Near-field Antenna Measurements Research Articles

A New Method for Avoiding the Truncation Error in Near-Field Antennas Measurements

A new method to avoid the truncation error in antenna near-field measurements is presented. The approach relies on the concept of information content of the field. According to this point of view, the truncation problem is solved by picking up the information that is lost due to the finite size of scanning area, in points of the space reachable by the measurement system. The method can be applied to any scanning geometry, including the planar and cylindrical ones, whenever the set-up allows to vary the distance between the antenna under test and the probe during the scanning procedure. Application of the method to cylindrical near-field scanning is numerically investigated, assessing the effectiveness of the proposed technique

Application of the iterative probe correction technique for a high-order probe in spherical near-field antenna measurements

An iterative probe-correction technique for spherical near-field antenna measurements is examined. This technique has previously been shown to be well-suited for non-ideal first-order probes. In this paper, its performance in the case of a high-order probe (a dual-ridged horn) is examined

Quantitative measures of comparison between antenna pattern data sets

Frequently in test, measurement and development, there is a requirement to compare two or more supposedly identical data sets. These data sets may be acquired as: test data (does the data set fall within a given level of conformance); validation data (do the results confirm the applicability of a test methodology or design process); and calibration data (the data is required to act as a benchmark against which other measurements will be assessed). An example of such data is the far-field three-dimensional radiation pattern of antennas, which may be measured repeatedly on the same or different antenna test ranges. The requirement for objective, quantitative and robust methods of assessing such data, is discussed and confirmed. In addition, the constraints placed on these assessment methods, applied by the nature of the measurement process and the measurand, are highlighted and examined. Data sets that can be used to illustrate the application of these comparison techniques are presented and a preliminary assessment of them made using previously established techniques. These data sets embody a variety of subtle and specific characteristics that stem from particular known error sources. The limitations of these established assessment techniques are discussed and used to motivate the development of newer, more sophisticated analysis, where the data sets are further processed to yield objective measures of comparison. A variety of new assessment techniques that satisfy the aforementioned constraints are then presented and their various merits are compared and contrasted to illustrate their applicability to the classification and analysis of large data sets derived from near-field antenna measurements.

Iterative probe correction technique for spherical near-field antenna measurements

An iterative probe correction technique is presented to correct for the errors caused by the application of the traditional first-order probe correction for nonideal first-order probes in spherical near-field antenna measurements. The technique may be applied, with certain restrictions, for more general probes as well.

Scan-plane reduction techniques for planar near-field antenna measurements [AMTA corner

In this work, two planar near-field scan-plane reduction techniques are considered and results are presented. It is shown how truncation based on field-intensity contours, instead of simple geometric truncation, can in some cases improve the efficiency of the truncation process. Both techniques are applied to measured data sets, and it is shown how these methods can be used to reduce data-acquisition times, while also assessing the impact of the total acquisition surface reduction on the far-field radiation-pattern integrity.

Scanner With Transmission Line for Conventional Planar Antenna Near-Field Measurement in the Short Millimeter Waveband

Design options are considered for scanning systems for conventional planar antenna near-field (complex) measurement in rectangular grid of coordinates in the short millimeter waveband. These mechanical scanners carry transmission lines made on superdimensional hollow waveguides and compensation mechanisms in the form of two trombones to maintain the constancy of the geometrical path length in the scanning process.

Modified two‐probe approach for amplitude‐only near‐field measurements

AbstractA simple, effective technique for phase retrieval of antenna near‐field measurements is presented. This technique is based on using two similar scanning probes to collect four scalar near‐field measurements simultaneously, namely, the squared voltages received by two probes, the squared value of the summation of the received voltages by the two probes in phase, and the squared value of the summation of the received voltages by the two probes shifted by an arbitrarily known phase shift. A simple relation is used to retrieve the phase distribution by utilizing these four scalar measurements. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 270–273, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20114

Control of scattering from probes for near-field antenna measurements by use of skirt

A novel approach to reducing the multiple reflections between the test antenna and the probe in near-field antenna measurements is proposed. Instead of absorbers, this approach makes use of a skirt on the probe to shield against the mounting structure behind the probe.

A general and effective clutter filtering strategy in near-field antenna measurements

A general strategy to reduce the effect of the clutter noise in near-field measurements is presented. The approach exploits the band-limitation properties of the radiated field in order to filter the noise in the near-field data before far-field pattern evaluation. The method requires a simple lowpass filtering of the data, collected at suitably chosen sampling positions, after the extraction of a proper phase function. It holds for general scanning and source geometries, and is robust with respect to truncation of measured data owing to the finite dimensions of the scanning area. Numerical and experimental results confirm the effectiveness of the technique.

The bi-polar near-field antenna measuring system at wroclaw university of technology

This paper presents a near-field antenna measurement system that was developed in-house. The capabilities of our bi-polar system were extended by a backward-projection processing of data. The amplitude and phase distribution within the array elements can thus be reconstructed. Major applications of the presented near-field system are in research on advanced beamforming, and in investigations into large-scale integration of lightweight arrays. The results presented were obtained for planar microstrip arrays, and for a phased array operating between 5 GHz and 12 GHz.

Strategy to avoid truncation error in planar and cylindrical near-field antenna measurement setups

A simple and effective method to avoid the truncation error in antenna near-field measurements is presented. The method can be applied to planar or cylindrical near-field setups, whenever it is possible to vary the distance between the antenna under test and the probe during the scanning procedure.

