Comments on "Exact solutions of electromagnetic fields in both near and far zones radiated by thin circular loop antennas: a general representation" [with reply

Abstract

For original paper see Li et al. (IEEE Trans. Antennas Propagat., vol. 45, p.1741-8, 1997 Dec.). The paper by Li et al. presents closed form expressions in series form for the electromagnetic (EM) fields for both near and far zones due to thin circular loop antennas. Special cases such as fields due to sinusoidal and uniform current distribution in the circular loop antenna are given in the equations (14)-(18) of Li et al. However, the assumption of taking just the first term in the summation in (18) for electrically small loops compromises the accuracy of the field calculations for the near zone where the observation point is on or around the sphere r=a. Since the current in the loop is filamentary, the magnetic field will be singular in nature at r=a when /spl theta/=/spl pi//2. However, this behavior is not displayed by the magnetic field, which is computed by taking just the n=1 term of (18b), as shown in Fig. 2(b) and Fig. 3 of Li et al.. The present comment has recast (18b) and (18c) of Li et al. to illustrate the need for more terms for accurate representation of fields in the near field. A reply is given by Li et al. in which they explain the simplification of equation (18) into (20 and then (23).