• Proposal 528 Ford ALMA Digital Back End Antenna Article Phase II

  • Reviewer 1

Grade: 3

Executive Summary: This proposal seeks to study high-speed interleaved ADCs for use in future ALMA signal digitizers.

Ford, Ephraim - ALMA Digital Back End Antenna Article, Phase II ALMA Development Review

1. Alignment with NA ALMA Partnership strategic goals; The proposal is well aligned with Strategic Goals in the NA development program. It seems to explore new technologies (1.x) which would enable a future high-bandwidth ALMA. By expanding the pool of potential ADCs, it could reduce the cost of such an upgrade, though not the cost of actual operations (3.x). It does little to address operating efficiency (2.x), nothing is done to include young researchers (5.x), while the expertise at NRAO is exploited, it is not leveraged into the broader community in an significant way (4.x).

2. Strength of the scientific case for the proposed ALMA upgrade concept; Comment on the relevance to the †̃ALMA 2030â€TM development documents. Interleaved ADCs would allow significantly higher sample rates, broadening the band and opening up a variety of new / more efficient science operations.

3. Quality of the upgrade conceptual design;

The conceptual design is light, but makes good sense to explore in the context of ALMA. I am unsure how novel this research is, it seems plausible that the technologies are already well understood.

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 proposed research is early-phase, and would not be ready for incorporation into a working ALMA before significant additional R&D.

5. Strength of the consortium organization (if applicable); The proposing organization is NRAO, so I have no concerns about the abilities of the institution.


6. Qualifications of the key personnel of the Study; The proposers have already studied high-speed direct sample ADCs in the ALMA context, and so are well placed to expand the study in this direction.

7. Technical expertise, past experience (also in series production, if relevant) and technical facilities in the Institutes taking part in the Study; No concerns here, the team has the necessary experience and resources.

8. Assessment of the level of risk inherent in the design; There is very little risk at this stage of technology development: few personnel are involved, so turnover would significantly alter the feasibility, but otherwise the proposal looks secure. 
 9. Strength of the Scientific Team supporting the Study; Only one member of the Key personnel is listed as part of the scientific team (Scientific Lead), and it does not appear that a significant scientific team is supporting this proposal. Nonetheless, the scientific case for a broader band and higher spectral resolution is clearly laid out, and I think well justified. 
 10. Level of support guaranteed by the Institutes; The NRAO is providing significant in-kind in the form of key personnel, but this constitutes a small fraction of the overall project cost. 
 11. Budgeted cost of the Study; At >$10M, the cost of this upgrade is significant, but largely in-line with what would be expected for a next-generation correlator. Since it follows a well-trod technology path, this forecast is likely reliable.

  • Reviewer 2

Grade: Good (5)

Title ALMA Digital Back End Antenna Article, Phase II (PI: Ford)

1. Alignment with NA ALMA Partnership strategic goals;

The proposed Study is well aligned with at least two of the NA ALMA strategic goals. Developing the hardware to implement a wider processed bandwidth would have immediate gains for the scientific productivity and operational efficiency of ALMA. It is less clear how this proposed Study responds to the goal of strengthening the NA radio astronomy community as the work is concentrated at one institution with an already strong link to ALMA.

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

The proposed Study is excellent with respect to the extent that the developed hardware could touch on many aspects of the ALMA science case, and it is clearly responsive to the ALMA 2030 Roadmap, which calls for a larger bandwidth.

3. Quality of the upgrade conceptual design;

There are several aspects of the conceptual design that are not clear, leading to potential risks in actually achieving the scientific promise of larger bandwidths. The text of the proposal provides no summary of the current state of the art, or what is required to achieve the goal of 16 GHz per IF (nor whether the architecture to obtain 16 GHz per IF is extensible to the notional goal of 32 GHz per IF). (The abstract does mention a 3-bit, 24 GHz ADC.) The importance of calibrating the interleaved ADCs is mentioned, but there are no metrics provided by which the team will be able to judge that sufficient calibration has been obtained.

An even more serious issue is that, by not addressing the current state of the art, it is not clear whether this Study is even required. A Study of this nature would seem to be required only if the pace of commercial development of ADCs is not sufficiently rapid that ALMA partners could not simply wait for an ADC capable of providing 16 GHz per IF is available. If that justification is provided in this proposal, this reviewer overlooked it.

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 readiness for production is modestly difficult to assess. There are ADCs that approach, or potentially even reach, the required performance. Thus, the proposed work should be capable of being able to be integrated rapidly into ALMA. As noted above, however, whether this work is even required or whether commercially available products could suffice is not clear.

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

The team consists of individuals from NRAO and one individual from the Harvard-Smithsonian CfA. The contributions of the individual from the CfA are not specified.

