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This paper will discuss the development of a VHF/UHF near field test range for the case where there are reflections from a realistic ground surface. We will show the results of a direct computation algorithm where a far field pattern is computed using plane wave synthesis. The performance of a C++ program that implements this algorithm will be discussed.
Abstract. Scientists at the National Institute of Standards and Technology (NIST) have measured the gain of several antennas using two different methods. The first method is the three-antenna extrapolation method developed at NIST in the early 1970s. The second method is the far-field pattern integration method. We compare gain results and gain uncertainties for several antennas using these two methods.
ABSTRACT A design of a spherical two-arch multi-probe antenna measurement system for measuring radiation patterns of mobile phones is presented. The proper functioning of the designed system is shown partly by computer simulations and partly by practical measurements with Rapid Antenna Measurements System (RAMS) at Helsinki University of Technology.
A method is presented to measure the antenna pattern of an AUT where the antenna port is inaccessible. That means that it is not possible to connect a test cable, nor can the termination be changed physically. In some cases there is no test port at all. The only variation possible is to change the input impedance of the first receiver or LNA by switching it on and off. An RCS-technique can be used to retrieve the radiation pattern. By experimental comparison between the conventional pattern measurement technique and the RCS-technique it is shown that pattern determination via RCS-measurements is feasible. In addition, the measurement method offers the advantage of directly reducing the influence of systematic measurement errors. On the other hand, the penalty is put on power efficiency and a subsequent limited dynamic range.
Payload testing is the only measurement where the real Significant reductions in the overall test time radiated end-to-end performances of the satellite are requirements for satellite EIRP/IPFD measurements measured and compared with respect to predictions. These are achievable if the traditional single polarization or critical measurements are performed in the ALCATEL narrow band dual polarization illuminators are ALENIA SPACE Compact Antenna Test Range in substituted with efficient wideband probes in dual Cannes as shown in Figure. 1. polarization. For C-band payload testing, the frequency bands of interest cover more than an entire octave: 3.4-4.8GHz (Tx) and 5.6-7.1GHz (Rx). The cross polarization and taper requirements on the field of view are such that a flared aperture horn can satisfy the requirement but the polarization purity places rather stringent requirements on the orthomode transition in terms of on-axis cross polarization levels and port to port coupling. A suitable probe for this application consists of two components: orthomode transition and radiating aperture. A flared aperture horn, including a stepped matching section, has been designed by ALCATEL ALENIA SPACE to satisfy the illumination Fig 1: ALCATEL ALENIA SPACE Compact Antenna specification. A wide-band dual polarized orthomode Test Range in Cannes. transition covering the entire C-band Tx and Rx During payload testing the antenna pattern measurements ranges has been developed by SATIMO to feed the and other systems tests are carried out. Two of the key horn. The effective bandwidth of the orthomode payload tests are the Equivalent Isotropic Radiated Power transition more than exceeds the specification and it is (EIRP) and Input Power Flux Density (IPFD) of the usable even throughout the Ku band. The final spacecraft [14]. illuminator has been manufactured by SATIMO and delivered to ALCATEL ALENIA SPACE for test in The EIRP is an indication of the power level capability of the Compact Antenna Test Range in Cannes. the telecommunication satellite within a given coverage This paper describes the definition of the performance on the earth surface. This performance is directly linked to specifications, the baseline horn and applied OMT the power budget of the satellite and to the requirements technology and final validation measurements. on the end user parabola diameter. The IPFD is a useful parameter to determine the needed power on the earth
This paper presents measurements of the CloudSat Collimating Antenna (CA) as fabricated for the 94.05 GHz CloudSat radar, which is to be used to measure moisture profiles in the atmosphere. The CloudSat CA is a 3 reflector system consisting of the 3 "final" (relative to the transmitted energy) reflecting surfaces of the CloudSat instrument. This assembly was fed by a horn designed to approximate the illumination from a Quasi-Optical Transmission Line (QOTL). This same horn was employed as a "standard" for measurement of the CA gain via substitution, and its patterns were also measured (this substitution represents a departure from the standard insertion loss technique in the near field range). The CloudSat CA presented a substantial measurement challenge because of the frequency and the electrical size of the aperture is approximately 600 wavelengths in diameter, with a nominal beamwidth of 0.11 degrees. In addition, very high accuracy was needed to characterize the lower sidelobe levels of this antenna. The CA measurements were performed on a 3122-ft outdoor range (this distance was 41% of the far field requirement), which were immediately followed by measurements in an indoor cylindrical Near Field (NF) range. The instrumentation challenges, electrical, mechanical, and environmental are described. Comparison of the outdoor vs. indoor pattern data is presented, as well as the effect of the application of tie-scans to the near field data.
