Probe compensation characterization in cylindrical near-field scanning

Hussein, Z.A.; Rahmat‐Samii, Y.

doi:10.1109/aps.1993.385554

Cited by 11 publications

(13 citation statements)

References 2 publications

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“…The near to far field conversion algorithm could be represented in the following diagram − see [4], [5], [6], [7] and [8] So, to obtain the far field from the cylindrical near field measured, the following calculations are completed: 1. First, the AUT cylindrical near field is acquired and sampled.…”

Section: Transformation Softwarementioning

confidence: 99%

Design of a cylindrical near field system for RADAR antennas

Jiménez¹,

Martínez²,

Castañer³

et al. 2006

2006 First European Conference on Antennas and Propagation

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A cylindrical near field measurement system for huge L-band RADAR antennas has been designed, and it is under construction. The cylindrical near field system consists of a 17 meters tower (15.5 meters linear scanning), placed at a distance between 4 and 7 meters from the centre of the RADAR antenna. The RADAR antenna is placed on its azimuth positioner, and the system must allow the measurement of the antenna without stopping the rotation movement, measuring two linear polarizations (horizontal and vertical). The system can work in both transmission and reception. The system must work in an open and windy area. To assure the rectitude of the z-axis, a servo controlled by an optical detector has been implemented. This paper presents the main specifications of the measurement system (mechanical and electrical) and its design process. The paper will explain the acquisition routines (optimised for reducing measurement time without stopping the rotational movement of the RADAR), the control of the motors and RF equipment, the near field to far field transformation software, the algorithms used to compensate some errors (as temperature variations) and, finally, the user friendly environment.

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Section: Transformation Softwarementioning

confidence: 99%

Design of a cylindrical near field system for RADAR antennas

Jiménez¹,

Martínez²,

Castañer³

et al. 2006

2006 First European Conference on Antennas and Propagation

View full text Add to dashboard Cite

show abstract

“…A third approach, introduced by Brown and Jull in [Brown & Jull, 1961] and Leach and Paris in [Leach & Paris, 1973], is based on the three-dimensional vector cylindrical wave expansion of an electromagnetic field which applies the Lorentz reciprocity theorem formulation to attain the complete vector farfield pattern of an arbitrary antenna. In addition to the procedure proposed by Leach, Bucci in [Bucci, 1988] and Hussein and Rahmat-Samii in [Hussein & Rahmat-Samii, 1993] studied some improvements in efficiency of this method. In the last years, some approaches to solve the problem of near-to-far-field transformation using equivalent currents have been presented, i.e.…”

Section: Introductionmentioning

confidence: 99%

Error Analysis and Simulator in Cylindrical Near-Field Antenna Measurement Systems

Sara¹,

Silva²,

Fernando³

et al. 2010

Advances in Measurement Systems

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Large antennas need special measurement systems because of their considerable dimensions. Typically, cylindrical near-field systems are appropriate measurement systems for omnidirectional antennas due to the characteristics of their radiation patterns. Furthermore, these systems are also appropriate for sizeable RADAR antennas, since they can be measured on their azimuthal positioner and the probe can be easily translated through a vertical linear slide. Thus, mechanical aspects of measurement systems are rather important since errors in the mechanical set-up can directly affect far-field radiation patterns. This chapter presents an error estimation tool to analyze the most important errors for large L-band RADAR antennas in an outdoor cylindrical acquisition system and the effect of these errors in the calculated far-field radiation pattern. This analysis can be very convenient to evaluate the error budget of the Antenna Under Test (AUT). The simulator computes the far-field with an array of vertical dipoles over a ground plane and compares an ideal infinite far-field with the electric field obtained using the cylindrical near-to-far-field (NF-FF) transformation algorithm. The influence of the inaccuracies on the final results is evaluated by introducing random and systematic sources of errors and then, analyzing the variations produced in the principal far-field patterns, antenna parameters and in the side lobe levels (SLL). Finally, this simulator can be employed to analyze the errors for L-band RADAR antennas. One of the objectives of this investigation is thus to analyse how mechanical and electrical inaccuracies could affect the results of a cylindrical antenna measurement system, in order to minimize them as much as possible. This is highly important not only to meet the specifications, but also to reach high accurate results. There are several error sources studies for near-field patterns: the most complete are the ones developed by Joy and Newell in [Joy,

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“…Once near-field data is acquired on a cylindrical surface surrounding the antenna as shown in Fig. 2, a data processing algorithm is used to give more details information on antenna radiation properties which would have required much conventional measurement work [4]- [8].…”

Section: Introductionmentioning

confidence: 99%

Application of cylindrical near-field measurement technique to the calibration of spaceborne radar antennas: NASA scatterometer and SeaWinds

Hussein

Rahmat‐Samii

1999

IEEE Trans. Geosci. Remote Sensing

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Modern spaceborne radar scatterometers such as the NASA Scatterometer (NSCAT) and SeaWinds radar instruments require precise determination of the normalized backscattered radar cross section within a few tenth of a decibel in order to achieve the desired wind velocity and direction measurement accuracy of 2 m/s and 20 degrees respectively. This high level of precision requires a priori pre-launch accurate knowledge and determination of the radar antenna's absolute gain and relative radiation patterns characteristics over wide angular range. Such characterizations may be performed on a far-field range or in an indoor near-field measurement facility. Among the unique advantage of the latter is that many information of the radar antenna radiation properties can be obtained anywhere outside the near-field measurement surface. Two different recently designed radar scatterometers are considered in this paper, NASA Scatterometer (NSCAT) and SeaWinds, to demonstrate the utility of a newly completed cylindrical near-field measurement range for the calibration of spaceborne antennas. As an example of an advanced calibration methodology, the data based on a recently measured JPL/NASA scatterometer (NSCAT) radar antenna are used to experimentally demonstrate the role of the probe pattern compensation, probe multiple reflection effects, probe mis-positioning effects, scan area truncation effects, etc, A measurement test on a standard gain horn have been performed to achieve and verify the absolute gain calibration accuracy. A comparison between direct far-field measured data and those obtained from cylindrical near-field measurements for the SeaWinds radar antenna was found in excellent agreement.

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Probe compensation characterization in cylindrical near-field scanning

Cited by 11 publications

References 2 publications

Design of a cylindrical near field system for RADAR antennas

Design of a cylindrical near field system for RADAR antennas

Error Analysis and Simulator in Cylindrical Near-Field Antenna Measurement Systems

Application of cylindrical near-field measurement technique to the calibration of spaceborne radar antennas: NASA scatterometer and SeaWinds

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