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AMTA Paper Archive

Tracking and Classification of Vehicles and Humans Using a Ground Wave Radar
E.K. Walton (ElectroScience Laboratory),S. Stevens (ElectroScience Laboratory), November 2003

This paper presents results from a tracking and classification radar that is contained in a coffee-can sized cylinder that sits directly on the ground. The 50 mW radar operates in the 3.1 to 3.6 GHz band using horizontal polarization. The results from earlier radar propagation channel studies will be discussed, including propagation characteristics as a function of polarization and frequency band. The design for this radar that exploits the channel propagation characteristics will be described. Data from tracking of vehicles and humans will be presented. Examples of the range profiles of groups of humans and of moving vehicles will be shown. We will also show a test of the capability of such a system to track humans through building walls.

A New Gated-CW Radar Implementation
J.F. Aubin (ORBIT/FR, Inc.),J. Caserta (ORBIT/FR, Inc.), M.A. Bates (ORBIT/FR, Inc.), November 2003

This paper describes the new ORBIT/FR StingRay Gated-CW radar implementation that provides both performance and speed improvements over those previously utilized and fielded in RCS measurement systems. The radar is implemented using one or multiple pulse modulators used to provide gating of the transmit and receive signals, in conjunction with the new class of Performance Network Analyzer recently introduced by Agilent Technologies. The radar features an order of magnitude improvement in speed over that previously offered using implementations with the Agilent 8510 or 8530 network analyzer/receiver. In addition, base sensitivity improvements are realized, and the radar is more flexible with user selection among many IF bandwidth settings now available. The physical profile of the radar is also improved, meaning that additional performance gains may be realized by creating a more efficient packaging scheme where the radar may be located closer to the radar antennas, either in a direct illumination configuration or in a compact range implementation. These factors, when considered in aggregate, result in the new ORBIT/FR StingRay Gated-CW radar offering that provides a higher performance-to-cost value trade-off than was previously available to the RCS measurement community.

HP8530 Compatible mm-Wave Front-End Instrumentation for Octave Band Coherent Antenna Measurements
M.H.A. Paquay (ESA-ESTEC),D. Korneev (ELVA-1 Millimeter Wave Division), D.R. Vizard (Farran Technology Ltd), P. Ivanov (ELVA-1 Millimeter Wave Division), November 2003

Upcoming space exploration missions will have microwave instruments operating well beyond 100 GHz. Test techniques and instrumentation have to keep up with these developments. Although most of these instruments operate in a few narrow bands, a test engineer, faced with the combined requirements of a range of instruments will prefer full octave band coverage. As a goal, he would like to have the same functionality as at lower frequencies, i.e. sweep or step frequency capability, high dynamic range in the order of 80 dB, coherent, computer controllable and compatible with existing receiver equipment (HP8530). A concept based on a Backward Wave Oscillator, locked by PLL to a synthesizer was chosen. On the receiver side, sub-harmonic mixing was applied. The 110-170 GHz band was chosen as a first step to test the concept. The realized equipment has unsurpassed performance in terms of band coverage and dynamic range. In fact, all the requirements were achieved.

Absorber Placement for Process for Achieving Free-Space Conditions
W. Schaefer (Cisco Systems Inc.), November 2003

The ongoing rapid introduction of new and enhanced electronic products, especially in the area of wireless communications, put an increasing burden on manufacturers in regard to demonstration of product compliance with applicable EMC standards. Wireless communication systems use higher operational frequencies than ever before and PCs, a commodity item in many regions of the world, use clock frequencies in excess of 2 GHz. These technical innovations require emissions measurements above 1 GHz to minimize interference of products with communication systems. The accelerated technical innovation presents a real challenge for national and international standardization bodies which have to determine suitable limits, reflecting the necessary protection, along with the specifications for test measurement equipment and test procedures. At this point in time (May 2002), only very few general EMI standards do contain requirements for emissions measurements above 1 GHz. For instance CFR 47 Part 15 calls out emissions limits up to 40 GHz; the accompanying measurement standard, ANSI C63.4-2000, includes a generic procedure to perform the measurements. However, currently there is no criterion available for the validation of the test site above 1 GHz, similar to the normalized site criterion for the 30 MHz to 1000 MHz frequency range. Therefore, the test environment, which has a significant impact on the test results, cannot be qualified against an independent reference. The international standardization community, i.e., CISPR/A/WG1, is actively working on a verification criteria and procedure for test sites above 1 GHz to address this shortcoming. The following paper presents an alternative method for evaluating a test site above 1 GHz. Test data is presented and discussed which resulted from measurements, conducted to determine the suitability of an existing site for measuring emissions above 1 GHz.

