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A Ground to Air Imaging Radar system (GAIR) used to perform diagnostic imaging and total RCS measurements on low observable airborne targets has been developed by the Environmental Research Institute of Michigan (ERIM). In order to ensure accurate measurement of the scatterers contributing to a target's radar signature, proper calibration in imperative. The use of external calibrators to measure the end-to-end system transfer function is the ideal way to perform a system calibration. However, this is a more difficult and challenging task with a ground based radar viewing an airborne target, as opposed to a traditional airborne SAR which views an array of ground based trihedral corner reflectors. This paper will discuss the internal and external calibration methods used in performing an end-to-end system calibration of the GAIR. Primary emphasis is placed upon the external calibration of the GAIR and the three independent measurements utilized: a ground based corner reflector, a sphere drop, and an in-scene calibrator. The system calibration results demonstrate that the GAIR is an accurately calibrated radar system capable of providing calibrated images and total RCS data. Moreover, only the ground and internal measurements are required on a daily basis in order to maintain system calibration
A Ground to Air Imaging Radar system (GAIR) used to perform diagnostic imaging and total RCS measurements on low observable airborne targets has been developed by the Environmental Research Institute of Michigan (ERIM). In order to ensure accurate measurement of the scatterers contributing to a target's radar signature, proper calibration in imperative. The use of external calibrators to measure the end-to-end system transfer function is the ideal way to perform a system calibration. However, this is a more difficult and challenging task with a ground based radar viewing an airborne target, as opposed to a traditional airborne SAR which views an array of ground based trihedral corner reflectors. This paper will discuss the internal and external calibration methods used in performing an end-to-end system calibration of the GAIR. Primary emphasis is placed upon the external calibration of the GAIR and the three independent measurements utilized: a ground based corner reflector, a sphere drop, and an in-scene calibrator. The system calibration results demonstrate that the GAIR is an accurately calibrated radar system capable of providing calibrated images and total RCS data. Moreover, only the ground and internal measurements are required on a daily basis in order to maintain system calibration
This paper demonstrates modem parametric modeling techniques that can be used to form high resolution ISAR images of full scale flying aircraft. Both parametric spectral estimation techniques and autoregressive data extrapolation techniques are shown. We demonstrate imaging. In each case, the modem spectral estimation or data extrapolation techniques produce higher image resolution than that which is obtained by classical Fourier techniques.
This paper demonstrates modem parametric modeling techniques that can be used to form high resolution ISAR images of full scale flying aircraft. Both parametric spectral estimation techniques and autoregressive data extrapolation techniques are shown. We demonstrate imaging. In each case, the modem spectral estimation or data extrapolation techniques produce higher image resolution than that which is obtained by classical Fourier techniques.
A Superresolution technique for estimation of the time-delays, and amplitude/phase dispersion of the electromagnetic scattering is presented. In order to estimate the frequency dependence of individual scattering features, a pre-processing technique for the MUSIC (Multiple SIgnal Classification) algorithm is developed and applied to the theoretical and experimental scattering data.
A Superresolution technique for estimation of the time-delays, and amplitude/phase dispersion of the electromagnetic scattering is presented. In order to estimate the frequency dependence of individual scattering features, a pre-processing technique for the MUSIC (Multiple SIgnal Classification) algorithm is developed and applied to the theoretical and experimental scattering data.
Effectiveness of data extrapolation to generate high resolution radar images is studied. It is shown that polar formatted scattered field data can be extrapolated more effectively than (f, 0) domain scattered field data. The reason for this is that the forward backward linear prediction is not suitable for extrapolating the scattered field data with respect to aspect angle (0). Also, when the scattered field data is extrapolated with respect to frequency to increase the down range resolution, there can be some degradation in the cross range resolution.
Effectiveness of data extrapolation to generate high resolution radar images is studied. It is shown that polar formatted scattered field data can be extrapolated more effectively than (f, 0) domain scattered field data. The reason for this is that the forward backward linear prediction is not suitable for extrapolating the scattered field data with respect to aspect angle (0). Also, when the scattered field data is extrapolated with respect to frequency to increase the down range resolution, there can be some degradation in the cross range resolution.
