Fresnel-field range design: array element pattern considerations

Real-time antenna pattern measurements are usually performed using either a far-field range or compact range. Alternative measurement techniques have been proposed in order to reduce the measurement distance without using an optical device (i.e., reflector or lens) required for compact range implementation. Generally, this is accomplished by using an array to synthesize a uniform plane wave at near-field distances. Recently, an alternative plane wave synthesis method which employs a ring array geometry similar to that of Hald has been proposed. In this technique (McKay and Rahmat-Samii, 1993), a uniformly excited ring array is employed to compensate for the phase taper associated with a concentric radiator. Compensation is achieved using Fresnel zone approximations in conjunction with a graphical design approach carried out in the complex plane. The method results in simple design formulas and provides insight into fundamental limitations on the extent of the plane wave which can be generated. Several range design issues related to array element pattern effects are examined in this paper.<>