Gain Enhancement of Transversely Slotted Substrate Integrated Waveguide Leaky-Wave Antennas Based on Higher Modes

A technique for gain enhancement of transversely slotted substrate integrated waveguide (SIW) leaky-wave antennas is proposed based on higher modes. Two SIW leaky-wave antennas based on the TE
_m0
( m = 3, 5) higher modes are investigated. The antennas possess the advantage of simplicity, in which the feeding structures are compact and simple. Compared with published transversely slotted SIW leaky-wave antenna based on the fundamental mode (TE
₁₀
mode), the proposed antennas exhibit higher and more consistent gains. Besides, the antennas maintain the scanning capability from near broadside to endfire. The working principles of the antennas are explained. The propagation characteristics are investigated with a magnetic field integral method. The aperture efficiencies are analyzed. Two leaky-wave antenna designs based on the TE
₃₀
and TE
₅₀
higher modes are demonstrated and compared with a TE
₁₀
-mode antenna design (with almost the same dispersion characteristics). Prototypes of the three designs are fabricated and measured for comparisons. Compared with the TE
₁₀
-mode antenna, the TE
₃₀
- and TE
₅₀
-mode antennas have the transverse beamwidths markedly narrowed and have the gains improved by about 5.5 and 8 dB, respectively.