Warm Front End (2-meter)

1. Warm Front End (2-meter) Wes Grammer NRAO EOVSA Preliminary Design Review

2. Outline • Design requirements • Block diagrams • Cascaded gain/noise analysis (FE + BE) • Component selection • Thermal management • Mechanical layout and enclosure • Interfaces (mechanical and electronic) • Production assembly and test • Costing and schedule EOVSA Preliminary Design Review

3. 2-meter Warm Front End Design Requirements and Specifications • 1-18 GHz instantaneous BW, dual linear polarizations • Overall Tsys < 400K, at ambient (~298K) • Gain stability < 1%, phase stability < 1°, over TBC sec. • Receiver outputs modulated on SMF, range > 2 km • Active temperature control, < ±0.1C diurnal stability • Overall volume should fit within a 12” dia. x ~12” long cylinder, excluding antenna feed and connectors • Total weight < 20 lbs (9.1 kg) • Sealed enclosure and bulkhead connectors to IP67, suitable for outdoor installation • MTBF > 26,000 hrs (3 yrs) EOVSA Preliminary Design Review

4. Front End Assembly Block Diagram EOVSA Preliminary Design Review

5. 2-Meter Front End Optical Fiber, M&C and DC Supply Routing EOVSA Preliminary Design Review

6. System Cascade Analysis (1) • Excel workbook created to perform stage-by-stage cascaded analysis of the following: • System gain, including mismatch loss • Noise temperature • Gain ripple and slope over IF bandwidth • Output spectral power density and total power • 1 dB compression point, and output margin • Third-order intercept point (IP3) • Output IMD level, assuming strong interference EOVSA Preliminary Design Review

7. System Cascade Analysis (2) • Component data entered in tables • Effect of cables and adapters estimated • Analyzed at four different input levels: -73, -60, -50 and -35 dBm, at 18 GHz • Simplifications and assumptions: • Worst-case parameters mostly used (min. gain, IP3 and P1dB; max. loss, VSWR and NF) @ 18 GHz • Average of mismatch error used for cascade • Antenna conductor and dielectric loss unknown, a figure of 0.5 dB was arbitrarily assigned • Input level of optical TX is nominally +6 dBm EOVSA Preliminary Design Review

8. EOVSA Preliminary Design Review

9. System Cascade Analysis (3) • Key results, after optimization: • ENR of 30 dB required with specified splitter and 20 dB coupler, in order to inject ~ 400K noise • LNA still ~6 dB below compression at -35 dBm max input, other amps better. • Overall Tsys < 330K up to -50 dBm, but rises way over 400K for strongest input, from added atten. • Effect greatly reduced by driving optical TX at upper end of its linear range (+11 dBm) for this case. Overall Tsys is still slightly higher than spec, ~420K • May slightly complicate software to set atten. levels EOVSA Preliminary Design Review

10. System Cascade Analysis (4) • Results (cont): • Optical TX drive at lowest signal input: • +4.3 dBm, at 18 GHz w/min. nom. setting -> -0.7 dB margin! • Extreme case, due to steep gain slope of LNA at this end (~2 dB/GHz). Gain over most of band nearly 5 dB higher, thus total power from 1-18 GHz will be higher than worst-case above. • Around 10 dB headroom in the digital attenuator, for reducing system gain, for non-worst case EOVSA Preliminary Design Review

11. System Cascade Analysis (5) • Limitations of analysis tool: • Cascaded gain ripple and slope are incomplete; lack of component data, unknown dependence on phase • No broadband frequency dependence of component parameters is modeled; lack of time and hard data • Output power is assumed linear; no attempt made to model saturation or near-saturation behavior • Did not model change in solar input power across frequency, or effect on total output power through components having significant gain slope (e.g., LNA) • Analyzed only main signal path; noise source with splitter and coupler done separately and manually EOVSA Preliminary Design Review

12. Component Selection Criteria • Flat frequency response, where possible • Good VSWR, where possible, to limit mismatch loss and gain ripple • Integration of multiple functions into a single package where cost-effective, for better performance, fewer interconnects, saves critical space • For amplifiers, lowest power dissipation that still meets output drive requirements • Common bias voltages (e.g., +12V), where possible • Cost is critical: As there are 30 each of most Front End component types in the array, an expensive item can have a large impact in the overall budget. EOVSA Preliminary Design Review

