Interpolation of Missing Antenna Measurements or RCS Data Using the Matrix Pencil Method

When measuring the near-field of an antenna, often there are gaps in the measured data where the radiated fields are too low in magnitude to be measured or the measurement probe can't physically reach. Similarly in the measurement of RCS data such gaps can also be observed due to various physical limitations. To address this problem in the measurement of the field data, the antenna characteristic is measured over a certain elevation range, theta, up to the point where measurement becomes difficult or inaccurate. The gap in the data is then approximated using the matrix pencil method. By applying the matrix pencil method, the data is interpolated or extrapolated using estimated residues and poles of an exponential signal model. The Total Least Squares (TLS) implementation of the Singular Value Decomposition (SVD) is used to obtain the residues and poles from the data. Once these parameters are obtained, the nearfield can be estimated by a sum of complex exponentials. The far-field is obtained by using a spherical near to far-field transformation. A numerical example is provided to show the applicability of the matrix pencil method in interpolating a gap in antenna measurement data. Similar methodology can be applied to the RCS data.