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 6

Stanford Research Rb Source

March 15-17, 2012

EOVSA Preliminary Design Review 7

ALMA 16-way Optical Splitter

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 installation

March 15-17, 2012