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Dynamic ground-to-air measurement of aircraft RCS has several advantages over static measurements. The target may be measured in flight configuration and the support pylon is eliminated. Although dynamic RCS imagery has been performed since the late 1970s, the cost and complexity of such measurements have limited their utility for routine testing. In this paper, an easily deployable ground-to-air radar imaging system developed by Aeroflex Lintek is presented. This system forms images of aircraft in straight flight, requiring no on-board instrumentation or special pilot training. The radar system, flight profiles, and processing tools required for generating images of aircraft in flight are presented, along with examples of measured target data.
NSI recently completed installation of two large 7m x 7m horizontal planar scanners to support the Globalstar satellite program test activity. These systems were installed at Alcatel in France, and Alenia in Italy. These two systems are similar to the NSI system installed at Space Systems/ Loral in Palo Alto, CA. described in previous AMTA papers. The companies are part of the Globalstar satellite consortium, committed to launching a constellation of satellites for mobile telephone communications. The paper will summarize the hardware configuration and the unique features of the two new test systems including high power phased array testing and the interface to the Globalstar payload for active antenna control and payload testing. In addition, range data comparing all 3 test ranges will be shown.
A cost-effective, versatile instrumentation system for measuring antennas and radomes is described. The system features the use of high load capacity, high accuracy stepper motor based positioners as the primary system axes. The system is capable of being easily reconfigured to perform tests on antenna/radome systems with antennas fixed relative to the radome, or with the antenna and radome capable of movement relative to one another. Measurements may be performed at RF, IF or baseband, depending on the portions of the seeker or monopulse assembly to be included in the test. The system also contains analysis capabilities that simulated mode forming and beam forming functions to isolate antenna effects.
A new 1-50 GHz Near-Field measurement system is now in operation at Matra Marconi Space, Portsmouth, UK. The system has the largest vertical planar scanner installed so far. The planar scanner is constructed of steel and has four moving axes: 22 meter horizontal X axis, 8 meter vertical Y axis, 25 cm Z axis for probe alignment and a 540o Roll axis for polarization. Precision bearings are used to ensure straightness over the full length of the X-Y travel. The vertical Y axis is exceptionally fast, 500 mm/sec, to minimize acquisition time. The scanner has extremely high positioning accuracy and planarity - ±0.2 mm over the entire 22m x 8m range – allowing uncorrected operation (without laser) up to 26.5 GHz. To achieve higher accuracy and a higher frequency range an advanced 3-axis (X, Y, Z) laser correction system automatically creates correction tables for use by the transformation routines. The scanner’s exceptional repeatability allows the use of correction tables created off-line, without need for an on-line laser correction system, considerably reducing measurement time. To create these correction tables, the scanner is fitted with laser interferometers for X and Y axes and with a spinning-diode laser to calibrate for planarity. Additional features include a shielded constant-radius cable carrier, giving minimal phase errors due to cable flexing.
Modem antenna measurements require not only fast measurement but also quick transport of data to a multitude of computer for post-processing and analysis. Issues in the of a networked computer architecture for an antenna measurement laboratory are discussed. A case study is presented to highlight some of the considerations. Description and performance of a facility employing the concepts are included.
The imaging of radar targets is typically accom plished by measuring the radar cross section (RCS) of the target as a function of frequency and az imuth angle. We measure a third dimension of the RCS by tilting the target and collecting data for conical cuts of the RCS pattern. This third dimension of data provides the ability to estimate the three-dimensional location of scattering centers on the target. Three algorithms are developed in order to process the three-dimensional RCS data.
New windows which allow the user to select the level of sidelobe suppression near the DFT resolution limit are reported. By a parametric study, we identify the truncated Lorentzian and Gaussian functions as better choices compared with the popular Hann windows.
The Hughes Space and Communications Company (HSC) has recently undertaken the task to modify a RCS range once operated by Hughes Radar and Communications Systems, to accommodate the testing of Satellite Antennas. This measurement facility's configuration, design and current status will be discussed herein. This RCS range is located in El Segundo, California.
RCS data measured under near-field conditions is corrected to the far-field. The algorithm uses the HUYGEN's principle approach. The processing technique is describes and validates using anechoic chamber data and simulations taken on flat plate target at a distance from the radar R << 2D2/A, where D is the target cross range extend and A the wavelength. Good agreement with the theoretically predicted far-field RCS patterns is obtained.
Both Near-field Antenna Measurement Technology and Beam Waveguide Antenna techology have been in existence for some time. This paper describes a measurement combining both of these technologies. During an internal study of beam waveguide implementation, a near-field antenna measurement was made of a development model. The model and techniques of measurement are described herein.
At high frequencies, the scattered fields from a radar target can be modeled as a sum of contri butions from a finite number of scattering centers. We use a parametric model based on the Geometric Theory of Diffraction (GTD) to estimate the location and type of scattering centers present in a frequency domain data set. The parameters of the model are estimated using a modified MUSIC algorithm that incorporates the GTD model. A new spatial smoothing algorithm is also introduced.
A portable system for measuring the RF environment at remote sites is described. A frequency range between 500 MHz and 18 GHz is covered by this system. The design, calibration and use of this system are discussed.
Modem antenna measurements require not only fast measurement but also quick transport of data to a multitude of computer for post-processing and analysis. Issues in the of a networked computer architecture for an antenna measurement laboratory are discussed. A case study is presented to highlight some of the considerations. Description and performance of a facility employing the concepts are included.
The imaging of radar targets is typically accom plished by measuring the radar cross section (RCS) of the target as a function of frequency and az imuth angle. We measure a third dimension of the RCS by tilting the target and collecting data for conical cuts of the RCS pattern. This third dimension of data provides the ability to estimate the three-dimensional location of scattering centers on the target. Three algorithms are developed in order to process the three-dimensional RCS data.
New windows which allow the user to select the level of sidelobe suppression near the DFT resolution limit are reported. By a parametric study, we identify the truncated Lorentzian and Gaussian functions as better choices compared with the popular Hann windows.
The Hughes Space and Communications Company (HSC) has recently undertaken the task to modify a RCS range once operated by Hughes Radar and Communications Systems, to accommodate the testing of Satellite Antennas. This measurement facility's configuration, design and current status will be discussed herein. This RCS range is located in El Segundo, California.
RCS data measured under near-field conditions is corrected to the far-field. The algorithm uses the HUYGEN's principle approach. The processing technique is describes and validates using anechoic chamber data and simulations taken on flat plate target at a distance from the radar R << 2D2/A, where D is the target cross range extend and A the wavelength. Good agreement with the theoretically predicted far-field RCS patterns is obtained.
Both Near-field Antenna Measurement Technology and Beam Waveguide Antenna techology have been in existence for some time. This paper describes a measurement combining both of these technologies. During an internal study of beam waveguide implementation, a near-field antenna measurement was made of a development model. The model and techniques of measurement are described herein.
At high frequencies, the scattered fields from a radar target can be modeled as a sum of contri butions from a finite number of scattering centers. We use a parametric model based on the Geometric Theory of Diffraction (GTD) to estimate the location and type of scattering centers present in a frequency domain data set. The parameters of the model are estimated using a modified MUSIC algorithm that incorporates the GTD model. A new spatial smoothing algorithm is also introduced.
A portable system for measuring the RF environment at remote sites is described. A frequency range between 500 MHz and 18 GHz is covered by this system. The design, calibration and use of this system are discussed.