Antenna Pattern Measurement of Microstrip Antennas Using Photonic Sensor and Spherical Scanning Techniques
M. Hirose (National Metrology Institute of Japan, AIST),J. Komiyama (National Metrology Institute of Japan, AIST), T. Ishizone (Toyo University), November 2003

We have developed the spherical near-field measurement system using a photonic sensor as the probe of the spherical scanning. Because the photonic sensor is a few gram of weight and a few mm in length, the measurement system can be compact and simple. The probe compensation is not needed because the photonic sensor can be considered as an ideal infinitesimal electric dipole antenna in the spherical near-field measurements as well as the planar near-field measurements as shown before. To demonstrate the validity of the system, we have measured the antenna patterns of a microstrip antenna on a finite printed board at 5.85 GHz. The measurements by the photonic sensor agreed with the one by the far-field method.

Antenna Alignment of Near-Field Facility
G.M. Hagenbeek (Royal Netherlands Navy),A.R. Boomstra (Royal Netherlands Navy), November 2003

This paper will discuss the application of alignment techniques and tools in a near-field testfacility. Standard alignment telescopes are not directly applicable in a general purpose near-field set-up because of limited dimensions of such a facility, where a direct target is not available and is often to close to the antenna to be in the focus region of the telescope itself. Self-made optical tools will be presented to overcome this problem, including some estimates about the required and obtained accuracies. Using these tools is demonstrated as a fast and accurate way to align an antenna to the measurement set-up.

Evaluation of Radome Performance From Cylindrical Near-Field Measurements
B. Dixon (Chelton Radomes Ltd.),D.J. van Rensburg (Nearfield Systems Inc), November 2003

This paper describes the installation and implementation of a Cylindrical Near-field Test Facility at Chelton Radomes Ltd, Stevenage, (formerly British Aerospace Systems and Equipment Ltd.), in the UK for the testing of large radome/antenna combinations. Test site commissioning and validation activities to determine measurement accuracy & repeatability for the radome performance parameters of transmission loss and boresight error, are discussed. Test data from actual measurements are presented.

Interactions Between Probe Arrays and Antenna Under Test in Cylindrical and Spherical Near-Field Test Ranges: Numerical Assessment and Compensation Schemes
A. Ziyyat (Mohammed first University),D. Picard (Supélec), J-Ch Bolomey (Supélec), November 2003

While probe arrays are now recognized to allow rapid and accurate near-field measurements, the interaction with the Antenna Under Test (AUT) is still sometimes considered as a potential limitation, especially for electrically large directive antennas [1]. Based on numerical simulations, this paper reports the results of a thorough investigation of the interaction mechanism and analyses its impact on the far-field pattern accuracy. The most often, interaction effects can be maintained at an acceptable level, thanks to an appropriate design of the probe array element and structure. However, the efficiency of a posteriori compensation schemes has also been investigated. The Pattern Coherent Averaging Technique (PCAT) [2], which is well known for compensating plane wave deviations in the quiet zone of antenna far-field test ranges or interactions from single probe near-field facilities, also proved very efficient to reduce the interaction effects with a probe array.

Readily Made Comparison Among the Three Near-Field Measurement Geometries Using a Composite Near-Field Range
D.W. Hess (MI Technologies), November 2003

In this paper I demonstrate how our current technology now very readily permits a standard of accuracy and utility to be realized, that was formerly available only in research laboratories. This is accomplished with standardly available positioning equipment and standardly available software. Accurate alignment of the range is enabled by a tracking laser interferometer. This composite nearfield scanning antenna range has afforded us the opportunity to compare readily, far-field results from the classic planar, cylindrical and spherical coodinate systems. Comparison data are presented.

