PrepSKA WP2 work in Canada continues apace in a number of areas, with much of the technical work being advanced at NRC-HIA and

SKA Consortium News

Russ Taylor (Calgary) and Sean Dougherty (NRC-HIA)

SKA Conceptual Design Review

The international SKA is nearing the completion of its 4-year design phase coordinated among the 20 participating countries under the PrepSKA program. In February the SKA design underwent a System Conceptual Design Review. The review panel included Wolfgang Wild (European Project Manager for ALMA), John Webber (Head of Central Technical Laboratories, NRAO), Lyn Evans (Project Manager, Large Hadron Collider, CERN), Jim Yeck (Director, Icecube Neutrino Observatory), and Robin Sharpe (former Director of Strategic Research for Phillips Semiconductors UK). The purpose of the review was to evaluate the overall progress on the systems design concept, the technical readiness of SKA design, and to identify any gaps in the system. Key outcomes of the CoDR are modification of the project timeline, and a focusing of the technology definition for Phase I of the SKA.

The preconstruction phase begins in 2012 following completion of the costed system design and the selection of the SKA site. During this phase (2012-2015) the SKA headquarters and project office will ramp up, and the detailed design and design to manufacture in industry will be completed. Construction of SKA Phase 1 would then begin in 2016.

SKA Phase I will comprise approximately 10% of the collecting area of the full SKA. It will consists of sparse aperture array technology receptors for low-frequencies (below 450 MHz) combined with approximately 250, 15-metre dish antennas equipped with feed systems for the mid-frequency band up to a few GHz. This design will allow a major advance in the SKA key science goals to a) observe the history of hydrogen from the epoch or re-ionization to the present era, b) detect gravitational waves using pulsar timing arrays, and c) trace the evolution of black holes and galaxies from dawn of galaxies.

New Appointments

The international project is governed by two bodies constituted via multi-national agreements among the SKA partners: the SKA Science and Engineering Committee (SSEC) which is the decision making body that steers the overall direction of the project, and the Board of Directors of PrepSKA, which provides oversight on the coordinated research and development program among the 20 countries participating in the SKA design. At the SKA project meetings new appointments of Canadian representatives were made within each. Russ Taylor was elected to the position of vice-chair of the SSEC, and Sean Dougherty was appointed to the Executive Committee of PrepSKA.

SKA 2011

Each year the international SKA project holds a week-long series of meetings called the SKA Forum. In 2011 the SKA Forum will be jointly hosted in North America by the Canadian and US SKA Consortia. SKA2011 will occur the week of 4 – 8 July in Banff Alberta. The schedule of events includes a two-day science meeting entitled “Astronomy in the Era of Big Data”, as well as a workshop on the interface of SKA engineering challenges and industry. There will also be a public Forum Day including keynote talks from leaders in science, industry and government. As planning matures, more details on SKA2011 will be posted on the SKA Canada site a www.skatelescope.ca.

SKA R&D in Canada

Technology R&D for the SKA is being carried out under the auspices of the European Commission Framework 7 (FP7) supported preparatory
 study, PrepSKA. The R&D effort in Canada continues apace in a number of areas, with much of the technical work being advanced at
 NRC-HIA, the University of Calgary and at the University of Victoria.

The Dish Verification Antenna.

The CART group at NRC-HIA and the US TDP group are collaborating on the design and construction of a 15m offset Gregorian radio
 telescope prototype (known as DVA-1) as part of the Dish Verification Programme.  The current design work is focusing on an interesting
 blend of composites and metal materials. The dish surface structure is a thin (< 8mm) molded composite, while the backup structure and the
 feed/secondary support system consists of both metallic and composite tubes.  A Conceptual Design Review is anticipated for the
 Fall of 2010, with construction of the first prototype starting early in 2012, at the VLA site in New Mexico.

Figure 1. Latest design from NRC for the 15-m offset reflector and feed-support structure being developed for the Dish Verification Antenna project in collaboration with the TDP

Antenna systems

Work at NRC-HIA continues on an Advanced Focal Array Demonstrator (AFAD) with sensitivity and bandwidth suitable for astronomy 
Improved sensitivity due to low-loss structures incorporated into Vivaldi elements is being investigated.  Wide-band operation
 will be realized with direct sampling by high-speed analog-to-digital converters followed by a large FPGA-based beamformer.

At the recent phased-arrays workshop in Provo Utah, we made two contribution: A  practical introduction to FPA polarimetry that showed that
 empirical beamformer calibration can be extended to two polarizations and the synthesized beams have orthogonal polarizations; and a
 study on the compatibility of shaped reflector optics and PAFs , where the key result is that the FPA (including down-stream processing)
 needs to be ~20% larger to accommodate distortions introduced by the shaped primary reflector.

