the ALMA Band 6 receivers, and has and as such is in line with NA priorities. It also offers a potential pathway for modest improvements in the majority of the ALMA bands. However, even with a successful outcome, the proposal lacks vision as the proposed increase in performance is relatively modest: reducing the receiver noise across part of the IF of receiver band 6 and a doubling the IF bandwidth for the majority of the ALMA receivers, including band 6. As written, and without a proper accounting, the proposal overestimates the expected gain in performance by using the worst case noise in the IF of receiver band 6 as reference.

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the ‘ALMA 2030’ development documents. Comment: This proposal is aimed at increasing the bandwidth of the ALMA receiver sets by first doubling the bandwidth of the band 6 receivers, and is therefore aligned to the ALMA 2030 development plan. However, the proposed bandwidth increase is relatively modest. Assuming that ALMA receiver bandwidth upgrades will not occur frequently, it would be more reasonable to propose a significant increase over the current status. Furthermore, the proposed development would offer no increase in bandwidth for the ALMA band 9 receiver sets.

3. Quality of the upgrade conceptual design; Comment: The conceptual design is sound.

4. Readiness for production in the context of the ALMA Development Plan (the aim is to support a range of upgrades including both those which can be implemented rapidly and those requiring longer-term research and development); Comment: Assuming a successful development within the 2-year timeframe of this proposal, with no revision or redesign of the hybrid and no fabrication difficulties at UVML, it would appear that production of balanced IF amplifiers to replace the current IF amplifiers of the Band 6 receivers could begin on a timescale of 2 - 3 years. However, procurement and full implementation in even a single ALMA band would not seem possible for several years after that.

5. Strength of the consortium organization (if applicable); Comment: Staff members at NRAO and UVA have a long history of successful collaboration in the development of mm instrumentation for radio astronomy.

6. Qualifications of the key personnel of the Study; Comment: The identified team members are qualified to perform the tasks as described.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study; Comment: Team members were largely responsible for the initial development and production of the current ALMA band 6 front-ends, and the facilities at the partner institutions are consistent with the proposed work.

8. Assessment of the level of risk inherent in the design; Comment: The team identifies two moderate to high risk areas: a potential revision of the initial superconducting hybrid design, and fabrication failure at UVML. Together these could result in a significant delay to the project. However, since there is no time allocated to fabricating the hybrid, it is difficult to make a good estimate of potential delays should the hybrid design need to be reworked and new hybrids made.

9. Strength of the Scientific Team supporting the Study; Comment: The science case for making ALMA receivers more wide band is well-established, and funding is requested for a single week of science support to be provided by Jeff Magnum, who is well-versed in ALMA science. 10. Level of support guaranteed by the Institutes; Comment: There is no in-house cost sharing within this proposal.

11. Budgeted cost of the Study; Comment: From the proposal it is not clear how many amplifier units will be delivered by Low Noise Factory, and therefore how many spare units would be available for testing. Furthermore, the Gantt chart provided has a mix of days and weeks (presumably the difference between in-house effort and contractor or vendor effort) and it it not at all clear how the funding matches the schedule in detail.

-- AlWootten - 2017-07-18
Topic revision: r3 - 2017-07-18, AlWootten
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