Reduction of Vertical Field Taper at a Ground-Bounce RCS Range
C. Larsson (AerotechTelub AB),C-G. Svensson (Saab Bofors Dynamics AB), November 2003

We have investigated a method that reduces the vertical field taper at a ground-bounce radar crosssection range using a vertical antenna array. An experiment was designed were the coherent data from two measurement channels were independently recorded and stored for post processing. The two datasets were weighted and added in the postprocessing to form the extended zone with improved vertical field taper. Vertically distributed point scatterers on a special test object were used to aid in optimizing the method using imaging techniques. The method is evaluated using simulations and measurements. The usefulness of this method for RCS measurements of full-scale objects such as vehicles and aircraft is discussed. We find that the method can be used to reduce the vertical field taper over a wide frequency band in the way that theory predicts.

An Approach to the Evaluation of Uncertainties for Complex RCS Measurement Data
J. Pinto (BAE SYSTEMS Advanced Technology Centre),K.L. Ford (BAE SYSTEMS Advanced Technology Centre), L.D. Hill (BAE SYSTEMS Advanced Technology Centre), November 2003

The Radar Cross Section (RCS) measurement facility operated by the Stealth Materials Department of BAE SYSTEMS Advanced Technology Centre in the UK is an invaluable tool for the development of low observable (LO) materials and designs. Specifically, it permits the effect of signature control measures, when applied to a design, to be demonstrated empirically in terms of the impact on the RCS. The facility is operated within a 3m by 3m by 12m anechoic chamber where pseudo-monostatic, co-polar, stepped frequency data for a target can be collected in a single measurement run over a frequency range of 2- 18GHz, and for a range of azimuth and elevation angles using a Vector Network Analyser (VNA). The data recorded consists of the complex voltage reflection coefficients (VRC) for the chosen range of aspect angles. This includes data for the target, mount, calibration object, and the associated calibration object mounting where significant. All data processing is conducted offline using a bespoke post processing software routine which implements software time domain gating of the raw data transformed into the time domain prior to calibration. The significant sources of type A (random) and B (systematic) uncertainties for the range are identified, grouped, and an approach to the determination of an uncertainty budget for the complex S21 data is presented. The method is based upon the UKAS M3003 guidelines for the treatment of uncertainties that may be expressed by the use of real, rather than complex numbers. However, a method of assessment of the uncertainties in both real and imaginary parts of the complex data is presented. Finally, the uncertainties estimated for the raw VRC data collected are propagated through the calibration and the uncertainty associated with the complex RCS of a simple target is presented.

Antenna Beam Shape - Effects on RCS Measurement
L. Oldfield (Defence Science Technology Laboratory),G. Wilson (Hutton Moor Measurement Facility), November 2003

This work is part of the UK Ministry of Defence initiative to examine causes of uncertainties in RCS measurements and to establish a network of certified facilities. Having developed a ‘best practice’ guide where causes of uncertainty were listed, the effect of polar diagram was selected as a priority topic. Correction algorithms for RCS measurements require knowledge of the beam shape and resolution in crossrange of the significant scatterers. Accordingly, the accuracy of polar diagram measurement, the effect of amplitude ripple and the applicability of the correction algorithms to near-field data were addressed. Measurements were made on two targets, a long cylinder and a small aircraft. Two antennas and two ranges were used to achieve 1dB, 3dB and 6dB illumination tapers across the cylinder. The 6dB taper situation was modelled for three different numbers of points. The work demonstrated that polar diagram effects are significant for point scatterers or simple targets, like the cylinder; however, for the small aircraft with a large number of distributed scatterers, the overall effect is less significant.