The performance of modern Satellites Antennas and Payloads is characterized by physical parameters like e.g. Antenna Pattern and Gain; EIRP, Flux Density, G/T and the overall PIM-performance. The available time frame for measurement of these parameters is getting constantly shorter. The EADS Astrium GmbH Compensated Compact Range (CCR) allows a time efficient measurement of all payload parameters with high accuracy under controlled environmental conditions. In addition to an efficient measurement facility high-performance measurement equipment is required. The economical budgets of most space programs demand the application of well-known measurement techniques in a cost efficient way. EADS Astrium GmbH supported by Agilent Technologies GmbH has developed an easy to handle and therefore cost optimized measurement platform for Satellite Payload Measurements. This platform consists mainly of a generic Agilent switch matrix operating up to 40GHz which can be connected to a wide range of measurement equipment. The matrix allows a highly flexible routing of the RF uplink and downlink signals including reference paths. Integrated and/or external RF components, like amplifiers, attenuators, and hybrids can be added to the paths, depending on the required test configuration. Starting from a minimum configuration the system can be modularly upgraded to satisfy any further test requirements. The software interface utilizes standard protocols and can be therefore easily addressed by any user specific measurement software. The EADS Astrium GmbH Advanced Antenna Measurement System (AAMS) includes an optional payload toolbox which provides a modular concept expandable for additional test functions.
ABSTRACT We have developed a new compact spherical near-field measurement system using a photonic sensor as a probe and successfully measured the 3D antenna patterns of a double-ridged horn antenna from 1 GHz to 10 GHz. This system consists of a compact spherical scanner and a photonic sensor that is used for the probe of the spherical near-field measurements. In our system, only one probe can be used for the wide frequency range measurements and the probe compensation is not needed in the measurements. For the system, we propose a simple calibration method using a double-ridged horn antenna for our system. We calibrate the system by measuring the double-ridged horn antenna on the reasonable assumption that the antenna efficiency is 100 %. Comparing the absolute gain obtained by the proposed calibration method with the one decided by using three-antenna method at far-field range, we show that the agreement is good within 1 dB over the whole frequency range.
In this paper is presented an experimental investigation of conventional array calibration in the presence of various kinds of joint discontinuities between array panels. Two rigid array panels were positioned such that the element lattice was continuous across a narrow joint. Three kinds of discontinuities were applied to the joint: (1) an angle, (2) a gap (including an edge), and (3) a step between panels. Each type was investigated for joints oriented in the E-plane and the H-plane. Each discontinuity was also varied in magnitude so as to observe parametric effects. Planar near-field-range (NFR) measurements were made in a conventional array calibration mode and a near-field pattern mode. Processing included separating the pattern component due to element transmission (impedance) change from that due to pattern shape change. Results show that conventional calibration methods quickly become inadequate to calibrate these discontinuities because they change element pattern shapes.
A system for measuring large linear arrays of antennas has been developed, fabricated and tested. The system consists on a 12 meters structure where the antenna under test (a L band array of dipoles in this case) is positioned. The measurement probe (another dipole) moves on a linear slide and stops in front of each element of the array to acquire the electric field. All the system is installed on an semi-anechoic chamber, that can be lifted (with two synchronized stepped motors). This semi-anechoic chamber covers the top and side parts of the structure. The bottom part consists on a metallic reflector, that controls the reflections from each antenna element. Once the data is acquired, the data are processed to obtain the far field patterns and parameters of the antenna array (element amplitude and phase, beam width, side level, beam pointing …) All the results are presented in a windows environment, and all the system is integrated in a friendly user interface.
