Welcome to the AMTA paper archive. Select a category, publication date or search by author.
(Note: Papers will always be listed by categories. To see ALL of the papers meeting your search criteria select the "AMTA Paper Archive" category after performing your search.)
A review will be made of advances in anechoic chamber technology from the precursors of World War II to the huge complex chamber of today. A glimpse of the technology of the 80’s will be offered.
A limited number of power gain measurements for some broadband airborne antennas were analyzed by comparing the measured values to the predictions from hypothetical models for the antennas. The difference between the predicted gain and measured gain is defined as the measurement uncertainty. The measurement uncertainties were statistically analyzed to determine the accuracy of the gain measurements. The results indicated that 79 percent of measurement uncertainties were written 1.5dB.
This data acquisition and pattern analysis system uses a standard set of Scientific Atlanta antenna-pattern-taking equipment as the basic operational gear. A Tektronix 4051 or 4052 Graphic System is used as a controller to operate the S/A gear and to obtain and store output data in digital format. The TEK 4051 does this by use of the IEEE General Purpose Interface Bus (GPIB), to which three interface boxes are connected. These three: • HP-59306A Relay Actuator • Model 4883 ICS Instrument Coupler • HP-3455A Digital Voltmeter message or digitize the S/A data and put it on the GPIB lines.
Antennas are an integral part of the communications, navigation, EMC systems installed on aircraft. Aircraft, such as the Douglas DC-9, C-9A, C-9B, DC-10, KC-10A, A-3 and A-4, use approximately 20 antennas. These antennas operate from VLF to approximately 20 GHz. The radiation patterns of these antennas are affected by aircraft structure such as wings, vertical stabilizer, engines, and landing gear. Douglas Aircraft Company measures the radiation patterns of these antennas using scale model aircraft (and/or aircraft sections) to predict the performance of the associated system. This paper describes some of the scale model measurement techniques used by Douglas Aircraft Company to obtain scale model radiation pattern data.
In the area of antenna measuring, there are many components offered that are useful in testing antennas. Placing the proper components together in a system that performs one’s desired results can be difficult. The results may leave no room for upgrading to a more sophisticated system. Scientific-Atlanta has introduced a new line of antenna measurement systems. This paper describes these manual amplitude and phase/amplitude systems and now they were put together to meet specific needs and allow for future expansion to semi-automatic systems. A survey of automatic systems is included.
The changeover of personnel in some laboratories has historically resulted in high costs for software maintenance. These high costs can be traced to poor documentation of the analysis and design process during the software development. This paper illustrates the structured analysis and design methodology used to analyze, design, and implement software to automatically test performance of an Air Force advanced development communications system. The requirements definition and preliminary design are accomplished using activity models to represent the functions performed during the test. The development of the activity models is the vehicle used to do a thorough requirements definition, while the resulting functional architecture represents an understandable preliminary design. The detailed design is formed using structure charts which better reveal system characteristics that illustrate design quality. The structure charts also facilitate the coding of the software to be implemented. The combination of activity models and structure charts provide the detailed documentation of the software analysis and design phases that are required to ensure ease of maintenance, broadening of understanding, and most importantly, a complete development package that can be passed on to a new user. These features ultimately result in a significant reduction in long term maintenance costs.
At a time of increased interest in computer-controlled antenna test ranges, it is worthwhile to consider the advantages, problems, and consequences inherent in the practical application of automated measurement techniques. This paper describes some of TRW’s experiences with the utilization of an automated far-field antenna test range to measure the characteristics of a Ku-band monopulse cassegrain spacecraft antenna. It also includes several conclusions drawn from those experiences.
Near-field antenna measurement techniques offer an alternative to conventional far-field antenna measurement techniques. Of the various coordinate systems used for near-field measurements, the spherical coordinate system provides the most natural extension from the conventional far-field characterization of an antenna to a more general characterization for arbitrary range lengths. This paper describes the Scientific-Atlanta Model 2022, a user-oriented implementation of a spherical near-field antenna measurement system. An example of typical system usage is provided. System capabilities and performance are described. Key concepts required to understand and use the spherical near-field method are discussed. The advantages and disadvantages of near-field antenna testing in relation to conventional far-field testing are considered. The particular merits of spherical near-field testing as compared to other forms of near-field testing are discussed. Antenna testing situations which provide the most likely candidates for the spherical near-field measurement technique are described.
