the alma data transmission system – digital portion
DESCRIPTION
The ALMA Data Transmission System – Digital Portion. Chris Langley ALMA Back End Integrated Product Team. The Challenge. Transmit 4 – 12 GHz Astronomical Data from the Front End (FE) Band Cartridges to the Correlator using Commercial Off The Shelf equipment wherever possible. The Challenge. - PowerPoint PPT PresentationTRANSCRIPT
5 - 8 January 2009 National Radio Science Meetings 1
The ALMA Data Transmission System – Digital Portion
Chris Langley
ALMA Back End Integrated Product Team
5 - 8 January 2009 National Radio Science Meetings 2
The Challenge
Transmit 4 – 12 GHz
Astronomical Data from the Front End (FE) Band
Cartridges to the Correlator using Commercial Off The Shelf equipment wherever possible.
5 - 8 January 2009 National Radio Science Meetings 3
The Challenge
Transmit 4 – 12 GHz
Astronomical Data from the Front End (FE) Band
Cartridges to the Correlator using Commercial Off The Shelf equipment wherever possible.
The Proposal
Convert FE data Digitally and Optically prior to transmission from each of 66 antennas.
5 - 8 January 2009 National Radio Science Meetings 4
The Flaw
COTS, or any other, D/A converters capable of
4 – 12 GHz inputs were not available during R&D.
5 - 8 January 2009 National Radio Science Meetings 5
The Flaw
COTS, or any other, D/A converters capable of
4 – 12 GHz inputs were not available during R&D.
The SolutionSeparate, or Down Convert, the 4 – 12 GHz two
polarity band into eight 2 – 4 GHz basebands prior to data conversion and transmission.
5 - 8 January 2009 National Radio Science Meetings 6
Astronomical Data Down Conversion & Transmission
P0 IFDCP0
LSB
Virtual Parallel Bus
10 Gb/s X 12≤ 15 Km
DTX 0
DTX 1
DTX 2
DTX 3 DRX 3
DRX 2
DRX 1
DRX 0BB 0
BB 1
BB 2
BB 3
BB 4
BB 5
BB 6
BB 7
BB 0
BB 2
BB 4
BB 6
BB 1
BB 3
BB 5
BB 7
BB 0
BB 1
BB 2
BB 3
BB 4
BB 5
BB 6
BB 7
P1 IFDC
4-12 GHz
USB
USB
LSB
P1
2-4 GHz
256 bits @ 125 MHz
Front End
Correlator
5 - 8 January 2009 National Radio Science Meetings 7
Data Transmission System
P0 IFDCP0LSB
Virtual Parallel Bus
10 Gb/s X 12≤ 15 Km
DTX 0
DTX 1
DTX 2
DTX 3 DRX 3
DRX 2
DRX 1
DRX 0BB 0
BB 1
BB 2
BB 3
BB 4
BB 5
BB 6
BB 7
BB 0
BB 2
BB 4
BB 6
BB 1
BB 3
BB 5
BB 7
BB 0
BB 1
BB 2
BB 3
BB 4
BB 5
BB 6
BB 7
P1 IFDC
4-12 GHz
USB
USB
LSBP1
2-4 GHz
256 bits @ 125 MHz
Front End
Correlator
5 - 8 January 2009 National Radio Science Meetings 8
Design Considerations (1/2)
• Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed
5 - 8 January 2009 National Radio Science Meetings 9
Design Considerations (1/2)
• Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed
• Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate
5 - 8 January 2009 National Radio Science Meetings 10
Design Considerations (1/2)
• Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed
• Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate
• Insertion of fill bits to convert input rate to signaling rate
5 - 8 January 2009 National Radio Science Meetings 11
Design Considerations (1/2)
• Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed
• Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate
• Insertion of fill bits to convert input rate to signaling rate• Use of time division digital de-multiplexing to transform
the channel signaling rate to the output signaling rate
5 - 8 January 2009 National Radio Science Meetings 12
Design Considerations (1/2)
• Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed
• Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate
• Insertion of fill bits to convert input rate to signaling rate• Use of time division digital de-multiplexing to transform
the channel signaling rate to the output signaling rate• Elimination of un-needed fill bits upon reception
5 - 8 January 2009 National Radio Science Meetings 13
Design Considerations (1/2)
• Operate at OC-192 (9.95328Gb/s) optical fiber signaling speed
• Use of time division digital multiplexing to transform the input signaling rate to the channel signaling rate
• Insertion of fill bits to convert input rate to signaling rate• Use of time division digital de-multiplexing to transform
the channel signaling rate to the output signaling rate• Elimination of un-needed fill bits upon reception• Use of three OC-192 channels per 2 GHz baseband to
achieve required capacity
5 - 8 January 2009 National Radio Science Meetings 14
Design Considerations (2/2)
• Low-voltage differential signaling (LVDS)– Fast rise/fall times– Noise resistant
5 - 8 January 2009 National Radio Science Meetings 15
Design Considerations (2/2)
• Low-voltage differential signaling (LVDS)– Fast rise/fall times– Noise resistant
• Multiple FPGA design per channel– More economical than single FPGA– Ball Grid Array package Lots of IO– 625+ MHz input signal capability
5 - 8 January 2009 National Radio Science Meetings 16
Design Considerations (2/2)
• Low-voltage differential signaling (LVDS)– Fast rise/fall times– Noise resistant
• Multiple FPGA design per channel– More economical than single FPGA– Ball Grid Array package– 625+ MHz input signal capability
• Commercial Optical “Half” Transponders– Change from original design– Became economical– Built in mux /demux, clock recovery
5 - 8 January 2009 National Radio Science Meetings 17
Design Considerations (2/2)
• Low-voltage differential signaling (LVDS)– Fast rise/fall times– Noise resistant
• Multiple FPGA design per channel– More economical than single FPGA– Ball Grid Array package– 625+ MHz input signal capability
• Commercial Optical “Half” Transponders– Economical– Built in mux /demux, clock recovery
• Air cooled (flow through) module, RFI shielded (-50 dBm)
5 - 8 January 2009 National Radio Science Meetings 18
Data Frame Organization
6 bits 5 bits 124 bits 16 bits4 bits4 bits
BIT
16
BIT
20
BIT
0
L
SB
(fir
st b
it)
BIT
6B
IT 7
LS
B
BIT
12
L
SB
of
pa
ylo
ad
BIT
14
4
L
SB
(fir
st b
it)
BIT
15
9
M
SB
(la
st b
it)
M
SB
of
pa
ylo
ad
LS
B’s
of
syn
c p
att
ern
Me
tafr
am
e in
de
x (1
bit)
Se
qu
en
ce c
ou
nt
4 L
SB
’s o
f p
ayl
oa
d
MS
B’s
of
syn
c p
att
ern
12
4 M
SB
’s o
f p
ayl
oa
d
che
cksu
m
5 - 8 January 2009 National Radio Science Meetings 19
Data Transmission SystemCloser View
Formatter &Optical
Transmitters
FiberOpticMUX
3-bit Digitizer
P0
3-bit Digitizer
P1
4 GHz
FiberOpticDe-
Mutiplexer
DRX 0Optical
Receivers &De-
Formatter
3-bits X 16@ 250 MHz
X4D (+/-)
D (+/-)
C
C
B
B
2 – 4 GHzP0
2 – 4 GHzP1
1-bit X 10 Gb/s X 12
DTX 1
DTX 2
DTX 3
EDFA
120 Gb/s
DRX 1
DRX 2
DRX 3
DTX 0
1-bit X 10 Gb/s X 12
3-bits X 32@ 125 MHz
X4
5 - 8 January 2009 National Radio Science Meetings 20
Data Transmitter Module(Digitizer and Formatter, 4 per Antenna)
5 - 8 January 2009 National Radio Science Meetings 21
Data Transmitter Module4 / Antenna
250 MHz, 15.6 psec stepped delay, 0 dBm
48ms, LVDS
4 GHz, 15.6 psec stepped delay, 0 dBm
125 MHz, 0 dBm
P0
P1
From IFP