The millimeter-wave instrument group at NRC-HIA is using its expertise in mass-produced high-frequency cooled receivers to investigate
 wide-band single-pixel feeds and cooled LNA’s for use above 1 GHz.  In addition, they have been collaborating with
 Emily McMilin (University of Victoria) in developing an innovative broad-band planer feed with a cone shaped ground plane.

FPGA-based Computing

We have been investigating design concepts for general purpose FPGA-compute boards, to be used in beamformers and correlators, as well as adaptive optics (AO) controllers for large optical telescopes e.g. Thirty Meter Telescope (TMT). The currently being designed will be used in the AFAD array feed (above) and in the University of Victoria “Raven”, project to demonstrate a Multi-Object Adaptive Optic (MOAO) system on the Subaru telescope in Hawaii. This work is the result of our successful concept design for a real-time controller for the AO system on the TMT.

A key feature of the board are huge data transfer and memory bandwidth. The preliminary specifications are data rates of 160 Gbps and memory data rates of 100+ GBps. We are working closely with industrial collaborator Lyrtech Signal Processing of Quebec to develop high-level programming and development tools for the board, for flexibility and ease in programming multi-FPGA boards.

Correlator
NRC-HIA is the lead institute for WP2.5.1, the correlator work package and have been in discussions with the SPDO on coordinating concept design contributions for the CoDR expected in late 2010. NRC-HIA is investigating scalable system architectures and refining ideas on a Common Array Processing Architecture (CAPA) and have a practical scheme for realizing a correlator using current technology, with clear growth paths for utilizing technology improvements to increase bandwidth and the number of beams without replacing system infrastructure. We are currently working on requirements definition and documentation templates for contributing design concepts for consideration at the CoDR. We hope to have this complete by late summer for review by the SPDO and others contributing to this work package.

University of Calgary High-Speed Data Transfer and Acquisition Group

The HIA group in Penticton is collaborating with Drs. Jim Haslett and Leo Belostotski and their research groups at the University of Calgary, targeting high-speed low-power Analog-to-Digital Converters (ADC’s) and high-speed data transfer circuits (SerDes) in CMOS at the antennas. The goal is the simplest possible circuitry in the low-noise antenna element signal chains, while providing either digital data or analog time-based data at the antenna locations, for transmission to a central data gathering site.

Two approaches are being pursued. The first is a new time-based approach to ADC design, and 3-bit CMOS prototypes are currently being tested. In parallel, a more conventional CMOS flash ADC is being designed that will allow higher resolution without adding a large amount of circuitry. The circuit is designed in 65nm CMOS, for submission to the foundry later this year.

Time-based SerDes circuits are also designed and are being tested in FPGA form for proof-of-concept. The new approaches allow very simple, low-power circuitry at the transmitter and receiver compared to conventional SerDes circuits that are becoming complex and power hungry.

University of Calgary SKA receiver group

Drs. Jim Haslett and Leo Belostotski and their research groups at the University of Calgary are investigating room-temperature low-noise receiver designs fabricated in CMOS. A number of concurrent projects are underway:

· Two 65nm CMOS LNAs have recently come back from fabrication and await testing.

· A 90nm CMOS low noise gain stage is under test and initial measurements look very good. When combined with the front end LNA, this will provide enough gain to drive one of the custom ADCs designed at the University of Calgary.

· A 65nm CMOS gate stage has being fabricated and is awaiting testing.

· A 65nm CMOS automatic gain control has been fabricated and is under initial testing.

· A new LNA topology is being investigated and a 65nm CMOS design is nearing submission for fabrication in July 2010.

· An optical data transport system is being investigated with initial work focusing on a CMOS optical receiver end. This system is envisioned to connect SKA receiver ICs with the circuitry located at the antenna base.

Multi-dimensional Signal Processing (MDSP) Research at University of Calgary and University of Victoria

The application of MDSP methods in radio astronomy remains the principal objective of this research, with the goal to improve, for a given level of signal-processing complexity, the signal-to-interference ratio (SIR) and the SNR for the various types of signals, RFI, and LNA-generated noise. The MDSP Group is also pursuing applications of their research in such fields as smart antennas for wide-band communications and software-defined cognitive radio systems.

