Publications
NextGen surveillance and weather radar capability (NSWRC) siting analysis
May 22, 2012
Project Report
Published in:
Project Report ATC-391, MIT Lincoln Laboratory
Summary
As the current radars that perform weather and aircraft surveillance over the United States age, they must be sustained through service life extension programs or replaced. In the latter case, the radars can be replaced by multiple types of radars with different missions or they can be replaced by scalable multifunction phased array radars (MPARs). State-of-the-art active phased array systems have the potential to provide improved capabilities such as earlier detection and better characterization of hazardous weather phenomena, 3D tracking of noncooperative aircraft, better avoidance of unwanted clutter sources such as wind farms, and more graceful performance degradation with component failure. As the U.S. aviation community works toward realizing the Next Generation Air Transportation System (NextGen), achieving improved capabilities for aircraft and weather surveillance becomes critical, because stricter observation requirements are believed to be needed. Hence, the Federal Aviation Administration (FAA) is considering the MPAR as a possible solution to their NextGen Surveillance and Weather Radar Capability (NSWRC). Cost is one hurdle to the deployment of a modern phased array radar network. One way of lowering the overall cost is to reduce the total number of radars. Because of the overlap in coverage provided by the current radar networks, a unified MPAR replacement network can potentially decrease the total number of radars needed to cover the same airspace. An earlier analysis conducted by MIT Lincoln Laboratory concluded that 510 legacy radars could be effectively replaced by 334 MPARs over the contiguous United States (CONUS). There was, however, some uncertainty whether the spatial resolution used in the terrain blockage calculations was fine enough to accurately depict radar coverage, and also if terminal area coverage was being adequately addressed. This study revisits the siting analysis using a much finer spatial resolution, expands the coverage domain to include all fifty states and U.S. territories, adds the Air Force long-range surveillance radars (FPSs) to the legacy pool, and allows scaling by number of faces per radar. The aim is to provide an estimate of the minimum number of MPARs needed to replace the existing radar coverage. We also provide an extensive statistical compilation of legacy versus MPAR coverage for various observational performance parameters.
Summary
As the current radars that perform weather and aircraft surveillance over the United States age, they must be sustained through service life extension programs or replaced. In the latter case, the radars can be replaced by multiple types of radars with different missions or they can be replaced by scalable...
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Rational design and optimization of plasmonic nanoarrays for surface enhanced infrared spectroscopy
May 21, 2012
Journal Article
Published in:
Opt. Express, Vol. 20, No. 11, 21 May 2012, pp. 11953-11966.
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Summary
We present an approach for rational design and optimization of plasmonic arrays for ultrasensitive surface enhanced infrared absorption (SEIRA) spectroscopy of specific protein analytes. Motivated by our previous work that demonstrated sub-attomole detection of surface-bound silk fibroin [Proc. Natl. Acad. Sci. U.S.A. 106, 19227 (2009)], we introduce here a general framework that allows for the numerical optimization of metamaterial sensor designs in order to maximize the absorbance signal. A critical feature of our method is the explicit compensation for the perturbative effects of the analyte's refractive index which alters the resonance frequency and line-shape of the metamaterial response, thereby leading to spectral distortion in SEIRA signatures. As an example, we leverage our method to optimize the geometry of periodic arrays of plasmonic nanoparticles on both Si and CaF2 substrates. The optimal geometries result in a three-order of magnitude absorbance enhancement compared to an unstructured Au layer, with the CaF2 substrate offering an additional factor of three enhancement in absorbance over a traditional Si substrate. The latter improvement arises from increase of near-field intensity over the Au nanobar surface for the lower index substrate. Finally, we perform sensitivity analysis for our optimized arrays to predict the effects of fabrication imperfections. We find that
Summary
We present an approach for rational design and optimization of plasmonic arrays for ultrasensitive surface enhanced infrared absorption (SEIRA) spectroscopy of specific protein analytes. Motivated by our previous work that demonstrated sub-attomole detection of surface-bound silk fibroin [Proc. Natl. Acad. Sci. U.S.A. 106, 19227 (2009)], we introduce here a general...
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A compressed sensing analog-to-information converter with edge-triggered SAR ADC core
May 20, 2012
Journal Article
Published in:
ISCAS 2012: IEEE Int. Symp. on Circuits and Systems, 20-23 May 2012, pp. 3162-3165.
Summary
This paper presents the design and implementation of an analog-to-information converter (AIC) based on compressed sensing. The core of the AIC is an edge-triggered charge-sharing SAR ADC. Compressed sensing is achieved through random sampling and asynchronous successive approximation conversion using the ADC core. Implemented in 90nm CMOS, the prototype SAR ADC core achieves a maximum sample rate of 9.5MS/s, an ENOB of 9.3 bits, and consumes 550 mu W from a 1.2V supply. Measurement results of the compressed sensing AIC demonstrate effective sub-Nyquist random sampling and reconstruction of signals with sparse frequency support suitable for wideband spectrum sensing applications. When accounting for the increased input bandwidth compared to Nyquist, the AIC achieves an effective FOM of 10.2fJ/conversion-step.
