Characterisation of a D-Band Horn Antenna: Comparison of Near-Field and OTA Measurements

The small wavelength, typically in the range of millimeters to micrometers, makes characterisation of antennas at sub-THz band particularly challenging as it requires measurement systems to accurately capture the details of the antenna radiation patterns. Additionally, sub-THz signals experience significant free-space path loss, making it harder to measure radiation patterns accurately over reasonable distances. This paper presents the characterisation of a D-band (110-170 GHz) horn antenna having nominal gain of 25 dBi using both planar near-field and over-the-air far-field measurement techniques. The E-plane co-polar patterns are determined from both measurement techniques and compared to electromagnetic simulations. Analysis of measured results is carried out to illustrate the validation of the planar near-field and OTA measurement systems at sub-THz frequencies.