Transcript Slide 1

Aperture Arrays system design
Front end RF combining:
an efficient way to reduce DC power requirements?
Philippe Picard Station de radioastronomie de Nançay [email protected]
Stephane Bosse Station de Radioastronome de Nançay [email protected]
Severin Barth Station de Radioastronomie de Nançay [email protected]
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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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
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
2
AA all digital system: generic design
2 pol antenna
elements
Tile level
LNA
LNA
LNA
LNA
LNA
LNA
Panc
Pdig = P1 + P2 + P3
P3=PSDP/N
P1
P2
Tile analogue conditioning,
Transport interface
Signal transport pol 1
Analogue
conditioning
ADC
Tile analogue conditioning,
Transport interface
Signal transport pol 2
Analogue
conditioning
ADC
Tile analogue conditioning,
Transport interface
Signal transport pol 1
Analogue
conditioning
ADC
Tile analogue conditionning,
Transport interface
Signal transport pol 2
Analogue
conditionning
ADC
Tile analogue conditioning,
Transport interface
Signal transport pol 1
Analogue
conditioning
ADC
Tile analogue conditioning,
Transport interface
Signal transport pol 2
Analogue
conditioning
ADC
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Station
digital processing
Plna
Philippe Picard
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AA with RF combining: generic design
16 x
2 pol antenna
elements
Panc
Tile level
LNA
LNA
LNA
Phase shif,t
Amplitude shift
Phase shift,
Amplitude shift
16 → 1

Phase shift,
Amplitude shift
Pdig
Tile analogue
conditioning,
Transport
interface,
Comand and
control interface
LNA
LNA
Phase shift,
Amplitude shift
Phase shift,
Amplitude shift
16 → 1

Phase shift,
Amplitude shift
Analogue
conditioning
ADC
Pint
beamformer chip pol 1
LNA
Pol. 1
Station
digital processing
Plna
Pbfc
Tile analogue
conditioning,
Transport
interface,
Comand and
control interface
Pol. 2
Analogue
conditioning
ADC
beamformer chip pol 2
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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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
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
N=75000 antennas
S=250 stations
2 pol.
Philippe Picard
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Parameter weights in the power_ratio:
Power saving
Emerging ASICs, FPGA and CPUs in 45nm and 32nm process
Today digital ASICs,FPGA and CPUs in
90nm and 65nm silicon process
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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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
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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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…
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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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
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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The end
Thank you
4th SKADS Workshop, Lisbon, 2-3 October 2008
System Design
Philippe Picard
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