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Design considerations for space-based radar phased arrays

June 12, 2005
  |
Conference Paper
Author:
Jeffrey S. Herd
…
Published in:
2005 IEEE MTT-S Int. Microwave Symp. Digest, 12-17 June 2005, pp. 1631-1634.
Topic:
radar
R&D area:
R&D group:

Summary

Space Based Radar (SBR) is being considered as a means to provide persistent global surveillance. In order to be effective, the SBR system must be capable of high area coverage rates, low minimum detectable velocities (MDV), accurate geolocation, high range resolution, and robustness against electronic interference. These objectives will impose challenging requirements on the antenna array, including wide-angle electronic scanning, wide instantaneous bandwidth, large poweraperture product, low sidelobe radiation patterns, lightweight deployable structures, multiple array phase centers, and adaptive pattern synthesis. This paper will discuss key enabling technologies for low earth orbit (LEO) SBR arrays including high efficiency transmit/receive modules and multilayer tile architectures, and the parametric influence of array design variables on the SBR system.
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Summary

Space Based Radar (SBR) is being considered as a means to provide persistent global surveillance. In order to be effective, the SBR system must be capable of high area coverage rates, low minimum detectable velocities (MDV), accurate geolocation, high range resolution, and robustness against electronic interference. These objectives will impose...

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Design considerations for space-based radar phased arrays

Multi-PRI signal processing for the terminal Doppler weather radar, part I: clutter filtering

May 1, 2005
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Journal Article
Author:
John Y. Cho
…
Published in:
J. Atmos. Ocean. Technol., Vol. 22, May 2005, pp. 575-582.
Topic:
algorithms
R&D area:
R&D group:

Summary

Multiple pulse repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to aggressively combat range-velocity ambiguity in weather radars. In the past, operational use of multi-PRI pulse trains has been hampered due to the difficulty in clutter filtering. This paper presents finite impulse response clutter filter designs for multi-PRI signals with excellent magnitude and phase responses. These filters provide strong suppression for use on low-elevation scans and yield low biases of velocity estimates so that accurate velocity dealiasing is possible. Specifically, the filters are designed for use in the Terminal Doppler Weather Radar (TDWR) and are shown to meet base data bias requirements equivalent to the Federal Aviation Administration's specifications for the current TDWR clutter filters. Also an adaptive filter selection algorithm is proposed that bases its decision on clutter power estimated during an initial long-PRI surveillance scan. Simulations show that this adaptive algorithm yields satisfactory biases for reflectivity, velocity, and spectral width. Implementation of such a scheme would enable automatic elimination of anomalous propagation signals and constant adjustment to evolving ground clutter conditions, an improvement over the current TDWR clutter filtering system.
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Summary

Multiple pulse repetition interval (multi-PRI) transmission is part of an adaptive signal transmission and processing algorithm being developed to aggressively combat range-velocity ambiguity in weather radars. In the past, operational use of multi-PRI pulse trains has been hampered due to the difficulty in clutter filtering. This paper presents finite impulse...

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Multi-PRI signal processing for the terminal Doppler weather radar, part I: clutter filtering

Design considerations and results for an overlapped subarray radar antenna

March 5, 2005
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Conference Paper
Author:
Jeffrey S. Herd
…
Published in:
2005 IEEE Aerospace Conf., 5-12 March 2005, pp. 1087-1092.
Topic:
antennas
R&D area:
R&D group:

Summary

Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of an overlapped subarray antenna includes many signal crossovers and a wide variation in splitting/combining ratios, which make it difficult to maintain required error tolerances. This paper presents the design considerations and results for an overlapped subarray radar antenna, including a custom subarray weighting function and the corresponding circuit design and fabrication. Measured pattern results will be shown for a prototype design compared with desired patterns.
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Summary

Overlapped subarray networks produce flattopped sector patterns with low sidelobes that suppress grating lobes outside of the main beam of the subarray pattern. They are typically used in limited scan applications, where it is desired to minimize the number of controls required to steer the beam. However, the architecture of...

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Design considerations and results for an overlapped subarray radar antenna

MIMO radar theory and experimental results

November 7, 2004
  |
Conference Paper
Author:
Frank C. Robey
…
Published in:
38th Asilomar Conf. on Signals, Systems and Computers, Vol. 2, 7-10 November 2004, pp. 300-304.
Topic:
radar
R&D area:
R&D group:

Summary

The continuing progress of Moore's law has enabled the development of radar systems that simultaneously transmit and receive multiple coded waveforms from multiple phase centers and to process them in ways that have been unavailable in the past. The signals available for processing from these Multiple-Input Multiple-Output (MIMO) radar systems appear as spatial samples corresponding to the convolution of the transmit and receive aperture phase centers. The samples provide the ability to excite and measure the channel that consists of the transmit/receive propagation paths, the target and incidental scattering or clutter. These signals may be processed and combined to form an adaptive coherent transmit beam, or to search an extended area with high resolution in a single dwell. Adaptively combining the received data provides the effect of adaptively controlling the transmit beamshape and the spatial extent provides improved track-while-scan accuracy. This paper describes the theory behind the improved surveillance radar performance and illustrates this with measurements from experimental MIMO radars.
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Summary

The continuing progress of Moore's law has enabled the development of radar systems that simultaneously transmit and receive multiple coded waveforms from multiple phase centers and to process them in ways that have been unavailable in the past. The signals available for processing from these Multiple-Input Multiple-Output (MIMO) radar systems...

