LO Distribution Subsystem Wes Grammer NRAO March 15-17, 2012EOVSA Preliminary Design Review1

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

LO Distribution Subsystem Design Requirements and Specifications Deliver +10 dBm min. LO power to 1 st and 2 nd IF mixers in all 15 Downconverter modules, over the specified tuning range 1 st LO (LO1) tuning range: 21.5 – 38 GHz, 0.5 GHz steps 2 nd LO (LO2) output frequency: GHz LO1 frequency switching time: < 1 ms, max. LO1 and LO2 both externally lockable to a 10 MHz reference (from Timing Gen.) Assume phase noise, spurious and harmonic output specs for Hittite 40 GHz synthesizer applicable to both LO1 and LO2 Alternate LO1 source, remotely selectable for each antenna (for subarrays) Monitor and control (except LO1 synthesizers): – Serial I/O bus, RS-485 signaling, ~ Mbps asynchronous transfer – Uses the same software protocol as Downconverter Monitor and control (LO1 synthesizers): – 10/100Base-T Ethernet; SCPI (Agilent) instrument control command protocol Environment: Indoor, temperature-controlled MTBF > 10 years, for subsystem elements common to entire array March 15-17, 2012EOVSA Preliminary Design Review3

LO Distribution Subsystem Block Diagram (1) March 15-17, 2012EOVSA Preliminary Design Review4

LO Distribution Subsystem Block Diagram (2) March 15-17, 2012EOVSA Preliminary Design Review5

LO System Cascade Analysis Excel workbooks created to perform stage-by- stage cascaded analysis of the following: – System gain, including mismatch loss – Output power – 1 dB compression point, and output margin – Third-order intercept point (IP3) Three different distribution configurations were evaluated on performance and cost LO1 distribution design a challenge, because of higher loss, especially cables, at high frequencies, and additional cascaded components. March 15-17, 2012EOVSA Preliminary Design Review6

LO1 Cascade Worksheet March 15-17, 2012EOVSA Preliminary Design Review7

LO2 Cascade Worksheet March 15-17, 2012EOVSA Preliminary Design Review8

Component Selection LO1 power amplifier is a single-source item, from Quinstar. Used modular x15 reference multiplier + PLO for LO2 source instead of a synthesizer, to save cost Mechanical switch for LO1 has lower loss, higher isolation and better VSWR than PIN diode type. Marki LO buffer amps have low power dissipation, small size, and are relatively low cost. Will need lots of flexible cables of various lengths with 2.92mm connectors. Astrolab offers a hand-formable type with low loss, and can be ordered to pre-made custom lengths at a reasonable cost. As with the Front End and Downconverter, linear power supplies will be used to run all analog electronics March 15-17, 2012EOVSA Preliminary Design Review9

Thermal Management Cooling of LO amplifiers in the Downconverter is not a real issue – dissipation is low. Conversely, total power dissipation in the LO Distribution Module may be close to 300W: – LO1 power amps each dissipate 60W – LO2 multiplier + PLO dissipate ~13W – LO2 power amplifier dissipates 7W – Linear power supplies with 50% efficiency will dissipate 140W – RF switches are latching self-cutoff type, so average is ~0W. Solutions: – Use a covered enclosure with a pair of rear-mounted fans to provide continuous flow-through cooling. – Add or design in automatic thermal shutdown protection for the amplifiers and PLO, in case of fan failure. – Make it impossible to power the electronics, unless the fans are on March 15-17, 2012EOVSA Preliminary Design Review10

Mechanical Details Enclosure and Interfaces: – Use a 19” rack-mount 3U or 4U aluminum chassis – LO1 inputs from Hittite synthesizers need to be on the front panel, to keep cables short – All RF outputs on rear panel, on the side closest the Downconverter rack – M&C bus connectors and AC or DC power input on the opposite end of rear panel Component layout considerations – Good heat sinking of amplifiers, and unobstructed airflow around them – Stacked arrangement for two LO1 splitters, with row of switches in between, to keep cable lengths short and well-matched – Allow for later addition of bi-phase modulators on LO2 outputs March 15-17, 2012EOVSA Preliminary Design Review11

LO Distribution Module Interfaces Hardware: – (16) 2.92mm-M LO1 outputs, to Downconverters – (16) SMA-M LO2 outputs, to Downconverters – (2) 2.92mm-M LO1 inputs, from Hittite sources – (1) BNC-M 10 MHz reference input, from TG – (2) DB-9 or 10-pin RJ-style connectors, M&C I/O – (1) AC fused power entry, IEC style w/switch Software: – Refer to table in following slide March 15-17, 2012EOVSA Preliminary Design Review12

March 15-17, 2012EOVSA Preliminary Design Review13 Signal NameDir.TypeModeRange MinRange MaxUnitConnectorFreq/RatePrecision X / Y Pol from FEInRF on fiberAnalog Fiber-30-35dBmSC/APC1-18 GHzN/A 10 MHz RefInRF CWAnalog Elec(TBD)16dBmBNC10 MHzN/A 50 Hz SyncInPulseAnalog Elec05VBNC50 Hz1 us LO1 Sub A Mon/CtrlI/OSCPI DataDigital Elecn/a Ethernet50 Hz10 us LO1 Sub B Mon/CtrlI/OSCPI DataDigital Elecn/a Ethernet50 Hz10 us Subarray SettingInIntegerDigital Elec05VRS-485~1/day1 s LO2 PLO Lock Alrm MonOutBoolDigital Elecn/a RS-4851 Hz1 s RX PwrOut Mon X-PolOutFloatDigital Elec-35-15dBmRS Hz1 ms RX PwrOut Mon Y-PolOutFloatDigital Elec-35-15dBmRS Hz1 ms Atten Ctrl X-PolInIntegerDigital Elec015dBRS-4851 Hz10 us Atten Ctrl Y-PolInIntegerDigital Elec015dBRS-4851 Hz10 us X Pol from DCOutIF PowerAnalog Elec-5-2dBmSMA MHzN/A Y Pol from DCOutIF PowerAnalog Elec-5-2dBmSMA MHzN/A

Production Assembly, Testing Production process steps – Two-port VNA and output power measurements of power amplifiers at all LO frequencies – Bench test of cascaded multiplier + PLO – Assembly and test of LO Distribution Module with RF output cables – Verification of M&C functionality – Test thermal shutdown features – Documentation: Test results, configuration (s/n) list March 15-17, 2012EOVSA Preliminary Design Review14

Component Costing, Delivery All RF components have been specified, and price/delivery quotes received Reasonable estimates or preliminary pricing on remaining components, except embedded controller Enclosure and power supply pricing are rough estimates, final TBD Longest lead times: – LO1 power amplifiers (16 weeks), because of req. NRE – LO2 PLO (10 weeks); semi-custom design March 15-17, 2012EOVSA Preliminary Design Review15

March 15-17, 2012EOVSA Preliminary Design Review16

Important Schedule Dates for LO Distributor Module Have all RF components, some cables, and COTS support electronics on order by mid-April at the latest Complete enclosure fabrication drawings by June 1, send out for quotes, begin fab in mid-June July 1 – July 15: Order rack, cables, connectors, wire, remaining components for prototype unit construction and site installation July 1 – August 1: RF component characterization August – September: Assemble and test prototype module October 1: Ship prototype to California for installation Embedded firmware and test software may need to be farmed out, in the interest of saving time. This could happen during July and August, in parallel with assembly. March 15-17, 2012EOVSA Preliminary Design Review17