Extension of Single-Cut NFFFT to Multi-Cut Fresnel- Field FFT Depending on Antenna Height

We propose an extension of a single-cut near-field far-field transformation (SCNFFFT) to a multi-cut Fresnel-field far-field transformation (MCFFFFT) depending on the height of an antenna under test. The new transformation is a natural extension of the SCNFFFT proposed in [1] and makes it possible to measure the single-cut plane pattern for an antenna with the height of many wavelengths, whose patten cannot be obtained by the SCNFFFT. Using our cylindrical near-field measurement system composed of an EO probe and a lock-in amplifier, that does not need a vector network analyzer [2], we demonstrate that the MCFFFFT gives the correct patterns of a horn antenna with 23 dBi at 76.2 GHz when the antenna is rotated around the boresight direction and the SCNFFFT cannot be applied, in simulations and measurements.

I. Introduction

Beyond 5 G or 6G communication is predicted to use 300 GHz band and the characterization of the antennas for the Beyond 5G or 6G are required. In order to realize the measurement system for 300 GHz band, the new photonics-based near-field measurement system without a vector network analyzer has been proposed [2] and demonstrated that the planar near-field scanning system can measure the patterns of a horn antenna with 25 dBi at 286 GHz.