6. Qualifications of the key personnel of the Study;

The key person for this study is Co-I Aston, who would be funded at just slightly more than half-time. This individual has worked previously on a number of similar projects, including for ALMA, and appears quite capable of doing the work required.

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

See response to #6.

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

Modest. Most of the technical development appears straightforward, but there are concerns about the (unspecified) level of calibration required and about whether the budget accurately reflects the required work.

9. Strength of the Scientific Team supporting the Study;

No explicit science team is identified, but this reviewer judges it likely to include Co-Is Carilli and Ricci. Both individuals are quite capable of providing guidance and feedback on the proposed work to a broad range of ALMA science, both continuum and spectral line.

10. Level of support guaranteed by the Institutes;

None is detailed. In particular, the scientific guidance offered by neither Co-I Carilli nor Ricci appear in the description of in-kind contributions (though this level of guidance is likely to be modest).

11. Budgeted cost of the Study;

There are numerous concerns about the budget. The most severe is that the text and Figure 1 refer to a test bed, with the implication the procurements would be required, but there are none listed in the budget. As noted in #10 above, there appears to be no support, either explicit or in-kind, for the assumed scientific Co-Is. Funding is requested for a project manager, but that individual does not appear amongst the list of Co-Is.

  • Reviewer 3

Grade: 6

ALMA Digital Back End Article, Phase II

1. Alignment with NA ALMA Partnership strategic goals; -- Good. Increasing ALMA's bandwith is a key goal.

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

3. Quality of the upgrade conceptual design; -- Characterizing the performance of an interleaved ADC, and developing calibration algorithms for it, would be a useful exercise. However, the proposal gives little background information (are interleaved ADCs used in other astronomical correlators?) and few details about exactly what tests are envisioned. Hence it is difficult to be confident that the study would adequately retire the risk associated with using an interleaved ADC.

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 is a medium to long term project.

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

6. Qualifications of the key personnel of the Study; -- Uncertain. Ephraim Ford, the PI, is basically a manager. Most of the work will be done by Sylas Ashton; his CV does indicate that he has experience in high speed ADC design, but gives few details about his role in previous projects.

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

8. Assessment of the level of risk inherent in the design; -- High risk. Subtle problems with an interleaved ADC could compromise the performance of the new correlator.

9. Strength of the Scientific Team supporting the Study; -- Not applicable for this engineering study.

10. Level of support guaranteed by the Institutes; -- More involvement by Rich Lacasse or some of the other correlator experts at NRAO would be reassuring.

11. Budgeted cost of the Study; -- OK.

  • Reviewer 13

Grade: 5.0

Title: ALMA Digital Back End Antenna Article, Phase II

1. Alignment with NA ALMA Partnership strategic goals;

Comment:It is very clear that widebanding of ALMA is a very high priority with enormous potential scientific and strategic returns. While interleaved ADCs are a technology worthy of investigation, this proposal has significant weaknesses in that it has virtually no technical detail on how the interleaving will be dealt with.

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

Comment: It is very clear that widebanding of ALMA is a very high priority with enormous potential scientific and strategic returns, and is completely aligned with the ALMA 2030 goals. The science case in the proposal is well explored.

3. Quality of the upgrade conceptual design; Comment: Very poor. While the proposers correctly identify interleaved ADCs as a technology worthy of exploration, and they clearly state that interleaving artifacts need to be dealt with, section 4.1 gives no detail whatsoever as to specifically what these challenges are, nor the proposed approach to dealing with them. This leaves me lacking confidence that the proposal team has the technical background to address these issues. Apart from giving an outline of the artifacts associated with errors in Offset, Gain, Phase, non linearity, and their impact on spurious free dynamic range (SFDR), Signal-to-Noise and Distortion (SINAD) and related effective number of bits (ENOB), as well as Noise Power Ratio (NPR), there is no attempt to outline what these impacts are, steps to be taken to reduce them, nor any references to extensive literature on this topic in general, and the application of interleaved ADCs to ultra wideband radio astronomy, which is already documented in the literature.

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: In the context of the comment in 3. not ready.

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

Comment: Very NRAO-centric, and lacking in a broad view of prior art.

6. Qualifications of the key personnel of the Study;

Comment: The personnel are fine, but the proposal leaves me lacking in confidence for this particular work.

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

Comment: See comment in 6.

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

Comment: There is no indication the proposers have the technical skill to support the study.

9. Strength of the Scientific Team supporting the Study;

Comment: for what it is worth, the science case was fine, but good science representation doesn’t improve the technical case.

10. Level of support guaranteed by the Institutes;

Comment: no applicable.

11. Budgeted cost of the Study;

Comment: Not justified so I can’t comment.

-- AlWootten - 2017-07-19
Topic revision: r1 - 2017-07-19, AlWootten
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