Antenna phase centre movement in UHF radio positioning systems

Yagi array configurations, such as those commonly used in UHF Electronic Distance Measuring (EDM) systems, are analyzed to show that antenna phase center movements may occur within the antenna main-beam pattern and the movement of phase center is directly related to the angular derivative of the polar radiation pattern. A simple technique is proposed for qualitatively estimating the suitability of any antenna for this type of EDM application. A complete model is presented to evaluate the error introduced for any transmitter-receiver antenna orientation. Extensive results are presented for 7- and 12-element Yagis such as are commonly used in the SYLEDIS UHF radio positioning system.