Millimeter-wave phaseless antenna characterization

Phaseless antenna characterization at millimeterwave frequencies is an awkward task for a number of reasons. First, suitable network analyzers appropriately working at a high frequency, as well as a complex hardware ensuring high positioning and alignment accuracies, are required. Furthermore, the characterization algorithm should be reliable and accurate and should require a reasonable measurement time, which is a key issue in the millimeter and submillimeter ranges. In this paper, we present an efficient algorithm that faces this problem by exploiting the available a priori information on the shape and size of the antenna. The reliability, accuracy, and stability of the approach reside on “effective” expansions of the unknown aperture field distribution, reducing the “effective” number of unknowns. “Fast” acquisitions are enabled by nonuniformly distributed near-field measurements. Rectangular and circular apertures are dealt with by introducing prolate spheroidal wave functions and a Jacobi–Bessel series representation of the aperture field, respectively. The performances of the approach and its effectiveness in the millimeter frequency range are proven by the experimental results at 40, 94, and 100 GHz, made at the Antenna Laboratory of the University of Napoli Federico II, on horn antennas and a Cassegrain reflector.