A Crane-Based Portable Antenna Measurement System—System Description and Validation

A portable near-field (NF) antenna measurement system for frequencies up to Ka-band is presented and evaluated in detail. The system follows the idea to collect measurement samples on arbitrary scan surfaces in the NF, where strong irregularities of the sample distribution may be tolerated as long as appropriate sampling criteria are fulfilled. The radio frequency (RF) equipment is integrated in a gondola, which is positioned by a standard overhead crane. During an NF scan, the exact position and orientation of the probe antenna are measured by a 6-D laser tracking system with high accuracy. The RF measurement system works with a phase-coherent measurement loop, where the signal transmission from the ground station to the RF equipment within the portable gondola is performed by an optical fiber transmission system with three optical fibers, realizing magnitude as well as phase compensation. The NF measurement samples are merged with the position and orientation data and, finally, transformed into the far-field by a flexible and highly efficient equivalent source algorithm. The complete setup of this measurement system is presented and discussed in detail, focusing on both hardware and software aspects. A series of validation and practical antenna measurement results is presented to demonstrate the feasibility of this approach.