In this paper, different arrangements of infinite arrays of nonlinearly loaded antennas are analyzed in the frequency domain by an efficient approximate method and compared with the exact one with the aim of validity. The approximate method is based on the nonlinear current approach, while the second one is based on the harmonic balance. In one hand, although the harmonic balance technique is suitable for strongly nonlinear load, it is suffering from gradient operation and initial guess in the iteration process especially under multi tone excitations. On the other hand, although the approximate approach is very efficient, it is limited to weakly nonlinear loads and low-valued incident waves. Finally, validity ranges for the approximate method versus different parameters such as nonlinearity effect of the load are extracted.