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AMTA Paper Archive

Reflectivity Measurements of Various Commercial Absorbers in the 200-600 GHz Range
J. Saily(Helsinki University of Technology),A.V. Raisanen (Helsinki University of Technology), J. Mallat (Helsinki University of Technology), November 2001

Reflectivities of several commercial absorbers measured at frequencies of 200, 300, 400, 500, and 600 GHz with different incident angles are presented in this paper. The measurements were done using a specially built bistatic test setup with a vector network analyzer and a linear scanner. The presented results show the measured peak reflectance values, i.e., the maximum reflection from the object. The reflectance requirement for absorbers used in compact antenna test ranges (CATRs) is usually –40 dB for all incident angles. According to our measurements, this is not possible with the tested absorbers over the whole frequency range.

Broadband Dielectric Probe for Near Field Measurements
C-C Chen (ElectroScience Laboratory),P.A. Diez (ElectroScience Laboratory), W.D. Burnside (ElectroScience Laboratory), November 2001

A novel broadband dielectric rod probe design that has the characteristics of broad bandwidth; symmetric probe pattern; low RCS; low antenna clutter and dual polarization operation is discussed. The RCS level reduces the interaction between the probe and antenna under test (AUT). The lower antenna clutter level improves the sensitivity in detecting responses from wide angles with greater time delays. During the transmission mode, the rod is excited with a broadband microwave launcher from one end. The radiation then occurs at the other terminal of the rod. Measurement results of the far-field patterns, RCS and reflection coefficient for a prototype rod probe (DRP) are presented.

Controlling Scattering From Near-Field Probes Without Using Absorbers
A. Frandsen (TICRA),O. Breinbjefg (Technical University of Denmark), Pivnenko. S. (Technical University of Denmark), November 2001

The level of multiple reflections in near-field antenna measurements is an important issue in a measurement error budget. Traditionally, the interactions between the test antenna and the measuring probe have been reduced by covering the probe mounting structure with absorbing material. In this paper, a novel approach to alleviating the problem is discussed. This implies the use of a skirt to act as a shield against the mounting structure behind the probe, thereby eliminating the need for an absorber, which is a fragile material when exposed to wear and tear. This also has the added advantage that probe calibration data will not depend on a particular absorber that must be considered as an integral part of the probe. With a suitable design of the skirt, the level of multiple reflections can be reduced, whilst at the same time maintaining the pattern of the probe in the boresight direction unchanged. Prototypes of probes for 20 GHz and 30 GHz have been manufactured and tested, and excellent agreement between experimental results and theoretical predictions has been observed.

Near Real-Time Spherical Near-Field Antenna Measurements
D. Burrell (e-tenna Corporation),P.O. Iversen (Satimo), Ph. Garreau (Satimo), S. Rogers (e-tenna Corporation), W. Klimzcak (e-tenna Corporation), November 2001

High growth in the mobile telephone industry is forcing the development of new terminal antennas at an everincreasing pace. The future multi-standard telephones demand antennas that need to be designed and tested for a variety of radiation and bandwidth specifications. New wireless communications devices, such as those using the new Bluetooth and IEEE 802.11 standards, will require testing of a whole range of new products containing antennas, such as computers, household appliances and consumer electronics. The radiation characteristics of the small antennas used in such devices are strongly dependent on the environment into which they are radiating. For example, the presence of the operator or the mounting and positioning equipment of a test set-up can severely change their radiation characteristics. etenna Corporation addresses this problem by employing a Satimo spherical near-field test system. This system allows for rapid, and in some cases, real-time observation of in situ antenna patterns. A brief description of the test facility is presented in this paper along with sample data.

Prediction of BTS Antennas Safety Perimeter from NF to NF Transformation: An Experimental Validation
A. Ziyyat (Mohammed 1st University),D. Picard (Supélec), J.Ch. Bolomey (Supélec), L. Casavola (Bouygues Telecom), November 2001

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 Simple Analysis of Near-Field Boresight Error Requirements
D.W. Hess (MI Technologies), November 2001

