A Symmetrical Periodic Leaky-Wave Antenna With Backward-to-Forward Scanning

In this letter, a symmetrical periodic leaky-wave antenna is proposed using an annular-elliptical-shaped unit cell loaded with balanced shorting pins across the E-plane. The proposed structure is a series-fed antenna array with a microstrip feed-line. The even symmetry field distribution across the longitudinal plane of the unit cell has the controllable propagation constant feature. With excitation of double symmetry (even TM21) mode of an annular elliptical patch at broadside frequency, the open stopband is suppressed. Thus, the antenna shows a wideband and a wide scanning capability of 105° (-78° to 27°). The measured results validate the proposed antenna with a maximum realized gain of 16 dB. The possibility of independent control of the directivity and the main beam direction is also presented at a fixed frequency by simultaneously varying two geometrical parameters.