1. Astronomical Telescopes and Instrumentation (SPIE) 8/28/021 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Wide band, ultra low noise cryogenic InP IF amplifiers for the HERSCHEL mission radiometers Isaac López-Fernández, Juan Daniel Gallego, Carmen Diez, Alberto Barcia, Jesús Martín-Pintado Centro Astronómico de Yebes Observatorio Astronómico Nacional Guadalajara, SPAIN

2. Astronomical Telescopes and Instrumentation (SPIE) 8/28/022 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Outline n Introduction n Device characterization n Amplifier design n Amplifier fabrication n Amplifier performance l Noise and gain measurements l Reflection and stability measurements l Gain fluctuations measurements l Isolator measurements n Conclusions

3. Astronomical Telescopes and Instrumentation (SPIE) 8/28/023 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Introduction: HERSCHEL requirements n HERSCHEL: Far Infrared and Submillimeter 3.5 m Telescope orbiting in L2 with 3 cryogenic instruments n HIFI: Heterodyne Instrument for the Far Infrared with 7 dual polarization submillimeter SIS and HEB receivers n Our contribution: low noise, wide band 4-8 GHz cryogenic IF preamplifiers for each mixer channel (14) n Sensitive parameters: l Noise temperature: the contribution to the receiver noise is significant l Power dissipation: mission life limited by liquid helium mass l Gain fluctuations: impact in the chopping frequency l Other mechanical and electrical constraints

4. Astronomical Telescopes and Instrumentation (SPIE) 8/28/024 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Introduction: CAY experience n More than 150 cryogenic LNAs built for different applications (not including to HERSCHEL developments) l IRAM: Grenoble, PdB interferometer, 30m (IF amplifiers) l ESOC: New Northia DSN antenna (Rosetta, SMART) l Burdeos Observatory l EMCOR (Atmospheric sensing) l PRONAOS (mm receiver in stratospheric balloon) l INPE: 14m Brazil l CAY: VLBI receivers (X and K band) n Wide experience with HEMT devices l More than 30 batches of commercial GaAs transistors tested l Several models of InP transistors measured è JPL-TRW (CHOP program): 14 batches, 9 models è ETH Zürich: 7 batches, 4 models è Chalmers University: 1 batch

5. Astronomical Telescopes and Instrumentation (SPIE) 8/28/025 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Introduction: Initial developments n Prototypes in the 8 – 12 GHz band n Successful testing of InP in this band and comparison with GaAs results n Demonstration of InP in the 4 – 8 GHz band

6. Astronomical Telescopes and Instrumentation (SPIE) 8/28/026 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Device characterization: Transistors Measurement procedures n InP technology selected based on previous experience in IF amplifiers è lower power dissipation, factor of 2 better noise, higher g m n Cryogenic S parameter measurements to model devices è In-house test fixture with microstrip lines to allow two-tier TRL calibration è Device measured with bonding wires è DC and coldFET complete the small signal model n Noise model according to Pospieszalski è The noise measured in a wide band test amplifier sets the T D of the model

7. Astronomical Telescopes and Instrumentation (SPIE) 8/28/027 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) EXAMPLE OF CRYOGENIC S PARAMETERS (1 – 40 GHz) MODEL Circuit model MEAS Raw data MEASG Time domain filter

8. Astronomical Telescopes and Instrumentation (SPIE) 8/28/028 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Device characterization: Transistors Results TRW T-42 CRYO3  200×0.1 μm gate  Best performance TRW T-45 CRYO4  200×0.1 μm gate  Used in DMs  Space qualifiable, to be used in FMs  CHOP developed ETH T-35  200×0.2 μm gate  Experimental transistor  Design by request  Used in MPAs 0.22 mm 0.19 mm

9. Astronomical Telescopes and Instrumentation (SPIE) 8/28/029 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Device characterization: Components n Selection of components based on previous experience at cryogenic temperatures l SOTA thick film resistors l ATC 111 parallel plate capacitors with CA dielectric l ATC 100 multilayer porcelain capacitors l RT/Duroid 6002 substrates 20 mils thick n Simple models of concentrated elements are adequate for this frequency range

10. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0210 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Amplifier design n Microstrip hybrid design simulated by MMICAD software n Developed cryogenic models for transistors, connectors, critical capacitors, resistors and bonding wires n Each InP device is independently stabilized by resistive loading and inductive feedback n Input circuit: wideband noise matching n Tuning elements incorporated in the design (adjustable bonding wires, microstrip islands) n Box resonances avoided with careful EM design and the use of microwave absorbers n Multiple bias networks requirements è Contribute to the unconditional stability of the amplifier è Comply with EMC mission requirements è Provide ESD protection of sensitive InP HEMTs è Have a low drain voltage drop è Filter RF

11. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0211 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Amplifier fabrication: several series n 37 4-8 GHz YCF amplifiers fabricated at CAY in different series n All processes performed in our labs n Design transferred to Alcatel Espacio to build Flight Models n Series analyzed here: l YCF 2 – ETH transistors (Mixer Program Amplifiers) l YCF 6 – TRW transistors (Development Models)

12. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0212 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) MP amplifier YCF 2  2 stages ETH 200 µm  Gold plated brass  61.4×35×11.5 mm, 149 g  Duroid 6002 substrates DM amplifier YCF 6  2 stages TRW 200 µm  Gold plated aluminum  58×32×15 mm, 65 g  Duroid 6002 substrates  Improved bias circuits  Additional cavity for filtering

13. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0213 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Amplifier fabrication: reliability n Reliability is a priority over performance for the selection of components, substrates and mounting techniques è Spatial design è Cryogenic operation n Past experience in cryogenic designs obviates most of the work in testing, modeling and pre-qualifying components n An example: ‘O’ ribbon connection in the SMA tab contact: l Allows mobility in three axis l Excellent electrical properties compared with traditional SMA connections

14. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0214 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Noise and Gain Measurement procedures n Measurement procedure: Cold attenuator n Two measurement systems available at our labs: l System 350: è Older è More pessimistic è Used to keep traceability with past measurements è All noise tests shown here were performed with 350. l System 1020: è Newer calibration. è Gives 0.75 K better results n Estimated error (both) 1.4 K (repetitivity < 0.2 K)

15. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0215 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Noise and Gain Results  Average of 3.57 K mean noise in the band for the complete DM series

16. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0216 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Reflection and Stability n Worst case output reflection l Average MPAs:-14.3 dB l Average DMs:-13.0 dB n Model prediction of output return losses needs refinement n Isolator at the input (not designed for low input ref.) n Unconditionally stability for most bias points checked with sliding shorts

17. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0217 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Gain fluctuations Cryogenic measurements of DMs (TRW transistors) n Characterized by spectral density of normalized gain fluctuations: 1.Measure S21 @ 6 GHz with HP8510 VNA (attenuator and air lines) 2.Normalize and FFT each VNA scan (0.012-2.34 Hz) 3.Average 50 spectra and subtract the system fluctuations n Fit, in the region where 1/f noise dominates, the expression β represents the fluctuatons @ 1 Hz and is used as a reference for comparison between amplifiers

18. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0218 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Gain fluctuations Correlation with voltage fluctuations n Fluctuations of gate voltage measured with HP35670A n Moderate correlation with gain fluctuations for different amplifiers measured at the same bias point n This simple DC measurements may be useful for pre-selecting least fluctuating devices from a batch 1 Hz

19. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0219 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Gain fluctuations Bias dependence n Tested the variation of gain and voltage fluctuations with drain voltage l Found a steep change in gain voltage around 0.5 V l The behaviour of gain and voltage fluctuations is similar as Vd varies n High fluctuation zones could be avoided with no penalty in noise or gain n Voltage fluctuations may help detecting these bias regions

20. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0220 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Isolators Impact in overall performance n Isolators measured @ 14 K (PAMTECH gives data @ 77 K) n Good agreement between measurement and estimation of isolator noise: n Mean contribution 1.1 – 1.4 K

21. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0221 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Performance: Isolators Results

22. Astronomical Telescopes and Instrumentation (SPIE) 8/28/0222 Centro Astronómico de Yebes, Obs. Astronómico Nacional, IGN (Spain) Summary n 34 InP HEMT 4-8 GHz cryogenic amplifiers fabricated for HERSCHEL, including the Development Models with TRW transistors n Cryogenic S parameters of InP transistors measured in microstrip and noise models developed n Cryogenic isolators used at the input allow wide-band mixer- independent design with small penalty in noise n Exceptional performance and repeatability For the final DMs 3.5 K noise and 27±1.1 dB gain dissipating 4 mW n Gain fluctuations exhibit a greater dispersion l Low frequency noise of gate bias may help selecting more stable devices n High sensitivity of gain fluctuations to bias point l Gate bias noise measurements could detect bias regions of high fluctuations