1PPS Timing and Reference Distribution Subsystem Wes Grammer NRAO March 15-17, 2012EOVSA Preliminary Design Review1

Outline Design requirements Top-level block diagram Component selection Packaging and cooling Interfaces (mechanical and electronic) Costing and schedule (TBD) March 15-17, 2012EOVSA Preliminary Design Review2

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, 2012EOVSA Preliminary Design Review3

Timing Module Block Diagram March 15-17, 2012EOVSA Preliminary Design Review4

Component Selection GPS receiver is pre-existing unit at site, Arbiter Systems model 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 – 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, 2012EOVSA Preliminary Design Review5

Stanford Research Rb Source March 15-17, 2012EOVSA Preliminary Design Review6

ALMA 16-way Optical Splitter March 15-17, 2012EOVSA Preliminary Design Review7

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, 2012EOVSA Preliminary Design Review8

Timing Distribution Module Hardware Interfaces March 15-17, 2012EOVSA Preliminary Design Review9 ToSignal NameDir.TypeModeRange MinRange MaxUnitConnector Antenna (GN)1 ppsInPulseAnalog Elec05VBNC DC/LO (WG)1 ppsInPulseAnalog Elec05VBNC 10 MHz RefInRF CWAnalog Elec(TBD)16dBmBNC 50 Hz SyncInPulseAnalog Elec05VBNC Correlator (NS)1 ppsInPulseAnalog Elec05VSMA 10 MHz RefInRF CW PowerAnalog Elec(TBD)16dBmSMA 50 Hz SyncInPulseAnalog Elec05VSMA DPP (GH)1 ppsInPulseAnalog Elec05VSMA 50 Hz SyncInPulseAnalog Elec05VSMA Control (GN)1 ppsInPulseAnalog Elec05VSMA

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 March 15-17, 2012EOVSA Preliminary Design Review10