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In general, the RF test setups of antenna test facilities are designed and optimized for antenna pattern and gain measurements. However, the operation of test facilities, especially the here considered 'Double Reflector Compact Ranges', can be extended, so that they can also be used for RCS testing. A simple and very practical expansion of the RF antenna test setup - while maintaining the real-time capability - can be achieved with the aid of a hardware gating system. With this type of setup, RCS measurements have successfully been performed in the Compensated Compact Ranges of EADS Astrium. The applied gating system was the high resolution Hard- gating System HG2000 of EADS Astrium, developed together with the Munich Univ. of App. Sciences. Within this paper, the applied facility and the gating system will be described firstly. Subsequently, the modified test setup and the test results obtained by calibration measurements will be shown. They will give an indication of the achievable resolution for the extended test system w.r.t. object size detection and resulting amplitude dynamic range.
This paper describes the methodologies and processes used for the development, installation, alignment and qualification of a Compact Range Rolled Edge Reflector purchased by the MIT Lincoln Laboratory and installed at their test facility located at Hanscom Air Force Base. The Ohio State University, under contract to MIT Lincoln Laboratory, performed the electromagnetic design and analysis to determine the desired surface shape and required mechanical accuracy of various zones of that surface. The requirement for operation over a very broad frequency range (400 MHz to 100 GHz) resulted in a surface specification that was both physically large (24 ft × 24 ft) and included extremely tight tolerance requirements in the center section. The mechanical design process will be described, including the generation of a solid “Master Surface” created from the “cloud” of data points supplied by The Ohio State University, verification of the “Master Surface” with The Ohio State University, segmentation of the reflector body into multiple panels, design, fabrication and factory qualification of the structural stands, panel adjustment mechanisms, and panels. Results of thermal cycling of the reflector panels during the fabrication process will be presented. The processes used for installation of the reflector and the alignment of each panel to the “Master Surface” will be presented and discussed. Final verification of the surface accuracy using a tracking laser interferometer will be described. Color contour plots of the reflector surface will be provided, illustrating the final surface shape and verifying compliance to the surface accuracy requirement
CAMELIA is one of the three anechoïc chambers of the French Atomic Energy Center (CEA). It is equipped with a compact range reflector and a pulsed radar allowing antenna and RCS measurements from 800 MHz to 18 GHz. Below 800 MHz, measurements are made with different kind of antennas (log- periodic, horns, arrays…). Nevertheless, measurements at such low frequencies suffer from serious artifacts due to coupling effects. This paper describes a particular array we designed, realized and characterized to cover the 100 MHz – 2000 MHz bandwidth. Although the antenna diagram shape was the most constraining factor, the ability to cover the whole bandwidth with as few handling as possible was the major issue.
More and more wireless services such as satellite radio (SDAR), navigation systems, OnStar, and mobile telephones are installed in GM vehicles. This has created a need to make quick and accurate vehicle antenna measurements. For the frequency range of 500 MHz to 6 GHz, one solution is to use a spherical near-field system. The Satimo rapid probe array technology was selected to develop a vehicle antenna test system (ATS) to reduce test time and maintain data accuracy. The ATS was designed to operate inside of an existing GM electromagnetic compatibility (EMC) anechoic chamber equipped with a nine-meter turntable. The ATS was completed and received XM certification in the first quarter of 2004. The ATS performs multi-frequency dual-polarized complex measurements for every one-degree in azimuth and elevation, over a full hemisphere, in approximately five minutes. The autonomous transport and deployment system, allows the ATS hardware to be removed and the chamber returned to its EMC configuration. This paper presents the ATS design and a summary of the verification test results. A detailed uncertainty budget, as defined by NIST, is also presented.
We characterize here the performance of a time domain antenna range by measuring a number of antennas, comparing the results to frequency domain measurements. Our time domain antenna range consists of a fast pulser and a sampling oscilloscope. We have demonstrated good performance of this range for all types of antennas (resonant and non-resonant) that operate between 900 MHz and 20 GHz. Furthermore, if the antenna is non-resonant, then good performance is observed as low as 200 MHz. Finally, it seems likely that by using a longer time window we can extend below 900 MHz the bandwidth of the antenna range for resonant antennas.
Spherical near-field measurements require an increased level of sophistication and care to achieve accurate results. This paper will demonstrate an automated set of self-comparison tests, which can be used for establishing and optimizing a spherical system's performance. An over-determined set of measurements can help to qualify positioner alignment, range reflection levels, truncation effects, and additional parameters of interest. These results will help in optimizing the test configuration to achieve accurate near-field measurement results.