From DGCKLRU
3 bitA/D
3 bitA/D
1:16Demux
1:16Demux
1:16Demux
1:16Demux
1:16Demux
1:16Demux
AMB 0x5X, X = 0, 1, 2, 3From ABM
FPGAB
FPGAD
FPGAC
TXP
TXP
TXP
AMBSI-2
SPI
SPI DG
To FOM
B Bits
D Bits
C Bits
DG FR
MCPS
Backplane
5.0 VDC
15.0 VDC
Power Harness
PCB
-5.2 VDC
3.3 VDC
PWR FILTERSFrom PSAC
48 VDC
3.3
VD
C
5.0
VD
C
-5.2
VD
C
3.3
VD
C
5.0
VD
C
15
.0 V
DC
48 VDC
From FOMOptical Keep Alive
2.13-3.95 GHz0 +/- 1 dBm
- 10 dB
- 10 dB
P0
P1
ITU Wavelength
21, 27, 33, or 39
ITU Wavelength
25, 31, 37, or 43
ITU Wavelength
23, 29, 35 or 41
5 - 8 January 2009 National Radio Science Meetings 22
Digitizer AssemblyUniversity of Bordeaux
5 - 8 January 2009 National Radio Science Meetings 23
Formatter with 3 Optical Transmitting Transponders
5 - 8 January 2009 National Radio Science Meetings 24
Data Receiver Module(De-Formatter with 3 Optical Receiving Transponders)
5 - 8 January 2009 National Radio Science Meetings 25
Data Receiver Module4 / Antenna
AMBSI-2
FPGAAltera EP1S20F780C5 D Bits
RX Transponder with 1:16 DeMux
From FOAD
156.25 MHz
Data (D Bits)
16 bits @ 625 Mb/s
Recovered Data Clk
625 MHz
Steering Clk
FPGAAltera EP1S20F780C5 C Bits
RX Transponder with 1:16 DeMux
From FOAD
156.25 MHz
Data (C Bits)
16 bits @ 625 Mb/s
Recovered Data Clk
625 MHz
Steering Clk
FPGAAltera EP1S20F780C5 B Bits
RX Transponder with 1:16 DeMux
From FOAD
156.25 MHz
I2C Bus
Control Bits
Data (B Bits)
16 bits @ 625 Mb/s
Recovered Data Clk
625 MHz
Steering Clk
JTAG ChainSPI
-5.2 VDC
1.8 VDC
3.3 VDC
5.0 VDC
-5.2 VDC
1.8 VDC
3.3 VDC
5.0 VDC
-5.2 VDC
1.8 VDC
3.3 VDC
5.0 VDC
DC Power Regulation1
.5 V
DC
-5.2
VD
C
1.8
VD
C
3.3
VD
C
5.0
VD
C
5.0 VDC 3.3 VDC
48 VDC
SPI
SPI
JTAG Chain
JTAG ChainFPGA Comm.
FPGA Comm.
1.5 VDC
3.3 VDC
1.5 VDC
3.3 VDC
1.5 VDC
3.3 VDC
From Station Bin Motherboard
125 MHz
48 ms
10 Gb/s
10 Gb/s
10 Gb/s
3.3 VDC
P0
P1
P0
P1
P0
P1
32 bits each @ 125 MHz
32 bits each @ 125 MHz
32 bits each @ 125 MHz
Configuration EEPROM Altera EPC16QC100
AMB
To / From Correlator Station Bin Motherboard
5 - 8 January 2009 National Radio Science Meetings 26
DTS Modules for 1 Antenna
Digitizer Clock
IRAM, NRAO
Data Transmitters
U of Bordeaux,NRAO
Fiber Optic Multiplexer
Jodrell Bank Observatory
Fiber Optic Amplifier /
Demultiplexer
Jodrell Bank Observatory
Data Receivers
NRAO
5 - 8 January 2009 National Radio Science Meetings 27
DTS Link Tests - ALMA Antenna to LabChile, 8/2008
5 - 8 January 2009 National Radio Science Meetings 28
DTS Link Tests - ALMA Antenna to LabChile, 8/2008
5 - 8 January 2009 National Radio Science Meetings 29
Things We’d Do Differently …
• Single FPGA per channel!– FPGA logic timing is difficult– Economics will likely catch up
• Closer interaction between hardware and firmware designers– Each should be the other’s backup
• Invite external expert’s opinions sooner during the design process
• Test Stand– Design and build once assembly form factors are determined
• Communication between remote team members was good, but could have been better– Specify an early DTS design review for the international partners
5 - 8 January 2009 National Radio Science Meetings 30
Acknowledgements
• Robert Freund, Principle Engineer, Arizona Radio Observatory
• Paula Metzner, DTS Product Engineer, Atacama Large Millimeter Array, National Radio Astronomy Observatory
… and the entire DTS teams from North America, the University of Bordeaux, IRAM (Grenoble, FR), and Jodrell Bank Observatory (~Manchester, UK).