The need to measure the boresight pointing direction of radar antennas to a high degree of accuracy yields a requirement for excellent positioning accuracy on near-field antenna ranges. Evaluation of this requirement can be accomplished by a full and complete sensitivity analysis. Alternatively, to gain an understanding of the effects of errors more simply, one can approach the question of accuracy required in the setup, by use of a physical model and straightforward physical reasoning. The approach starts with the assumptions of a collimated wave with planar phase fronts and the premise that the boresight direction of such a sum beam is along the normal to the phase fronts. A sensitivity analysis of the simple trigonometric boresight relationship between mechanical boresight and phase front normal, shows how accurate the receiver and the positioner must be to achieve a given boresight determination. Such an approach has been known for many years as it regards planar scanning; and, the results are known to be applicable. In this paper this consideration is extended to spherical scanners to arrive at estimates of the mechanical positioner accuracies and electrical receiver accuracies needed to make boresight measurements of radar antennas with spherical near-field ranges.

Experimental Studies With Comparisons to Computational Model for Automobile Antennas
Y. Kim (ElectroScience Laboratory),E.K. Walton (ElectroScience Laboratory), November 2001

A series of experimental and theoretical tests designed to develop techniques for reliable computational modeling of automobile antenna performance is presented. The results from the experimental measurements are compared with the results of computational techniques to verify their accuracy and reliability. The Electromagnetic Surface Patch (ESP5) code, a theoretical Method of Moment (MoM) general-purpose code developed at the Ohio State University, is used for computational modeling. We progress from the simple geometry of a single square plate and a monopole, to the more complex structure of a small copper-coated plastic model of an automobile. The computational simulation and measurements are configured with both a monopole antenna mounted at the center of the automobile roof and a backlite heater grid FM antenna. The input impedance, pattern, and polarization are all measured. Comparisons between the results of the computational simulations are presented, as well as the procedures used to measure the antenna characteristics and compare the experimental data with the measured data.

3D Antenna Measurement Technique for Mobile Phone Characterization Including the User's Influence
Chr. Bornkessel (IMST GmbH),A. Schramm (IMST GmbH), D. Heberling (IMST GmbH), M. Neikes (IMST GmbH), November 2001

A new 3-dimensional measurement method for the determination of the radiated power of mobile phones is presented. In contrast to usual 2D cut plane measurements, the 3D method gives the whole 3D radiation pattern. From this, insight into the detailed angular dependent radiation characteristics can be derived, which is very useful for mobile phone manufacturers and antenna developers. Furthermore, the overall radiated power as well as the directivity of the mobile phone can be post processed from the measured data. A very interesting feature is the ability of the measurement set up to carry a phantom head. With it, measurements of the whole system user and mobile phone can be performed to study the user's influence. The measurements are carried out in an EMC anechoic chamber, which has been specially optimized regarding reflection absorption. Some examples demonstrate the comprehensive measurement capabilities of the presented method.

Towards More Reduction of EMW Hazard in Mobile Telephones Using Three-Covered Monopole Array Antenna
S.I. Al-Mously (The Higher Institute of Electronics),A.Z. Abdalla (The Higher Institute of Electronics), K.F. Omran (The Higher Institute of Electronics), M.M. Abousetta (The Higher Institute of Electronics), O.A. Soltan (The Higher Institute of Electronics), November 2001

In this paper, a three-covered monopole array antenna with 155o phase-shift and 0.1 ë spacing was suggested to give a minimum power radiation in the direction of the mobile user’s head, consequently the hazard that may the EMW inflects on the human health can be considerably reduced. Several experiments were conducted in this work to measure the power radiation pattern of the monopole, as a common antenna used in mobile telephones, and the three-element array antenna in free-space and with human head adjacent to the antenna. The frequencies were chosen to be 1800 MHz and 1985 MHz, for uncovered and covered designs, respectively, to cover the GSM-1800, PCS-1900, and DECT frequencies. A dielectric material with år = 2.33 , tanä = 0.0005 , and thickness equal to the radius of the monopole was used to cover each array element. It was found that the length of the covered monopole is about 90% of the uncovered length. A practical method was suggested in this work for attaching the adopted array to the mobile telephone.

Adaptive Antennas Power-Azimuth Spectrum Using a Geometric-Based Channel Model with a Semi-Elliptic Scenario
S.A. Zekavat (Colorado State University),C.R. Nassar (Colorado State University), November 2001

In this paper, considering a wireless communication network, we use the geometric-based channel modeling technique to create an innovative model for the power azimuth spectrum (PAS). Comparing the PAS model we generate (refered to as secant-square model) to the Laplacian model introduced in the literature for outdoor environments, we demonstrate that our model is a better fit to the TSUNAMI II project measurements. Specifically, our model is a simple mathematical representation, demonstrating a lower squared error when compared to measurement data, and considers effects and relationships ignored in the earlier modeling.

