Comments on "Resolution of coherent sources incident on a circular antenna array"

In the above letter, a technique is presented for using a circular array of N equally spaced antennas to obtain the azimuths and strengths of M (M less than or equal to N/2) far-field sources. The procedure involves two basic steps: (1) use of a FFT (assuming N is a power of 2) to transform the N individual antenna-element strengths; (2) solution of an Mth-order linear system composed of the transformed data to find the coefficients of an Mth-order polynomial whose roots provide the azimuth angles. It is the purpose of this brief letter to mention that step 2 above is identical to Prony's Method, a procedure which underlies much of modern signal processing.