A circular loop antenna with nonuniform current distribution

An analysis for the far field of a filamentary loop antenna with nonuniform current distribution is presented. In order to obtain a possible current distribution, an analogy between a circular transmission line and a parallel-wire transmission line is made. This analogy yields a standing wave of current similar to that found on a lossy parallel-wire line. Considering only the far field of the antenna, the differential expressions for magnetic flux density are set up and the resulting equation is solved. The solution gives the magnetic flux density at a distant point from the antenna. Loops with uniform current and loop with sinusoidal current distributions are own to be special case of the general solution. To verify the validity of the assumed current distribution, the experimental patterns of a loop long are compared with calculated patterns. Results indicate that the field solutions are probably applicable to loops many wavelengths long.