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1PPS Timing and Reference Distribution Subsystem

1PPS Timing and Reference Distribution Subsystem. Wes Grammer NRAO. Outline. Design r equirements Top-level block d iagram Component selection Packaging and cooling Interfaces (mechanical and electronic) Costing and schedule ( TBD ).

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1PPS Timing and Reference Distribution Subsystem

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  1. 1PPS Timing and Reference Distribution Subsystem Wes Grammer NRAO 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) 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 Rbosc. calibration) • Environment: Indoor, temperature-controlled • MTBF > 10 years EOVSA Preliminary Design Review

  4. Timing Module Block Diagram 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 EOVSA Preliminary Design Review

  6. Stanford Research Rb Source EOVSA Preliminary Design Review

  7. ALMA 16-way Optical Splitter 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 EOVSA Preliminary Design Review

  9. Timing Distribution ModuleHardware Interfaces 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 installation EOVSA Preliminary Design Review

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