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This paper will discuss the design and performance of a small step-frequency homodyne monopulse radar. The radar is designed to sit on the ground and penetrate weedy foliage to observe moving vehicles. It operates with horizontal polarization near 3.3 GHz with approximately 500 MHz bandwidth. Only 8 dBm power is needed. We will show the results of tests done with a corner reflector and with a walking human. Tracking performance in both range and azimuth will be shown.
This paper presents a near-field approach for the characterization of BTS antennas. Thanks to Near-Field Near-Field transformation, the near-field radiated by an antenna and its safety perimeter can be determined rapidly and very accurately. An experimental validation of this approach is provided.
A novel application for contoured beam reflector antennas in wireless applications is described. The problem of wireless coverage planning using existing basestation antenna types is discussed and a potential solution for these problems is demonstrated by examples. The implementation of this solution is made possible by using an inexpensive manufacturing technique involving a reconfigurable mould and a foam extrusion process.
This paper describes the results of a research program performed to support a Ball product development. Of particular interest to the customer was demonstrating the ability to make inexpensive measurements of millimeter antennas by retrofitting harmonic frequency converters into existing range instrumentation and evaluating whether the range had sufficient quiet zone quality to evaluate extremely beam efficient radiometers.
Test results of the compact range facility in the National University of Singapore are presented in this paper. The tests were performed for antenna and RCS measurements from L-band to Ka-band. Errors of experimental measurements are compared to errors in measurements calculated by results of field measuring in the quiet zone.
As the demands on the RF spectrum increase, there is a growing need for antenna test capability at ever higher frequencies. To support our current needs and to accommodate future growth, Ball has outfitted its’ antenna ranges for antenna test from 100MHz through 210GHz. This paper will discuss the considerations and techniques used in extending Ball’s antenna test capability up to 210GHz. The final setup will be discussed and measured pattern data will be presented.
From the earliest days of antenna development, the need for measurement of performance and function has been present. Some characteristics of antennas, such as radiation pattern, are measured by moving one antenna with respect to another. In early antenna testing, outdoor ranges were used to provide a close approximation to the pattern. However, due to the challenges of weather and other environmental effects, antenna testing moved indoors with a number of methods used to compensate for the lack of available space. This paper presents an overview of the history of testing at BATC, from the early days of outdoor testing to the transition to conventional anechoic chambers and nearfield probe facilities. During this time, a variety of techniques have been used to augment standard methods for special requirements, and this paper seeks to communicate some of these methods to the testing community as well as providing a general history of antenna measurement.
A system has been developed for acquiring an antenna’s complete (3D) radiation pattern and radar cross-section (RCS) measurements. The system consists of a motion controller, a network analyser and tower assembly. The tower assembly is in an anechoic chamber. The tower has a novel design. It uses three motors in a special configuration, thereby allowing 2 ½ degrees of freedom. This freedom gives the ability to run complete antenna or RCS measurements automatically. Another advantage stemming from the degrees of freedom is expansion of the range of measurements. This is enabled by a variety of possible positions inside the chamber. Tests have also been carried out on system performance. The data acquisition rate becomes crucial when dealing with 3D pattern measurements. The performance of an HP 8720 or 8753 network analyser series can be dramatically increased by using the power sweep mode for data acquisition. Together with the “external trigger-on-point” mode, this gives the best positioning accuracy. The six-month experience has demonstrated the flexibility and reliability of the set up and ideas.
We discuss progress in developing a new broadband (10 MHz to 40 GHz) RF field standard to be used for calibrating small electromagnetic field probes. The technique generates a well-defined and uniform TEM mode field between the conductors of an air-filled coaxial transmission line of conical geometry (termed a “co-conical” line) that is terminated in a well-matched, high-power, distributed load. We show that generation of higher-order mode fields will be minimal due to the line’s circular and symmetrical crosssection. Internal field levels equivalent to power density levels in excess of 10 mW/cm2 can be generated using broadband power sources of only 20 watts output. The new system will be capable of rapid, automated and accurate calibration of small field probes and can realize significant savings in both equipment/facility expenses and operational costs.
In June 2001, the DoD Range Commanders Council Signature Measurement and Standards Group (RCC/SMSG) certified that the Helendale Measurement Facility (HMF) outdoor radar cross section (RCS) measurement Range Book met the ANSI-Z-540 documentation standards established by the DoD demonstration project. This paper describes how Lockheed Martin Aeronautics (LM Aero) applied the ANSI Z-540 [1,2,3] standard to obtain National Certification of the HMF RCS range. The dual calibration results for Pit #1 and Pit #3 are presented showing upper and lower uncertainty error bounds established by this process. Schedule, cost, range book format, and “lessons learned” from the LM Aero experience are also discussed.
This paper reviews the Helendale Measurement Facility (HMF) ground plane range uncertainty analysis and associated data collection. Range uncertainty analysis is a requirement for ISO-25/ANSI-Z-540 range certification and is a priority one section in the Helendale Range Book. Targets used for the analysis were two sets of right circular “squat” calibration cylinders. These cylinders are the dual calibration cylinders for HMF. Calibration measurement uncertainties are established statistically from a large number of repeated measurements at S, C, X, and Ku bands. Each measurement was taken at two target support locations down range. The field data collected included monostatic scattering from two calibration cylinders, backgrounds with no target and support, and drift data for quality control. I and Q imbalance, frequency stability, range accuracy, linearity, and field uniformity at target locations were considered in the analysis. The uncertainty analysis is based on RSS addition of errors and assumes all errors are additive and that targets are not LO. The statistical approach used to perform the uncertainty analysis reported in this paper was developed cooperatively at AFRL and Mission Research Corporation.
