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Three-dimensional integration technology for advanced focal planes

Summary

We have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using it.
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Summary

We have developed a three-dimensional (3D) circuit integration technology that exploits the advantages of silicon-on-insulator (SOI) technology to enable wafer-level stacking and micrometer-scale electrical interconnection of fully fabricated circuit wafers. This paper describes the 3D technology and discusses some of the advanced focal plane arrays that have been built using...

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The MIT-LL/AFRL IWSLT-2008 MT System

Published in:
Int. Workshop on Spoken Language Translation, IWSLT, 1-2 December 2009.

Summary

This paper describes the MIT-LL/AFRL statistical MT system and the improvements that were developed during the IWSLT 2008 evaluation campaign. As part of these efforts, we experimented with a number of extensions to the standard phrase-based model that improve performance for both text and speech-based translation on Chinese and Arabic translation tasks. We discuss the architecture of the MIT-LL/AFRL MT system, improvements over our 2007 system, and experiments we ran during the IWSLT-2008 evaluation. Specifically, we focus on 1) novel segmentation models for phrase-based MT, 2) improved lattice and confusion network decoding of speech input, 3) improved Arabic morphology for MT preprocessing, and 4) system combination methods for machine translation.
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Summary

This paper describes the MIT-LL/AFRL statistical MT system and the improvements that were developed during the IWSLT 2008 evaluation campaign. As part of these efforts, we experimented with a number of extensions to the standard phrase-based model that improve performance for both text and speech-based translation on Chinese and Arabic...

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Time delay integration and in-pixel spatiotemporal filtering using a nanoscale digital CMOS focal plane readout

Summary

A digital focal plane array (DFPA) architecture has been developed that incorporates per-pixel full-dynamic-range analog-to-digital conversion and orthogonal-transfer-based realtime digital signal processing capability. Several long-wave infrared-optimized pixel processing focal plane readout integrated circuit (ROIC) designs have been implemented, each accommodating a 256 x 256 30-um-pitch detector array. Demonstrated in this paper is the application of this DFPA ROIC architecture to problems of background pedestal mitigation, wide-field imaging, image stabilization, edge detection, and velocimetry. The DFPA architecture is reviewed, and pixel performance metrics are discussed in the context of the application examples. The measured data reported here are for DFPA ROICs implemented in 90-nm CMOS technology and hybridized to HgxCd1-xTe (MCT) detector arrays with cutoff wavelengths ranging from 7 to 14.5 m and a specified operating temperature of 60 K-80 K.
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Summary

A digital focal plane array (DFPA) architecture has been developed that incorporates per-pixel full-dynamic-range analog-to-digital conversion and orthogonal-transfer-based realtime digital signal processing capability. Several long-wave infrared-optimized pixel processing focal plane readout integrated circuit (ROIC) designs have been implemented, each accommodating a 256 x 256 30-um-pitch detector array. Demonstrated in this...

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A multi-sensor compressed sensing receiver: performance bounds and simulated results

Published in:
43rd Asilomar Conf. on Signals, Systems, and Computers, 1-4 November 2009, pp. 1571-1575.

Summary

Multi-sensor receivers are commonly tasked with detecting, demodulating and geolocating target emitters over very wide frequency bands. Compressed sensing can be applied to persistently monitor a wide bandwidth, given that the received signal can be represented using a small number of coefficients in some basis. In this paper we present a multi-sensor compressive sensing receiver that is capable of reconstructing frequency-sparse signals using block reconstruction techniques in a sensor-frequency basis. We derive performance bounds for time-difference and angle of arrival (AoA) estimation of such a receiver, and present simulated results in which we compare AoA reconstruction performance to the bounds derived.
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Summary

Multi-sensor receivers are commonly tasked with detecting, demodulating and geolocating target emitters over very wide frequency bands. Compressed sensing can be applied to persistently monitor a wide bandwidth, given that the received signal can be represented using a small number of coefficients in some basis. In this paper we present...

