Characterization of Omnidirectional Antennas by Measurement of Their Complex Normalized Effective Height

Abstract

A systematic way is proposed to fully characterize omnidirectional antennas by measuring their complex normalized effective height (CNEH). Usually, antennas are utilized to convert the voltage waves in a waveguide into the vectorial electromagnetic fields in free space and vice versa; however, this conversion relationship cannot be fully expressed with the traditional antenna parameters, e.g., the antenna gain, and so on, because they are not vectorial and possess no phase information. CNEH is a versatile parameter, which can reveal accurately the relationship between the voltage waves in waveguides and the radiated fields in free space. The feature makes it particularly useful for the distributed antenna system or multi-probe array system. The measurement of a CNEH usually uses the far-field method; however, it is a challenge for omnidirectional antennas. We propose a novel method to precisely generate CNEHs based on the broadband calculable antennas. Experimental results show that the difference in transmission coefficient between a pair of calculate dipole antennas resonating at 90 MHz is less than 0.2 dB for amplitude and 2° for phase from 20 to 330 MHz; equivalently, the difference in CNEHs generated from calculable dipole antennas (CDAs) between measurements and calculations will be half of the above results. The key points for CDAs to achieve the superior performance are briefly introduced. Eventually, a way to calibrate the CNEHs of any omnidirectional antennas is illustrated by experiments. Some common antenna parameters are calculated from the CNEH; thus, we present a method to get many antenna parameters by one measurement.