1pps timing and reference distribution subsystem wes grammer nrao march 15-17, 2012eovsa preliminary...
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EOVSA Preliminary Design Review 1
1PPS Timing and Reference Distribution Subsystem
Wes GrammerNRAO
March 15-17, 2012
EOVSA Preliminary Design Review 2
Outline
• Design requirements• Top-level block diagram• Component selection• Packaging and cooling• Interfaces (mechanical and electronic)• Costing and schedule (TBD)
March 15-17, 2012
EOVSA Preliminary Design Review 3
1PPS Timing, Reference Distribution Subsystem Requirements
• Distribute 1PPS pulse from GPS to:– Front End controllers in all 15 antennas, via SM fiber, with 10 us time precision, 0-5V
TTL level– Correlator, DPP, Control system, LO1 synthesizer (2), with 1 us time precision, 0-5V
TTL level• Generate and distribute stable 10 MHz sine wave reference to:
– LO1 synthesizer (2), P_in = -5 dBm, min.– LO2 multiplier (1), P_in = +13 dBm, nom.– Correlator (1), P_in = +16 dBm, max.
• Generate and distribute 50 Hz timing pulse:– Derived from 10 MHz reference, and synchronized to GPS 1PPS within 100 ns– To Correlator, DPP, LO1 synthesizer (2), with 1 us time precision, 0-5V TTL level
• Monitor and Control: RS-232 (opt., for 10 MHz Rb osc. calibration)• Environment: Indoor, temperature-controlled• MTBF > 10 years
March 15-17, 2012
EOVSA Preliminary Design Review 4
Timing Module Block Diagram
March 15-17, 2012
FPGA
TEGen
BPSKMod
10MHz
Correlator
0-5V TTL
OpticalTX
1532 nm
DPP
LO1-A
TE (Coax) 1PPS (Copper/Coax)
Timing Generator Module
1PPS (Fiber)
0-5V TTL
0-5V TTL
Rb Osc
6-way Splitter
GPS RX
10 MHz Reference
0-5V TTL
LO1-B
1:16 16 Ant 1-15
Correlator
0-5V TTL
DPP
LO1-A
0-5V TTL
0-5V TTL
0-5V TTL
LO1-B
50 Hz pulse
Control Sys.0-5V TTL
In
Correlator
LO2 x15
LO1-A
LO1-B
(Spare)
1PPS
1PPSInput
GPSAntenna
EOVSA Preliminary Design Review 5
Component Selection• GPS receiver is pre-existing unit at site, Arbiter Systems model 1093• 10 MHz reference is Stanford Research PRS10c, purchased by NJIT• 16-way fiber splitter can be a planar waveguide type used on ALMA
– Well-matched path lengths, within 50 mm– 1500-1560 nm operation– FC/APC connectorized– Low cost, ~$400 (or possibly free)
• Fiber modulator/demodulator link for 1PPS can use similar components to ALMA CRD and LORR modules, which perform almost the same function (1532 nm)
• RF distribution uses a single medium-power amplifier• Individual buffer amps could be used, for better port-port isolation. Down
side is larger differential phase drift (spec?) • Other components TBD
March 15-17, 2012
EOVSA Preliminary Design Review 8
Packaging and Cooling
• All components other than the GPS can likely fit in a single 2U or 3U high rack mount chassis
• Integrated linear DC power supply• A single 10 MHz distribution amplifier may
need a cooling fan; output would be > 250 mW. For individual amps, good heat sinking to the chassis is sufficient
March 15-17, 2012
EOVSA Preliminary Design Review 9
Timing Distribution ModuleHardware Interfaces
March 15-17, 2012
To Signal Name Dir. Type Mode Range Min Range Max Unit Connector
Antenna (GN) 1 pps In Pulse Analog Elec 0 5 V BNC
DC/LO (WG) 1 pps In Pulse Analog Elec 0 5 V BNC
10 MHz Ref In RF CW Analog Elec (TBD) 16 dBm BNC
50 Hz Sync In Pulse Analog Elec 0 5 V BNC
Correlator (NS) 1 pps In Pulse Analog Elec 0 5 V SMA
10 MHz Ref In RF CW Power Analog Elec (TBD) 16 dBm SMA
50 Hz Sync In Pulse Analog Elec 0 5 V SMA
DPP (GH) 1 pps In Pulse Analog Elec 0 5 V SMA
50 Hz Sync In Pulse Analog Elec 0 5 V SMA
Control (GN) 1 pps In Pulse Analog Elec 0 5 V SMA
EOVSA Preliminary Design Review 10
Important Schedule Dates for Timing Distribution Subsystem
• Specify and quote remaining system components, get these on order by the end of April.
• Complete enclosure fabrication drawings by June 1, send out for quotes, begin fab in mid-June
• July 1 – July 15: Order cables, connectors, wire, remaining components for prototype unit construction and site installation (for central building + 3 antennas)
• August – September: Assemble and test Timing Distribution module, 1PPS RX/demodulators for 3 antennas
• October 1: Ship hardware to California for installationMarch 15-17, 2012
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