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Probe Array Correction With Strong Target Interactions
Interim rept. 1 May 2011-31 May 2012
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIR
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We analyze technical problems associated with using an array of probes to measure simultaneously the near fields scattered by a target to decrease collection times. Array-target coupling distorts the fields to be measured. Element mutual coupling modifies measurements. To minimize coupling, active loading at array elements with strong target interaction is analyzed numerically. Loading minimizes perturbations in the target currents. There is little advantage to using in-situ mutual impedances to determine loads. We provide a probe array compensation theory based on the Lorentz reciprocity theorem giving the open circuit probe array voltages. Voltage corrections are developed from array calibration and measurements of the incident plane wave. Numerical study shows that a corrections to the measured voltages due to the presence of the array are small and b corrections due to the other elements of the array can be important but corrected with calibration. Errors introduced by the use of realizable calibration sources and loads and experimental errors are estimated. Results of this study suggest a hybrid measurement process.
APPROVED FOR PUBLIC RELEASE