A high gain quasi-monolithic horn antenna

Abstract

Integrated horn antennas have been proved to be very well suited for millimeter-wave applications. They consist of a strip-dipole antenna suspended on a thin dielectric membrane inside a pyramidal cavity etched in silicon [1]. The antennas are free from surface-wave losses and fully monolithic. However their large flare-angle of 70°, which is inherent in the anisotropic etching of silicon, limits their gain below 13dB and their 10dB beamwidth above 90°. In this paper a quasi-monolithic dual-mode horn is introduced which increases the gain to 20dB with a high circular symmetry and a high 97p Gaussian coupling (fig. 1). As shown in figure 1, a machined section has been superimposed on a standard integrated horn antenna to increase the radiating aperture to 3.56λ. The junction of the integrated section and the machined section acts as a mode converter which mainly converts some of the incident TE 10 mode to the TE 12 , TM 12 modes. The modes are properly phased on the radiating aperture by selecting the flare-angle and the length of the machined section. This results in highly symmetric, low cross-polarization far-field patterns.