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Digital pixel CMOS focal plane array with on-chip multiply accumulate units for low-latency image processing

May 5, 2014
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Conference Paper
Author:
Jeffrey W. Little
…
Published in:
SPIE, Vol. 9070, Infrared Technology and Applications XL, 5 May 2014, 90703B.
Topic:
semiconductor (CMOS)
R&D area:
R&D group:

Summary

A digital pixel CMOS focal plane array has been developed to enable low latency implementations of image processing systems such as centroid trackers, Shack-Hartman wavefront sensors, and Fitts correlation trackers through the use of in-pixel digital signal processing (DSP) and generic parallel pipelined multiply accumulate (MAC) units. Light intensity digitization occurs at the pixel level, enabling in-pixel DSP and noiseless data transfer from the pixel array to the peripheral processing units. The pipelined processing of row and column image data prior to off chip readout reduces the required output bandwidth of the image sensor, thus reducing the latency of computations necessary to implement various image processing systems. Data volume reductions of over 80% lead to sub 10us latency for completing various tracking and sensor algorithms. This paper details the architecture of the pixel-processing imager (PPI) and presents some initial results from a prototype device fabricated in a standard 65nm CMOS process hybridized to a commercial off-the-shelf short-wave infrared (SWIR) detector array.
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Summary

A digital pixel CMOS focal plane array has been developed to enable low latency implementations of image processing systems such as centroid trackers, Shack-Hartman wavefront sensors, and Fitts correlation trackers through the use of in-pixel digital signal processing (DSP) and generic parallel pipelined multiply accumulate (MAC) units. Light intensity digitization...

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Digital pixel CMOS focal plane array with on-chip multiply accumulate units for low-latency image processing

Impact ionization in AlxGa1-xASySb1-y avalanche photodiodes

April 21, 2014
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Journal Article
Author:
Michael J. Grzesik
…
Published in:
App. Phys. Lett., Vol. 104, No. 16, 21 April 2014, 162103.
Topic:
photonics
R&D area:
R&D group:

Summary

Avalanche photodiodes (APDs) have been fabricated in order to determine the impact ionization coefficients of electrons (alpha) and holes (beta) in AlxGa1-xAsySb1-y lattice matched to GaSb for three alloy compositions: (x=0.40, y=0.035), (x=0.55, y=0.045), and (x=0.65, y=0.054). The impact ionization coefficients were calculated from photomultiplication measurements made on specially designed APDs, which allowed for both pure electron and pure hole injection in the same device. Photo-multiplication measurements were made at temperatures ranging from 77K to 300K for all three alloys. A quasi-physical model with an explicit temperature dependence was used to express the impact ionization coefficients as a function of electric-field strength and temperature. For all three alloys, it was found that alpha < beta at any given temperature. In addition, the values of the impact ionization coefficients were found to decrease as the aluminum concentration of the AlGaAsSb alloy was increased. A value between 1.2 and 4.0 was found for beta/x, which is dependent on temperature, alloy composition, and electric-field strength.
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Summary

Avalanche photodiodes (APDs) have been fabricated in order to determine the impact ionization coefficients of electrons (alpha) and holes (beta) in AlxGa1-xAsySb1-y lattice matched to GaSb for three alloy compositions: (x=0.40, y=0.035), (x=0.55, y=0.045), and (x=0.65, y=0.054). The impact ionization coefficients were calculated from photomultiplication measurements made on specially designed...

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Impact ionization in AlxGa1-xASySb1-y avalanche photodiodes

High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy

February 1, 2014
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Journal Article
Author:
Charles M. Wynn
…
Published in:
Opt. Eng., Vol. 53 No. 2, February 2014, 021103.
Topic:
detection systems
R&D area:
R&D group:

Summary

Lincoln Laboratory of Massachusetts Institute of Technology has developed a technique known as dynamic photoacoustic spectroscopy (DPAS) that could enable remote detection of trace gases via a field-portable laser-based system. A fielded DPAS system has the potential to enable rapid, early warning of airborne chemical threats. DPAS is a new form of photoacoustic spectroscopy that relies on a laser beam swept at the speed of sound to amplify an otherwise weak photoacoustic signal. We experimentally determine the sensitivity of this technique using trace quantities of SF6 gas. A clutter-limited sensitivity of ~100 ppt is estimated for an integration path of 0.43 m. Additionally, detection at ranges over 5 m using two different detection modalities is demonstrated: a parabolic microphone and a laser vibrometer. Its utility in detecting ammonia emanating from solid samples in an ambient environment is also demonstrated.
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Summary

Lincoln Laboratory of Massachusetts Institute of Technology has developed a technique known as dynamic photoacoustic spectroscopy (DPAS) that could enable remote detection of trace gases via a field-portable laser-based system. A fielded DPAS system has the potential to enable rapid, early warning of airborne chemical threats. DPAS is a new...

