Acceleration of Measurement of Array Antennas Using Inverse Source Techniques and Information on a Single Radiating Element

In most current professional indoor antenna measurement systems, the far-field distance is often too large for a practical shielded and anechoic chamber; hence, the measurement is done in the near field region, and the collected data computationally processed to yield the desired far field pattern; this process is called the "Near-Field to Far-Field transformation". The cost of a measurement is proportional to the number of samples to be measured; the minimum number of necessary samples is ruled by a result equivalent to the sampling theorem for signals, and usually called the Nyquist limit. In this work, the number of necessary near-field samples is reduced beyond the Nyquist limit by adding information on the geometry of the antenna under test (AUT), and by simulations of parts of the AUT. This endeavor is made specific for an array antenna, composed of several (nearly) identical antennas interconnected by a network call beam-forming network. The approach is based on the equivalence theorem, and a technique called inverse source; the latter yields the fields on a given source from field samples measured outwards. The on-surface fields on individual antennas (called equivalent currents) are used as basic building blocks to describe the far-field radiation. The relative reconstruction error with respect to the reference and different methods are discussed.