For many years now, GDAIS has described the development, characterization, and performance of an image-based circular near field-to-far field transformation (CNFFFT) for predicting far-field radar cross-section (RCS) from near-field measurements collected on a circular path around the target. In this paper, we present an improved version of the algorithm that avoids a stationary phase approximation inherent in earlier versions of the technique. The improvement is realized by modifying the range-domain weighting used to implement the frequency derivative in the existing method. A similar modification was presented in the context of linear near-field measurements in an earlier AMTA paper. Numerical simulations are presented that demonstrate the improvement afforded by the technique in predicting far-field RCS patterns from near-field data collected using typical bandwidths and standoff distances. An additional benefit of the revised algorithm is that it readily admits a formulation that includes antenna pattern compensation, as described in a companion paper.
In previous work [1], we presented an antenna pattern compensation technique for linearly-scanned near field measurements. In this paper, we present a similar technique to mitigate the errors from uncompensated azimuthal antenna pattern effects in circular near-field monostatic radar measurements. The antenna pattern co mpensation is implemented as part of an improved algorithm for transforming the near-field measurements to the far-field RCS. A description of this improved circular near field-to-far field transformation CNFFFT technique for isotropic antennas is presented in a companion paper [2]. In this paper, we formulate the near-field signal model in the presence of an azimuthal antenna pattern under the same scattering approximation used in the isotropic CNFFFT. Using this model, we derive a modified version of the CNFFFT that includes antenna pattern compensation. Numerical simulations are presented that demonstrate the ability of the technique to remove antenna pattern errors and improve the accuracy of the far field RCS patterns and sector statistics.
ABSTRACT Electronic devices designed for purposes other than transmitting and receiving electromagnetic fields nonetheless act as unintentional antennas. Measurements methods are needed to characterize these antennas for electromagnetic compatibility tests; however, the rigor of precision antenna measurements is typically too costly and time consuming for electromagnetic compatibility applications. Alternate approaches are needed. This paper presents analytical estimates for the directivity of unintentional antennas based on the assumption that unintentional antennas will only randomly excite the available propagating spherical modes at a given frequency. This directivity estimate is then compared to simulated and measured data. Good agreement is shown. Directivity estimates combined with simple total radiated power measurements represent a useful alternative to direct antenna measurements for electromagnetic compatibility tests.
Antenna systems are increasing in complexity at a rapid pace as advances are made in electronics, signal processing, communication, and navigation technologies. In the past, antenna design requirements have focused on parameters such as gain, efficiency, input impedance, and radiation pattern (e.g., beamwidth and sidelobe level). For some new systems, the group delay characteristics of the antenna are important, where the group delay is proportional to the derivative of the insertion phase as a function of frequency. The group delay is required to stay within certain bounds as a function of frequency and pattern angle. Unfortunately, there are not well established methods or standards for calibrating antenna group delay like the standard methods used for gain and input impedance. This paper presents a method for calibrating the group delay of three antennas based on an extension of the widely used three-antenna gain and polarization calibration methods. No prior knowledge of the gain or group delay of the three antennas is required. The method is demonstrated by a measurement example where it is shown that multipath errors and time gating can be critical for calibrating the group delay.
Parallax occurs in antenna measurements when the antenna under test (AUT) is located off the center of rotation (COR) of the test positioner axis. As the AUT is rotated while located off of the COR of the axis, the angle to the AUT as viewed from the source antenna is different than the angle to which the positioner is commanded. This results in a distortion of the antenna pattern, and can result in errors in beam shape and beam width. Knowledge of the test geometry allows for the determination of an appropriate mapping from the recorded test angles to the actual angles to the AUT as viewed from the source. This, in turn, allows for the possibility that the antenna pattern may either be corrected for the parallax error, or measured at the correct angles in order to avoid pattern distortion. ORBIT/FR has implemented a parallax correction in the 959Spectrum Antenna Measurement Workstation software that allows for flexibility in positioning angle correction, and in addition provides a useful tool for implementing unusual measurement test scenarios, such as measuring antenna data at a “list” of angles. This paper describes the parallax problem, the implemented solution, and provides examples of use of the implemented software feature.
