Development of Time-Domain Planar Near-Field Scanning Measurement Techniques

Near-field frequency domain meaasurements of antennas over a planar aperture are commonly used to obtain far-field patterns. This technique has now bben formulation in the time domain, which is very desirable for short pulse signals. An additional benefit, particularly significant for antennas with low-sidelobes, arises from time domain measurements in that edge effects of a finite aperture size can potentially be eliminated. Furthermore, the computational efficiency and simplicity of a time domain approach is comparable to a frequency domain approach when only a part of the far-field is calculated. Analytic Design, Incorporated (ADI) will develop an approach for a time domain measurement system to characterize target scattering and antenna radiation over wide bandwidths. This approach will be based upon ADI's experience in anechoic chamber integrated with measurement and numerical techniques. Using our extensive and detailed experience with time domain antenna systems, we have a unique broadband sensing probe concept which delivers a very flat frequency response with a broad pattern to produce very smooth time domain receiver characteristics. While this probe will require somewhat more numerical compensation, we believe that this concept is an excellent candidate for comparison against the electrically small, resistively-loaded dipole probe. In this effort, we will provide a comprehensive caparison of the two probe designs.