Advantages of Silicon Carbide (SiC) RF Transistors for Driving Antenna Impedances
A. Torres (Xetron Corporation), November 2001

This paper presents the advantages of the next generation of RF Transistors and Amplifier units based on Silicon Carbide (SiC) and Gallium Nitride (GaN) materials. The use of these devices, having higher output and input impedances, allow easier matching to antenna impedances without compromises in power levels. These devices are basically wide bandgap semiconductors having superior properties to other competing technologies such as Silicon (Si) or Gallium Arsenide (GaAs). Implementation of SiC RF transistors will provide higher temperature operation than Si, higher breakdown voltages and extremely good ft operation. A typical SiC unit with a 0.7 ìm configuration will have an ft of 10 GHz.; similarly, a 0.4 ìm configuration will have an ft of greater than 20 GHz. Typical power density is up to 4.5 watts per mm. of transistor structure. In general, SiC Metal Semiconductor Field Effect Transistor (MESFET) will have up to 10 times higher impedances than a Silicon LDMOSFET (input and output). The devices are also very low noise, which allows the use of SiC as high dynamic range Low Noise Amplifiers (LNAs). The paper presents measured data on both SiC Power Amplifiers units and LNAs operating in the frequency domain between 30 to 2800 MHz.

Contoured Beam Reflector Antenna for Wireless Applications
W.H. Theunissen (ElectroScience Laboratory),W.D. Burnside (ElectroScience Laboratory), November 2001

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.

Millimeter Testing at Large Facilities -- Quiet Zone Exceeding 3 Meters
W.N. Kefauver (Electromagnetic Laboratories), November 2001

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.

Estimating the Contribution to RCS Uncertainty From Non-Planar Illumination in a Compact Range
B. Welsh (Mission Research Corporation),B. Kent (Air Force Research Laboratory), November 2001

Compact RCS measurement ranges all suffer from some level of non-ideal field illumination. Stray fields from interactions with the chamber wall and diffraction effects are major contributors to the non-uniformity of the incident field at the target. This non-uniformity gives rise to unavoidable errors in RCS measurements. We present a detailed analysis of how non-uniform illumination manifests itself into RCS measurement errors. The analysis approach is based on the plane wave spectral decomposition of the illumination. We compute the energy scattered by the planar components of the illumination and determine how much of this energy is coupled backi nto the radar antenna. We model the target as a diffuse scatterer by using a collection of point scatterers distributed within a specified volume. We present uncertainty results based on a simulation as well as field probe data collected from AFRL’s Advanced Compact Range (ACR).

Wide Band Compact Antenna Test Range
P. Bengtsson (Ericsson Microwave Systems AB),H. Eriksson (Ericsson Microwave Systems AB), M. Boumans (ORBIT/FR-Europe), November 2001

Ericsson Microwave Systems (EMW) in Sweden has several outdoor and indoor test ranges in operation [1], [2], [3]. In line with future needs and requirements EMW has started building a new Compact Antenna Test Range to be used for a large range of projects and applications. The Compact Antenna Test Range will cover the frequency range of 800 MHz to 75 GHz. The test range will have the possibility for both active and passive antenna measurements at both system and subsystem / unit levels. The test zone will be 3 meters diameter. The maximum load the positioner can carry will be 700 Kg with very high position accuracy for special applications. Due to the relatively low design frequency and the desired size of the test zone, special considerations have been taken in the conceptual design of the reflector system as well as the choice of absorbers. Another important parameter in the design of the facility will be the access to the quiet zone and the time needed to change frequency bands and test objects. To accomplish this, preparations have to be made for easy alignment, very precise interfaces and a fast access to the test area.