An antenna measurement system was developed to complement a new rectangular anechoic chamber (20’L x 10’W x 9’7”H) that has been established at California Polytechnic State University (Cal Poly) through donations and financial support from industry and Cal Poly departments and programs. Software algorithms were written to provide four data acquisition methods: continual sweep and step mode for both single and multiple frequencies. Log magnitude and phase information for an antenna under test is captured over a user-specified angular position range and the antenna's radiation pattern is obtained after post processing. Pattern comparisons against theoretical predictions are performed. Finally an RF link budget is calculated to evaluate the performance of the antenna measurement system.
Reflections in antenna test ranges can often be the largest source of measurement errors, dominating all other error sources. This paper will show the results of a new technique developed by NSI to suppress reflections from the radome and gantry of a large hemi-spherical automotive test range developed for Nippon Antenna in Itzehoe, Germany. The technique, named Mathematical Absorber Reflection Suppression (MARS), is a post-processing technique that involves analysis of the measured data and a special filtering process to suppress the undesirable scattered signals. The technique is a general technique that can be applied to any spherical near-field test range. It has also been applied to extend the useful frequency range of microwave absorber in a spherical near-field system in an anechoic chamber. The paper will show typical improvements in pattern performance and directivity measurements, and will show validation of the MARS technique using data measured on antennas in a conventional anechoic chamber.
ABSTRACT A unified theory of near-field spiral scans is proposed in this work by introducing a sampling representation of the radiated electromagnetic field on a rotational surface from the knowledge of a nonredundant number of its samples on a spiral wrapping the surface. The obtained results are general, since they are valid for spirals wrapping on quite arbitrary rotational surfaces, and can be directly applied to the pattern reconstruction via near-field–far-field transformation techniques. Some numerical tests, assessing the accuracy of the technique and its stability with respect to random errors affecting the data, are reported with reference to the case of the helicoidal scan.
At the Institut Fresnel in Marseille (France), we created an original experimental setup in order to test antennas and carry out scattering measurements in both monostatic and bistatic configurations. The main advantage of this setup is, of course, the multipurpose feature. Two main mechanical systems are installed in a large anechoic chamber. The first system is a spherical positioning setup which allows measurements of antennas and scattered fields for both bi-dimensional (2D) and three-dimensional (3D) targets. This setup consists of two carriages moving on a circular vertical arch and a third carriage which follows a circular path on a horizontal plane. A transmitter and a receiver can be fixed on any of these three carriages. A fourth rotating stage in the center of the spherical setup fixes the angular position of the antenna under test or of the scattering target. The second system is a far-field positioner which allows the measurement antenna patterns and RCS. To illustrate our activities with this original setup, we first show measurements of a metamaterial antenna prototype and then some results of scattered fields obtained on 2D and 3D targets used in studies of electromagnetic direct and inverse problems.
Abstract This paper describes the development of an inexpensive high-precision Compact Antenna Test Range (CATR) located at CSIRO, Australia, for the measurement of electrically large aperture antennas (>250.) at 200GHz. The CSIRO designed CATR is based on a single parabolic offset reflector that has been machined from a single billet of cast aluminum plate to provide a RMS error of better than 16 µm as determined from photogrammetry. The design is unique as it leverages CSIRO’s ability to accurately design and manufacture feed horns with highly optimized radiation patterns; in this case corrugated feed horns with flat amplitude tapers at the beam maximum and fast amplitude roll-off at the edge illumination angle of the reflector. The advantage of using this type of feed horn is that it eliminates the need to specially treat the edges of the CATR reflector and therefore greatly reduces the cost of the system.