DUAL-POLARIZED COMPACT FIRST-ORDER P-BAND PROBE FOR SPHERICAL NEAR-FIELD ANTENNA MEASUREMENTS

A number of European Space Agency's (ESA) initiatives planned for the current decade require metrology level accuracy antenna measurements at frequencies extending from L-band to as low as 400 MHz. The BIOMASS radar, the Galileo navigation and search and rescue services could be mentioned among others. Existing probes for Spherical Near-Field (SNF) antenna measurements, which is one of the most accurate antenna measurement techniques, are either classical first-order probes based on conical horns and open-ended circular waveguides excited by the fundamental TE11-mode, or wide-band higher-order probes, as for example, those developed by the Technical University of Denmark (DTU) under ESA project “HigherOrder Near-Field Probes (HONFP)” [ESA Contract No. 22812/09/NL/JD/al]. In either case, these probes become excessively bulky and heavy at frequencies below 1 GHz, so that they cannot be handled by a single person and dedicated lifting tools are necessary. In this project, a compact dual-polarized first-order P-band probe has been developed (Figure 1). The height of the probe is just 365 mm over a 720-mm circular ground plane and it weighs 7 kg. The probe covers the bandwidth 419-445 MHz with more than 9 dBi directivity and parasitic |μ| ≠ 1 spherical modes suppressed below −35 dB. The probe has been designed, manufactured and tested by the Technical University of Denmark (DTU)