DEVELOPMENT OF SECOND GENERATION SIS RECEIVERS FOR ALMA A. R. Kerr - - PowerPoint PPT Presentation

DEVELOPMENT OF SECOND‐GENERATION SIS RECEIVERS FOR ALMA

• A. R. Kerr

24 August 2016

ALMA Future Science Workshop 2016 ‐‐ ARK04.pptx 1

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• Shortcomings of the current Band 6 receivers.
• Potential improvements to the higher‐frequency ALMA Bands

and beyond (Band 11, SOFIA, etc.)

• Increased intermediate frequency and IF bandwidth for ALMA.

Summary

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Shortcomings of the Current Band 6 Receivers (211‐275 GHz)

• Increase in TRX at ends of the IF band
• Gain variation across the IF band
• LO sideband noise at some frequencies with some LO modules.

Ref: ▫ A. R. Kerr, J. Effland, A. W. Lichtenberger, and J. Mangum, "Towards a Second Generation SIS Receiver for ALMA Band 6," ALMA Development Study Report, 23 March 2016, https://science.nrao.edu/facilities/alma/alma‐development‐cycle4/2nd%20Gen%20Band%206%20Rcvr

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(a) Excess noise at the upper and lower ends of the IF band (4‐12 GHz). Measured SSB noise temperature of 80 production Band‐6 receivers across the extended (4‐12 GHz) IF band. The LO is at 225 GHz.

FLO = 225 GHz

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(b) Excessive gain variation with frequency ("gain slope" or "power density slope)". Measured gain for the better Band‐6 mixer‐preamps. The LO was stepped from 221 to 265 GHz in 4 GHz increments at each of which the mixers were measured from 4 to 12 GHz IF in 100 MHz increments.

Ref: ▫ Kerr et al., IEEE Trans. Terahertz Science and Technology, v. 4, no. 2, pp. 201‐212, Mar 2014.

Sideband‐Separating Mixer Receivers on ALMA receivers

Current ALMA front‐ends (Bands 3‐8)

• All except for Band 6

6

• Band 6

Disadvantages:

• Loss of hybrid and

isolator at lowest signal point contribute to TRX.

• Isolator limits IF

bandwidth. Disadvantages:

• Interaction between

mixer and preamp gives more variation of gain and TRX across the IF band.

• Imbalance of amplifiers

degrades image rejection.

• All bands will benefit from improved mixers with lower noise

and wider, flatter IF and RF response, and reduced LO sideband noise.

ALMA Future Science Workshop 2016 ‐‐ ARK04.pptx

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90° hybrid

4‐12 GHz Balanced Amplifier

Miniaturized version

3 mm 1 mm

Superconducting 90° 4‐12 GHz hybrid

Ref: ▫ A. R. Kerr, IEEE Microwave and Guided Wave Letters, vol. 8, no. 11, pp. 390‐392, Nov. 1998.

Note that the power dissipation is twice that of a single amplifier.

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Regions of excess noise temperature in the same ALMA Band‐6 cartridge with two different LO modules. → The excess noise could be suppressed effectively using a balanced (sideband‐ separating) SIS mixer. (More below.)

ALMA Future Science Workshop 2016 ‐‐ ARK04.pptx

(c) Excess noise at some frequencies due to sideband noise from the LO chain.

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• New circuit fabrication technology
• Si membrane beam‐lead mixer chips.
• Drop‐in beam‐lead waveguide elements.
• Balanced and balanced sideband‐separating SIS mixers.
• New SIS junction technology
• AlN barriers
• NbTiN
• New IF preamplifier technology
• Balanced 4‐12 GHz IF amplifiers.

New Receiver Technology for the Higher‐Frequency ALMA Bands and Beyond

ALMA Future Science Workshop 2016 ‐‐ ARK04.pptx

Ref: ▫ A. R. Kerr, J. Effland, A. W. Lichtenberger, and J. Mangum, "Towards a Second Generation SIS Receiver for ALMA Band10," ALMA Development Study Report, 23 March 2016, https://science.nrao.edu/facilities/alma/alma‐development‐cycle4/ALMA‐B10v2studyRpt2016o.pdf

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Ref: ▫ A. R. Kerr, S.‐K. Pan, W. G. Lyons, 2015 IEEE Int. Microwave Symp., 20 May 2015.

