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System Approach to RFI Mitigation for the SKA Rob Millenaar – SKA Program Development System Approach to RFI Mitigation for the SKA Rob Millenaar – SKA Program Development Office Albert-Jan Boonstra – ASTRON Rodolphe Weber – University of Orleans 30 March, 2010 RFI 2010 1

Overview • SPDO Introduction – Concepts of the SKA – Receptor technology types – Overview • SPDO Introduction – Concepts of the SKA – Receptor technology types – Array layout • System wide approach to RFI mitigation – – the RFI/EMI Environment EMC Reduction of susceptibility to RFI Mitigation in hardware and software 30 March, 2010 RFI 2010 2

SPDO Introduction Setting the scene 30 March, 2010 RFI 2010 3 SPDO Introduction Setting the scene 30 March, 2010 RFI 2010 3

The Square Kilometre Array SPDO In a nutshell: • The next generation radio telescope The Square Kilometre Array SPDO In a nutshell: • The next generation radio telescope with ~50 times sensitivity and ~10, 000 times the survey speed of the best current day radio telescopes. • It will operate from 70 MHz to 10 GHz • Baselines of 3000+ km • Candidate sites: – Southern Africa, Karoo – Australasia, Boolardy 30 March, 2010 RFI 2010 4

The Square Kilometre Array SPDO The SKA will have: – up to 3000 dishes, The Square Kilometre Array SPDO The SKA will have: – up to 3000 dishes, with: – wide band single pixel feeds – phased array feeds – ~1 GHz (300 MHz) to >10 GHz – up to 250 dense Aperture Array stations (56 m dia), with: – ~70, 000 dual pol elements, so ~150, 000 receiver chains for a total of ~4 107 – ~400 -~1400 MHz – up to 250 sparse Aperture Array stations (180 m dia), with: – ~10, 000 dual pol elements, so ~20, 000 receiver chains, for a total of ~5 106 – ~70 -~450 MHz 30 March, 2010 RFI 2010 5

Configuration 30 March, 2010 RFI 2010 SPDO 6 Configuration 30 March, 2010 RFI 2010 SPDO 6

Configuration 30 March, 2010 RFI 2010 SPDO 7 Configuration 30 March, 2010 RFI 2010 SPDO 7

The challenge • The conclusion should be that: SPDO – There will be various The challenge • The conclusion should be that: SPDO – There will be various types of technology, much of which is concentrated in high densities risk of strong electromagnetic coupling – With differing frequency ranges what is out-of-band RFI for one is inband for the other technology type, so all designs must be done for entire SKA frequency range! – With extreme required operational sensitivity RQZ and handpicked remote sites, plus further regulation – Systems and parts should be cheap to produce, to maintain challenges expensive shielding methods – Requires manageable data rates must limit number of bits to be transported and processed • This results in a nightmare for EMI and RFI control, the scale of which was never seen before. • Requires a rigorous system-wide mitigation approach. 30 March, 2010 RFI 2010 8

SPDO System Wide Mitigation of RFI 30 March, 2010 RFI 2010 9 SPDO System Wide Mitigation of RFI 30 March, 2010 RFI 2010 9

System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment EMC policy Reduction of susceptibility to RFI Mitigation in hardware and software 30 March, 2010 RFI 2010 10

System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment EMC policy Reduction of susceptibility to RFI Mitigation in hardware and software 30 March, 2010 RFI 2010 11

EMI/RFI Environment SPDO Provide best RFI/EMI environment • Investigate and select sites • Establish EMI/RFI Environment SPDO Provide best RFI/EMI environment • Investigate and select sites • Establish RQZ • Spectrum regulation/law making on local + national levels + active support of local community • Once the perfect site is found, place antennas sensibly (Configuration design) 30 March, 2010 RFI 2010 12

Site Selection • • • SPDO The two shortlisted sites are the best in Site Selection • • • SPDO The two shortlisted sites are the best in the preferred region on the globe. Further site characterisation is underway RFI has been measured and will be done again with higher sensitivity. 30 March, 2010 RFI 2010 13

RFI environment at the core • • • SPDO Site characterisation results of the RFI environment at the core • • • SPDO Site characterisation results of the campaign of 2005 are available. Next slide shows ‘mode 1’ results: inventory of strong RFI, potentially detrimental because of receiver linearity. Includes high speed sampling results (2μs) from 960 to 1400 MHz. Was done for 4 to 6 antenna pointings, two polarisations. Next slide shows results of two sites combined: 1. Take maximum level of pointings/polarisations per site; 2. Plot minima and maxima of the two datasets. 30 March, 2010 RFI 2010 14

RFI environment at the core SPDO Mode 1 overall spectrum, 70 MHz to 22 RFI environment at the core SPDO Mode 1 overall spectrum, 70 MHz to 22 GHz 30 March, 2010 RFI 2010 15

Unavoidable RFI SPDO It is evident that, regardless of all measures that we take, Unavoidable RFI SPDO It is evident that, regardless of all measures that we take, receiver systems will have to deal with unavoidable types of RFI: • Airborne – Comms – Narrow pulse & high power: nav/ATC (DME, SSR, …) • Satellites – – NOAA series Iridium, GPS, Galileo Geostationary (broadcasting, FLTSATCOM) … 30 March, 2010 RFI 2010 16

New RFI Campaign SPDO Purpose: High sensitivity measurements (close to RA 769 levels) at New RFI Campaign SPDO Purpose: High sensitivity measurements (close to RA 769 levels) at the core, and some remote sites at slightly less sensitivity. In addition high time resolution measurements to capture strong short events. The campaign: • Deployment at AUS and SA core sites, start measurements for ~2 months – Target start June 2010 – To coordinate with precursor site activities – Measure with identical equipment (tested and verified at same facility), same period. • • Measure selection (~4 per country) of remote sites Write site reports, by April 2011. 30 March, 2010 RFI 2010 17

