AMTA Paper Archive
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Antenna pattern data acquisition
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.
A Laboratory application of structured analysis and design
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.
Empass - an airborne emission measurement system
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.
Full-Scale Aircraft Test Facility
A new, major facility is being developed at the NAVAIRDEVCEN to provide a wide range of capabilities for test and evaluation of both antennas and complete avionics systems mounted in full-size fleet aircraft. Under the joint sponsorship of NAVAIR (PMA-253, AIR-5492, and AIR-5334) and NAVAIRDEVCEN, this facility is configured to allow efficient, high speed, high-reliability data acquisition and analysis.
US Army Electronic Proving Ground
The US Army Electronic Proving Ground is in Southeastern Arizona with outlying facilities located throughout Southern Arizona. The Proving Ground is an independent test and evaluation activity under the command of the US Army Test and Evaluation Command. It was established in 1954. EPG’s role in the material acquisition cycle is to conduct development (DT I & II), initial production (first article), and such other engineering (laboratory-type) tests and associated analytical studies of electronic materiel as directed. The results (reports) of these efforts are used by the developer to correct faults, and by Army and DOD decision-makers in determining the suitability of these materiels/systems for adoption and issue. Customer tests to satisfy specific customer requirements and foreign materiel exploitations are also done. EPG is assigned test responsibility for Army ground and airborne (aircraft-mounted) equipment/systems which utilize the electromagnetic spectrum to include: tactical communications; COMSEC (TEMPEST testing included); combat surveillance, and vision equipment (optical, electro-optical, radar, unattended sensors); intelligence acquisition; electronic warfare; radiac; imaging and image interpretation (camera, film, lens, electro-optical); camouflage; avionics; navigation and position location; remotely piloted vehicle; physical security; meteorological; electronic power generation, and tactical computers and associated software. Facilities and capabilities to perform this mission include: laboratories and electronic measurement equipment; antenna pattern measurement’ both free-space and ground-influenced; unattended and physical security sensors; ground and airborne radar target resolution and MTI; precision instrumentation radars in a range configuration for position and track of aerial and ground vehicles; climatic and structural environmental chambers/equipment; calibrated nuclear radiation sources; electromagnetic compatibility, interference and vulnerability measurement and analysis; and other specialized facilities and equipment. The Proving Ground, working in conjunction with a DOD Area Frequency Coordinator, can create a limited realistic electronic battlefield environment. This capability is undergoing significant development and enhancement as a part of a program to develop and acquire the capability to test Army Battlefield Automation Systems, variously called C3I, C4, and/or CCS2 systems. The three principal elements of this capability which are all automated include: Systems Control Facility (SCF), Test Item Stimulator (TIS), and Realistic Battlefield Environment, Electronic (REBEEL). In addition to various instrumentation computers/processors, EPG currently utilizes a DEC Cyber 172, a DEC VAX 11-780, a DEC System 10, and has access to both a CDC 6500 and a 6600. Under the Army Development and Acquisition of Threat Simulators (ADATS) program, EPG is responsible for all non-air defense simulators. The availability of massive real estate in Southern Arizona, which includes more than 70,000 acres on Fort Huachuca, 23,000 acres at Willcox Dry Lake, and 1.5 million acres near Gila Bend, is a major factor in successful satisfaction of our test mission. Fort Huachuca itself is in the foothills of the Huachuca Mountains at an elevation of approximately 5,000 feet and has an average annual rainfall of less than 15 inches. Flying missions are practical almost every day of the year. The Proving Ground is ideally situated between two national ranges and provides overlapping, compatible instrumentation facilities for all types of in-flight test programs. The clear electromagnetic environment, the excellent climatic conditions, and the freedom from aircraft congestion make this an unusually fine area for electronic testing. The Proving Ground consists of a multitude of sophisticated resources, many of them unique in the United States, which are an integral part of the USAEPG test facility and have resulted from an active local research and development effort over a 28-year period.