R. W. Freund, ALMA Memo 420: Digital Transmission System Signaling Protocol, 2002
R. W. Freund and C. Langley, BE Critical Design Review, 2004.
References
5 - 8 January 2009 National Radio Science Meetings 31
Auxiliary Slides
5 - 8 January 2009 National Radio Science Meetings 32
Data Transmission System Overview The Partners
UB Effort
UK Effort
US Effort
To FOAD#2 - #50
To FIR/Correlator
Fibers
10 GB/s Fibers
Cable
15 Km
~185 Similar CablesAntennas & Sites
Control Building
Cables Fibers
12 1
50 49
~186 Cables
LO M/C Fibers
1
50
Fibers
12
1
Fiber
DG
(4)
FRTXT(4)
FOMux
FOPatchPanel
SpliceRack
FOADAnt #1
DFRRXT(4)
LO, M/C Fibers
FromIFP,2 - 4 GHz,Two
Polarities
2 base bands x 96 bits
@ 125 MHz
Antennas 2- 50
Antenna 1
Positions for 49 more Antennas
120 GB/s Fibers
5 - 8 January 2009 National Radio Science Meetings 33
System Requirements
• Repeatable latency with no loss of samples
5 - 8 January 2009 National Radio Science Meetings 34
System Requirements
• Repeatable latency with no loss of samples• Bit error rate < 10-6 (End of Life)
5 - 8 January 2009 National Radio Science Meetings 35
System Requirements
• Repeatable latency with no loss of samples• Bit error rate < 10-6 (End of Life)• Multi-channel synchronization loss < 10-4 s
5 - 8 January 2009 National Radio Science Meetings 36
System Requirements
• Repeatable latency with no loss of samples• Bit error rate < 10-6 (End of Life)• Multi-channel synchronization loss < 10-4 s• 16 GHz analog bandwidth source
5 - 8 January 2009 National Radio Science Meetings 37
System Requirements
• Repeatable latency with no loss of samples• Bit error rate < 10-6 (End of Life)• Multi-channel synchronization loss < 10-4 s• 16 GHz analog bandwidth source• Nyquist sampled data
5 - 8 January 2009 National Radio Science Meetings 38
System Requirements
• Repeatable latency with no loss of samples• Bit error rate < 10-6 (End of Life)• Multi-channel synchronization loss < 10-4 s• 16 GHz analog bandwidth source• Nyquist sampled data• 3-bit data word
5 - 8 January 2009 National Radio Science Meetings 39
System Requirements
• Repeatable latency with no loss of samples• Bit error rate < 10-6 (End of Life)• Multi-channel synchronization loss < 10-4 s• 16 GHz analog bandwidth source• Nyquist sampled data• 3-bit data word• Data transmission synchronized with ALMA
timing
5 - 8 January 2009 National Radio Science Meetings 40
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel
5 - 8 January 2009 National Radio Science Meetings 41
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample
5 - 8 January 2009 National Radio Science Meetings 42
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels
5 - 8 January 2009 National Radio Science Meetings 43
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels• 96 Gb/s per antenna (120 Gb/s encoded data)
5 - 8 January 2009 National Radio Science Meetings 44
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels• 96 Gb/s per antenna (120 Gb/s encoded data)• 250 MHz input word rate (96-bit wide parallel word)
5 - 8 January 2009 National Radio Science Meetings 45
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels• 96 Gb/s per antenna (120 Gb/s encoded data)• 250 MHz input word rate (96-bit wide parallel word)• 125 MHz output word rate (192-bit wide parallel
word)
5 - 8 January 2009 National Radio Science Meetings 46
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels• 96 Gb/s per antenna (120 Gb/s encoded data)• 250 MHz input word rate (96-bit wide parallel word)• 125 MHz output word rate (192-bit wide parallel
word)• Grouping of a polarization pair: 24 Gb/s per pair
5 - 8 January 2009 National Radio Science Meetings 47
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels• 96 Gb/s per antenna (120 Gb/s encoded data)• 250 MHz input word rate (96-bit wide parallel word)• 125 MHz output word rate (192-bit wide parallel
word)• Grouping of a polarization pair: 24 Gb/s per pair• Walsh function 180° switching
5 - 8 January 2009 National Radio Science Meetings 48
System OverviewExplicit requirements