We propose a simple method for estimating uncertainties due to multiple reflections between the test antenna and probe in near- field spherical-scanning measurements. To estimate uncertainties in far-field parameters, we measure the test antenna by scanning the probe over two spheres whose radii differ by a quarter wavelength (?/4). We compare this estimate to that obtained with a reduced data set (containing all values of ? but only a few values of f). In our example, we find that measuring only two f cuts suffices to obtain RMS uncertainties within 1 dB of those obtained using full-sphere data.
The gain patterns of VHF/UHF antennas on ground structures and vehicles are influenced by the characteristics of the ground. The measurement of the performance of such antennas is more accurate with a test chamber that incorporates a realistic ground surface. This paper will discuss the near field to far field transformation process for the case where there are reflections from a ground surface outside the probing hemisphere. We will show that the ground reflection term in the transformation must be based on the characterization of the ground outside the probe region.
In this paper, we describe a new method for improving the true-position accuracy of a very large, spherical near- field measurement system. The mechanical positioning subsystem consists of 10-meter diameter, 180 circular- arc scanner and an MI Technologies MI-51230 azimuth rotator and position controller. The principle components of the error correction method are the error measurement system, the position correction algorithm, and a pair of very high precision, mechanical error correction stages. Using a tracking laser interferometer, error maps are constructed for radial, planar and elevation errors. A position correction algorithm utilizes these discrete-point error maps to generate error correction terms over the continuous range of the elevation axis. The small position correction motions required in the radial and planar directions are performed using the mechanical correction stages. Corrections to the position of the elevation axis are made using the primary elevation axis drive. Results are presented that show the geometry of the spherical scanning system before and after error correction. It is observed that the accuracy of the radial, planar and elevation axes can be significantly improved using the error correction system.
Probe correction aspects for the spherical near-field antenna measurements are investigated. First, the spherical mode analyses of the radiated fields of several antennas are performed. It is shown that many common antennas are essentially so-called odd-order antennas. Second, the errors caused by the use of the first-order probe correction [1] for a rectangular waveguide probe, that is an odd-order antenna, are demonstrated. Third, a recently developed probe correction technique for odd-order probes is applied for the rectangular waveguide probe and shown to provide accurate results.
The input reflection coefficient of a probe-driven dielectric resonator antenna operating in the HEM11 mode is measured in the frequency range 8 to 13 GHz. The equivalent circuit of the antenna is postulated to be of Foster-type, with resistances added to account for the losses and for the radiation. The element values are data-fitted with the help of Marquardt optimization. The antenna is then covered with the conductive cap and the unloaded Q factor is determined. Based on the equivalent circuit values, the radiation efficiency is then computed from the measured data. The electromagnetic simulations of the structure are in agreement with the measured input reflection coefficient and the radiation Q factor.
A novel antenna miniaturization approach utilizing artificial transmission-line (ATL) structures whose impedance and phase velocity are mainly controlled by distributed reactive elements is explored. First, the slow- wave phenomena and impedance control in ATL will be demonstrated. Then, miniaturization of a resonating structure will be presented. Finally the application of ATL on antenna structure will be demonstrated. The proposed miniaturization approach is inherently suitable for broadband miniature antenna designs, such as spiral antennas, and provides additional design degree of freedom.
Exploitation of MIMO (Multiple-Input Multiple-Output) system in laptop type device, which size is adequate to integrate several antennas on it, would be the solution to increase attainable capacity e.g. in wireless local area networks (WLAN). Thus, a microstrip prototype antenna with two polarizations is developed for MIMO and also for diversity system purposes. Firstly, two antennas of this type were placed against to each other, which guarantees a good coverage over a whole propagation area. Secondly, two antennas of this type were placed next to each other. The simulated radiation patterns of the prototype antenna are used in the capacity studies of MIMO system using real indoor propagation data. The effect of shadowing by human body as well as different tilting angles of “laptop cover/screen” are considered. Further, different locations of the “device” in azimuth plane were considered identifying the fluctuation of the results due to the environmental and antenna properties. The developed antenna systems perform well as compared to the ideal dipole system.
