Design of a leaky-wave long slot antenna using ridge waveguide

A new design of the leaky-wave long slot waveguide antenna with low cross-polarisation is proposed. The proposed antenna consists of a straight long slot located at the centre of the broad wall of the ridge waveguide. By properly designing the ridge, the amount of leakage power along the slot is controlled, which results in the desired aperture distribution. The aperture has a Taylor distribution with a sidelobe level of -35 dB. Such a design has a low cross-polarisation level as well as a desired beam pointing angle, which is defined at the beginning of the design procedure. The simulation results confirm the high accuracy of the design procedure. The proposed antenna is also fabricated and measured. According to the measurement results, the structure has a cross-polarisation of -41.9 dB and a sidelobe level of -26.3 dB. The measured reflection coefficient of the proposed antenna is -22.8 dB at the design frequency.