DEVELOPMENT OF SECOND GENERATION SIS RECEIVERS FOR ALMA A. R. Kerr 24 August 2016 ALMA Future Science Workshop 2016 ARK04.pptx 1
Summary o Shortcomings of the current Band 6 receivers. o Potential improvements to the higher frequency ALMA Bands and beyond (Band 11, SOFIA, etc.) o Increased intermediate frequency and IF bandwidth for ALMA. ALMA Future Science Workshop 2016 ARK04.pptx 2
Shortcomings of the Current Band 6 Receivers (211 275 GHz) o o o Increase in T RX 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 ALMA Future Science Workshop 2016 ARK04.pptx 3
(a) Excess noise at the upper and lower ends of the IF band (4 12 GHz). F LO = 225 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. ALMA Future Science Workshop 2016 ARK04.pptx 4
(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 from4to12ghzifin100mhzincrements. Ref: Kerr et al., IEEE Trans. Terahertz Science and Technology, v. 4, no. 2, pp. 201 212, Mar 2014. ALMA Future Science Workshop 2016 ARK04.pptx 5
Sideband Separating Mixer Receivers on ALMA receivers Current ALMA front ends (Bands 3 8) All except for Band 6 Disadvantages: Loss of hybrid and isolator at lowest signal point contribute to T RX. Isolator limits IF bandwidth. Band 6 Disadvantages: Interaction between mixer and preamp gives more variation of gain and T RX across the IF band. 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 Imbalance of amplifiers degrades image rejection. 6
4 12 GHz Balanced Amplifier 90 hybrid Note that the power dissipation is twice that of a single amplifier. Miniaturized version 1mm 3 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. ALMA Future Science Workshop 2016 ARK04.pptx 7
(c) Excess noise at some frequencies due to sideband noise from the LO chain. 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 (sidebandseparating) SIS mixer. (More below.) ALMA Future Science Workshop 2016 ARK04.pptx 8
New Receiver Technology for the Higher Frequency ALMA Bands and Beyond 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. 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 ALMA Future Science Workshop 2016 ARK04.pptx 9
Ref: A. R. Kerr, S. K. Pan, W. G. Lyons, 2015 IEEE Int. Microwave Symp., 20 May 2015. ALMA Future Science Workshop 2016 ARK04.pptx 10
Atmospheric transmission at the ALMA site 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. Ref: J. Mangum, NRAO, private communication. ALMA Future Science Workshop 2016 ARK04.pptx 11
Typical ALMA Band 10 Receiver Noise Temperatures Band 10 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 T R,DSB =150 300 K. The new technology mixer has T R,SSB = 150 300 K. ALMA Future Science Workshop 2016 ARK04.pptx 12
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. ALMA Future Science Workshop 2016 ARK04.pptx 13
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. 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. ALMA Future Science Workshop 2016 ARK04.pptx 14
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 15 ALMA Future Science Workshop 2016 ARK04.pptx
Sideband Separating and Balanced mm/sub mm SIS Mixers Sideband separating mixer Balanced sideband separating mixer ALMA Future Science Workshop 2016 ARK04.pptx 16
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: o o o 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 ALMA Future Science Workshop 2016 ARK04.pptx 17
Comparison of LNF Amplifiers measured at 5 K From M. Pospieszalski ALMA Future Science Workshop 2016 ARK04.pptx 18