• 4 GSa/s per 2 GHz bandwidth IF channel• 3 bits per sample• 2 Polarizations x 4 IF channels• 96 Gb/s per antenna (120 Gb/s encoded data)• 250 MHz input word rate (96-bit wide parallel word)• 125 MHz output word rate (192-bit wide parallel
word)• Grouping of a polarization pair: 24 Gb/s per pair• Walsh function 180° switching• 15 Km (maximum) distance
5 - 8 January 2009 National Radio Science Meetings 49
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
5 - 8 January 2009 National Radio Science Meetings 50
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
• Fast frame synchronization
5 - 8 January 2009 National Radio Science Meetings 51
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
• Fast frame synchronization• Continuous transmission of data
5 - 8 January 2009 National Radio Science Meetings 52
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
• Fast frame synchronization• Continuous transmission of data• Low error rates throughout operational life
5 - 8 January 2009 National Radio Science Meetings 53
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
• Fast frame synchronization• Continuous transmission of data• Low error rates throughout operational life• Operation independent of payload content
5 - 8 January 2009 National Radio Science Meetings 54
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
• Fast frame synchronization• Continuous transmission of data• Low error rates throughout operational life• Operation independent of payload content• Testing strategies
5 - 8 January 2009 National Radio Science Meetings 55
System OverviewImplied requirements
• Configurable if not deterministic timing (repeatable latency)
• Fast frame synchronization• Continuous transmission of data• Low error rates throughout operational life• Operation independent of payload content• Testing strategies• Economical implementation
5 - 8 January 2009 National Radio Science Meetings 56
Auxilary Slides
DTS Single Bit Data Path(VHDL Top Level)
5 - 8 January 2009 National Radio Science Meetings 57
Frame Implementation
• 160 bit frame• 128-bit payload• 10-bit synchronization word• 5-bit meta-frame sequence word• 1-bit meta-frame index• 16-bit odd parity check word
5 - 8 January 2009 National Radio Science Meetings 58
Design Decisions
• Use of a data block (frame) to facilitate multiplexing
5 - 8 January 2009 National Radio Science Meetings 59
Design Decisions
• Use of a data block (frame) to facilitate multiplexing• Use of a synchronization (framing) word to facilitate
frame detection
5 - 8 January 2009 National Radio Science Meetings 60
Design Decisions
• Use of a data block (frame) to facilitate multiplexing• Use of a synchronization (framing) word to facilitate
frame detection• Use of scrambling techniques to minimize bit sequence
effects, low frequency content, and to maintain signal balance
5 - 8 January 2009 National Radio Science Meetings 61
Design Decisions
• Use of a data block (frame) to facilitate multiplexing• Use of a synchronization (framing) word to facilitate
frame detection• Use of scrambling techniques to minimize bit sequence
effects, low frequency content, and to maintain signal balance
• Use of a meta-frame to synchronize the reception of multiple channels
5 - 8 January 2009 National Radio Science Meetings 62
Design Decisions
• Use of a data block (frame) to facilitate multiplexing• Use of a synchronization (framing) word to facilitate
frame detection• Use of scrambling techniques to minimize bit sequence
effects, low frequency content, and to maintain signal balance
• Use of a meta-frame to synchronize the reception of multiple channels
• Use of a meta-frame index to synchronize reception to ALMA timing under varying propagation delays
5 - 8 January 2009 National Radio Science Meetings 63
Design Decisions
• Use of a data block (frame) to facilitate multiplexing• Use of a synchronization (framing) word to facilitate
frame detection• Use of scrambling techniques to minimize bit sequence
effects, low frequency content, and to maintain signal balance
• Use of a meta-frame to synchronize the reception of multiple channels