In this paper the influence of mutual coupling on the capacity of a multiple-input multiple-output (MIMO) antenna system is demonstrated. No direct relation between the envelope correlation and the actual location and orientation of the antennas is found. Even though being essential for high MIMO capacity, configurations with the lowest envelope correlations are not necessarily the most suitable for a MIMO system. A certain bandwidth is required as well. Three planar inverted F-antennas (PIFA) located on the same 40 mm 100 mm ground plane. The antennas that haves a resonant frequency of 1.8 GHz yields envelope correlations ?e below 0.4.
Adaptive type smart antennas have not been implemented yet on the deployed UMTS systems, although UTRA-UMTS preview their operation and they also could improve capacity especially in a multiservice environment. This paper describes a set of novel measurement techniques that must be performed to evaluate the correct operation of a smart antenna system. The paper also describes the measurements carried out on a UMTS smart antenna prototype.
This paper presents the complete Antennas radiated performance measurement process within the frame of the AMC12 satellite program for SES-AMERICOM customer, from antenna sub-system level to spacecraft system level. Three long focal offset antennas are implemented on AMC12 spacecraft (see Figure 1-1). Each antenna was measured at both sub-system and system levels, within two different test ranges: • a Near-Field Antenna Test Range (NFATR), • a Compact Antenna Test Range (CATR), at sub-system and system levels respectively. Comparisons for co-polarization gain, XPD and co-polarization isolation between predictions and sub-system measurements on one part, between sub-system and system measurements on the second part will be presented. An effective correlation will be shown at each level. Two antennas are located on the West panel of the spacecraft. This configuration required to measure one antenna in presence of the adjacent reflector with the aim to validate the minimal coupling effect according to the conclusion of the antenna design. With this measurement method, all the physical effects are taken into account and the RF performances are directly representative of in- orbit spacecraft deployed configuration. Comparisons between sub-system level measurements and predictions will be presented.
ELTA is now in the process of designing and building a new spaceborn SAR “TECSAR” – Israel Synthetic Aperture Radar (SAR) X-Band lightweight satellite. TECSAR contains an ultra-light weight high accuracy Paraboloid deployable reflector antenna. TECSAR’s electronic beam steering capability is achieved by using a feed array in the focal plane. For future testing at ELTA, Israel, an horizontal Planar near-field antenna test range (7m x 8m scan) has recently been completed by ORBIT/FR to allow testing of large fully integrated space antennas as stand alone as well as integrated with a satellite The paper will describe: o Short TECSAR SAR antenna description o The special requirements of the measurement system o System design and measured performance
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, 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 for the 110-170 GHz band. For the next leap, the 170-260 GHz band, a solid- state concept based on multipliers has been chosen. The experience with both systems and the pro’s and cons will be clarified
The purpose of this paper is to present antenna measurement techniques of antenna modules for Satellite Digital Audio Radio System (SDARS). SDARS employs dual-transmitter broadcasting formats which include simultaneous transmission of signals from both satellites and terrestrial transmitters. An SDARS antenna efficiently receives both satellite and terrestrial signals: it has relatively good circularly polarized gain at high elevation angles and acceptable linearly-polarized gain at the horizon. Popular SDARS antennas are small ground- depended patch antennas etched on ceramics and ground- independent mast antennas such as quadrifilars. Ceramic patch antennas have a relatively narrow bandwidth of operation. Thus, tuning such antennas to the right frequency is critical. The measurement techniques presented help engineers and technicians evaluate SDARS antennas and determine whether they are correctly designed. We shall describe hardware platforms for evaluating impedance, radiation characteristics, and real-world performance. Parameters such as VSWR, antenna gain, axial ratio, as well as receiver satellite C/N and terrestrial BER will be discussed.
Satimo’s STARGATE probe array systems are now well established as an efficient tool for testing radiated performances of wireless devices and antennas. Since 1998, about forty STARGATE measurement systems have been successfully installed worldwide. Recently, a range of new applications have also demonstrated the suitability of probe arrays for large radiating structures and directive antennas. These new generation of measurement set-ups present innovative aspects regarding their rapidity, dynamic range, and accuracy. This paper will describe several novel antenna testing concepts based on probe arrays that cover automotive, aerospace, and military applications and a wide range of frequencies. The basic difference between traditional approaches using single probe and the STARGATE approach using an array of probes will be explained along with probe array calibration procedures. An error analysis budget using the conventional NIST error terms will be presented including the specific terms related to the use of probe arrays. Also a discussion will be made on some of the key technical challenges to making large probe arrays including such issues as dynamic range, mechanical tolerances, and data truncation effects.