Research on the potential application of 3D cone filters to the mitigation of broadband RFI signals on focal-plane arrays (FPAs) and on dense-aperture-arrays (DAAs) is focused on the characterization of the 3D (space-time) spectra of the signals and the design of the corresponding 3D filters to improve the SIR. A single digital real-time 3D cone filter operates on the 3D FPA array of signals (as a pre-processor), prior to frequency-division in the FX architecture. We are also investigating applications of cone filters for improving SNR by attenuating the noise generated by the LNAs, thereby reducing the overall system noise temperature. Theoretical results indicate that substantial attenuation of LNA noise is possible with this technique and we await observational data in order to further investigate this possibility. Models have been developed to simulate mutually-coupled (MC) FPA noise. It is has been shown that moderate attenuation of MC noise is possible over the SKA mid-frequency range. A FPA field simulator package (UC-FPFC) has been developed that accurately determines the FPA field. It is now used as a research tool for our FPA-related work. This simulator package is available to SKA researchers.

During 2009-2010, much of the above has been summarized in the form of presentations at numerous SKA Workshops in Canada, the U.K. and New Zealand. A partial list of related and smart-antenna-related publications and a manuscript on cognitive radio systems is provided below.

Bibliography.

Thushara K. Gunaratne and Len T. Bruton, "A Polyphase Architecture For Broadband Bandpass Beamforming For Arrays of Arbitrarily Placed Sensors", Proceedings of IEEE Pacific Rim Conference on Communications, Computers and Signal Processing (PACRIM) 2009, Victoria, BC, Aug. 23-26 2009

Gunaratne, T.K., Bruton, L.T., ‘Adaptive Complex-Coefficient 2D FIR Trapezoidal Filters for Broadband Beamforming in Cognitive Radio Systems’,

journal manuscript, under review

G.J. Hovey, R. Conan, F. Gamache, G. Herriot, Z. Ljusic, D. Quinn, M. Smith, J.P. Veran and H. Zhang, “An FPGA Based Computing Platform for Adaptive Optics Control”, in the 1st AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes proceedings, 07006, 2010, edited by Y. Clénet, J.-M. Conan, T. Fusco and G. Rousset, published by EDP Sciences (ao4elt.edpsciences.org), DOI: 10.1051/ao4elt/201007006.

S.V. Hum, A. Madanayake, and L.T. Bruton, “UWB Beamforming using 2D Beam Digital Filters”, IEEE Transactions on Antennas and Propagation (TAP), vol. 57, no. 3, March 2009, pp. 804-807.

N. Liyanage, L. Bruton, and P. Agathoklis, ‘On the attenuation of interference and mutual coupling in antenna arrays using 3D space-time filters’, IEEE Pacific Rim Conference, PACRIM09, Victoria, B.C. Canada, 146–151, 2009.

N. Liyanage, ‘3D space-time digital filtering for radio astronomy’, Master’s thesis, Dept. of Electrical and Computer Eng., University of Victoria, BC, Canada, 2009

Liyanage, N.W., Bruton, L.T., Agathoklis, P. and Edussooriya, C., ‘Space-Time Digital Filtering of Radio Astronomy Signals using 3-D Cone Filters’, RFI Mitigation Workshop, Groningen, Netheleands, 29-31 March 2010.

Andrew R. Macpherson, Kenneth A. Townsend, James W. Haslett, “A 5GS/s Voltage-to-Time Converter in 90nm CMOS”, European Microwave Week, Nuova Fiera Di Roma, Rome, Italy, pp. 254 – 257, Sept. 28-Oct. 2, 2009.

A. Madanayake and L.T. Bruton, “Multidimensional Raster-Scanned LC-Ladder Wave-Digital Filter Hardware For Directional Filtering in Space-Time”, IEEE International Symposium on Circuits and Systems (ISCAS’2010), Paris, France, In Press, May 2010

E McMilin, D. Henke, S.Claude and J. Borneman  "A Low-Cost Directional Log Periodic Log Spiral Antenna", IEEE International Symposium on Antennas and Propagation, July 11-17 2010 Toronto.

Mostafa Rashdan, Abdel Yousif, James Haslett and Brent Maundy, “A New Time-Based Architecture for Serial Communication Links”, IEEE International Conference on Electronics, Circuits, and Systems, Yasmine Hammamet, Tunisia, Africa, December 13-16, 2009.

M. Rashdan, A. Yousif, J. Haslett and B. Maundy, "New Time-Based Serial Link Measurements on FPGA Board", 2010 IEEE International Symposium on Circuits and Systems, Paris, France, pp. 3977-3980, June 1-3, 2010.

K. A. Townsend, A. R. Macpherson, and J. W. Haslett, "A Fine-Resolution Time-to-Digital Converter for a 5GS/s ADC", 2010 IEEE International Symposium on Circuits and Systems, Paris, France, pp. 3024-3027, June 1-3, 2010.