THE BIPOLAR PLANAR NEAR-FIELD MEASUREMENT TECHNIQUE .2. NEAR-FIELD TOFAR-FIELD TRANSFORMATION AND HOLOGRAPHIC IMAGING METHODS

A novel customized bi-polar planar near-field measurement technique Is presented in a two-part paper. This bi-polar technique offers a large scan plane size with minimal ''real-estate'' requirements and a simpl e mechanical implementation, requiring only rotational motions, result ing in a highly accurate and cost-effective antenna measurement and di agnostic system. Pert I of this two-part paper introduced the hi-polar planar near-field measurement concept, discussed the implementation o f this technique at the University of California, Los Angeles (UCLA), and provided a comparative survey of measured results. This paper exam ines the data processing algorithms that have been developed and custo mized to exploit the unique features of the hi-polar planar near-field measurement technique. Nearfield to far-held transformation algorithm s investigated include both interpolatory and non-interpolatory algori thms due to the atypical arrangement of the bi-polar near-field sample s. The algorithms which have been tailored for the bi-polar configurat ion include the optimal sampling interpolation (OSI)/fast Fourier tran sform (FFT), Jacobi-Bessel transform, and Fourier-Bessel transform. Ad ditionally, holographic imaging for determination of antenna aperture fields has been incorporated to facilitate antenna diagnostics. Result s for a simulated measurement of an array of infinitesimal dipoles and a measured waveguide-fed slot array antenna are included. Appropriate guidelines with respect to the advantages and disadvantages of the va rious processing algorithms are provided.