Electromagnetic modeling of radiating structures and antenna ranges with comparison to measured examples
Large scale electromagnetic simulation programs such as NEC (Numerical Electromagnetic Code) which employ method of moments and/or geometrical theory of diffraction are available. These codes are effective design and analysis tools for both the antenna designer and the antenna metrologist. This paper illustrates the ability of these codes to model actual antennas and antenna ranges. Several comparison examples are provided of electromagnetic models and the physical devices.
RADC electromagnetic test facility at Ipswich, MA
The USAF Rome Air Development Center has recently constructed a laboratory building which has recently constructed a laboratory building which has been designed to implement the measurement of microwave antennas and electromagnetic systems. The new facility consists of dual elevated open-ended chambers with retractable doors, a 2700 foot outdoor range, a variable short range and a 40 x 20 x 18 foot anechoic chamber. Wide frequency band instrumentation is installed to provide efficient high speed data collection and analysis required to support the center’s technology development mission in C3I. A presentation of the facility’s capability and design will be given as well as a brief historic overview of significant antenna measurements of the past.
Conceptual Analysis of Radar Cross-Section Measurements on Compact Ranges
A strong emphasis is now being placed on techniques for reduction of radar cross-section. A missile or aircraft which is invisible to radar has an important strategic advantage. With this fact in mind, the user of a weapons system may place an upper limit on the radar cross-section that he will permit his missile or aircraft to have. The designer must then make use of “stealth technology” to reduce the cross-section to an acceptable level. In order to verify the design, radar cross-section measurements must be made. Thus the current emphasis on cross-section reduction leads to an important need for accurate and reliable methods of measuring radar cross-section.
Transmission Lines/Antenna Systems Analysis
A new technique with utilizes Digital Signal Processing algorithms in conjunction with Frequency Domain Reflectometry (FDR) to characterize transmission line system is discussed. Algorithms are developed which include tbe Windowed Fast Fourier Transform (WFFT) to determine the location and amplitude of single or multiple mismatches in a single pass. Refinement techniques include quadratic interpolation for increased location and amplitude accuracy and correlation for rejecting harmonics and high power “foreign” (interference) signals.
A Simple method for measuring ohmic losses in radiating systems
Conventional methods for measuring the ohmic losses of radiating systems usually faces two basic difficulties: a) Need for accurate measurements, of very high VSWR values; b) Manufacturing of specially designed devices such as spherical short-circuit plates in order to terminate the radiating aperture. To circunvent such difficulties an experimental program is now under way in order to establish how accurately such losses can be determined from the associated increase in this antenna noise temperature. Experimental results obtained with the present method, for a corrugated feed horn at 4 GHz, compared quite favorably with those obtained by VSWR measurements using a spherical short-circuit termination. Proposed presentation will include: a) Error analysis; b) Experimental set-ups and discussion of measured results obtained so far; c) Possible extensions of the method. Conventional methods for measuring the ohmic losses of radiating systems usually faces two basic difficulties: a) Need for accurate measurements, of very high VSWR values; b) Manufacturing of specially designed devices such as spherical short-circuit plates in order to terminate the radiating aperture. To circunvent such difficulties an experimental program is now under way in order to establish how accurately such losses can be determined from the associated increase in this antenna noise temperature. Experimental results obtained with the present method, for a corrugated feed horn at 4 GHz, compared quite favorably with those obtained by VSWR measurements using a spherical short-circuit termination. Proposed presentation will include: a) Error analysis; b) Experimental set-ups and discussion of measured results obtained so far; c) Possible extensions of the method.
A Modular antenna analyzer
Recognizing that testing requirements differ, an automated system must be capable of adapting different instrumentation to a specific test. The Series 2080 Modular Antenna Analyzer consists of a computer and processing subsystem (CPS) and four subsystems for antenna measurement applications. The CPS being the nucleus of the Series 2080 system is composed of a computer, appropriate peripherals for interface capability, data storage, data analysis and acquisition software and console. The four subsystems can be comprised of variable instrumentation for a receiving, a positioner control, a signal source and an antenna pattern plotting subsystems. The instrumentation can be supplied by the customer, by Scientific-Atlanta or by other manufacturers.
