Antenna Radiation Efficiency Measurement in an Ultrawide Frequency Range

Conventional antenna radiation efficiency measurement techniques, such as the Wheeler cap, are generally narrowband and, thus, well suited for resonant antennas. In this work, the Johnston-Geissler (J-G) method based on the Wheeler cap principle is used in a wide frequency range. First, a good agreement between measurement and simulation in an ultrawide frequency band is shown on a straight wire monopole antenna with different attenuators emulating antenna losses. Then, this technique is used to measure the radiation efficiency of several ultrawideband (UWB) antennas.