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Timing models for high-level synthesis
In this paper, we describe a timing model for clock estimation during high-level synthesis. In order to obtain realistic timing estimates, the proposed model considers all delay elements, including datapath, control and wire delays, and several technology factors, such as layout architecture, technology mapping, buffers insertion and loading effects. The experimental results show that this model can provide much better estimates than previous models. This model is well suited for automatic and interactive synthesis as well as feedback-driven synthesis where performance matrices must be rapidly and incrementally calculated
Flux-driven Josephson parametric amplifier for sub-GHz frequencies fabricated with side-wall passivated spacer junction technology
We present experimental results on a Josephson parametric amplifier tailored
for readout of ultra-sensitive thermal microwave detectors. In particular, we
discuss the impact of fabrication details on the performance. We show that the
small volume of deposited dielectric materials enabled by the side-wall
passivated spacer niobium junction technology leads to robust operation across
a wide range of operating temperatures up to 1.5 K. The flux-pumped amplifier
has gain in excess of 20 dB in three-wave mixing and its center frequency is
tunable between 540 MHz and 640 MHz. At 600 MHz, the amplifier adds 105 mK
9 mK of noise, as determined with the hot/cold source method.
Phase-sensitive amplification is demonstrated with the device
Technologies for 3D Heterogeneous Integration
3D-Integration is a promising technology towards higher interconnect
densities and shorter wiring lengths between multiple chip stacks, thus
achieving a very high performance level combined with low power consumption.
This technology also offers the possibility to build up systems with high
complexity just by combining devices of different technologies. For ultra thin
silicon is the base of this integration technology, the fundamental processing
steps will be described, as well as appropriate handling concepts. Three main
concepts for 3D integration have been developed at IZM. The approach with the
greatest flexibility called Inter Chip Via - Solid Liquid Interdiffusion
(ICV-SLID) is introduced. This is a chip-to-wafer stacking technology which
combines the advantages of the Inter Chip Via (ICV) process and the
solid-liquid-interdiffusion technique (SLID) of copper and tin. The fully
modular ICV-SLID concept allows the formation of multiple device stacks. A test
chip was designed and the total process sequence of the ICV-SLID technology for
the realization of a three-layer chip-to-wafer stack was demonstrated. The
proposed wafer-level 3D integration concept has the potential for low cost
fabrication of multi-layer high-performance 3D-SoCs and is well suited as a
replacement for embedded technologies based on monolithic integration. To
address yield issues a wafer-level chip-scale handling is presented as well, to
select known-good dies and work on them with wafer-level process sequences
before joining them to integrated stacks.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Low-noise 0.8-0.96- and 0.96-1.12-THz superconductor-insulator-superconductor mixers for the Herschel Space Observatory
Heterodyne mixers incorporating Nb SIS junctions and NbTiN-SiO/sub 2/-Al microstrip tuning circuits offer the lowest reported receiver noise temperatures to date in the 0.8-0.96- and 0.96-1.12-THz frequency bands. In particular, improvements in the quality of the NbTiN ground plane of the SIS devices' on-chip microstrip tuning circuits have yielded significant improvements in the sensitivity of the 0.96-1.12-THz mixers relative to previously presented results. Additionally, an optimized RF design incorporating a reduced-height waveguide and suspended stripline RF choke filter offers significantly larger operating bandwidths than were obtained with mixers that incorporated full-height waveguides near 1 THz. Finally, the impact of junction current density and quality on the performance of the 0.8-0.96-THz mixers is discussed and compared with measured mixer sensitivities, as are the relative sensitivities of the 0.8-0.96- and 0.96-1.12-THz mixers
Implications of Selfish Neighbor Selection in Overlay Networks
