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We discuss recent advances in signal-to-noise and signal-to-clutter enhancement technology applied to RCS measurements, with an emphasis on post-processing techniques. Then, we outline a technique we refer to as Interactive Coherent CLEAN Editing (ICCE). ICCE permits the analyst to segregate scattering features of the model under test into various groups. Clutter sources, such as the target support pylon, can be subtracted with potentially less error and more flexibility than other techniques. Limitations and the current status of ICCE are discussed.
Today’s measurement systems are placing ever increasing demands upon the computer systems which control instrumentation and collect data. This paper investigates high speed control of instrumentation for RCS and antenna measurements. Off-loading of I/O from control and data acquisition computers is examined with a view toward improving measurement throughput and simplifying I/O control tasks. These methods are particularly important for multi-tasking systems and networked resources where high speed real time control is burdensome. Attributes of I/O enhancement architectures are examined and tradeoffs between performance and flexibility are reviewed.
This paper deals with design and evaluation of Compact Range Antenna and RCS measurement systems. Reflector subsystem and feeders design as well as quiet zone evaluation and system performance qualification are considered. Acquisition, process and presentation software to control the whole system has been developed and successfully implemented. Two systems have been designed and are now at implementation stage. A Gregorian concept Compact Range is now been constructed at RYMSA (Spain). This facility has been fully designed by IRSA and will be operative by the end of 1990. Compact Payload Test Range (CPTR) at ESTEC (ESA) is now been tested. System Instrumentation and PAMAS (Payload and Antenna Measurement and Analysis Software) have been developed.
A novel and very powerful measurement technique is presented which allows the determination of antenna radiation and scattering by radar-cross-section (RCS-_ measurements. The antenna under test is treated as a loaded scatterer using a polarization dependent network model that allows a complete antenna description in terms of scattered, radiated and absorbed waves. A load variation principle is used to determine the network model parameters and all commonly used antenna parameters like gain, antenna polarization, axial ratio, polarization decoupling, input impedance and also structural scattering can be derived from the backscatter measurement without using any additional standard antenna. With the antenna network description it is furthermore possible to examine the antenna behavior for arbitrary excitation or loading on their waveguide or radiation port.
A major objective in the design of an RCS measurement facility is to obtain the greatest possible productivity (overall measurement efficiency) while maintaining the accuracy and sensitivity necessary for low radar cross section targets. This paper will present parameters affecting the total throughput rates of an indoor facility including instrumentation, target handling, and band changes-one of the most time consuming activities in the measurement process. Sensitivity and accuracy issues to be discussed include radar capabilities, feeds and feed clustering, compact range, background levels, and diffraction control.
Mechanical and environmental considerations for outdoor operation of an inflatable column are discussed in the context of a 30-ft-high column. The column is designed to support a 900-lb load in a 30-knot wind. Column RCS is less than -40 dBsm below 1 GHz for both horizontally and vertically polarized illumination. Designs using Mylar and Teflon-coated Kevlar as skin materials are compared. The primary concerns are wind loading, pressure regulation, and solar heating. Wind effects include static loading, gusting, and vortex shedding. In addition, wind-driven particulates, such as sand or stones propelled by passing vehicles can puncture the column. A pneumatic control system maintains a constant internal support pressure in the presence of leaks or pressure fluctuations due to changes in solar illumination.
This system provides improved techniques for controlling positioning axes, and secure transmission of position data from remotely located control systems. Advancements in controls technology have allows more complex configurations for use in the manipulation of RCS targets in indoor ranges. This paper will discuss a unique system design that provides automated testing and positioning of RCS test bodies. The current system uses seven axes of motion, and allows for simultaneous motion as well as synchronous motion of any axis pairs in the system. These axes include Target azimuth and elevation, Pylon azimuth and elevation, Upper and Lower turntable azimuth, and carriage linear drives. In addition, the concepts of secure data transmission through the use of specialized fiber optics are addressed. Finally, a complex set of safety interlocks and man and machine protection is discussed. The entire system is currently implemented and running in the Boeing range.
The Hughes Aircraft Company recently completed the design, development, and construction of a new engineering facility that is dedicated to providing state-of-the-art Radar Cross Section Measurements. The facility is located at the Radar Systems Group in El Segundo, California and consists of two secure, tempest shielded anechoic chambers, a secure high bay work area, two large secure storage vaults, a secure tempest computer facility, a secure conference room, and the normal building support facilities. This RCS measurement test facility is the result of Hughes committing the time and money to study the problems which influence user friendly RCS measurement facility design decisions. Both anechoic chambers contain compact ranges and RCS measurement data collection systems. A description of the facility layout, instrumentation, target handling capability, and target access is presented.
There are two main parts to an antenna or RCS measurement system: the measurement instrumentation, and the measurement environment or “range”. Performance of the measurement system is dependent upon both the instrumentation and the range. Developing a successful measurement system requires understanding both parts of the system. This paper describes a Compact Test Range that has been designed and built for the purpose of demonstrating antenna and RCS measurement performance of a complete measurement system. Additionally the Compact Test Range will serve as a development platform for future antenna and RCS products and systems. The purpose of the chamber, design objectives, design techniques, expected and measured performance are all discussed.