Progress in Georgia Tech's research in Near-Field Spherical Microwave Holography (NFSMH) is reported. Previously, the amplitude resolution of Spherical Microwave Holography (SMH) was defined and demonstrated. The definition of resolution has been altered to include phase resolution. The resolution of phase is shown to be equivalent to the resolution of amplitude, and both depend on the highest mode order used in the spherical wave expansion. Previous measurements showed that SMH can easily achieve x/2 phase resolution where X refers to free space wavelengths. Current measurements show that the X/2 resolution limit of planar microwave holography can be surpassed by using evanescent energy in the NSMFH technique. Measurements of small, closely spaced, insertion phase defects placed on a hemispheric ally shaped radome are used to demonstrate the improved resolution. The measurement of evanescent energy is achieved by using a specially designed small aperture probe and a small separation distance between small aperture probe and a small separation distance between the radome surface and the measurement surface. The relationship between measured and theoretical insertion phase of a known radome defect is shown. Given the defect size and the maximum mode order used in the spherical wave expansion, measured insertion phase can be used to predict the actual defects electrical thickness.
Progress in Georgia Tech's research in Near-Field Spherical Microwave Holography (NFSMH) is reported. Previously, the amplitude resolution of Spherical Microwave Holography (SMH) was defined and demonstrated. The definition of resolution has been altered to include phase resolution. The resolution of phase is shown to be equivalent to the resolution of amplitude, and both depend on the highest mode order used in the spherical wave expansion. Previous measurements showed that SMH can easily achieve x/2 phase resolution where X refers to free space wavelengths. Current measurements show that the X/2 resolution limit of planar microwave holography can be surpassed by using evanescent energy in the NSMFH technique. Measurements of small, closely spaced, insertion phase defects placed on a hemispheric ally shaped radome are used to demonstrate the improved resolution. The measurement of evanescent energy is achieved by using a specially designed small aperture probe and a small separation distance between small aperture probe and a small separation distance between the radome surface and the measurement surface. The relationship between measured and theoretical insertion phase of a known radome defect is shown. Given the defect size and the maximum mode order used in the spherical wave expansion, measured insertion phase can be used to predict the actual defects electrical thickness.
A small compact range measurement facility has been installed at the Environmental Research Institute of Michigan (ERIM) for research aimed at improving RCS measurement and radar imaging techniques. This paper describes the facility, which is referred to as the Experimental Range Facility (ERF). The ERF has two instrumentation radars; a Flam & Russell FR959 gated CW radar and a Hughes MMS-300 pulsed radar. The radars are connected to a suite of workstations, which support a variety of internally and externally developed radar imaging and data exploitation software. The ERF is also equipped with sophisticated target positioning control and sensing equipment.
A small compact range measurement facility has been installed at the Environmental Research Institute of Michigan (ERIM) for research aimed at improving RCS measurement and radar imaging techniques. This paper describes the facility, which is referred to as the Experimental Range Facility (ERF). The ERF has two instrumentation radars; a Flam & Russell FR959 gated CW radar and a Hughes MMS-300 pulsed radar. The radars are connected to a suite of workstations, which support a variety of internally and externally developed radar imaging and data exploitation software. The ERF is also equipped with sophisticated target positioning control and sensing equipment.
The U.S.Army Redstone Technical Test Center (RTTC), Test and Evaluation Command, has developed a comprehensive antenna metrology and Radar Cross Section (RCS) evaluation facility. This facility features the compact antenna test range technique for millimeter wave measurements and the near-field scanning technique for microwave measurements. This paper described RTTC's use of these measurement techniques, instrumentation with PC Windows based automation software, anechoic chambers, and types of tests performed. Planned future thrust areas are also discussed.
The U.S.Army Redstone Technical Test Center (RTTC), Test and Evaluation Command, has developed a comprehensive antenna metrology and Radar Cross Section (RCS) evaluation facility. This facility features the compact antenna test range technique for millimeter wave measurements and the near-field scanning technique for microwave measurements. This paper described RTTC's use of these measurement techniques, instrumentation with PC Windows based automation software, anechoic chambers, and types of tests performed. Planned future thrust areas are also discussed.