Analysis of Range Ambiguity Effects in a Gated Linear FM Homodyne Receiver
J. Ashton (Sensor Concepts, Inc.),D. Miller (Sensor Concepts, Inc.), T. Lim (Sensor Concepts, Inc.), November 2003

Radar systems that use pulsed waveforms for detection can be adversely affected by target returns whose round-trip time of flight is longer than the radar’s interpulse period. Unless techniques such as pulse repetition frequency (PRF) jitter or pulse phase encoding are employed, the receiver has no way of determining whether a target’s range is accurate. If this radar system is being used to collect radar cross section (RCS) data, the range ambiguities may exhibit themselves as clutter and cause unacceptable levels of data contamination. A Gated Linear FM Homodyne (gated LFMH) radar modulates its transmitted signal during the time of an individual chirp, or frequency sweep, which leads to two distinct PRFs; the chirp PRF and the interchirp pulse PRF. The chirp PRF is typically very low, on the order of tens to hundreds of chirps per second, and therefore insignificant with respect to range ambiguities. It is the interchirp pulse PRF that is typically of sufficient rate to factor significantly in the processing of data collected with range ambiguities present. This paper provides analysis of the effects of range ambiguities in a typical gated LFMH radar that occur during wideband RCS data collections. In addition, a method for optimizing the radar system parameters through the prediction of the range ambiguities will be shown.

ARKEN, A Measurement System for Dynamic Full-Scale RCS Measurements and ECM Evaluations in Operational Environments
S. Gadd (Swedish defence research agency FOI),J. Gustavsson (Swedish defence research agency FOI), M. Wilow (Swedish defence research agency FOI), N. Karlsson (Swedish defence research agency FOI), N-U Jonsson (Swedish defence research agency FOI), November 2003

To determine the radar cross section of full-scale objects in their operational environment, and for doing countermeasure evaluations, a radar measurement system has been developed. The system is mobile and flexible and can hence be placed in different surroundings. Its main objective is to make trustworthy and accurate measurements of the RCS of ground-, seaand air targets. This is achieved by a calibration procedure that is performed in connection to all measurements. The measurement system is well suited for RCS measurements in dynamic scenarios. The system can transmit radar signals that resemble the signals of existing threat systems. This property together with the fact that the system at the same time measures both the RCS of the target and the effects of ECM make the system well suited for ECM evaluation. Measurements have been made of many different types of targets on land, at sea and in the air. Different types of ECM, e.g. chaff, has also been evaluated.

Use of a Low-Cost Compact Measurement System for the Characterisation of Backscattering from Ship Superstructure Details
R. Cioni,A. Sarri (IDS Ingegneria Dei Sistemi SpA), G. De Mauro (IDS Ingegneria Dei Sistemi SpA), L. Botto (Fincantieri CNI S.p.A.), S. Sensani (IDS Ingegneria Dei Sistemi SpA), November 2003

In this paper, the use of a low cost compact RCS measurement system is described, aimed at the characterisation of superstructure details. This system has been installed in a large room available within a shipyard, so that the measurement process is quite simple and efficient, even though under near-field conditions. Results are relevant to radar images and RCS, and can be used for the selection of details, for the optimisation of their backscattering and/or their installation process, and for the improvement of simulation codes. Comparison with simulations is also reported.

Thermal Sensitivity of a Compact Range
W.G. Forster (Mission Research Corporation), November 2003

The ability to perform radar cross section (RCS) measurements, where background subtraction is applied, requires a measurement system that is very stable throughout the measurement time span. Background subtraction allows the measurement of low RCS components mounted in high RCS test bodies by permitting the scattering from the test body to be removed by coherently subtracting the test body (background) RCS from the target RCS measurement. Amplitude and phase variation of the illumination signal between the time that the target and background measurements are performed will limit the quality of subtraction achievable. Modern instrumentation radars can maintain extraordinary stability when exposed to controlled temperature environments, but controlling the temperature of a large compact range can be difficult. Other components of the measurement system, such as the reflector, can also be influenced by temperature fluctuations. Methods of controlling the thermal environment can have significant consequences. Lessons learned in the Advanced Compact Range at the Air Force Research Laboratory will be described.

Comparisons at 100 GHz Between Measurement and Prediction for the Planck Radio Frequency Development Model
B. Buralli (Alcatel Space),C. Bouvin (Alcatel Space), C. Nardini (Alcatel Space), D. de Chambure (ESA / ESTEC, Herschel / Planck Project), D. Dubruel (Alcatel Space), G. Forma (Alcatel Space), H. Garcia (Alcatel Space), J.M. Canales (ESA / ESTEC, Herschel / Planck Project), M. Nadarassin (Alcatel Space), S. Hanany (University of Minnesota / Twin cities), November 2003