• Use of a meta-frame index to synchronize reception to ALMA timing under varying propagation delays
• Use of a checksum word to facilitate continuous monitoring of received data integrity
5 - 8 January 2009 National Radio Science Meetings 64
Auxilary Slides
DTX Formatter FPGAs and Transponders
625 MHz
625 MHz
625 MHz
625 MHz
625 MHz
625 MHz
FIBER10 GBs
FIBER10 GBs
FIBER10 GBs
TTX FRAME DATA D
TTX FRAME DATA C
TTX FRAME DATA B
TTX 1
TTX 2
TTX 3
u100
u200
u300
ADC
D
C
B
TTX SPI
DATA
CLK
SPI
DATA
DATA
CLK
CLK
SPI
SPI
SPI
TE
GE
NT
E G
EN
AM
BS
I SP
IA
MB
SI S
PI
FR
AM
E
SY
NC
FR
AM
E
SY
NC
BB0
BB1
FRAMECLK
BB0
BB1
BB0
BB1
FRAMECLK
FRAMECLK
SPI
DIGITIZER SPI
TESYS
SYSCLK
AMBSI
DIGITIZER
CLOCK DIVIDER
BB0A
BB1A
4GHz
250MHzphase shifted
16
16
16
16
16
16
16
5 - 8 January 2009 National Radio Science Meetings 65
Auxilary Slides
DRX De-Formatter FPGAs and Transponders
BB0
BB1
BB0
BB1
BB0
BB1625 MHz
625 MHz
625 MHz
FIBER10 GBs
FIBER10 GBs
FIBER10 GBs
TRX MUX’D DATA D
TRX MUX’D DATA C
TRX MUX’D DATA B
TRX 1
TRX 2
TRX 3 TOP_C
MID_B
BOT_A
EEPROM
D
C
B
TRX I2C
DATA
CLK
I2C
DATA
DATA
CLK
CLK
I2C
I2CSPI
TE
GE
NT
E G
EN
AM
BS
I SP
IA
MB
SI S
PI
FR
AM
E S
YN
CF
RA
ME
SY
NC
SYSCLK
AMBSI
16
16
16
FR
AM
E C
OU
NT
FR
AM
E C
OU
NT
SP
EC
DE
LAY
REF CLK
REF CLK
REF CLK
32
32
32
32
32
32
CORRELATORDATA
196 BITS @ 125 MHz
TE
4
5 - 8 January 2009 National Radio Science Meetings 66
Auxiliary Slides
Frame Synchronizations
►Frame synchronization (10-bit synchronization word)
• Multi-channel synchronization (5-bit meta-frame sequence word)
• Determination of propagation delay (1-bit meta-frame index)
5 - 8 January 2009 National Radio Science Meetings 67
Auxilary Slides
Frame Synchronizations
• Frame synchronization (10-bit synchronization word)• Multi-channel synchronization (5-bit meta-frame
sequence word)• Determination of propagation delay (1-bit meta-frame
index)
5 - 8 January 2009 National Radio Science Meetings 68
Auxiliary Slides
Frame synchronization (10-bit synchronization word)
• Unique or “unique enough” pattern to minimize acceptance of erroneous patterns in random data
• Long enough pattern to eliminate the acceptance of erroneous pattern in static data
• Partitioned pattern to eliminate the acceptance of a correct pattern in an incorrectly configured system
• Three acceptance stages required to qualify a 10-bit quantity as the synchronization pattern
5 - 8 January 2009 National Radio Science Meetings 69
Auxiliary Slides
Stages for Frame Synchronization
• Search:
selection of an initial location within the serial bit-stream followed by the shifting of the location until a candidate synchronization word is located
• Check:
continued observations in subsequent frames until unsuccessful criterion (failure)
• Monitor:
once confirmed, continuous monitoring of all frames to ensure proper operation
5 - 8 January 2009 National Radio Science Meetings 70
Auxiliary Slides
Frame Synchronizations
• Frame synchronization (10-bit synchronization word)
►Multi-channel synchronization (5-bit meta-frame sequence word)
• Determination of propagation delay (1-bit meta-frame index)
5 - 8 January 2009 National Radio Science Meetings 71
Auxiliary Slides
Multi-channel synchronization (5-bit meta-frame sequence word)
• Sequence word large enough to accommodate worst case relative variation in propagation delay across the three channels
• Integer number of meta-frames contained within one 48.000ms timing period
• Transmitter simultaneously writes the identical incrementing sequence number in frames of all three channels
• Receiver compares and re-times the frames from the three channels thus synchronizing the meta-frames
5 - 8 January 2009 National Radio Science Meetings 72
Auxiliary Slides
Frame Synchronizations
• Frame synchronization (10-bit synchronization word)
• Multi-channel synchronization (5-bit meta-frame sequence word)
►Determination of propagation delay (1-bit meta-frame index)
5 - 8 January 2009 National Radio Science Meetings 73
Auxiliary Slides
Determination of propagation delay (1-bit meta-frame index)
• Transmitter uniquely identifies the first meta-frame following a 48.000ms timing event
