Wideband circularly polarized high accuracy survey active antenna for global navigation satellite systems applications

This letter presents a new circularly polarized (CP) active antenna for global navigation satellite systems (GNSS) operating in the L1-band (1.164–1.28 GHz) and L2-band (1.525–1.615 GHz). The active antenna consists of a passive antenna and a two-channel low-noise amplifier (LNA) circuit. To achieve wideband coverage of the L1/L2 bands while maintaining a low profile, a new electroplating process is utilized in fabricating the passive antenna. Additionally, to realize CP performance, the passive antenna is sequentially fed by four ports with a wideband feeding network. To minimize phase variations, a 90° phase shifter loaded with open-short-stub is integrated into the feeding network. Furthermore, to improve noise immunity, out-of-band rejection, and amplify GNSS signals, the LNA circuit cascades two-stage dielectric bandpass filters and three-stage LNAs. Consequently, the circuit features a low noise figure of below 1.65 dB, a maximum out-of-band rejection level of 60 dB, and a stable active gain of 30 dB. The performance of the active antenna is evaluated in an outdoor open field using a GNSS receiver.