“…Multiple types of antennas have been adopted to realise endfire radiation on a large conducting plane, such as log-periodic antennas [1][2][3], surface wave antennas [4,5], horn antennas [6,7], Yagi antennas [8][9][10][11][12][13][14][15], and leaky-wave antennas [16][17][18][19]. However, for the antennas in [1][2][3][4][5][6][7][8][9][10][11][12][13][14], the lengths of radiating apertures are too short, which results in a low endfire gain. Moreover, the antennas in [1][2][3][4][5] have the problem of non-uniform energy distribution on the radiating aperture, because only part of the radiating aperture is used at a single frequency point.…”