• Monitor and Control system obtains the count of frames received following the local 48.000ms timing event and the detection of the meta-frame index bit
• Monitor and Control system command the receiver to adjust its internal frame delay to a specific relative value
5 - 8 January 2009 National Radio Science Meetings 74
Auxilary Slides
Scrambling
• Modification of source data to accommodate specific characteristics of the communication channel
• Provides adequate timing for the clock and data recovery electronics
• Provides a signal balance for the AC coupled circuits which minimizes threshold errors
• Pattern is easily produced by a maximally length shift register generator
• Sync word is exempt from scrambling• For 149 -> 0, Result <= output pattern (shifted +1) XOR
input pattern
5 - 8 January 2009 National Radio Science Meetings 75
Auxilary Slides
Data Integrity
• Parity computation is easier than CRC• 16-bit parity word over 144 bits• Each parity bit monitors 9 other bits• Permits continuous monitoring of transmission quality
5 - 8 January 2009 National Radio Science Meetings 76
Auxiliary Slides
Self Test Methods
• 10 GHz clock recovery• Frame detection• Multiple channel synchronization• Scrambled pattern exercises• Random Number Generation• Checksum (parity) checks• FFT of pseudo Front End data (gain flatness,
CW beacon)
5 - 8 January 2009 National Radio Science Meetings 77
Formatter Block Diagram
Protocol Encoder
HalfTransponder
Protocol Encoder
HalfTransponder
Protocol Encoder
HalfTransponder
Sixteen10:1 Mux’s
Sixteen10:1 Mux’s
Sixteen10:1 Mux’s
1:4 Demux
1:4 Demux
1:4 Demux
250 Mb/s 625 Mb/s62.5 Mb/s 62.5 Mb/s 10 Gb/s(1bit optical)
20.833 Hz
125 MHz
(128 bits) (160 bits) (16bits)
MCEngine
X5MultiplierDC-DC
Converters
Monitor PointA/D’s & Mux’s
(32 bits)
FPGA 1
FPGA 2
FPGA 3
P0
P1
P0
P1
P0
P1
3.3 VDC
From Digitizer Assembly
From DGCK
To FOM
To / From Digitizer Assembly
From MC / PS
To / From MC / PSBoard
-5.2 VDC
5 VDC
15 VDC 625 MHz
Laser Keep Alive
From FOM
5 - 8 January 2009 National Radio Science Meetings 78
Auxilary Slides
Digitizer Clock Module
5 - 8 January 2009 National Radio Science Meetings 79
Auxilary Slides
Digitizer Clock AssemblyIRAM, Grenoble
5 - 8 January 2009 National Radio Science Meetings 80
Auxilary Slides
Fiber Optic MultiplexerJodrell Bank Observatory
5 - 8 January 2009 National Radio Science Meetings 81
Auxilary Slides
Fiber Optic Amplifier / Demultiplexer
5 - 8 January 2009 National Radio Science Meetings 82
Auxilary Slides
Transmitter Module – Internal View
Formatter
Digitizers
Monitor Control &Power Supply
Backplane
5 - 8 January 2009 National Radio Science Meetings 83
Auxilary Slides
DTS Test Stand
• “Golden” Modules– 2 Data Transmitters– 1 Digitizer Clock– 2 Data Receivers
• Support Electronics– PC with LabView
Interface– System timing– Data Receiver
backplane
5 - 8 January 2009 National Radio Science Meetings 84
Things We’d Do Differently …
• Single FPGA per channel!– FPGA logic timing is difficult– Economics will likely catch up
5 - 8 January 2009 National Radio Science Meetings 85
Things We’d Do Differently …
• Single FPGA per channel!– FPGA logic timing is difficult– Economics will likely catch up
• Closer interaction between hardware and firmware designers– Each should be the other’s backup
5 - 8 January 2009 National Radio Science Meetings 86
Things We’d Do Differently …
• Single FPGA per channel!– FPGA logic timing is difficult– Economics will likely catch up
• Closer interaction between hardware and firmware designers– Each should be the other’s backup
• Invite external expert’s opinions sooner during the design process
5 - 8 January 2009 National Radio Science Meetings 87
Things We’d Do Differently …
• Single FPGA per channel!– FPGA logic timing is difficult– Economics will likely catch up
• Closer interaction between hardware and firmware designers– Each should be the other’s backup
• Invite external expert’s opinions sooner during the design process
• Test Stand– Design and build once assembly form factors are determined