Summary
This paper presents the design and implementation of an analog-to-information converter (AIC) based on compressed sensing. The core of the AIC is an edge-triggered charge-sharing SAR ADC. Compressed sensing is achieved through random sampling and asynchronous successive approximation conversion using the ADC core. Implemented in 90nm CMOS, the prototype SAR...
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Dallas/Fort Worth field demonstration #2 (DFW-2) final report for Tower Flight Data Manager (TFDM)
May 16, 2012
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-393
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Summary
The Tower Flight Data Manager (TFDM) is the next generation air traffic control tower (ATCT) information system that integrates surveillance, flight data, and other sources, which enables advanced decision support tools (DSTs) to improve departure and arrival efficiency and reduce fuel burn at the airport. TFDM was exercised as a prototype installed at the Dallas / Fort Worth International Airport (DFW) during a two-week demonstration in the spring of 2011 termed DFW-2. MIT Lincoln Laboratory conducted this demonstration for the FAA in coordination with DFW air traffic control (ATC) and the DFW airport authority. The objective of this TFDM field demonstration was to validate the operational suitability and refine production system requirements of the Tower Information Display System (TIDS) surface surveillance display and Flight Data Manager (FDM) electronic flight data display and to evaluate the first iteration of the Supervisor Display and DSTs. These objectives were met during the two-week field demonstration. Results indicated that the TIDS and FDM exhibited capabilities considered operationally suitable for the tower as an advisory system and as a primary means for control given surface surveillance that is approved for operational use. Human factors data indicated that TIDS and FDM could be beneficial. The prototype Supervisor Display and DSTs met a majority of the technical performance criteria, but fewer than half of the human factors success criteria were met. As this was the first iteration of the Supervisor Display and DST capabilities, subsequent prototype iterations to achieve the target concept of operations, functionality and information presentation with accompanying field demonstrations to evaluate these honed capabilities were recommended and expected. FLM/TMC feedback will help refine subsequent system design.
Summary
The Tower Flight Data Manager (TFDM) is the next generation air traffic control tower (ATCT) information system that integrates surveillance, flight data, and other sources, which enables advanced decision support tools (DSTs) to improve departure and arrival efficiency and reduce fuel burn at the airport. TFDM was exercised as a...
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Vertically stacked RF switches by wafer-scale three-dimensional integration
May 10, 2012
Journal Article
Published in:
Electron. Lett., Vol. 48, No. 10, 10 May 2012.
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Summary
Vertically stacked RF switches implemented by wafer-scale three-dimensional (3D) integration of three completely fabricated silicon-on-insulator wafers are demonstrated. The individual switch performance was maintained through the 3D integration process while the signal path is shortened by vertical interconnects. The footprint of the switch can be shrunk in proportion to the number of tiers it is distributed between, demonstrating the potential of significant size reduction of multiple-throw switches commonly required in many applications.
Summary
Vertically stacked RF switches implemented by wafer-scale three-dimensional (3D) integration of three completely fabricated silicon-on-insulator wafers are demonstrated. The individual switch performance was maintained through the 3D integration process while the signal path is shortened by vertical interconnects. The footprint of the switch can be shrunk in proportion to the...
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The MIT IAP radar course: build a small radar system capable of sensing range, Doppler, and synthetic aperture (SAR) imaging
May 7, 2012
Conference Paper
Published in:
Proc. of the 2012 IEEE Radar Conf., 7-11 May 2012.
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Summary
MIT Lincoln Laboratory sponsored a radar short course at MIT campus during the January 2011 Independent Activities Period (IAP). The objective of this course was to generate student interest in applied electromagnetics, antennas, radio frequency (RF) electronics, analog circuits, and signal processing by building a short-range radar sensor and using it in a series of field tests. Lectures on the fundamentals of radar, modular RF design, antennas, pulse compression and synthetic aperture radar (SAR) imaging were presented. Teams of three students built a radar system from a kit. This kit was developed by the authors and uses a frequency modulated continuous wave (FMCW) architecture. To save costs, empty metal coffee cans are used for antennas, components are mounted on a wood block, the system uses only six coaxial microwave parts, analog circuitry on a solderless breadboard, and runs on eight AA batteries. Analog data is acquired by the audio input port on a laptop computer. The total cost of each kit was $360 which made this radar technology accessible to students. Of the nine student groups, all succeeded in building their radar, acquiring Doppler vs. time and range vs. time plots, seven succeeded in acquiring SAR imagery, and some groups improved the radar system. By presenting these difficult topics at a high level while at the same time making a radar kit and performing field experiments, students became self motivated to explore these topics and much interest in radar design was generated.
