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The objective of this paper is to outline test procedures, test set-up, and antenna measurements collected on a multi-element adaptive antenna processor. The elements used are UHF blade antennas located on a pedestal mounted A-10 aircraft at the RADC Newport Test Range. The measurement data to be presented will include basic element, and adaptively weighted element patterns. Methods of interpreting system performance and problems in collecting the data will also be provided.
Today I would like to describe this unique antenna Test Facility and its background, capabilities, typical tests and problem areas.(Figure 1) First of all by way of introduction: I’m in the Test and Evaluation Branch of the Rome Air Development Center (RADC). We are an R&D laboratory under the Air Force Systems Command. RADC’s prime mission is R&D in the area of Command, Control, Communication and Intelligence often referred to as C3I. We are located at Griffiss AFB which is in the City of Rome, in the center of beautiful upstate New York. The outdoor antenna range which is the subject of this briefing is at the RADC Newport Test Site is located about 30 miles east of Griffiss in the foothills of the Adirondack mountains.(Figure2)
The Defense Electronic Supply Center in Dayton, Ohio has recently issued a specification, MIL-A-87136, for testing Airborne Antennas. This specification covers all aspects of testing antennas including a section dealing specifically with radiation pattern tests. Further, this specification defines the data format to be used when antenna pattern measurement data is required to be furnished on magnetic tape. Scientific-Atlanta’s Series 2030 Antenna Data Collection System’s magnetic tape format and test instrumentation meets the requirements set forth in MIL-A-87136. The system is a complete instrumentation/firmware package designed and programmed to perform commonly made antenna pattern measurements. After initial operator set-up, measurements can be made automatically at frequencies in the 1-18 GHz range. The test results are digitally recorded on magnetic tape and may be displayed as radiation distribution plots, data listings, or as conventional data patterns. The presentation describes the Antenna Data Collection System, its application to automatic antenna testing and to the requirements of MIL-A-87136. Features of the Data Collection System are included, as well as advantages of automatic measurement and digital recording of antenna data.
A novel application of the variable-range outdoor antenna measurement system is the test and evaluation of various active optical weapons systems such as missile and projectile fuses. These devices are tested as optical-wave length antennas. The entire test program, including positioning, stimulus and measurement, is performed under computer control by the SA 2021A Automatic Antenna Analyzer. Outdoor testing of optical weapons system affords the opportunity to evaluate the effectiveness of various countermeasure and counter-countermeasure techniques.
The E-2C Hawkeye aircraft is a carrier based airborne early warning sensor platform. The primary sensor is the APS-125 radar which is operated in the 400 to 446 MHz frequency range and utilizes a 10-element, Yagi end-fired array antenna integrated into a rotating, 2,400 pound rotodome mounted on top of the E-2C aircraft. As is the case for most airborne antennas, the performance in free space when the antenna is off the aircraft can be readily measured on a ground antenna range, but the accurate measurement of the antenna’s performance under actual flight conditions presented project engineers with a unique problem: Pattern interaction between the rotating rotodome and the aircraft fuselage and turning propellers could not be evaluated using existing ground range facilities. The proposed improvements to these facilities to accomplish this task were estimated to cost in excess of five million dollars.
Automatic testing is becoming more and more prevalent in the antenna measurement field. With this new technology, the antenna test engineer is faced with the problem of controlling the antenna test positioner system automatically. Automatic operation may simply consist of driving the test positioner axes to make several scans of a test antenna; or it could involve complete computer control of a multi-axis positioning system to perform a complex routine. This presentation discussed a positioner programmer designed to meet these requirements. The 2012 can be programmed from its front panel to perform common position and raster scan routines. Using the IEEE-488 interface bus, the programmer will accept commands from a digital calculator or computer to control up to six (6) axes of motion through any desired sequence of operation. During record scans, the 2012 will output commands at selected angular intervals to allow the digital processor to update and read measurement instruments and perform other functions such as tuning signal sources and receivers. Various features, options, and accessories for the 2012 enhance its overall flexibility and compatibility in the antenna measurement system.
Near field antenna measurements have long been of interest to the antenna community and of particular interest to those in the design and measurement of antennas. Efforts in this area using analog computers for data reduction were already under way in the late 1950’s. These applications were limited, primarily due to the limitations of the analog computer. Two planar near field probe positioners were built by Scientific-Atlanta during this period and delivered; on to Martin Denver and one to the Georgia Institute of Technology. These units were used for development on planar near field measurements. The unit at Martin Denver was also used by the Bureau of Standards. Experimental work at Georgia Tech led to Dr. Joy’s thesis on spacial sampling and filtering.1 This work on sampling was particularly important because it gave an understanding of the required data density for meaningful transformation by digital computer. Numerical integration is a time and core intensive process and it was the utilization of the Fast Fourier Transform in the early 1970’s that made the digital computer a viable approach to the problem.
This paper will present a basic explanation of the IEEE Standard 488-1978, concerning what it is, and how and why it concerns people in the RF world. In addition, the practical side of the IEEE 488 will be discussed, touching on such topics as the types of instrumentation available with IEEE, custom systems design and installation, the new one-chip interfaces, computer enhancement of measurements and generation of analytical graphic data. This up dated review is made with an eye towards enhancing both speed and accuracy of contemporary antenna testing techniques.
Methods of remotely controlling source transmitters and antennas over long distances is described. The remote range controller instrumentation currently available is limited to a 5.5 mile separation, over voice grade telephone lines. Unfortunately the phone line routes are not line of sight. In fact, the most direct route available for source control over dedicated phone lines at the Westinghouse antenna range complex is 13 miles in length. We wanted to utilize the Scientific Atlanta Model 4580 Remote Range Controller since it is fully compatible with out existing signal sources, programmable receivers and positioner controls. However, the data set available with the Model 4580 is limited to 5.5 miles separation between the master control unit and the remote control unit. The data set requires four wires or two dedicated phone lines. Transfer speed is 0-9600 bits per second asynchronous. The solution to overcome the 5.5 mile limitation and permit full use of the Model 4580 capabilities is described. Lightning protection and alternate control methods using tone controls over phone lines and method of employing a microwave link is discussed.
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.