In a typical overlay network for routing or content sharing, each node must select a fixed number of immediate overlay neighbors for routing traffic or content queries. A selfish node entering such a network would select neighbors so as to minimize the weighted sum of expected access costs to all its destinations. Previous work on selfish neighbor selection has built intuition with simple models where edges are undirected, access costs are modeled by hop-counts, and nodes have potentially unbounded degrees. However, in practice, important constraints not captured by these models lead to richer games with substantively and fundamentally different outcomes. Our work models neighbor selection as a game involving directed links, constraints on the number of allowed neighbors, and costs reflecting both network latency and node preference. We express a node's "best response" wiring strategy as a k-median problem on asymmetric distance, and use this formulation to obtain pure Nash equilibria. We experimentally examine the properties of such stable wirings on synthetic topologies, as well as on real topologies and maps constructed from PlanetLab and AS-level Internet measurements. Our results indicate that selfish nodes can reap substantial performance benefits when connecting to overlay networks composed of non-selfish nodes. On the other hand, in overlays that are dominated by selfish nodes, the resulting stable wirings are optimized to such great extent that even non-selfish newcomers can extract near-optimal performance through naive wiring strategies.Marie Curie Outgoing International Fellowship of the EU (MOIF-CT-2005-007230); National Science Foundation (CNS Cybertrust 0524477, CNS NeTS 0520166, CNS ITR 0205294, EIA RI 020206
Magnetic Calorimeter Option for the Lynx X-Ray Microcalorimeter
One option for the detector technology to implement the Lynx x-ray microcalorimeter (LXM) focal plane arrays is the metallic magnetic calorimeter (MMC). Two-dimensional imaging arrays of MMCs measure the energy of x-ray photons by using a paramagnetic sensor to detect the temperature rise in a microfabricated x-ray absorber. While small arrays of MMCs have previously been demonstrated that have energy resolution better than the 3 eV requirement for LXM, we describe LXM prototype MMC arrays that have 55,800 x-ray pixels, thermally linked to 5688 sensors in hydra configurations, and that have sensor inductance increased to avoid signal loss from the stray inductance in the large-scale arrays when the detectors are read out with microwave superconducting quantum interference device multiplexers, and that use multilevel planarized superconducting wiring to provide low-inductance, low-crosstalk connections to each pixel. We describe the features of recently tested MMC prototype devices and simulations of expected performance in designs opti- mized for the three subarray types in LXM
The Thermal Design, Characterization, and Performance of the SPIDER Long-Duration Balloon Cryostat
We describe the SPIDER flight cryostat, which is designed to cool six
millimeter-wavelength telescopes during an Antarctic long-duration balloon
flight. The cryostat, one of the largest to have flown on a stratospheric
payload, uses liquid helium-4 to deliver cooling power to stages at 4.2 and 1.6
K. Stainless steel capillaries facilitate a high flow impedance connection
between the main liquid helium tank and a smaller superfluid tank, allowing the
latter to operate at 1.6 K as long as there is liquid in the 4.2 K main tank.
Each telescope houses a closed cycle helium-3 adsorption refrigerator that
further cools the focal planes down to 300 mK. Liquid helium vapor from the
main tank is routed through heat exchangers that cool radiation shields,
providing negative thermal feedback. The system performed successfully during a
17 day flight in the 2014-2015 Antarctic summer. The cryostat had a total hold
time of 16.8 days, with 15.9 days occurring during flight.Comment: 15 pgs, 17 fig
Josephson parametric reflection amplifier with integrated directionality
A directional superconducting parametric amplifier in the GHz frequency range
is designed and analyzed, suitable for low-power read-out of microwave kinetic
inductance detectors employed in astrophysics and when combined with a
nonreciprocal device at its input also for circuit quantum electrodynamics
(cQED). It consists of an one wavelength long nondegenerate Josephson
parametric reflection amplifier circuit. The device has two Josephson junction
oscillators, connected via a tailored impedance to an on-chip passive circuit
which directs the in- to the output port. The amplifier provides a gain of 20
dB over a bandwidth of 220 MHz on the signal as well as on the idler portion of
the amplified input and the total photon shot noise referred to the input
corresponds to maximally 1.3 photons per second per Hertz of bandwidth. We
predict a factor of four increase in dynamic range compared to conventional
Josephson parametric amplifiers.Comment: Main article (5 pages plus 2 pages references) plus supplemental
material (14 pages
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