Number of degrees of freedom of the radiated field over multiple bounded domains

The problem of determining the number of degrees of freedom (NDF) of the field radiated by an electric current supported over a bounded rectilinear domain and observed over multiple bounded domains parallel to the source is addressed. The analysis is achieved by means of the singular value decomposition of the radiation operator so that the NDF is identified as the number of 'significant' singular values. The aim is to analyze whether the multidomain observation allows to increase the available NDF. By analytical arguments, we show that collecting data over multiple domains shapes the singular value behavior but it still presents a steep decay in correspondence to an index dictated by the observation domain that subtends the largest observation angular sector.