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Deutsche Aerospace is developing and testing high performance communications antennas for the INTELSAT program. A large number of antenna measurements must be performed, for two polarizations, multiple frequencies and multiple beams. To measure all parameters in a single rotation of the antenna, a highspeed instrumentation system is required. The instrumentation was upgraded using the latest technology in receivers, sources and control systems. Commercially available components were used for all components. The resulting system can perform a complex antenna measurement consisting of over four million data points within only two hours.
INMARSAT (International Maritime Satellite Organization) provides satellite communication services to civil aviation operations. Aircraft Earth Station (AES) installations aboard all types of commercial transport and business aircraft must meet strict requirements as specified by INMARSAT. The purpose of these requirements is to ensure that all AES shall be able to perform correctly with standard INMARSAT Ground Earth Station (GES) throughout the INMARSAT space segment, and shall not endanger the integrity of the satellite network. To have INMARSAT approval for multi-carrier mode, the AES must meet specifications for levels of transmitted intermodulation products before satellite access is provided.
The Spherical Near-Field measurement technique has been in existence for a number of years. The cost associated with this type of measurement system has often been assumed to be substantial. Herein is presented the system configuration for a low cost Spherical Near-field System whose design goals include the capability for production line testing while retaining simplicity in approach. NSI has been contracted to provide a Spherical Near-field antenna measurement system. This paper focuses upon the design considerations undertaken during the prototype development of that system.
The Sacramento Air Logistics Center at McClellan AFB has developed near-field (NF) antemia test capability over the past three years. With assistance from the National Institute of Standards and Teclmology (NIST), McClellan has assembled a modem planar near-field antenna range using components from various vendors. Although the LH( division of McClellan AFB) team's current range has been operating for over a year, it is being continuously improved for measurement accuracy, user-friendliness, and safety. This paper will briefly discuss the evolution of McClellan's near-field program, and then focus on the building of the LH near-field antenna range. Radio-frequency (RF) issues, such as RF design and electromagnetic shielding will be covered. Precision measurement teclmiques such as positioning accuracy and temperature control are discussed. Finally, relevant safety and constrnction issues affecting the McClellan facility will be examined.
Martin Marietta has developed a new, automated facility for high-volume production testing of the Longbow millimeter wave missile. Two dedicated far field anechoic chambers were designed, both automated to support component test and analysis in the production environment. One standard far field chamber is used to perform the complete characterization of the antenna and rac1orne; it allows very accurate measurements of power sidelobes, monopulse errors, and cross polarization isolation. The completed radar missile sensor group is evaluated in the second far field chamber, which can reach higher-level parameters of the antenna, transceiver, and gimbal. This paper describes chamber and test station capabilities; time reduction benefits; and the novel, new assembly technique which allows for future portability of these chambers with limited downtime.
One of the world's most sophisticated antenna test ranges is now fully operational. This was designed by the Deutsche Aerospace (DASA) and is operated by Siemens Plessey Systems (SPS). The presented paper will describe the pioneering design philosophy adopted to ensure the stringent performance features. Although this facility is located outside, it allows extremely high precision probing of cylindrical near field of large and very complex antenna systems, with turning diameters up to 16 meters and up to 20 GHz. Besides the RCS optimized 36 m large scanner tower the significant highlights of this facility consist of a comprehensive air-conditioning system for all accuracy dependent components, a permanent autoalignment system, which ensures high precision cylindrical measurements and an interleaved high speed data collection system, which delivers a maximum of data performance within a minimum time frame. Test results including a pattern comparison of the Ref erence Antenna between measurements in DASA facilities and the SPS Cylindrical Near-Field Test Facility show good range performance. The evaluation of the range performance data demonstrates the measurement integrity of the facility and proves to be qualified to characterize a wide range of antennas.
New results on very precise, computer controlled manipulation of string supported targets suspended from an upper turntable (UTT) in the Boeing 9-77 compact radar range are presented. A computer program was developed that uses the precision optical measurement system (POMS) information for feedback to automatically control the conic_pitch and conic_roll of arbitrary radar targets to within ± 0.066° (RMS) of the desired pitch and roll. The system provides quick and accurate maneuvering of targets to any desired static position with accuracy in the static yaw, pitch, and roll of ± 0.01°. Automatic volumetric field probes are also possible using a sphere suspended from computer operated strings. Sphere movement can be continuous or stepped along any desired path and is controlled to within ±0.05 inches anywhere within the quiet zone (± 14 ft high by ± 20 ft wide by ± 25 ft).
