Compact Integrated Receivers Using Custom and Commercial MMIC Technology

1. Compact Integrated Receivers UsingCustom and Commercial MMIC Technology Matt Morgan 9/7/2006

2. Compact Integrated Receivers 1. critical for focal plane arrays  beam spacing  field of view 2. lower mass  more efficient cryogenics  tighter temperature control  reduced mechanical load 3. fewer connectors and cables  greater reliability  reduced VSWR effects  reduced gain slopes  fewer entry points for RFI

3. MMIC Modules are More Compact, Lightweightand Manufacturable than Conventional Assemblies Assembly of Individually Packaged Components Multi-Chip Module

4. Many MMICs available Commercially Most things below 50 GHz are available off-the-shelf for less than $50 Exceptions include:  balanced port configurations  non-standard impedance  some wide IF-Band mixers Some things in the 50-100 GHz range can be found in commercial product listings, but  sparse frequency coverage  usually narrow-band, targeted for specific applications (communication and radar bands, etc.)  some exotic functions not supported (compound switches, etc.) Finally, there is a large pool of proven custom designs to draw from, designed by NRAO and our collaborators (JPL, ATA, universities, foundry IRAD designs, etc.)

5. Some Examples: W-Band Signal Source 2.5 cm

6. Some Examples: Compact Water Vapor Radiometer All Commercial MMICs!

7. Some Examples: ALMA Active Multiplier Chain

8. Some Examples: DSN Array Ka-Band Downconverter

9. Working Toward an All-MMIC Receiver 1. Once a design is set, MMIC components and assemblies can be mass- produced with exceptional repeatability  especially in the cm-wave range, where most MMICs are commercially available – chips are screened by the manufacturer and their specs guaranteed.  module assembly is insensitive to small variations – bondwires are used for 50  interconnects, not for tuning! 2. Repairs are relatively easy to diagnose and repair  because of the inherent uniformity in performance, device failure is usually apparent from the DC bias alone.  when it isn't, the chips are cheap enough to simply replace them one at a time until the culprit is found. It is therefore reasonable to think about implementing even very sophisticated front-ends in a single module using all MMIC technology.  no internal connectors!  no internal cables!  only 1 block to machine  small, lightweight, manufacturable

10. Shall we take integration a step further:Receiver-on-a-Chip? I would say no...  LNAs, mixers, and multipliers have all been demonstrated on common semiconductor technologies, but with compromised performance – better to pick the right MMIC process for the right chip  even if it works, the yield is too low on III-V semiconductors for large-scale integration  a lot of expensive wafer real estate is wasted on passives  can no longer take advantage of commercial components – have to design it all from scratch  no opportunity for chip reuse  Microwave substrates are thin! A large, floppy chip would be too hard to handle and mount without damaging it.

11. Could We Put the Whole Receiver in OneModule and Cool Everything? Not if it is a heterodyne receiver, because  LO generation dissipates too much power for cryogenics  IF components are usually Silicon, which will not function cold However, special-purpose direct detection receivers could occupy a single cold module  even more compact  better sensitivity  better temperature stability  better component lifetime

12. Another Problem: Why are those bias boards so big? Because we put a lot on them!  linear regulators  potentiometers for tuning and gain control  digital logic for configuration switching and channel selection  Op-Amps for gate servo loops and monitor points  IF circuitry It makes for a user-friendly module, but if we're serious about compactness, particularly for focal plane arrays, then we must find a way to trim this part down.

13. Option #1: Develop Common Bias Blocks in Die Formor Integrated SMT Packages Two external resistors set the desired drain voltage and current. Probably very expensive! (unless we buy millions of them) Not suitable for cooling if done in Silicon.

14. Option #2: Limit DC inputs to analog bias voltages Put nothing in the block except basic EMI and over-voltage protection. All current control, monitoring, and tuning functions can be implemented in a central M&C unit (more efficiently, in fact...)

15. Option #2: continued... With all monitor functions in one place, some parts can be shared.

16. What About LNAs? MMIC LNAs MIC LNAs  higher-Q passive components  allows pre-selection of active devices for optimum performance Pros  more compact  easier to integrate in large multi-function modules  easy to replicate  module assembly can be done commercially  difficult to transfer assembly "know-how" to commercial manufacturers.  larger development cost Cons

17. A "Nearly Monolithic" LNA Maybe we can compromise between optimum performance and large-scale manufacturability by using a hand-picked first-stage discrete device followed by a MMIC. Discrete stage MMIC stage

18. Case Study: Ka-Band All-MMIC Receiver Calculated Performance:  noise temperature = 10 K  gain = 60 dB  P1dB = -45 dBm (input)  LO = 2 mW (6-9 GHz)  power dissipation = 150 mW (cold part), 3.5 W (warm part)

19. All-MMIC Cold Receiver Module IF outputs IF hybrids RF inputs MMICs LO input (underneath)

20. All-MMIC Cold Receiver Module The size of a well-designed MMIC module is typically dominated by connectors and waveguide flanges.

21. MMIC-Based Cold Receiver Assembly Cooled Focal Plane Array OMT MMIC Module Bias/M&C IF LO IF

22. Backup slides follow

23. If the entire receiver is cooled anyway, should we considerusing superconducting passive elements (couplers, filters, etc)? I don't think so  excellent LNA performance can be achieved at ~20K, but a good microwave superconductor would force you to much lower temperatures (~5K)  not really a commercial process – your passive elements could be more expensive than the MMICs!  you lose the ability to test it at room temperature  not much to gain anyway? – superconductors are not lossless at high frequency, and cooled copper may be competitive if it is reasonably pure