The RFDM (Radio Frequency Development Model) of the PLANCK satellite has been tested in the Alcatel Space CATR (Compact Antenna Test Range) in 2002. The antenna was constituted by a telescope designed by the University of Minnesota for the Archeops balloon borne payload, and corrugated horns manufactured by electroforming process. At the beginning, characterization of the quiet zone of the Compact Range with a planar scanner is presented. A full amplitude/phase/co-pol and amplitude/cross-pol discrimination probing of a 5m x 5m quiet zone at 100 GHz is displayed. Then, we focus on measurements of the antenna response at 100 GHz performed in 4ð steradian with a dynamic range better than 100 dB. We cross-validate the measurement results with the RF predictions of the numerical model using the GRASP8 software developed by TICRA.

RCS Measurement of Large Scale Target in the V/UHF Range: Analysis of the Performances of <> Facility
Y. Chevalier (CEA/CESTA/DEV/SFUR),A. Menard (CELAR/DIRAC), G. Maze-Merceur (CEA/CESTA/DEV/SFUR), P. Bonnemason (CEA/CESTA/DEV/SFUR), S. Morvan (CEA/CESTA/DEV/SFUR), November 2003

SOLANGE is a large RCS indoor measurement facility operated at SHF and V/UHF frequencies. In the V/UHF band, couplings between the target and the walls can be exhibited. These perturbations due to non-directive transmitting/receiving antenna, and non-absorbing walls must be eliminated to derive the intrinsic response of the target. To reduce their levels CELAR introduced smart methods («SAV »: Site Altitude Variable and « EAV »: Environnement Altitude Variable): the transmitting/receiving antenna (and also the target in the EAV method) is translated along the elevation axis, and the acquired data are averaged. CELAR and CEA collaborated to qualify the chamber in the U/VHF band. The aim of the study is to identify and quantify the error sources, and to suggest some improvements. The analysis, based on RCS measurements of canonical targets, includes data processing (clutter reduction) and evaluation of the effects of SAV and EAV on the couplings. A theoretical algorithm is used to assess the performances of the processing, and to optimize measurement altitudes. It introduces an analytical model for the antenna and its images with respect to the walls, and calculates the scattered near field. This study enabled us to suggest improvements in the parameters of the processing, as well as in the RCS facility configuration.

Shipboard EMI Reduction with Low Sidelobe Modifications
Y-C Chang (Raytheon Company),B. Murphy (Raytheon Company), J. Bardine (Naval Surface Warfare Center), L. Hubbard (SPAWAR), November 2003

Undesirable antenna to antenna coupling has caused EMI problems between the WSC-6 SATCOM system and various systems in many shipboard installations. Long term solutions are currently being explored to resolve this EMI problem, which include adaptive interference cancellers and redesign of the WSC-6 feed and subreflector. However, these solutions are expensive and require several years to develop. An intermediate solution using RAM shrouds around the main reflector and subreflector edges of the WSC- 6 antenna has been proposed. The RAM shrouds were designed to reduce the spillover and diffraction of the antenna while having minimal impact on the antenna performances. A lightweight RAM was chosen to minimize the weight increase of the antenna. A prototype unit with the proposed modifications has been fabricated, assembled and tested in a tapered anechoic chamber, a near-field range, and a compact range. Significant reductions in the WSC-6 antenna sidelobes and backlobe have been verified via these measurements. Highlights of these modifications are described. Measured data (near field, compact range, tapered chamber, and shipboard) are presented.

Test and Assessment of a Direction Finding Antenna Measured on the Nose of an MH-47A Helicopter
S. Abbott (US Army), November 2003

One basic Direction Finding (DF) technique for Radar is Amplitude Based Comparison DF. Multiple directional antennas are placed around an aircraft to get a 360 deg view of the area. By placing these antennas on the aircraft, the antennas are subjected to reflections from the aircraft, which distorts the antenna characteristics. This antenna distortion causes errors in the measurement of the angle of arrival. The work presented here describes the measurement of the antenna characteristics of a cavity backed spiral antenna both by itself and attached to the nose of an MH- 47A helicopter nose measured in an anechoic chamber. The spiral antenna’s pattern was changed when it was measured on the helicopter. The effect this change in pattern has on the DF accuracy is discussed.







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