Low-Profile Wideband GNSS Antenna with Enhanced Front-to-Back-Ratio Without Additional Ground Plane

A low-profile wideband circularly polarized (CP) antenna for global navigation satellite system (GNSS) applications is proposed in this paper. The proposed CP antenna composes of quadruple antenna had a pair of a fed and parasitic T-branch antenna element formed the inner side of the resin case based on molded interconnect device technology. This operation mechanism is related to a combination of a monopole and dipole mode, accomplishing stable gain and enhancing Front-to-back-ratio (FTBR) for all GNSS band (lower band <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(1164-1299 \text{MHz})$</tex> and upper band (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1525-1614 \text{MHz}$</tex>)). The measured boresight righthand CP gain and FTBR of the proposed antenna are respectively <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-1.1-1.1 \text{dBic}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$9.4-14.0 ~\text{dB}$</tex> at the lower band and are respectively <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.7-3.1 \text{dBic}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10.9-13.1 ~\text{dB}$</tex> at the upper band. Simulated and measured results showed that the proposed antenna has excellent and stable performance over the entire operating band, which means that it is an ideal low-profile antenna (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$60 \text{mm} \times 60 \text{mm} \times 20 \text{mm}$</tex>) for GNSS applications.