Techniques for editing RFI from antenna measurements are developed for vector network analyzer instrumentation, and include the processing within the analyzer. An algorithm was devised for identifying data that may contain RFI; this algorithm is based on the electrical size of the antenna. Once data containing RFI are identified, extrapolation techniques based on the electrical size of the antenna are used to produce continuous data.
The radiation characteristics for a dual-frequency, dual-polarized millimeter wave antenna for a radar operating at 33 and 95-GHz were measured at the Ipswich Research Facility. On-pole and cross-pole radiation patterns were measured using the 2600 foot far field range. In this paper we'll discuss the general design of the antenna feed system and the instrumentation ensemble used to perform the far field characterization of this high performance large aperture dielectric lens antenna.
A simple change to the HP8510C or HP8720C vector network analyzer block diagram coupled with the TRM (Thru Reflect Match) calibration leads to accurate measurements of the material properties of flat samples. Algorithms developed for transmission line measurements can also be used in free space measurements. A description of recent improvements in the transmission/reflection algorithms is reviewed. Free space measurement results based on the transmission/reflection algorithms found in the HP85071B materials measurement software package are presented.
Applications that require tight tolerances on dielectric thickness control need accurate sensors. A technique has been developed that will allow for the measurement of thickness without requiring surface contact. High resolution radar imaging, commonly used in RCS measurements , is now being used to measure thickness. Electromagnetic fields reflected from the front and rear surface are detected and the time response delta is converted into thickness. A major advantage of this method is that it is not affected by varying sensor offset height.
Test sequencing flexibility and high throughput are essential ingredients to a state-of-the-art near-field test range. This paper will discuss methods used by NSI to aid the operator through the near-field measurement process. The paper will describe NSI's expert system and customer applications of a unique test and processing sequencer developed by NSI for optimizing range measurement activities. The sequencer provides powerful control of software functions including multiplexed measurements, data processing and unattended test operations.
This paper describes the most recent version of the Model 200 portable RCS diagnostic radar. The Model 200 was designed to provide high-resolution RCS measurements in unprepared rooms indoors as well as on outdoor ranges. The system can provide real aperture measurements, ISAR measurements, or SAR measurements without changing system configuration.
The initial phase of METRATEK's new Model 300 Radar System has been installed at the Navy's Chesapeake Tests Range (CTR) at Patuxent River, MD. This ground-to-air Multimode, Multifrequency Instrumentation Radar System (MMIRS) is a high-throughput frequency-and-polarization agile radar that is designed to drastically reduce the cost of measuring the radar cross section of airborne targets by allowing simultaneous measurements to be made at VHF through Ku Band.
Today's requirements for dynamic Radar Cross Section (RCS) test data set new demands upon instrumentation Radar systems. Transmitters must deliver high power and operate at high data rates. Additionally, noise floor reduction of coherent spurious signals improves raw data and minimizes the need for manipulation of data.
A method is presented to qualify a compact range measurement system for low sidelobe antenna measurements. The method uses the target zone fields (probe data) of the compact range. Using the method, one can identify the angular regions around which the measurement errors can be significant. The sidelobe levels which can be measured around these angular regions with less than a 3 dB error are also defined.
The far-field radar cross section (RCS) of a conducting sphere is obtained by transforming scattered near-fields measured on a spherical surface. A simple and convenient calibration procedure is described that involves measuring the incident field directly at the target location. Although a non probe-corrected transmission formula was used in this study the importance of prove correction in practice is demonstrated.
An efficient and accurate spherical near field to far field transformation without probe correction is presented. The indices m of the Legendre polynomials is summed up analytically, thereby reducing the computation time. Computations with both synthetic and experimental data illustrate the accuracy of this technique.
The mathematical language of wave polarization has been somewhat cryptic; usually involving vectors, tensors, or complex numbers or symbolic equations. By using the Poincare' sphere and dot product multiplication, it is possible to reduce the comutation of wave polarization mathematics to simple trigonometric formulas. Furthermore, visual representation of wave polarization on the Poincare; sphere is straight-forward and simple.
The interdependence of accuracy and speed should be considered when analyzing measurement requirements. Tradeoffs can be made to optimize the measurement when accuracy is of primary importance, or where speed is critical. Several different measurement modes of the HP 8530A Microwave Receiver are presented, each with different measurement speed and accuracy tradeoffs. Examples are given that illustrate which acquisition modes would be appropriate to optimize the acquisition speed and accuracy in a variety of applications