A Beam Scanning Leaky-Wave Slot Antenna With Enhanced Scanning Angle Range and Flat Gain Characteristic Using Composite Phase-Shifting Transmission Line

In this communication, a planar beam scanning substrate integrated waveguide (SIW) slot leaky-wave antenna (LWA) is proposed for enhancing scanning range and gain flatness using a modified composite right/left-handed transmission line (CRLH TL) structure. The curved phase-shifting characteristics of the modified CRLH TLs positioned between the radiation slots are adopted to increase the scanning range of the proposed antenna. Compared with conventional SIW CRLH LWAs, this antenna offers less gain variation due to its better balance between left-handed and right-handed bands and less sensitivity to its geometrical dimensions. The proposed antenna operating at the center frequency of 25.45 GHz is designed and experimentally verified for an automotive collision avoidance radar. The results show that the antenna achieves a twofold improvement in beam scanning ability with identical overall size.