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MIMO radar theory and experimental results

Wideband aperture coherence processing for next generation radar (NexGen)

July 30, 2004
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Project Report
Author:
Kevin M. Cuomo
…
Published in:
MIT Lincoln Laboratory Report NG-3
Topic:
radar
R&D area:
R&D group:

Summary

This report develops robust signal processing architectures and algorithms specifically designed to achieve multi-aperture coherence on transmit and receive. A key feature of our approach is the use of orthogonal radar waveforms that allow the monostatic and bistatic target returns to be separated at each receiver's matched filter output. By analyzing these returns, we may determine the appropriate transmit times and phases in order to cohere the various radar apertures using both narrowband and wideband waveforms. This process increases the array gain on receive to N2 instead of N for the single transmitter case. Furthermore, when hll coherence on transmit is achieved, the array gain is N3. The performance of our coherence algorithms is quantified using Monte Carlo simulations and compared to the Cramer-Rao lower bound. A computational complexity study shows that our aperture coherence algorithms are suitable for a realtime implementation on an SGI Origin 3000 multi-processor computer.
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Summary

This report develops robust signal processing architectures and algorithms specifically designed to achieve multi-aperture coherence on transmit and receive. A key feature of our approach is the use of orthogonal radar waveforms that allow the monostatic and bistatic target returns to be separated at each receiver's matched filter output. By...

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Wideband aperture coherence processing for next generation radar (NexGen)

Power-law scattering models and nonlinear parametric estimation for super-resolution radar

April 26, 2004
  |
Technical Report
Author:
Nicholas A. Hatch
…
Published in:
MIT Lincoln Laboratory Report TR-1095
Topic:
radar
R&D area:
R&D group:

Summary

This paper introduces a direct solution of the frequency-dependent, GTD-based, scatterer-model parameters leading towards a new modern spectral-estimation technique to be used for enhanced, super-resolution radar analysis. The overcomplete nature of the full GTD scatterer-model basis (positive and negative half-integer power laws) is recognized and overcome by introducing the vector-channel method, well known from communication theory. This physically motivated discretemodel- based analysis eliminates the need for computationally intensive and potentially nonconvergent local optimization procedures. Each scatterer is assigned a half-integer power law that identifies its cross-section frequency dependence and hence restricts the possible underlying physical feature geometries. This analysis opens the possibility for vector-attribute-based feature processing for target recognition that offers the potential for significant improvement in target identification performance.
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Summary

This paper introduces a direct solution of the frequency-dependent, GTD-based, scatterer-model parameters leading towards a new modern spectral-estimation technique to be used for enhanced, super-resolution radar analysis. The overcomplete nature of the full GTD scatterer-model basis (positive and negative half-integer power laws) is recognized and overcome by introducing the vector-channel...

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Power-law scattering models and nonlinear parametric estimation for super-resolution radar

Range-velocity ambiguity mitigation schemes for the enhanced Terminal Doppler Weather Radar

August 6, 2003
  |
Conference Paper
Author:
John Y. Cho
…
Published in:
37th Int. Conf. on Radar Meteorology, 6-12 August 2003.
Topic:
algorithms
R&D area:
R&D group:

Summary

The Terminal Doppler Weather Radar (TDWR) radar data acquisition (RDA) subsystem is being replaced as part of a broader FAA program to improve the supportability of the system. An engineering prototype RDA is under development that will provide a modern, open-systems hardware platform and standards-compliant software. The new platform also provides an opportunity to insert algorithms to improve the quality of existing base data products, as well as support future enhancements to the aviation weather services provided by TDWR. There are several outstanding data quality issues with the TDWR. In this paper, we focus on mitigation schemes for the range-velocity ambiguity problem that is especially severe for C-band weather radars such as the TDWR.
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Summary

The Terminal Doppler Weather Radar (TDWR) radar data acquisition (RDA) subsystem is being replaced as part of a broader FAA program to improve the supportability of the system. An engineering prototype RDA is under development that will provide a modern, open-systems hardware platform and standards-compliant software. The new platform also...