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Atmospheric transmission at the ALMA site as a function of the precipitable water vapor, indicating the percentage of the time during which the transmission is above each curve.

Atmospheric transmission at the ALMA site

Ref: ▫ J. Mangum, NRAO, private communication.

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Typical ALMA Band 10 Receiver Noise Temperatures

System noise temperature: (left) the current DSB receiver, (middle) a sideband‐separating receiver based on the current Band‐10 mixers, and (right) a sideband‐separating receiver using new technology mixers. The system noise is calculated at frequencies corresponding to the peak and the edge of Band 10. The current DSB mixers have TR,DSB =150‐300 K. The new technology mixer has TR,SSB = 150‐300 K.

Band 10

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Si membrane beam‐lead mixers

The quartz substrates normally used for mm‐wave circuits become impractical above ~300 GHz. Scaling the quartz substrates from Bands 3 and 6 to band 10 would require a substrate 20 μm thick x 60 μm wide at Band 10. A new process, developed at UVML, allows a mixer circuit to be fabricated on a 3‐μm Si membrane, and suspended by gold beamleads which also make the IF, DC, and ground connections.

NbN/Al-AlN/Nb SIS mixer for 385-500 GHz. The mixer has 4 junctions in series on a 3-μm Si membrane with gold beam leads.

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Si membrane & beamlead LO coupler for 385‐500 GHz. Coupling is 20, 16, or 10 dB for 1, 2, or 3

• sections. The Smith chart shows the reflection coefficient of the coupler across the full band.

Drop‐in LO Couplers for sub‐mm Mixers

Standard waveguide branch‐line LO couplers require several deep but very narrow waveguide channels to be machined between two full‐height waveguides. For Band 10, full‐height waveguide is 140 x 280 μm and machining branch‐line couplers is impractical. Coupling between the LO and signal waveguides in a mixer block can be accomplished using a Si‐membrane coupler. The coupling can be adjusted between 20, 16, and 10 dB by using 1, 2, or 3 coupler sections.

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Topology of Single‐Ended and Balanced mm/sub‐mm SIS Mixers

Single‐ended mixer Balanced mixer

* *Ref: ▫ A. R. Kerr, A. W. Lichtenberger, C. M. Lyons, E. F. Lauria, L. M. Ziurys, and M. R. Lambeth, "A Superconducting 180° IF Hybrid for Balanced SIS Mixers," Proc. 17th Int. Symp. on Space THz Tech., Paris, pp. 29‐32, May 2006. http://www.nrao.edu/meetings/isstt/papers/2006/2006029034.pdf

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Sideband‐Separating and Balanced mm/sub‐mm SIS Mixers

Sideband‐separating mixer Balanced sideband‐separating mixer

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Higher and/or Wider IF Band for ALMA

It has been suggested that ALMA might benefit from an increase of intermediate frequency and/or IF bandwidth. These trade‐offs must be considered:

• Increasing the intermediate frequency comes with an inevitable noise penalty.
• Increasing the IF bandwidth beyond 3:1 (e.g., 4‐12 GHz) eliminates the use of

most commercial components (isolators, hybrids).

• Currently, the ALMA back‐end can only handle 8 GHz per polarization channel

(4 GHz per sideband).

Ref: ▫ J. Mangum, M. Pospieszalski, and A. R. Kerr, "Maximum Receiver Bandwidth," ‐‐ in preparation. ▫ A. R. Kerr, J. Effland, A. W. Lichtenberger, and J. Mangum, "Towards a Second Generation SIS Receiver for ALMA Band 6," ALMA Development Study Report, 23 March 2016, https://science.nrao.edu/facilities/alma/alma‐development‐cycle4/2nd%20Gen%20Band%206%20Rcvr

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Comparison of LNF Amplifiers measured at 5 K

From M. Pospieszalski