The Naval Air Engineering Center has been assigned the task of developing Near Field Measurement Techniques and Equipment for testing Navy Aircraft-mounted antennas. These efforts will be applied to Nose-mounted and Wing-mounted antennas. The ultimate objective is the development of a portable near-field test system for the Navy’s ‘O’ level. The test system will produce far field pattern predictions of installed airborne antennas by measuring and processing near field data. NAEC would, also, like the test system to determine if an installed antenna is mission capable or degraded; and in the event of a failed antenna, the test system will isolate the fault of that antenna. This paper will describe NAEC’s progress in this task by descriptions of the following: I. Electrical Hardware i.e. transmitter, receiver, interfaces, controllers II. Mechanical Hardware i.e. translator, probe carriage III. Mathematical approaches Also, recent laboratory results will be described.
The paper describes a simple but unique antenna test facility suitable for aerospace antenna developments. The total idea can be easily adopted by organizations who wish to carry out antenna measurements with minimum required instrumentation. The facility majorly caters for omni and wide beam antenna measurements, has been set up at ISRO Satellite Centre, Bangalore, India. It has been extensively used for omnidirectional antenna developments in VHF, UHF, L, S, and X-bands for India’s various space programs. Radiation pattern, gain, polarization and impedance measurements can be carried out both in near free space conditions as well as the ground reflection modes. The main feature of the facility is the use of large fiber-glass mounting structures for avoiding reflections and perturbations in radiation patterns due to impressed surface currents, specially in VHF ranges. Field probing is done by the use of a fiber-glass X-Y probe positioner. The facility used Scientific Atlanta 1752 Receiver and 1540 Recorder. Suitable software has been added to the facility for contour plotting of radiation levels, calculation of efficiency isotropy, and polarization properties.
Currently the Fleet lacks a quantitative description of their electromagnetic (EM) capabilities and vulnerabilities. A ship’s mission can be seriously degraded because of unsatisfactory performance of EM systems due to various factors found in the operational environment. In addition, a ship can become vulnerable to a potential enemy by inadequate emission control (EMCON) of EM energy. The EMPASS measurement platform is capable of collecting and analyzing three-dimensional emission data in the operational environment. The word EMPASS is the acronym of Electromagnetic Performance of Aircraft and Ship Systems. EMPASS consists of a calibrated, special equipped, measurement platform situated on an EP-3A aircraft with complementary ground based data reduction and analysis facilities. The products of the EMPASS program are the effectiveness evaluation of operational EM systems, development of the criteria for the most effective tactical use of EM systems, and the providing of the capability to conduct RDT&E in the operational EM environment. This paper presents a description of the EMPASS capabilities and the results of measurements of some representative EM systems used in the fleet.
The compact antenna range has been recognized as an effective means of testing microwave antennas. Antennas which normally require long outdoor ranges for testing can be tested under far field conditions at an indoor facility, using the compact range. The compact range operates on the principal that a parabolic reflector will transform an incident spherical wave into a collimated plane wave in its near zone. The plane wave produced is suitable for testing antennas, thus simulating far field electromagnetic criteria in the near zone. The typical compact range is housed in a room approximately 20 feet wide, 40 feet long and 20 feet high. The performance of the compact range has been well documented and specified over a frequency range of 3.95 GHz to 18.0 GHz. Now, through recent testing performed at Scientific-Atlanta, the compact range can be specified for operation up through 60.0 GHz. This paper describes the tests that were performed, discussed the results of these tests and establishes performance specifications for operation at these millimeter frequency bands.
The spectacular growth and developments of microprocessors make it highly likely that they will form the bases for all future data acquisition systems. Microprocessors combined with numeric processor chips even give computational capability comparable to the larger and faster mini computers of only a few years ago. The hardware cost of complete data acquisition microprocessor systems has continued to decline to where this cost is comparable to or less than one of the test instruments it reads.