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Range-velocity ambiguity mitigation schemes for the enhanced Terminal Doppler Weather Radar

Observations of non-traditional wind shear events at the Dallas/Fort Worth International Airport

February 28, 2003
  |
Project Report
Author:
Justin D. Shaw
…
Published in:
MIT Lincoln Laboratory Report ATC-308
Topic:
wind shear
R&D area:
R&D group:

Summary

During the past 20 years there has been great success in understanding and detecting microbursts. These "traditional" wind shear events are most prominent in the summer and are characterized by a two-dimensional, divergent outflow associated with precipitation loading from a thunderstorm downdraft or evaporative cooling from high-based rain clouds. Analysis of wind shear loss alerts at the Dallas/Fort Worth International Airport (DFW) from August 1999 through July 2002 reveals that a significant number of the wind shear events were generated by "non-traditional" mechanisms. The "non-traditional" wind shear mechanisms, linear divergence, divergence behind gust fronts, and gravity waves, accounted for one half of the alert events in the period studied. Radar-based algorithms have shown considerable skill in detecting wind shear events. However, the algorithms were developed to identifl features common to the "traditional" events. If the algorithms were modified to detect "non-traditional" wind shear, the corresponding increase in false detections could be unacceptable. Therefore, in this report a new radar-based algorithm is proposed that detects linear divergence, divergence behind gust fronts, and gravity waves for output on the Integrated Terminal Weather System by identifying the radar signatures that are common to these features.
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Summary

During the past 20 years there has been great success in understanding and detecting microbursts. These "traditional" wind shear events are most prominent in the summer and are characterized by a two-dimensional, divergent outflow associated with precipitation loading from a thunderstorm downdraft or evaporative cooling from high-based rain clouds. Analysis...

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Observations of non-traditional wind shear events at the Dallas/Fort Worth International Airport

Analysis and comparison of separation measurement errors in single sensor and multiple radar mosiac display terminal environments

October 21, 2002
  |
Project Report
Author:
Steven D. Thompson
Published in:
MIT Lincoln Laboratory Report ATC-306
Topic:
radar
R&D area:
R&D group:

Summary

This paper presents an analyis to estimate and characterize the errors in the measured separation distance between aircraft that are displayed on a radar screen to a controller in a single sensor terminal environment compared to a multiple radar mosiac terminal environment. The error in measured or displayed separation is the difference between the true separation or distance between aircraft in the air and the separation displayed to a controller on a radar screen. In order to eliminate as many variables as possible and to concentrate specifically on the differences between displayed separation errors in the two environments, for the purposes of this analysis, only full operation Mode S secondary beacon surveillance characteristics are considered. A summary of the Mode S secondary radar error sources and characteristics used to model the resultant errors in measured separation between aircraft in single and multi-radar terminal environments is presented. The analysis for average separation errors show that the performance of radars in providing separation services degrades with range. The analysis also shows that when using independent radars in a mosiac display, separation errors will increase, on average, compared to the performance when providing separation with a single radar. The data presented in the section on average separation errors is summarized by plotting the standard deviation of the separation error as a function of range for the single radar case and for the independent mosiac display case. The sections on typical and specific errors in separation measurements illustrate that the separation measurement errors are highly dependent on the geometry of the aircraft and radars. Applying average results to specific geometries can lead to counter intuitive results is illustrated in an example case presented in analysis.
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Summary

This paper presents an analyis to estimate and characterize the errors in the measured separation distance between aircraft that are displayed on a radar screen to a controller in a single sensor terminal environment compared to a multiple radar mosiac terminal environment. The error in measured or displayed separation is...

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Analysis and comparison of separation measurement errors in single sensor and multiple radar mosiac display terminal environments

Machine intelligent gust front algorithm for the WSP

June 10, 2002
  |
Project Report
Author:
Seth W. Troxel
…
Published in:
MIT Lincoln Laboratory Report ATC-274
Topic:
radar
R&D area:
R&D group:

Summary

The Machine Intelligent Gust Front Algorithm (MIGFA) utilizes multi-dimensional image processing and fuzzy logic techniques to identify gust fronts in Doppler radar data generated by the ASR-9 Weather Systems Processor (WSP). The algorithm generates products that support both safety and planning functions for ATC. Outputs include current and predicted locations of gust fronts, as well as estimates of the wind shear and wind shift associated with each gust front. This document provides both high level and detailed functional descriptions of FAA build 2.0 of the WSP MIGFA. The document was written with many explicit references to data structures and routines in the actual software in order that it may serve as a useful algorithm development and programmers reference guide.
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Summary

The Machine Intelligent Gust Front Algorithm (MIGFA) utilizes multi-dimensional image processing and fuzzy logic techniques to identify gust fronts in Doppler radar data generated by the ASR-9 Weather Systems Processor (WSP). The algorithm generates products that support both safety and planning functions for ATC. Outputs include current and predicted locations...

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Machine intelligent gust front algorithm for the WSP
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