Measurement model based uncertainty evaluations for calibrations of dipole-like antennas

Dipole-like antennas are typical calibrated over a conducting ground plane using the standard site method (SSM) in the VHF band. This paper provides an uncertainty evaluation for antenna factor (AF) measurement results obtained from use of the SSM for these type of antennas (using biconical antennas as an example). The paper addresses two critical issues, i.e., the applicability of the GUM approach, and the completeness of the measurement equation used. The uncertainty analysis for antenna calibrations begins with a basic equation for transmission between two antennas over a ground plane. The basic SSM equation, which includes the ground plane reflection consideration, is used to derive the measurement model. We study how various parameters that are not included in the basic SSM model (such as antenna mutual couplings, near field effects, site imperfections, and reflections from antenna supports, etc.) are encompassed by the uncertainty analysis. In addition, the non-linearity of the measurement model equation raises the question whether the GUM approach is appropriate. We implement a Monte Carlo method based on Supplement 1 to the GUM (GUMS1), because it overcomes the limitations of the GUM method. We also provide the programming codes for the expanded uncertainty calculation, so that others can easily adapt the approach for their specific use.