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Rapid prototyping of radar algorithms

Author:
Published in:
IEEE Sig. Proc. Mag., Vol. 26, No. 6, November 2009, pp. 158-162.

Summary

Rapid prototyping of advanced signal processing algorithms is critical to developing new radars. Signal processing engineers usually use high level languages like MATLAB, IDL, or Python to develop advanced algorithms and to determine the optimal parameters for these algorithms. Many of these algorithms have very long execution times due to computational complexity and/or very large data sets, which hinders an efficient engineering development workflow. That is, signal processing engineers must wait hours, or even days, to get the results of the current algorithm, parameters, and data set before making changes and refinements for the next iteration. In the meantime, the engineer may have thought of several more permutations that he or she wants to test.
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Summary

Rapid prototyping of advanced signal processing algorithms is critical to developing new radars. Signal processing engineers usually use high level languages like MATLAB, IDL, or Python to develop advanced algorithms and to determine the optimal parameters for these algorithms. Many of these algorithms have very long execution times due to...

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CompositeMatch: detecting n-ary matches in ontology alignment

Published in:
OM 2009: Proc. 4th Int. Workshop on Ontology Matching, 25 October 2009, pp. 250-251.

Summary

The field of ontology alignment still contains numerous unresolved problems, one of which is the accurate identification of composite matches. In this work, we present a context-sensitive ontology alignment algorithm, CompositeMatch, that identifies these matches, along with the typical one-to-one matches, by looking more broadly at the information that a concept's relationships confer. We show that our algorithm can identify composite matches with greater confidence than current tools.
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Summary

The field of ontology alignment still contains numerous unresolved problems, one of which is the accurate identification of composite matches. In this work, we present a context-sensitive ontology alignment algorithm, CompositeMatch, that identifies these matches, along with the typical one-to-one matches, by looking more broadly at the information that a...

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TCAS multiple threat encounter analysis

Published in:
MIT Lincoln Laboratory Report ATC-359

Summary

The recent development of high-fidelity U.S. airspace encounter models at Lincoln Laboratory has motivated a simulation study of the Traffic Alert and Collision Avoidance System (TCAS) multiple threat logic. We observed from archived radar data that while rarer than single-threat encounters, multiple threat encounters occur more frequently than originally expected. The multithreat logic has not been analyzed in the past using encounter models. To generate multi-threat encounters, this report extends the statistical techniques used to develop pairwise correlated encounters. We generated and simulated a large number of multi-threat encounters using the TCAS logic implemented in Lincoln Laboratory's Collision Avoidance System Safety Assessment Tool. Near mid-air collision (NMAC) count indicates how often close encounters are resolved, unresolved, or induced by TCAS. Change in vertical miss distance shows the effect of the additional threat on the vertical separation between the first two aircraft. Risk ratio measures how the probability of an NMAC changes when an aircraft is equipped with TCAS versus being unequipped. Study results indicate that in multi-threat encounters, the TCAS logic results in a more than twofold increase in unresolved NMACs and approximately five times more induced NMACs than one-on-one encounters. TCAS provides a safety benefit in multi-threat encounters by issuing resolution advisories that result in increased vertical separation between the equipped aircraft and the first intruder.
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Summary

The recent development of high-fidelity U.S. airspace encounter models at Lincoln Laboratory has motivated a simulation study of the Traffic Alert and Collision Avoidance System (TCAS) multiple threat logic. We observed from archived radar data that while rarer than single-threat encounters, multiple threat encounters occur more frequently than originally expected...

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Sinewave parameter estimation using the fast Fan-Chirp Transform

Published in:
Proc. IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, WASPAA, 18-21 October 2009, pp. 349-352.