This paper describes a new, automated, microprocessor controlled, dual-channel microwave vector ratio measurement receiver for the frequency range 10 MHz to 18 GHz. It provides a greater than 120 dB dynamic range and resolutions of 0.001 dB and 0.1 degree. Primarily designed as an attenuator and Signal Generator Calibrator, it offers solutions to antenna measurement problems where high accuracies and/or wide dynamic measurement ranges are required such as for broadband cross-polarization measurements on radar tracking antennas, highly accurate gain measurements on low-loss reflector antennas, frequency domain characteristics measurements on wide-band antennas with resulting data suitable for on-line computer conversion to time domain transient response and dispersion characteristics data and wideband near field scanning measurements for computing far field performances. The measurement data in the instrument is obtained in digital form and available over an IEEE-488 bus interface to an outside computer. Measurement times are automatically optimized by the built-in microprocessor with respect to signal/noise ratio errors in response to the measurement signal level and the chosen resolution. Complete digital measurement data amplitude of both channels and phase, is updated every 5 milliseconds.
This paper describes the modifications made to the Scientific-Atlanta 2020 Antenna Analyzer System, to make it more suitable for adaptive antenna testing. Three functional modifications are described: (1) Digital interfacing of a wideband microwave power meter (2) Creation of programs for manipulating stored data files (3) Operating system documentation and permanent program storage The general philosophy of the SA 2020 modification was to make the changes transparent with respect to the original operating system. Thus, although the antenna analyzer now possesses several new features, none of the original features has been degraded. An operator has no indications of the modifications unless he specifically selects the new system modes of operation. Altering the SA 2020 system software has been complicated by limited main frame memory in the 21MX computer. In some cases it has been necessary to limit the flexibility of new programs in order to fit the available memory space. In the future, when more memory becomes available, the routines can be easily expanded. In there present form, the programs are considered quite satisfactory for all planned adaptive antenna tests.
Digital signal processing techniques provide a method by which a finely resolved antenna pattern can be reconstructed from coarsly sampled data. Antenna pattern reconstruction offers several advantages over the direct measurement of a finely resolved pattern, and is applicable whenever a computer is available for implementation of the reconstruction algorithm. As computerized pattern measurement equipment becomes more prevalent, pattern reconstruction algorithms will become more common place. The advantages of pattern reconstruction include higher quality presentation of antenna patterns due to increased resolution, decreased data acquisition time due to coarser sampling, and decreased data storage requirements. The mean square error or a reconstructed antenna pattern is smaller than that of the directly measured pattern. In the context of near-field to far-field pattern transformations, pattern reconstruction becomes essential. The transformation is performed at a coarse spacing for maximum computational speed without compromising the quality of output data. This paper provides an introduction to the technique of antenna pattern reconstruction. Key concepts and terminology are discussed A generic reconstruction algorithm is developed. Examples of interpolated antenna patterns are shown.
This paper will briefly describe the RADC Antenna test facilities and their function. Considerable focus will be placed on the large amounts of data generated and the associated requirements for Real Time Data, Digital Data, Data Processing and Display, Quality Control and Fast Turnaround of Data. Also, the current process utilized to satisfy the data requirements will be described, followed by a discussion of techniques presently under development to further enhance the process. The use of 3-D displays with color enhancement will be included.
The Amecom Division of Litton Systems has developed several computerized antenna measurement systems designed to make the so-called standard antenna measurements plus relative and absolute phase and amplitude measurements of interferometer arrays. This paper will outline computerized measurement techniques for VSWR, swept phase and amplitude (vs) frequency (multi-octave bandwidths), phase and amplitude (vs) azimuth, radiation patterns and gain. The new computerized systems have reduced production system measurement time by 80 percent.
The AEGIS AN/SPY-1A antenna system is an S-band monopulse phased array system designed for monopulse operation. Its high performance and manifold capabilities have placed stringent demands on the test system used in its evaluation. This paper will describe the AEGIS Near-Field Antenna Test Set (ANFATS) currently being implemented for acceptance testing production models of the antenna, a system designed for operation by manufacturing test personnel
In recent years there has been an increasing requirement for more extensive and precise measurements of the polarization properties of antennas. Some of the more conventional polarization measurement techniques are no longer applicable because of the required measurement time or the achievable accuracy. This presentation is an overview of polarization measurement methods which may be employed on far-field antenna ranges. Instrumentation requirements and sources of error are also included.