A Compact Wideband SIW Horn Antenna for Applications in X and Ku Bands

In this paper, a compact wideband horn antenna design suitable for the X-band and Ku-band is proposed. Firstly, by introducing a double-sided offset parallel-strip line (DSPSL) structure onto the extended substrate of the substrate integrated waveguide (SIW) horn antenna, the low-frequency impedance characteristics are adjusted, significantly broadening the antenna’s operating frequency range. Secondly, by sequentially loading interdigitated structures at the horn aperture and periodically arranging metal vias inside the waveguide, the antenna’s input reactance at mid-to-high frequencies is gradually optimized, significantly enhancing the antenna’s matching performance. Finally, to adjust the antenna’s matching and radiation performance in the low-frequency band, an improved transition structure is introduced onto the antenna’s dielectric cladding. Ultimately, while maintaining a compact size of 1.35λ
0
×0.77λ
0
×0.16λ
0
(λ
0
is the free space wavelength at the center frequency), the proposed antenna achieves a relative bandwidth of up to 75.14%, stable end-fire radiation performance, and moderate gain. These characteristics make it an ideal choice for conformal integration on small aircraft.