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High-sensitivity detection of trace gases using dynamic photoacoustic spectroscopy

Adaptive RF canceller for transmit-receive isolation improvement

January 19, 2014
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Conference Paper
Author:
Kenneth E. Kolodziej
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Published in:
2014 IEEE Radio and Wireless Symposium (RWS), 19-23 January 2014.
Topic:
antennas
R&D area:
R&D group:

Summary

For effective operation, Simultaneous Transmit and Receive (STAR) systems require high isolation between the transmitted signals and the receiver input, the absence of which can lead to the saturation of a receiver's front end. This paper presents an adaptive RF canceller used to improve isolation. The canceller is configured as an RD tapped delay line with four taps, each with independent amplitude and phase weights that are tuned by a Dithered Linear Search algorithm. This canceller produces 30 dB of signal cancellation over a 20 MHz bandwidth centered at 2.45 GHz in an isolated environment. When combined with a high-isolation antenna, an overall STAR system isolation of 90 dB is achieved, while also maintaining omnidirectional transmit and receive antenna patterns.
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Summary

For effective operation, Simultaneous Transmit and Receive (STAR) systems require high isolation between the transmitted signals and the receiver input, the absence of which can lead to the saturation of a receiver's front end. This paper presents an adaptive RF canceller used to improve isolation. The canceller is configured as...

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Adaptive RF canceller for transmit-receive isolation improvement

Insensitivity of the rate of ion motional heating to trap-electrode material over a large temperature range

January 16, 2014
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Journal Article
Author:
John Chiaverini
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Published in:
Phys. Rev. A, At. Mol. Opt. Phys., Vol. 89, No. 1, 2014, 012318.
Topic:
advanced materials
R&D area:
R&D group:

Summary

We present measurements of trapped-ion motional-state heating rates in niobium and gold surface-electrode ion traps over a range of trap-electrode temperatures from approximately 4 K to room temperature (295 K) in a single apparatus. Using the sideband-ratio technique after resolved-sideband cooling of single ions to the motional ground state, we find low-temperature heating rates more than two orders of magnitude below the room-temperature values and approximately equal to the lowest measured heating rates in similarly sized cryogenic traps. We find similar behavior in the two very different electrode materials, suggesting that the anomalous heating process is dominated by non-material-specific surface contaminants. Through precise control of the temperature of cryopumping surfaces, we also identify conditions under which elastic collisions with the background gas can lead to an apparent steady heating rate, despite rare collisions.
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Summary

We present measurements of trapped-ion motional-state heating rates in niobium and gold surface-electrode ion traps over a range of trap-electrode temperatures from approximately 4 K to room temperature (295 K) in a single apparatus. Using the sideband-ratio technique after resolved-sideband cooling of single ions to the motional ground state, we...

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Insensitivity of the rate of ion motional heating to trap-electrode material over a large temperature range

A frequency selective atom interferometer magnetometer

January 13, 2014
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Journal Article
Author:
Danielle A. Braje
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Published in:
J. Mod. Opt., Vol. 61, No. 1, 2014, pp. 61-71.
Topic:
optics
R&D area:
R&D group:

Summary

In this article, we discuss the magnetic-field frequency selectivity of a time-domain interferometer based on the number and timing of intermediate pi pulses. We theoretically show that by adjusting the number of pi pulses and the pi-pulse timing, we can control the frequency selectivity of the interferometer to time varying and DC magnetic fields. We present experimental data demonstrating increased coherence time due to bandwidth filtering with the inclusion of a pi pulse between the initial and final pi/2 pulses, which mitigates sensitivity to low frequency magnetic fields.
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Summary

In this article, we discuss the magnetic-field frequency selectivity of a time-domain interferometer based on the number and timing of intermediate pi pulses. We theoretically show that by adjusting the number of pi pulses and the pi-pulse timing, we can control the frequency selectivity of the interferometer to time varying...

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A frequency selective atom interferometer magnetometer

Quantum information processing using quasiclassical electromagnetic interactions between qubits and electrical resonators

December 6, 2013
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Journal Article
Author:
Andrew J. Kerman
Published in:
New J. Phys., Vol. 15, 2013, 123011.
Topic:
quantum
R&D area:
R&D group:

Summary

Electrical resonators are widely used in quantum information processing, by engineering an electromagnetic interaction with qubits based on real or virtual exchange of microwave photons. This interaction relies on strong coupling between the qubits' transition dipole moments and the vacuum fluctuations of the resonator in the same manner as cavity quantum electrodynamics (QED), and has consequently come to be called 'circuit QED' (cQED). Great strides in the control of quantum information have already been made experimentally using this idea. However, the central role played by photon exchange induced by quantum fluctuations in cQED does result in some characteristic limitations. In this paper, we discuss an alternative method for coupling qubits electromagnetically via a resonator, in which no photons are exchanged, and where the resonator need not have strong quantum fluctuations. Instead, the interaction can be viewed in terms of classical, effective 'forces' exerted by the qubits on the resonator, and the resulting resonator dynamics used to produce qubit entanglement are purely classical nature. We show how this type of interaction is similar to that encountered in the manipulation of atomic ion qubits, and we exploit this analogy to construct two-qubit entangling operations that are largely insensitive to thermal or other noise in the resonator, and to its quality factor. These operations are also extensisble to larger numbers of qubits, allowing interactions to be selectively generated among any desired subset of those coupled to a single resonator. Our proposal is potentially applicable to a variety of physical qubit modalities, including superconducting and semiconducting solid-state qubits, trapped molecular ions, and possibly even electron spins in solids.
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Summary

Electrical resonators are widely used in quantum information processing, by engineering an electromagnetic interaction with qubits based on real or virtual exchange of microwave photons. This interaction relies on strong coupling between the qubits' transition dipole moments and the vacuum fluctuations of the resonator in the same manner as cavity...