Calibration and Verification Measurements in Compensated Compact Ranges Up to 500 GHz
J. Hartmann (Astrium GmbH, EADS),H.J. Steiner (Astrium GmbH, EADS), J. Habersack (Astrium GmbH, EADS), J. Lemanczyk (ESA/ESTEC), P. De Maagt (ESA/ESTEC), November 2001

Compensated Compact Ranges (CCR) represent a high standard of state-of-the-art test facilities with a fast and real time measurement capability up to the submm wave range. Future scientific and earth observation instruments of ESA/ESTEC such as MASTER, PLANCK and HERSCHEL are working within this frequency ranges and require a high measurement accuracy for large antenna apertures. Within the ADMIRALS study for ESA/ESTEC, transmit and receive modules up to 500 GHz and an appropriate large offset reflector antenna with precise surface accuracy in form of a Representative Test Object (RTO) were applied. Related tests in the CCR 75/60 of Astrium were performed in order to qualify the test facility and verify the antenna measurements with theoretical pattern calculations. The present paper shows measurement results with the highly accurate Plane Wave Scanner (PWS) of Astrium GmbH and the RTO. Through the measurements performed, the accuracy of the plane wave field as well as pattern accuracy in the quiet zone of the CCR 75/60 have been qualified up to 500 GHz.

A Compact Range for RCS & Antenna Measurements: Test Results
N. Balabukha (Russian Academy of Science),Tse-Tong Chia (DSO National Laboratories), A. Zubov (Russian Academy of Science), V. Solosin (Russian Academy of Science), November 2001

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.

Modeling of the Antenna-to-Range Coupling for a Compact Range
F. Jensen (TICRA),K. Pontoppidan (TICRA), November 2001

Two ways of modelling a compact range design are presented, and the coupling to a given antenna under test (AUT) is determined and compared to the AUT far field. The compact range models are both based on physical optics (PO). The first model applies a simple presentation of the serrations of the range reflector while the second model is based on a new feature of GRASP8, which allows a detailed description of the triangles of the range serrations. The AUT measurement is modelled by an accurate coupling analysis between the current elements on the compact range reflector and the antenna under test. This coupling pattern is compared to the real far-field pattern and the differences are discussed. By including known range imperfections in the AUT-torange coupling a better agreement to the measured patterns may be obtained. All computations are carried out by GRASP8.

Advanced Compact Antenna Test Range Quiet Zone Characterization and Extension Techniques
B. Buralli (ALCATEL SPACE INDUSTRIES),C. Bouvin (ALCATEL SPACE INDUSTRIES), C. Nardini (ALCATEL SPACE INDUSTRIES), G. Forma (ALCATEL SPACE INDUSTRIES), H. Garcia (ALCATEL SPACE INDUSTRIES), M. Vacarella (ALCATEL SPACE INDUSTRIES), November 2001

Telecommunication satellites capacity growth has lead to a new generation of antennas , larger in size and with extremely sharp performance in terms of gain , cross polarization and coverage isolation (frequency re-use). In order to test such kind of antennas (the largest one is a Ku-band 3.6 m diameter and 6 m focal length reflector antenna) Alcatel Space Industries has implemented several innovations in its Compact Antenna Test Range (CATR): - a powerful and flexible machine has been invested , which provides 6 degrees of freedom (the machine has been called “6DOF Table”) in a wide range of motion to any satellite, allowing to bring any antenna of this satellite into the quiet zone - thanks to this new machine a series of accurate scanner probing has been performed , not only in the central plane of the quiet zone , but also on an eight meter range along the Angle Of Arrival (AOA) of the CATR - the quiet zone has been extended by one meter in height thanks to defocusing techniques; this extension has been modeled with GRASP 8 and tested using the vertical degree of freedom of the “6DOF Table” and a very accurate scanner. - In addition , the Cross polarization of the quiet zone has been tested with high dynamic ranges, using very high purity gridded horns . An average Cross polarization isolation better than 55 dB has been evidenced.

Performance of an Experimental Outdoor RCS Range With R-Card Fences
I.J. Gupta (The Ohio State University),W.D. Burnside (The Ohio State University), November 2001

A 30-meter experimental outdoor RCS range designed to operate from 6-18 GHz is described. In the range, the radar antenna height is 60 cm; whereas the center of the quiet zone is 3 meters above ground. The test range, therefore, has features of many real world outdoor RCS ranges. The test range uses six R-card fences with edge taper to eliminate the ground bounce term. Using the quiet zone field probe data and backscatter measurements, it is demonstrated that the R-card fences are very effective in eliminating the ground bounce term.







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