13. EOVSA Preliminary Design Review

14. Hittite 5-bit Digital Attenuator EOVSA Preliminary Design Review

15. Optilab LT-20/LR-30 Link Loss EOVSA Preliminary Design Review

16. Thermal Management • Active cooling to be used, for following reasons: • Limited volume with high component packing density • Relatively large thermal dissipation (~64W max, est.) • External ambient temp can reach +45C or more, also has direct solar exposure • Will allow best receiver gain stability w/reliability • Requirements: • Robust, reliable system for harsh outdoor environment • Reasonable installation and operating costs • Compact and lightweight (portion mounted on antenna) EOVSA Preliminary Design Review

17. Options for Front End Cooling • Liquid cooling • Very compact, lightweight, quiet (on Front End side) • Works best when cooling a device to a temperature close to the surrounding ambient. Supply line (cold side) needs to be insulated for most efficient operation. • Requires a remote pump and chiller assembly – raises cost • Direct thermoelectric cooling • Compact, efficient, and light enough for use on antenna • Works well over wide ambient temperature range • No coolant required, only DC power – easier to test and install • Reversible; can heat or cool as required, with suitable controller • Fewer, lower-cost system components • Requires external fans, which limit MTBF EOVSA Preliminary Design Review

18. Laird 71W TE Assembly, Controller EOVSA Preliminary Design Review

19. Internal layout considerations • Cascade from feed outputs to LNAs should be as short and direct as possible, to minimize losses • Optical TX modules drive overall placement, because of their large size and power dissipation. • Good heat sinking for active components a must, for gain stability and long field life • Interface connectors should be located at the opposite end of enclosure to the feed, for ease of access and minimal antenna obstruction. • Design for easy assembly, testing, serviceability EOVSA Preliminary Design Review

20. Enclosure Design Requirements • Weather-tight to IP67 (no dust or non-submerged water ingress); one-piece replaceable seals • UV-resistant material, rated for outdoor use • Clamshell design, for easy assembly and service • Well-insulated, to minimize ambient thermal loading, for a stable internal environment • Base strong enough to support 9 kg max weight, nor break under expected handling in the field • Low cost COTS catalog item, if possible EOVSA Preliminary Design Review

21. Warm Front End AssemblyConceptual Mechanical Layout EOVSA Preliminary Design Review

22. Front End Assembly Interfaces • Hardware: • (2) SMA-M inputs from antenna feed • (1) SM fiber connector output; possibly LC/APC • (1) 10/100Base-T Ethernet I/O for all M&C • (3) MIL-DTL-26482 multi-pin connectors, for DC power input to Front End electronics, TE coolers • Software: • Refer to table in following slide EOVSA Preliminary Design Review

23. EOVSA Preliminary Design Review

24. Production Assembly, Testing • Production process steps • Two-port VNA measurement of amplifiers, filters, digital attenuators, couplers, and optical link sets • Assembly of receiver halves (w/o WDM, noise src) • Two-port VNA measurement of half-RX, w/Opt RX • Final assembly of full receiver • Test noise source functionality • Verification of M&C functionality and cooling system function in a test chamber at 50°C • Documentation: Test results, configuration (s/n) list EOVSA Preliminary Design Review

25. Production area at NTC Photonics Lab EOVSA Preliminary Design Review

26. Component Costing, Delivery • All RF components except LPF have been specified, price/delivery quotes received • Good estimates or preliminary pricing on remaining electronic components • Enclosure, connector and cable pricing are rough estimates, final TBD • Longest lead times: • TECOM antennas (21 weeks); use existing OVSA units for prototype Front Ends • 1-bit digital attenuator (18 weeks); can be shortened to 8 weeks for 30% extra • Many other have 12-16 week leads, but only for large qty EOVSA Preliminary Design Review

27. EOVSA Preliminary Design Review

28. Important Schedule Dates for Front End Prototypes • Have all RF components and COTS support electronics on order by mid-April at the latest • Complete mechanical CAD models and fabrication drawings by May 1, send out for quotes, begin fab in mid-May • May 1 – June 30: Design, PCB fab and component ordering for custom support electronic boards • July 1 – July 15: Order cables, connectors, wire, remaining components for prototype unit construction and site installation • July 1 – August 1: RF component characterization • August – September: Assemble and test 3 prototypes • October 1: Ship 3 prototypes to California for installation • Front End 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. EOVSA Preliminary Design Review