VHF antenna range design
The design concept for outdoor antenna ranges operated at frequency 50 MHz is discussed. The antenna range is designed for test of VHF antennas mounted on a full-scale satellite mockup. Due to the large size of test objects, a tradeoff between cost and test accuracy among carious range configurations is addressed. Due to near-omni directional characteristics of test antennas, the multipath interference may be severe. The interference ground reflection, surface wave and multiple scattering are quantified and evaluated.
Cylindrical near field test facility for UHF Television Transmitting Antennas
This paper describes a horizontal, cylindrical surface, near-field measurement facility which was designed and constructed in 1984 and is used for the determination of far field patterns from near field measurement of UHF television transmitting antennas. The facility is also used in antenna production as a diagnostic and alignment tool.
Structural Design of a vertical antenna boresight 18.3- by 18.3-M planar near-field antenna measurement system
The near-field antenna testing technique is now an established testing approach. It is based on the work done over a twenty-year period by the National Bureau of Standards (Boulder, Colorado), The Georgia Institute of Technology and others. The near-field technique is used for large aperture, high frequency antennas where the antenna to probe separation necessary to test in the far-field of the antenna is prohibitively large.
The New ANSI RF Radiation Exposure Standard: Its Background and Impact
This presentation will focus on the recently revised ANSI C95 RF Radiation Exposure Standard. Some of the research background for the new standard will be given, and its impact will be explained. Instrumentation guidelines for measuring potentially hazardous fields will be presented. The possible damaging effects of non-ionizing RF radiation is receiving increased attention in the public eye, and it behooves the practicing antenna engineer to be aware of the potential dangers to health and safety from exposure of RF energy.
A New antenna test facility at General Electric Space Systems Division in Valley Forge, PA.
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.
Automated wideband, phase coherent polarimetric radar cross section measurements
This paper describes the equipment, mechanics and methods of one of the outdoor ranges at Teledyne Micronetics. A computer controlled microwave transceiver uses pulsed CW over a frequency range of 2-18 GHz to measure the amplitude, phase and polarization of the signal reflected off the target. The range geometry, calibration and analysis techniques are used to optimize measurement accuracy and characterize the target as a set of subscatterers.
A Broadband RCS measurement system
The fast fourier transform capabilities of the Hewlett-Packard 8510 Network Analyzer provide the basis for an RCS measurement system covering the 50 MHz to 26 GHz frequency range. When used in the broadband mode, fine range resolution is achieved. Vector subtraction and gating capabilities permit the acquisition of accurate data in the presence of strong range reflections. Combining this instrument with a high speed data collection and analysis system yields a powerful RCS measurement capability.
A High speed, high accuracy position indicator
One of the variables to be quantified when making antenna measurements is position. Without accurate and timely position information, the spatially dependent data cannot be correctly interpreted. Scientific-Atlanta’s 1885 Positioner Indicator and 1886 Position Data Processor offer several improvements in providing position information which can enhance an antenna measurement system. New position indicating techniques have been implemented to allow a higher degree of accuracy and speed than previously attainable. These have been combined with advanced features for automatic system flexibility to create a high performance instrument for many applications. This paper describes the capabilities of these two instruments and how they can be used to improve system performance.
Satellite near field test facility
The paper describes a near field facility developed at Hughes Aircraft Space and Communications Group for the purpose of performing measurements on satellite antennas. The facility is designed for planar near field scanning with capability for adding cylindrical scanning. The facility has a scanner with a 21 foot square range and is capable of measuring large antennas with operating frequencies up to 15 GHZ. The measurement system is designed for testing multi-beam, multi-frequency antennas. Data collection, scan control and data analysis functions are all controlled by a single computer system. Growth plans include the addition of an array processor for the ability to perform Fast Fourier Transforms in near real time. Results for the antennas which have been measured will be shown along with far field range data for comparison.
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