Broadband pattern-reconfigurable water loop antenna, pattern-reconfigurable water loop antenna

A novel loop antenna is proposed here. This antenna uses an annular arm made of pure water to take the place of the metallic loop of a typical loop antenna. The water arm is enclosed by a resin loop tube. The arm has circular cross section to excite a travelling wave of the axially symmetric mode and propagates along the loop. To change the volumes of water in the tube, the proposed antenna may work in different states. When the tube is fully filled, the proposed water antenna works as a loop antenna. When the tube is partly filled, it looks like and also works as a water dipole antenna, which indicates pattern reconfigurability. Measured results show that the proposed water loop antenna achieves a broadband. The impedance bandwidth (|S-11| < -10 dB) of the antenna is from 0.9 to 2.3 GHz (87.5%) for the loop state and from 0.8 to 2.1 GHz (89.7%) for the dipole state. Maximum gain of 4.7 dBi for the loop mode and 1.7 dBi for the dipole mode are obtained. The proposed water loop antenna shows the advantages of pattern reconfigurability, good radiation performances, high transparency and low cost, which may be used in maritime communication.