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Aperture Arrays system design

Aperture Arrays system design. Front end RF combining: an efficient way to reduce DC power requirements?. Philippe Picard Station de radioastronomie de Nançay Philippe.Picard@obs-nancay.fr Stephane Bosse Station de Radioastronome de Nançay Stephane.Bosse@obs-nancay.fr

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Aperture Arrays system design

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  1. Aperture Arrays system design Front end RF combining: an efficient way to reduce DC power requirements? Philippe Picard Station de radioastronomie de Nançay Philippe.Picard@obs-nancay.fr Stephane Bosse Station de Radioastronome de Nançay Stephane.Bosse@obs-nancay.fr Severin Barth Station de Radioastronomie de Nançay Severin.Barth@obs-nancay.fr

  2. About DC power parameter DC power requirement is a driving parameter for yearly recurrent operating cost and could be very high for AA systems with millions of antenna elements and associated digital processing Need of ultra low power design wherever it can apply • An all digital system can be viewed as power hungry system • the most flexible system • « max. instantaneous FoV » ~ antenna element FoV • calibration parameters apply to the antenna element level • A system with front end RF combining can be viewed as a way to reduce power • « max. instantaneous FoV » reduced by the combining factor • not so easy to calibrate compared to an all digital system

  3. Pdig = P1 + P2 + P3 Panc Plna P3=PSDP/N P2 P1 AA all digital system: generic design Tile level 2 pol antenna elements LNA Signal transport pol 1 Tile analogue conditioning, Transport interface Analogue conditioning ADC LNA Signal transport pol 2 Analogue conditioning Tile analogue conditioning, Transport interface ADC LNA Signal transport pol 1 Tile analogue conditioning, Transport interface Analogue conditioning ADC Station digital processing LNA Signal transport pol 2 Analogue conditionning Tile analogue conditionning, Transport interface ADC LNA Signal transport pol 1 Tile analogue conditioning, Transport interface Analogue conditioning ADC LNA Signal transport pol 2 Analogue conditioning Tile analogue conditioning, Transport interface ADC

  4. Pbfc Pdig Panc Plna Pint AA with RF combining: generic design Tile level LNA 16 x 2 pol antenna elements Phase shif,t Amplitude shift LNA Tile analogue conditioning, Transport interface, Comand and control interface Pol. 1 16 → 1 Phase shift, Amplitude shift  Analogue conditioning ADC LNA Phase shift, Amplitude shift Station digital processing beamformer chip pol 1 LNA Phase shift, Amplitude shift LNA Tile analogue conditioning, Transport interface, Comand and control interface Pol. 2 Phase shift, Amplitude shift 16 → 1  Analogue conditioning ADC LNA Phase shift, Amplitude shift beamformer chip pol 2

  5. Pref= reference total power for 1 polarization, all digital design Peqc = power for 1 polarization with RF combining + digital processing power_ratio = Peqc / Pref plot versus Pdig Plna = DC power (LNA) Panc = DC power (tile analog contitioning + transport interface) Pdig = DC power ( ADC analog conditionning + ADC + station processing 1 pol.) Pbfc = DC power for 1 input of beamformer chip Pint = DC power for command and control interface comb = combining factor nbeam = number of RF beams DCeffan = analogue power supply efficiency (0.6) DCeffdig = digital power supply efficiency (0.72) Pref = (Plna +Panc)/DCeffan + Pdig/DCeffdig Peqc= Plna/DCeffan + (Pbfc/DCeffan).nbeam + ((Panc/DCeffan)+(Pdig+Pint)/DCeffdig) / comb).nbeam For a system with N antennas per station, 2 pol., S stations: DC power (all digital) = 2.N.S.Pref. DC power (RF combining) = 2.N.S.Pref.power_ratio N=75000 antennas S=250 stations 2 pol.

  6. Emerging ASICs, FPGA and CPUs in 45nm and 32nm process Power saving Today digital ASICs,FPGA and CPUs in 90nm and 65nm silicon process Parameter weights in the power_ratio:

  7. RF beams: multibeaming or not? • For the same total instantaneous FoV options are: • to combine a small number snb of elements in one RF beam • to combine k.snb elements in k separate RF beams For DC power efficiency, it’s better to combine a small number of elements in one RF beam

  8. Be aware, it’s only a tool… With clever input parameters it’s easy to show what we want to show… Only a deep documented analysis of the power budget for a specific design can deliver accurate input parameters…

  9. To do next: An all digital AA design gives the most flexible system and easiest to use, but if MW are not for free, RF combining can reduce DC power (with reduced instantaneous RF FoV and calibration to be considered) => Need to be able to test the two systems in the next AA developpment phases • Design front end with optional RF combiners (as front end « plug ins »?) • Design station digital processing being able to optionally accept RF combined antennas at inputs • Continue to work on RF combiners with the newest Si process

  10. The end Thank you

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