It is a very common practice to over specify the Quiet Zone performance requirements for an anechoic chamber. Very often what is done is a person who is in need of a chamber contacts someone with a similar facility, often a supplier or a customer, and simply patterns their performance requirement after what the other guy has done. This often results in a chamber, which is specified to a tighter performance requirement than is actually needed to perform the particular measurements required and can cost thousands of dollars more than is necessary. Qualcomm had a requirement to build a chamber for the evaluation of various antenna designs for mobile communication equipment. Due to building and space limitations the “ideal” size for a chamber operating in the 800 Mhz to 6.0 Ghz was not available. Qualcomm worked with AEMI to define the performance parameters to provide them with the best performing chamber that could be built within the restricted space available. Once the design parameters were defined adequately the chamber deign was developed and the chamber was built. Once the chamber was built Qualcomm went about defining the best test methods and parameters that could be achieved given the performance limitations that were evident in the design due to the compromises that had to be made in the limited space available to accommodate the chamber. This paper will discuss the design process, the design limitations and the methods used to overcome the performance compromises made in the development of the chamber and its intended purpose.
A new measurement technique based on an electromagnetic parametric scattering model has been described. The technique makes it possible to measure antenna gain and the newly defined radiation center by performing two wideband scattering measurements. This approach allows the measurement of the in-situ installed antenna performance. The dispersive nature of the wideband antennas is demonstrated. This dispersive nature of the antenna has significant impact on its use in imaging systems.
While there are standard test methods to characterize the performance of passive antennas, active antennas (with integrated amplifiers) and more complex systems with adaptive functionality create new testing challenges, both in definition and approach. Active antenna gain is a combination of the antenna gain and the embedded amplifier gain. Since these amplifiers may be distributed throughout the array with gain variations between amplifiers, there is a challenge in performing measurements that separate the two gain components. For adaptive antennas, the pattern changes with the incident angle of the test signal, so the adaptive function is often disabled to provide a snapshot of the system, like antenna patterns, for a particular set of conditions. In other cases of adaptive antennas, the composite system performance is measured for angular changes while the system adapts. This paper presents an overview of the testing of both active antennas and adaptive antenna combining systems. Examples of the types of test metrics and errors will be given.
A usual way of performing pattern-measurements on circularly polarized antennas is by measuring the linear components of the field and mathematically converting those to the left-hand and right-hand circular components. These synthesized circular components are sensitive for a number of factors: The exact orthogonality of the measured linear components, the measurement-accuracy of both phase and amplitude of the measured linear components, the polarization-pureness (or the accuracy of the description of the polarization-characteristics) of the probe, etc. This paper analyzes these factors, using a computer-model. An indication on the requirements to be imposed on the measurement-equipment is provided.
This paper presents the results of NCTR research performed at the POSTECH compact range. The radar cross section data of five scaled aircraft models, such as F4, F14, F16, F117 and Mig29, have been measured over a frequency region of X-band and an angular sector of 29.6o. Afterwards, one-dimensional radar signatures at several aspects of each target are obtained by modern spectral estimation techniques, including MUSIC, Fast Root-MUSIC, TLS-Prony, matrix pencil, TLS-ESPRIT. The proposed features are based on the central moments of a given radar signature distribution, and they can provide scale and translation invariance, which are essential for the improvement of NCTR performance. After the appropriate post-processing, the proposed features are classified by the Bayes classifier. Results show that our proposed technique has a significant potential for use in NCTR or ATR areas.
The National Bureau of Standards pioneered in the development of practical planar near-field measurement techniques for antennas. The basic theory was originally developed to determine a diffraction correction for a microwave measurement of the speed of light. Subsequently, this theory was adapted to antenna measurements, and NBS undertook the development of techniques for characterizing antennas from measurements in the near field. Implementation required development of (1) precision near-field scanners for measuring the phase and amplitude of EM fields over a precisely determined measurement plane, (2) efficient computer algorithms capable of processing large quantities of data, and (3) error analyses for reliably estimating the uncertainties in the computed antenna characteristics.
An empirical study on Planar Near-Field Scan Plane Truncation applied to the measurement of a large phased array radar antenna saves test time per antenna. Lockheed Martin has been manufacturing, aligning, and verifying the AEGIS SPY-1B/D phased array radar antenna for the past 17 yrs . A custom built planar nearfield scanner system (ANFAST II) was designed and built specifically for this purpose. Existing raw near-field measured data sets were cropped in both the X and Y scan planes, processed to the far field, and compared with the un-truncated data to determine the error sensitivity vs near-field amplitude level truncated. Near-field measurements were then acquired at the truncated scan plane dimensions and compared. It was demonstrated that 100 hrs of test time could be saved by applying this technique without adversely effecting the antenna measurement uncertainty. This paper discusses the application of the truncation technique, results of the experiments, and practical limitations.
Flexing of cables in planar near-field test systems may introduce significant phase errors to the measured vector values of the field. Submm-wave receivers require several flexible cables to be connected to them. The phase errors originated in the bending cables get multiplied and added to the phase of the final detected submm-wave signal. A complete submm-wave antenna measurement system with on-the-fly measurement of the phase errors in a flexing microwave cable is presented. The phase error measurement is based on the use of a pilot signal. Correction of the detected vector values is done as a postprocessing step. Quiet-zone fields and the corresponding phase error planes have been measured at 310 GHz for two different-sized CATRs based on a hologram. The measured maximum phase errors were 7o and 11o for 30 cm and 60 cm holograms, respectively.
Widespread deployment of cellular phones and use of wireless devices such as personal digital assistants, in-vehicle installs of Global Position-ing System (GPS) receivers, and the upcoming deployment of mobile satellite digital audio has sprung a revitalized interest in faster, more af-fordable measurement techniques for antennas. This paper presents information on several new Spherical Near-field antenna measurement ranges developed by ATDS-Howland.