The eSurvey UA91 adopts a high-gain broadband antenna to receive GNSS signals such as GPS, BDS, GLONASS, Galileo, IRNSS, QZSS, and L-Band. The scheme of multi-stage 3D choke coils with a symmetrical distribution is adopted to achieve higher phase center stability and excellent anti-multipath interference performance. It has excellent performance and the phase center coincides with the mechanical center.