Summary
MIT Lincoln Laboratory sponsored a radar short course at MIT campus during the January 2011 Independent Activities Period (IAP). The objective of this course was to generate student interest in applied electromagnetics, antennas, radio frequency (RF) electronics, analog circuits, and signal processing by building a short-range radar sensor and using...
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Evaluation of the Integrated Departure Route Planning (IDRP) Tool 2011 prototype
May 3, 2012
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-388
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Summary
The Integrated Departure Route Planning (IDRP) tool combines convective weather impact forecasts from the Route Availability Planning Tool (RAPT) with departure demand forecasts from the MITRE tfmCore system to aid traffic managers in formulating plans to mitigate volume congestion in fair weather and during convective weather impacts. An initial prototype was deployed in the summer of 2010 for a very limited field evaluation. A second, more comprehensive field evaluation of the "Phase 2" IDRP prototype was performed in the summer of 2011. The key focus of IDRP is the planning and implementation of departure reroutes to avoid weather impacts and volume congestion on departure fixes and routes. This evaluation assesses three facets of the IDRP prototype critical to the successful realization of its concept of operations: 1. performance of weather impact forecasts from RAPT and departure demand forecasts from tfmCore, 2. effectiveness of reroute decisions, and 3. potential impacts on procedures and decision making based on observations of IDRP use in the field. The evaluation concludes with suggestions for future enhancements to improve the performance and realization of potential benefits in operational use of IDRP.
Summary
The Integrated Departure Route Planning (IDRP) tool combines convective weather impact forecasts from the Route Availability Planning Tool (RAPT) with departure demand forecasts from the MITRE tfmCore system to aid traffic managers in formulating plans to mitigate volume congestion in fair weather and during convective weather impacts. An initial prototype...
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Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator
April 27, 2012
Journal Article
Published in:
Phys. Rev. Lett., Vol. 108, No. 17, 27 April 2012, 170503.
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Summary
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.
Summary
We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel...
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Readout circuitry for continuous high-rate photon detection with arrays of InP Geiger-mode avalanche photodiodes
April 23, 2012
Conference Paper
Published in:
SPIE, Vol. 8375, Advanced Photon Counting Techniques VI, 23 April 2012, 83750W.
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Summary
An asynchronous readout integrated circuit (ROIC) has been developed for hybridization to a 32x32 array of single-photon sensitive avalanche photodiodes (APDs). The asynchronous ROIC is capable of simultaneous detection and readout of photon times of arrival, with no array blind time. Each pixel in the array is independently operated by a finite state machine that actively quenches an APD upon a photon detection event, and re-biases the device into Geiger mode after a programmable hold-off time. While an individual APD is in hold-off mode, other elements in the array are biased and available to detect photons. This approach enables high pixel refresh frequency (PRF), making the device suitable for applications including optical communications and frequency-agile ladar. A built-in electronic shutter that de-biases the whole array allows the detector to operate in a gated mode or allows for detection to be temporarily disabled. On-chip data reduction reduces the high bandwidth requirements of simultaneous detection and readout. Additional features include programmable single-pixel disable, region of interest processing, and programmable output data rates. State-based on-chip clock gating reduces overall power draw. ROIC operation has been demonstrated with hybridized InP APDs sensitive to 1.06-Mm and 1.55-Mm wavelength, and fully packaged focal plane arrays (FPAs) have been assembled and characterized.
Summary
An asynchronous readout integrated circuit (ROIC) has been developed for hybridization to a 32x32 array of single-photon sensitive avalanche photodiodes (APDs). The asynchronous ROIC is capable of simultaneous detection and readout of photon times of arrival, with no array blind time. Each pixel in the array is independently operated by...
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Next-generation airborne collision avoidance system
April 11, 2012
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 19, No. 1, 2012, pp. 17-33.
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Summary
In response to a series of midair collisions involving commercial airliners, Lincoln Laboratory was directed by the Federal Aviation Administration in the 1970s to participate in the development of an onboard collision avoidance system. In its current manifestation, the Traffic Alert and Collision Avoidance System is mandated worldwide on all large aircraft and has significantly improved the safety of air travel, but major changes to the airspace planned over the coming years will require substantial modification to the system. Recently, Lincoln Laboratory has been pioneering the development of a new approach to collision avoidance systems that completely rethinks how such systems are engineered, allowing the system to provide a higher degree of safety without interfering with normal, safe operations.
Summary
In response to a series of midair collisions involving commercial airliners, Lincoln Laboratory was directed by the Federal Aviation Administration in the 1970s to participate in the development of an onboard collision avoidance system. In its current manifestation, the Traffic Alert and Collision Avoidance System is mandated worldwide on all...
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