A New Valid Angle Equation for PNF Measurements

A new valid far-field angle equation for rectilinear planar near-field measurements is presented. The new valid angle equation is derived by viewing the planar near-field to far-field transformation process as the generation of pseudo plane waves by a synthetic phased array. The synthetic phased array does not physically exist; rather, the array is formed during the post-processing of the planar near-field measurements. As part of this discussion, we present results from a numerical model, illustrating the total electric field present in the test zone due to the finite extent of the synthetic phased array. The new valid far-field angle equation accounts for the diffraction effects of the finite-sized synthetic array and uses the industry accepted test-zone magnitude ripple of +/- 0.5 dB to limit the valid far-field angle for a fixed scan plane size.