Lockheed’s Advanced Development Company (LADC), located in Burbank, California, has recently completed construction of a state-of-the-art indoor Antenna/RCS test facility. This facility is housed in a dedicated 40,000 square foot building which is a maximum of 80 feet high. This building contains three anechoic chambers providing Antenna/RCS measurement capability from 100 Mhz to 100 Ghz. The largest chamber, with dimensions of 64 feet by 64 feet by 97 feet is configured as a compact range. This chamber utilizes the largest collimating reflector that Scientific-Atlanta has ever constructed. Primary test usage of this chamber is for RCS measurements in the frequency band of 700 Mhz to 100 Ghz. The second chamber is configured as a tapered horn test range. Its dimensions are 155 feet long with a 50 foot by 50 foot by 55 foot volume measurement zone. This chamber is utilized for RCS tests in the VHF, UHF, and L frequency bands and antenna tests from 100 MHz and up. The third chamber, with dimensions 14 foot by 14 foot by 56 foot, is a far field chamber designed to check out and evaluate small items up to 100 GHz. The entire facility has been designed to maximize efficiency, minimize the cost of operation, and produce outstanding quality data from Antenna/RCS measurements. A number of innovative techniques in model handling, model access, and model security were incorporated into the facility design. These features, as well as utilization of unique Lockheed designed and built pylons, allowed achievement of all these goals.
Among its different facilities, C.E.A. has an indoor range for radar cross section (RCS) measurements over a wide frequency range from 0,1 GHz to 18 GHz. The dimensions of this anechoic chamber, 45m x 13m x 12m and a quiet zone diameter of about 3m, make it one of the largest in Europe. It consists in a parabolic reflector for frequencies higher than 0,8 GHz and a system using inverse synthetic aperture radar (ISAR) techniques for lower frequencies associated with a short pulse coherent radar instrumentation equipment. In addition to performant instrumentation and illumination systems, the main features of this installation dedicated to measure stealth objects, are low residual clutter, discrete target supports, and powerful processing software. The technical solutions adopted are described.
An HP 8510B based RCS measurement system is presented. It can be operated in CW, hardware gating, and fast-CW modes. A VAX-3800 computer and a MAP 4000 array processor are used to speed up the data analysis and a PS 390 graphic system is used to display graphic. Three ISAR techniques, i.e., DFT approximation, focusing image processing, and diffraction limited methods, are available in the analysis program to get the target image. With an amplitude taper removing technique, this system can measure large target whose size is almost up to the size of compact range reflector.
This paper summarizes the performance of the new Harris 1612 Compact Range Standard Product. The Harris 1612 is a dual shaped reflector collimator system. Measured data, both amplitude and phase from the 12-foot diameter quiet zone is presented. The quiet zone was characterized using an automated two-way HP8510B based measurement system. The inherent system benefits for both antenna and RCS measurements are also discussed.
This paper examines the economic justification process for a new Antenna or Radar Cross-Section (RCS) measurement system, and presents the techniques that can be used to determine the financial feasibility of a new system. Specific examples are given that will allow engineers to customize calculations to fit their company's specific accounting methods and labor rates.
In this paper, a general methodology for data reduction and analysis of wide-band RCS data is discussed. This methodology encompasses normal image processing, clutter removal, and noise filtering. Examples of the usefulness of the approach are presented.
This paper describes two signal processing techniques that have been used to overcome specific problems in a Lockheed Aeronautical Systems Corporation (LASC) indoor compact RCS measurement range. Both techniques are post processing techniques used to enhance the accuracy of RCS vs. Aspect measurements. These two techniques can speed up measurement time, increase measurement accuracy, and increase target sizes on a compact range.
This paper discusses the configuration and performance of millimeter-wave measurement systems comprised of standard Harris Shaped Compact Ranges, Hewlett Packard (HP) 8510B Network Analyzer, and Millitech frequency extenders designed for use with the network analyzer. Millimeter-wave capabilities have been integrated into the Harris automated measurement system to allow computer controlled millimeter-wave compact range characterizations. This system offers a new measurement alternative for antenna and Radar Cross Section (RCS) measurements. Measured 35 GHz data from the Harris Model 1606 compact range, and 95 GHz data from the Model 1603 compact range are included.
Measured component RCS results are frequently dominated by the test body and target mounting structures. This paper will present a measurement technique that will improve measurement accuracy using a less complex and expensive test body. The design of the test body and measurement geometry allows isolation in both range and cross range from the static return of the room and mounting structure. This is accomplished by first creating an ISAR image of the target and test body, gating the image in two dimensions, then transforming back into the frequency and spatial angle domains to determine the scattering levels of the target by itself. Details of this technique, covering both its advantages and limitations, will be discussed. Data will be presented to verify the approach and illustrate the level of performance attainable using this technique.
This paper describes methodology for performing high resolution target radar cross section (RCS) diagnostic measurements with a new type of portable multifrequency radar. The Model 200 radar system is capable of operating at extremely short ranges, and does not require an anechoic chamber for performing highly sensitive radar cross section measurements. Measurements can be made in conventional low range resolution polar plot modes, in high-range-resolution (HRR) mode, in Inverse Synthetic Aperture (ISAR) mode, and in Synthetic Aperture (SAR) mode. The radar is described and the implications for present and future measurement technology are discussed.
In the past, most radar-cross-section imaging has been done after data has been taken. At best, this off-line processing generates images that are returned to a customer the next day. Many projects can benefit significantly by having concurrent imaging and data acquisition. This allows for real-time cause and effect type diagnostics without rescheduling range time. As RCS range time becomes increasingly more expensive and difficult to schedule, real-time imaging provides the project engineer with a valuable tool to optimally use his range time. A technique has been developed to render real-time radar cross section images while acquiring data. All image processing is performed to achieve a fully enhanced image. Focussing, interpolation, and windowing are all used to give a detailed image. The system uses a Hewlett Packard 8510B for data taking and Hewlett Packard computers for data acquisition and image processing.