A modern outdoor test facility has been designed for comprehensive evaluation of antenna systems on full scale aircraft. The aircraft are mounted to a positioner/tower assembly in an underground handling facility, and are raised to a height of 25 meters by a hydraulically activated lift. A source site 1000 meters downrange provides illumination of a 7 meter radius test zone over a 0.1-18 GHz band. All source site functionality is remotely controlled from the operations center located near the aircraft support tower. The range is designed to provide the capability not only for conventional automated antenna pattern measurements, but also for the support of ECCM testing. This is accomplished by activating both fixed and mobile jamming transmitters available to illuminate the test zone using either CW or modulated waveforms. The FR Model 959 Automated Antenna Measurement Workstation is being enhanced to allow for control of the jammer sites as well as the primary range sited. The system design and operation is described.
A modern outdoor test facility has been designed for comprehensive evaluation of antenna systems on full scale aircraft. The aircraft are mounted to a positioner/tower assembly in an underground handling facility, and are raised to a height of 25 meters by a hydraulically activated lift. A source site 1000 meters downrange provides illumination of a 7 meter radius test zone over a 0.1-18 GHz band. All source site functionality is remotely controlled from the operations center located near the aircraft support tower. The range is designed to provide the capability not only for conventional automated antenna pattern measurements, but also for the support of ECCM testing. This is accomplished by activating both fixed and mobile jamming transmitters available to illuminate the test zone using either CW or modulated waveforms. The FR Model 959 Automated Antenna Measurement Workstation is being enhanced to allow for control of the jammer sites as well as the primary range sited. The system design and operation is described.
This paper demonstrates vertical bistatic Radar-Cross-Section measurement capability in the McDonnell Douglas Technologies, Inc. (MDTI) Radar Measurement Center )RMC). Data will be presented showing the system configuration, system specifications, and predicted and measured vertical bistatic RCF data on a variety of generic targets.
This paper demonstrates vertical bistatic Radar-Cross-Section measurement capability in the McDonnell Douglas Technologies, Inc. (MDTI) Radar Measurement Center )RMC). Data will be presented showing the system configuration, system specifications, and predicted and measured vertical bistatic RCF data on a variety of generic targets.
A complete description is given of the unique radar cross-section (RCS) measurement facility built at the Houston Advanced Research Center in The Woodlands, TX. The uniqueness of this chamber comes from its ability to independently move the transmit and receive antennas, which can each be moved to any position within their respective ranges of motion to a resolution of about 0.05 degrees. The transmit antenna is fixed in azimuth, but can be moved in elevation: the receive antenna is free to move in both azimuth and elevation. Additionally, the target can be rotated in azimuth by means of an azimuth positioner. Analysis has been performed to determine the impact of chamber effects on measurement accuracy. The most notable chamber effect comes from the two large aluminum truss structures, which are the mounting supports for the transmit and receive antennas. Fortunately, the scattering from these structures can be readily separated from the desired target return through the use of range (time) gating. Time domain results are presented showing the effects of these structures.
A complete description is given of the unique radar cross-section (RCS) measurement facility built at the Houston Advanced Research Center in The Woodlands, TX. The uniqueness of this chamber comes from its ability to independently move the transmit and receive antennas, which can each be moved to any position within their respective ranges of motion to a resolution of about 0.05 degrees. The transmit antenna is fixed in azimuth, but can be moved in elevation: the receive antenna is free to move in both azimuth and elevation. Additionally, the target can be rotated in azimuth by means of an azimuth positioner. Analysis has been performed to determine the impact of chamber effects on measurement accuracy. The most notable chamber effect comes from the two large aluminum truss structures, which are the mounting supports for the transmit and receive antennas. Fortunately, the scattering from these structures can be readily separated from the desired target return through the use of range (time) gating. Time domain results are presented showing the effects of these structures.