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Wideband RCS instrumentation systems can provide a high degree of range resolution. By combining wideband RCS data with a synthetic-aperture or Doppler processing, the spatial distribution of radar reflectivity can be determined. These systems provide diagnostic capabilities which are useful for locating scattering sources on complex objects and for assessing the effectiveness of modifications. The Proceedings of the 1983 meeting included a paper which described a linear-FM system operating over a 3 GHz bandwidth capable of measuring RCS vs range, cross range, and frequency using a single measurement set-up. This paper analytically demonstrates a procedure for extracting CW RCS patterns from the wideband data obtained using the linear-FM system. By combining the latter and the former processing, it is possible to obtain from a single data array both wideband responses showing the spatial distribution of scatterers and narrowband responses which are the traditional CW RCS patterns. The paper includes experimental verifications of these assertions by comparing results of CW measured data with data extracted from wideband RCS measurements.
This paper describes the new antenna test facility under construction at General Electric Space Systems Division in Valley Forge, PA. The facility consists of a shielded anechoic chamber containing both a Compact Range and a Spherical Near-Field Range. In addition, it provides for a 700’ boresight range through an RF transparent window. The facility will be capable of testing antenna systems over a wide frequency range and will also accommodate an entire spacecraft for both system compatibility and antenna performance tests.
For approximately 10 years the National Bureau of Standards has used the Extrapolation Technique (A. C. Newell, et al., IEEE Trans. Ant. & Prop., AP-21, 418-431, 1973) for accurately calibrating transfer standard antennas (on-axis gain and polarization). The method utilizes a generalized three-antenns approach which does not require quantitative a priori knowledge of the antennas. Its main advantages are its accuracy and generality. This is essentially no upper frequency limit and it can be applied, in principle, to any type of antenna, although some directivity is desirable to reduce multipath interence.
An 80 element linear phased array antenna was measured in the nearfield. The insertion phase and amplitude for each element were measured while the 8-bit ferrite phase shifters were individually stepped through their degrees for freedom.
A common method for determining gain on an antenna pattern range is to use the substitution method which involves comparing the response of the test antenna with that of an antenna of known gain. For situations where a standard gain horn is the appropriate reference, this does not present a problem. Calibration curves of these horns are available covering all frequencies for which horns are available, and the horns themselves can be conveniently stored in a cabinet or on a wall rack.
This paper deals with the design, calibration and performance of a new antenna test range facility at the David Florida Laboratory in Ottawa, making use of an existing 40 foot cube anechoic chamber and a Scientific-Atlanta 2020 system. The main purpose is to use the same test range for the calibration of a nominal seven foot by five foot Standard Gain Horn and ultimately for gain and pattern testing of an eight foot space qualified axial mode helix, which must be maintained inside the anechoic chamber. This rules out a completely outdoor test range.
Since 1976 the Technical University of Denmark (TUD), sponsored by the European Space Agency (ESA), has developed a facility for spherical near-field scanning of antennas. This range has been in operation since April 1979 and has undergone continuous refinement. Some of the measurement results obtained with the facility as well was various aspects of the measuring system itself have been published from time to time (Ref. 1-5).
The loop cell is fabricated using two intersecting metal sheets joined at the intersection and forming a 36 deg angle. A section of a loop is mounted between two coaxial panel jacks, one on each sheet at a distance equal to the loop radius from the intersection. A known current through this section of electrically small loop produced calculable E and H fields between the sheets in the plane of the loop. These known fields may be used to determine the antenna factor of small E and H antennas placed in the field if the mutual impedance due to the antenna images in the sheets is negligible and the antenna is not close to the open edges of the cell. Measured and calculated antenna factors agree within ±2 dB between 0.25 MHz and 1000 MHz.
Two major functions of the National Bureau of Standards are the development of reliable measurement techniques and the development and maintenance of primary reference standards which provide the basis for accurate measurements of important physical quantities. By this means, and through its various measurement and calibration services, NBS fulfills its obligations to support industry and other federal agencies and to help science prosper in the United States.
This paper summarizes the results of work performed for the Naval Air Development Center (NADC) on a new full-sized aircraft antenna range located in Warminster, PA. Because of the ever-increasing sophistication of aircraft systems, a facility capable of testing full scale mock-ups has become necessary to fully characterize the system in its operating environment. There are, however, several unique problems associated with such a range. Many systems of interest have a wing-tip to wing-tip baseline, which requires that the incident illumination be “uniform” over a significant aperture (approximately 40x15 feet for tactical aircraft). Differential path loss between wing-tip ends, as the aircraft is rotated, can be a source of large error, as can the parallax created by off-center rotation. Also, since today’s military aircraft carry a wide variety of systems, the range is required to be a “general use” range, operational over a wide frequency spectrum from 30 MHz to 40 GHz. A thorough examination of design trade-offs was performed relating the critical parameters of source beamwidth, specular reflection, path loss, phase error, and receive aperture size in order to choose the proper source antenna type, source height, and separation distance between source and test antennas for each frequency band of interest. Other factors in the range design were a maximum possible source height of 40 feet (approximately the height of the pedestal), and a desire to keep the separation distance fixed over the entire frequency range. Results are presented with indicate excellent performance over an 18 x 18 foot aperture for various polarizations. It was found that the range operates effectively as a ground reflection range from 30 MHz to 3 GHz, and as an elevated range at higher frequencies. Peak-to-peak amplitude ripples over the test aperture of 1.0 dB (corresponding to a reflection level of –25 dB) were acheived over a significant portion of the frequency spectrum.
This paper discusses some of the more unique problems involved in the performance of measurements on a ground plane type of antenna range generally required for the study and design of multiple antenna shipboard systems. The discussion concentrates on the installation and use of a computer automated antenna analyzer system on this type of range. The methods and results of various range calibration measurements are presented with emphasis on the use of the system’s computerized capability to perform measurements, analyze data, and produce various graphic output formats. The test results obtained from a pair of monopole antennas mounted on a simplified model ship hull are also presented and discussed.