Probe-position error correction for time-domain planar near-field antenna measurements

In order to construct the far-field pattern of an antenna in the time domain from its near-field samples, uniform sampling techniques have been widely used. If a signal is unequally sampled due to ...

Real-time spherical near-field handset antenna measurements

A new spherical near-field measurement system, dedicated to personal-communications applications, has been installed at e-tenna Corporation. The system, sold by Satimo, uses an electronically scanned probe array, and offers a dramatic reduction of the measurement time (by a factor ranging from 60 to 1,000) with respect to conventional mechanical scanners. This test range has undergone extensive acceptance testing, which has verified the specified measurement accuracy. The speed of the system, combined with the availability of full-sphere measurement data, enables rapid measurement of antenna efficiency. The system also enables the measurement of other parameters, such as the percentage of radiated power dissipated into the body of a human test subject operating a cellular telephone.

Spacecraft antenna measurement eliminating gravity effect by using planar near-field antenna measurement technique

Spacecraft antenna measurement eliminating gravity effect by using planar near-field antenna measurement technique

Phaseless bi-polar planar near-field measurements and diagnostics of array antennas

Antenna near-field measurements typically require very accurate measurement of the near-field phase. There are applications where an accurate phase measurement may not be practically achievable. Phaseless measurements are beginning to emerge as an alternative microwave antenna measurements technique when phase cannot be directly measured. There are many important aspects for successful implementation of a phaseless measurement algorithm. This paper presents appropriate phaseless measurement requirements and a phase retrieval algorithm tailored for the bi-polar planar near-field antenna measurement technique. Two amplitude measurements and a squared amplitude optimal sampling interpolation method are integrated with an iterative Fourier procedure to first retrieve the phase information and then construct both the far-field pattern and diagnostic characteristics of the antenna under test. In order to critically examine the methodologies developed in this paper, phaseless measurement results for two different array antennas are presented and compared to results obtained when the near-field amplitude and phase are directly measured.

Near-field antenna measurements using nonideal measurement locations

We introduce a near-field to far-field transformation algorithm that relaxes the usual restriction that data points be located on a plane rectangular grid. Computational complexity is O(Nlog N) where N is the number of data points. This algorithm allows efficient processing of near-field data with known probe position errors. Also, the algorithm is applicable to other measurement approaches such as plane-polar scanning, where data are collected intentionally on a nonrectangular grid.

Microwave antenna imaging, diagnostics, and phaseless reconstructions

Microwave antenna imaging techniques are a practical and popular method for antenna diagnostic analysis. Phase retrieval methods, however, are just beginning to emerge as an alternative microwave antenna measurements technique when phase cannot be directly measured. This article focuses on recent advances in microwave antenna imaging, diagnostic techniques, and phase retrieval methods for bi-polar planar near-field antenna measurements. An overview of the bi-polar planar near-field technique is included. The application of optimal sampling interpolation, holographic imaging and diagnostics, and iterative Fourier phase retrieval for the bi-polar planar near-field modality is explored in detail. Experimental results for a waveguide-fed slot array antenna are presented to illustrate these methods. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 396–406, 1997

Linear spiral sampling for the bipolar planar near-field antenna measurement technique

This paper investigates linear spiral sampling for bipolar planar near-field antenna measurements. This sampling scheme is, depending on range implementation, the most rapid polar near-filed data acquisition mode. The near-field to far-field transformation is performed using a modified optimal sampling interpolation (OSI)/fast Fourier transform (FFT) approach. Measured far-field pattern results for a waveguide-fed slot array antenna are presented and are shown to have excellent agreement with results obtained from a conventional bipolar measurement.

The bi-polar planar near-field measurement technique, part I: implementation and measurement comparisons

A novel customized bi-polar planar near-field antenna measurement technique is presented as an alternative to the plane-rectangular and plane-polar measurement techniques. The bi-polar near-field scanner incorporates an axially rotating test antenna and a rotating probe-carrying arm to sample the near-field on a data grid consisting of concentric circles and radial arcs. This technique offers a large scan plane size with reduced "real estate" requirements and a simple mechanical implementation resulting in a highly accurate and cost-effective antenna measurement and diagnostic system. Part I of this two-part paper gives an introduction to the bi-polar near-field technique and a description of the unique hardware implementation at the University of California, Los Angeles (UCLA). Measured results are compared with those produced by a far-field range and a plane-rectangular planar near-field range to verify the implementation and validate the method. Excellent agreement was obtained for both the co-polarized and cross-polarized fields.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Planar near-field scanning in the time domain .2. Sampling theorems and computation schemes

For part 1 see ibid. vol.47, no.9, p.1280 (1994). Two computation schemes for calculating the far-field pattern in the time domain from sampled near-field data are developed and applied. The sampled near-field data consists of the values of the field on the scan plane measured at discrete times and at discrete points on the scan plane. The first computation scheme is based on a frequency-domain near-field to far-field formula and applies frequency-domain sampling theorems to the computed frequency-domain near field. The second computation scheme is based on a time-domain near-field to far-field formula and computes the time-domain far field directly from the time-domain near field. A time-domain sampling theorem is derived to determine the spacing between sample points on the scan plane. The computer time for each of the two schemes is determined and numerical examples illustrate the use and the general properties of the schemes. For large antennas the frequency-domain computation scheme takes less time to compute the full far field than the time-domain computation scheme. However, the time-domain computation scheme is simpler, more direct, and easier to program. It is also found that planar time-domain near-field antenna measurements, unlike single-frequency near-field measurements, have the capability of eliminating the error caused by the finite scan plane, and thus can be applied to broadbeam antennas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>