Summary

Sinewave analysis/synthesis has long been an important tool for audio analysis, modification and synthesis [1]. The recently introduced Fan-Chirp Transform (FChT) [2,3] has been shown to improve the fidelity of sinewave parameter estimates for a harmonic audio signal with rapid frequency modulation [4]. A fast version of the FChT [3] reduces computation but this algorithm presents two factors that affect sinewave parameter estimation. The phase of the fast FChT does not match the phase of the original continuous-time transform and this interferes with the estimation of sinewave phases. Also, the fast FChT requires an interpolation of the input signal and the choice of interpolator affects the speed of the transform and accuracy of the estimated sinewave parameters. In this paper we demonstrate how to modify the phase of the fast FChT such that it can be used to estimate sinewave phases, and we explore the use of various interpolators demonstrating the tradeoff between transform speed and sinewave parameter accuracy.
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Summary

Sinewave analysis/synthesis has long been an important tool for audio analysis, modification and synthesis [1]. The recently introduced Fan-Chirp Transform (FChT) [2,3] has been shown to improve the fidelity of sinewave parameter estimates for a harmonic audio signal with rapid frequency modulation [4]. A fast version of the FChT [3]...

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Towards co-channel speaker separation by 2-D demodulation of spectrograms

Published in:
WASPAA 2009, IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, 18-21 October 2009, pp. 65-68.

Summary

This paper explores a two-dimensional (2-D) processing approach for co-channel speaker separation of voiced speech. We analyze localized time-frequency regions of a narrowband spectrogram using 2-D Fourier transforms and propose a 2-D amplitude modulation model based on pitch information for single and multi-speaker content in each region. Our model maps harmonically-related speech content to concentrated entities in a transformed 2-D space, thereby motivating 2-D demodulation of the spectrogram for analysis/synthesis and speaker separation. Using a priori pitch estimates of individual speakers, we show through a quantitative evaluation: 1) Utility of the model for representing speech content of a single speaker and 2) Its feasibility for speaker separation. For the separation task, we also illustrate benefits of the model's representation of pitch dynamics relative to a sinusoidal-based separation system.
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Summary

This paper explores a two-dimensional (2-D) processing approach for co-channel speaker separation of voiced speech. We analyze localized time-frequency regions of a narrowband spectrogram using 2-D Fourier transforms and propose a 2-D amplitude modulation model based on pitch information for single and multi-speaker content in each region. Our model maps...

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Moving clutter spectral filter for Terminal Doppler Weather Radar

Author:
Published in:
34th Conf. on Radar Meteorology, 5-9 October 2009.

Summary

Detecting low-altitude wind shear in support of aviation safety and efficiency is the primary mission of the Terminal Doppler Weather Radar (TDWR). The wind-shear detection performance depends directly on the quality of the data produced by the TDWR. At times the data quality suffers from the presence of clutter. Al-though stationary ground clutter signals can be removed by a high-pass filter, moving clutter such as birds and roadway traffic cannot be attenuated using the same technique because their signal power can exist any-where in the Doppler velocity spectrum. Furthermore, because the TDWR is a single-polarization radar, polarimetry cannot be used to discriminate these types of clutter from atmospheric signals. The moving clutter problem is exacerbated at Western sites with dry microbursts, because their low signal-to-noise ratios (SNRs) are more easily masked by un-wanted moving clutter. For Las Vegas (LAS), Nevada, the offending clutter is traffic on roads that are oriented along the radar line of sight near the airport. The radar is located at a significantly higher altitude than the town, improving the visibility to the roads, and giving LAS the worst road clutter problem of all TDWR sites. The Salt Lake City (SLC), Utah, airport is located near the Great Salt Lake, which is the biggest inland staging area for migrating seabirds in the country. It, therefore, suffers from bird clutter, which not only can obscure wind shear signatures but can also mimic them to trigger false alarms. The TDWR "dry" site issues are discussed in more detail by Cho (2008). In order to mitigate these problems, we developed a moving clutter spectral filter (MCSF). In this paper we describe the algorithm and present preliminary test results.
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Summary

Detecting low-altitude wind shear in support of aviation safety and efficiency is the primary mission of the Terminal Doppler Weather Radar (TDWR). The wind-shear detection performance depends directly on the quality of the data produced by the TDWR. At times the data quality suffers from the presence of clutter. Al-though...

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