New RFI Campaign SPDO Partners: • ASTRON data processing software, binary data format, reporting New RFI Campaign SPDO Partners: • ASTRON data processing software, binary data format, reporting software • SKA SA RF, trailer infrastructure, integration • CSIRO Digital spectrometer, data acquisition 30 March, 2010 RFI 2010 18

New RFI Campaign 30 March, 2010 RFI 2010 SPDO 19 New RFI Campaign 30 March, 2010 RFI 2010 SPDO 19

Campaign Sensitivity 30 March, 2010 RFI 2010 SPDO 20 Campaign Sensitivity 30 March, 2010 RFI 2010 SPDO 20

Radio Quiet Zones • • SPDO Both sites are establishing Radio Quiet Zones at Radio Quiet Zones • • SPDO Both sites are establishing Radio Quiet Zones at the location of the core. ~150 km radius Specific attention by ITU WP-7 D and Correspondence Group Activities are being monitored by a dedicated Task Force under the SCWG. Note: Presentations on RQZ’s yesterday 30 March, 2010 RFI 2010 21

Radio Quiet Zone Targets 30 March, 2010 RFI 2010 SPDO 22 Radio Quiet Zone Targets 30 March, 2010 RFI 2010 SPDO 22

Further spectrum regulation • • SPDO Spectrum regulation/law making on local + national levels. Further spectrum regulation • • SPDO Spectrum regulation/law making on local + national levels. Enforcement required. Support of local community – Alternative means of communication (cf. Adrian Tiplady’s talk) – Fibre to the farm – Fix noisy cars – Fix noisy electronics (cf. Pravin Raybole’s talk) • Work with industry on low noise power distribution, etc. 30 March, 2010 RFI 2010 23

Array Planning and Design SPDO Place antennas sensibly: • Zones of avoidance defined in Array Planning and Design SPDO Place antennas sensibly: • Zones of avoidance defined in ‘masks’ – buffer zones around EMI sources § Roads, rail, farms, towns – buffer zones around RFI sources § Mobile comms, broadcasting See presentation by Carol Wilson 30 March, 2010 RFI 2010 24

System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment EMC policy Reduction of susceptibility to RFI Mitigation in hardware and software 30 March, 2010 RFI 2010 25

EMC Policy SPDO Appoint EMC Manager, responsible for: • • Definition of standards, best EMC Policy SPDO Appoint EMC Manager, responsible for: • • Definition of standards, best practice descriptions from industry and radio astronomy community EMC requirements for all parts of project Application of these to all designs and equipment Assessment of COTS hardware risks and modification Development of test systems, methods Development of EMC plan including specifications Ongoing RFI monitoring ‘EMC police’ 30 March, 2010 RFI 2010 26

EMC Policy SPDO EMC rules apply in all directions: 30 March, 2010 RFI 2010 EMC Policy SPDO EMC rules apply in all directions: 30 March, 2010 RFI 2010 27

EMC Policy SPDO What are items to worry about? • • Radiating receivers or EMC Policy SPDO What are items to worry about? • • Radiating receivers or parts Digitisation at the receiver Telescope drive systems … But also: • • Wireless XX, remote YY, mobile ZZ in use by staff, contractors, visitors, tourists… This is a worry at any radio telescope, but for the SKA the scale is humongous. 30 March, 2010 RFI 2010 28

System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment EMC policy Reduction of susceptibility to RFI Mitigation in hardware and software 30 March, 2010 RFI 2010 29

Susceptibility SPDO Receiver robustness: a balancing act Design for • Wide band • High Susceptibility SPDO Receiver robustness: a balancing act Design for • Wide band • High gain • Low noise • Low cost • Manufacturability in large quantities 30 March, 2010 Design for • Sufficient Rx headroom • Linear operation, IP • Keep power requirements low RFI 2010 30

Susceptibility SPDO Digitisation: a balancing act Design for • High performance • SFDR • Susceptibility SPDO Digitisation: a balancing act Design for • High performance • SFDR • Required dynamic range: sky noise vs interference level that one aims to mitigate down the line • many bits 30 March, 2010 Design for • Low cost • Low power • Few bits, because of • Cost for hardware • Signal transport • Signal processing in station and correlator RFI 2010 31

System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment System Wide Approach SPDO What should be done • • Provide best RFI/EMI environment EMC policy Reduction of susceptibility to RFI Mitigation in hardware and software 30 March, 2010 RFI 2010 32

Mitigation • • SPDO Mike K: on-line RFI mitigation is possible and required, but Mitigation • • SPDO Mike K: on-line RFI mitigation is possible and required, but must be robust Hardware architecture/techniques: – Narrow channelisation in frequency and time allows old fashioned RFI excision to be efficient – Cancellation trough: § § § • ANC Parametric Estimation Spatial Filtering Subspace Filtering … Automated flagging/excision as part of the processing pipeline 30 March, 2010 RFI 2010 33

SPDO Conclusions 30 March, 2010 RFI 2010 34 SPDO Conclusions 30 March, 2010 RFI 2010 34

Conclusions • • We have a serious problem on our hands… But we can Conclusions • • We have a serious problem on our hands… But we can succeed if A system wide approach is followed, to SPDO – Select the best possible environment – Protect that pristine environment § By preventing self-generated RFI § By setting and enforcing appropriate design practices – Prevent unavoidable levels of RFI from hurting us § Robust receivers § Robust digitisation and processing – RFI consequences that still remain, dealt with by § Effective automatic detection and mitigation in hardware, pre- and postcorrelation, and in (pipeline) software 30 March, 2010 RFI 2010 35