Near-field to far-field pattern measurements for a low-frequency FR-ORA

This paper presents the radiation pattern of a low-frequency FR-ORA array based on the low-cost planar surface near-field to far-field measurement system. The far-field pattern was obtained from near-field measurements and by using a Fast Fourier Transformation (FFT) algorithm. This technique was used to characterize the radiation pattern of a prototype 4 × 4 fractal octagonal ring antenna array (FR-ORA). The low-frequency capacitively coupled array comprises fractal octagonal ring plates distributed to accommodate a dual-polarization feeding scheme, an electrical ground plane and a resistive substrate of square rings inserted between the radiating elements and the ground plane. The three-dimensional electromagnetic field simulation demonstrated that the near-field to far-field transformation is a convenient and cost-effective method of predicting far-field patterns for the FR-ORA.