Errors In Near-field Measurements Research Articles

Near-field qualification methodology

A methodology that is a combination of analysis, computer simulation, component certification, self-tests, and comparison tests is presented for the accuracy qualification of near-field antenna measurement ranges. The analysis uses closed-form equations to establish upper-bound far-field determination errors due to near-field measurement errors. Computer simulation is used to model the specific near-field measurement errors associated with the near-field measurement system components. The closed-form equations and computer simulations are used to form a near-field error budget for each of the near-field measurement system components. A near-field system component certification is undertaken to measure the near-field measurement system component error and establish that they are within the error budget. >

Far-field uncertainty due to random near-field measurement error

Recent planar near-field scanning tests with ultralow-sidelobe antennas have confirmed that random near-field measurement errors will ultimately limit the accuracy of far-field patterns. A formulation is outlined for estimating the spectral signal-to-noise ratio (SNR) arising from noncorrectable near-field random measurement errors. The formulation applies to arbitrarily directive test antennas and probes-even nulling probes. A far-field parameter, called the scan plane coupling factor, may be computed directly from the near-field data, and then used to form the spectral SNR. The accuracy of the spectral SNR is confirmed by simulation and by actual tests with low-sidelobe AWACS array antenna.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sampling errors in near field measurements on non-planar surfaces

Techniques of predicting the radiated field of a vibrating structure from measurements of its near field are well known. The effects of spatial sampling and measurements errors on the calculated radiated field have been investigated by several authors for planar measurement surfaces. In this paper an extension of these analyses to non-planar surfaces is presented. Examples of the application of the new sampling criteria and error calculations are shown for a cylindrical near field measurement surface.

Errors in near-field measurements and their effect on computed radiation patterns

An upper limit is deduced for the error produced in radiation patterns computed by Fourier analysis of near-field measurements owing to deviations from a prescribed transfer function.