Investigation on Current Reduction Effects of Baluns for Measurement of a Small Antenna

When connected to a small antenna that is undergoing testing, metal cables, such as coaxial cables, sometimes cause significant errors. This effect can be large when the antenna and ground plane are small and asymmetric. A balun is proposed for use in antenna measurement to reduce the influence of measurement cables. Baluns were originally utilized for a transformer set between unbalanced and balanced lines to feed a balanced antenna, such as a dipole antenna. Many types of baluns are used to transform unbalanced lines into balanced lines, and vice versa. However, when it comes to the utilization of baluns for antenna measurement, it is not clear whether all types of baluns can reduce the influence of the measurement cable. In this paper, baluns are sorted into two groups with regard to their effect on the reduction in unbalanced current when measuring a small antenna. Furthermore, the effect of a balun on improving the accuracy of impedance and radiation pattern measurements is also investigated.