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Quantum information processing using quasiclassical electromagnetic interactions between qubits and electrical resonators

Reagent assessment for detection of ammonium ion-molecule complexes

December 1, 2013
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Journal Article
Author:
Kerin E. Gregory
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Published in:
Rapid Commun. Mass Spectrom., Vol. 27, 2013, pp. 2797-2806.
Topic:
detection systems
R&D area:
R&D group:

Summary

An MS-based framework was developed to quantitatively assess API ion-molecule reagent chemistries based on ammonium selectivity versus competing ions, and intrinsic ammonium binding strength and complex survivability for detection. Methyl acetoacetate is an attractive ammonium reagent for vapor-phase API techniques given its high vapor pressure, preferential selectivity, and high critical energy for dissociation.
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Summary

An MS-based framework was developed to quantitatively assess API ion-molecule reagent chemistries based on ammonium selectivity versus competing ions, and intrinsic ammonium binding strength and complex survivability for detection. Methyl acetoacetate is an attractive ammonium reagent for vapor-phase API techniques given its high vapor pressure, preferential selectivity, and high critical...

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Reagent assessment for detection of ammonium ion-molecule complexes

Ultrawideband superstrate-enhanced substrate-loaded array with integrated feed

November 1, 2013
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Journal Article
Author:
William F. Moulder
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Published in:
IEEE Trans. Antennas Propag., Vol. 61, No. 11, November 2013, pp. 5802-7.
Topic:
antennas
R&D area:
R&D group:

Summary

A superstrate-enhanced substrate-loaded array (SESLA) with an integrated feed is presented. The design allows for a practical implementation of the SESLA, a concept previously presented by the authors for realizing extremely wideband (> 10 : 1) low-profile arrays. Specifically, the feed provides unbalanced to balanced transformation allowing the balance-fed SESLA to be excited with a 50 omega unbalanced line. The resulting array/feed combination is matched across a 13.9 : 1 bandwidth (infinite array, V SW R less than or equal to 2.4). When scanned to 45 degrees in the E-, H-, and D-planes, the unit cell operates across a 13.3 : 1 bandwidth using a relaxed matching criterion of V SW R less than or equal to 3. The design is validated through extensive measurement of an 8x8 prototype array.
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Summary

A superstrate-enhanced substrate-loaded array (SESLA) with an integrated feed is presented. The design allows for a practical implementation of the SESLA, a concept previously presented by the authors for realizing extremely wideband (&gt; 10 : 1) low-profile arrays. Specifically, the feed provides unbalanced to balanced transformation allowing the balance-fed SESLA...

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Ultrawideband superstrate-enhanced substrate-loaded array with integrated feed

Flux-charge duality and topological quantum phase fluctuations in quasi-one-dimensional superconductors

October 18, 2013
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Journal Article
Author:
Andrew J. Kerman
Published in:
New J. Phys., Vol. 15, 2013, 105017.
Topic:
quantum
R&D area:
R&D group:

Summary

It has long been thought that macroscopic phase coherence breaks down in effectively lower-dimensional superconducting systems even at zero temperature due to enhanced topological quantum phase fluctuations. In quasi-one-dimensional wires, these fluctuations are described in terms of 'quantum phase-slip' (QPS): tunneling of the superconducting order parameter for the wire between states differing by plus or minus 2 pi in their relative phase between the wire's ends. Over the last several decades, many deviations from conventional bulk superconducting behavior have been observed in ultra-narrow superconducting nanowires, some of which have been identified with QPS. While at least some of the observations are consistent with existing theories for QPS, other observations in many cases point to contradictory conclusions or cannot be explained by these theories. Hence, our understanding of the nature of QPS, and its relationship to the various observations, has remained incomplete. In this paper we present a new model for QPS which takes as its starting point an idea originally postulated by Mooij and Nazarov (2006 Nature Phys. 2 169): that flux-charge duality, a classical symmertry of Maxwell's equations, can be used to relate QPS to the well-known Josephson tunneling of Cooper pairs. Our model provides an alternative, and qualitatively different, conceptual basis for QPS and the phenomena which arise from it in experiments, and it appears to permit for the first time a unified understanding of observations across several different types of experiments and materials systems.
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Summary

It has long been thought that macroscopic phase coherence breaks down in effectively lower-dimensional superconducting systems even at zero temperature due to enhanced topological quantum phase fluctuations. In quasi-one-dimensional wires, these fluctuations are described in terms of 'quantum phase-slip' (QPS): tunneling of the superconducting order parameter for the wire between...

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Flux-charge duality and topological quantum phase fluctuations in quasi-one-dimensional superconductors
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