This paper presents a complementary analysis to the computation scheme previously introduced by Hansen and Yaghijan [1] and [2] for the time-domain near-field to near- or far-field transformation technique. The approach presented here aims to reduce the computation time and memory requirements, which represent the main drawbacks that make difficult the application of the technique to practical cases of interest. Computations with electromagnetic simulation of a circular X-band horn antenna illustrate the accuracy of the proposed method and the rapidity of the resulted near-field to near- or far-field transformation, while using the minimum number of measurement samples.