Integration of $S$ /Ka/ $D$ -Band Antennas in LTCC With a Cylindrical Radome for Triband Applications

This paper presents the integration of
${S}/\textit {Ka}/{D}$
-band antennas in a low-temperature cofired ceramic (LTCC) package. Three types of antennas, microstrip patch, grid array, and step-profiled horn, operating at different bands are compactly assembled in the same substrate. For electromagnetic isolation, a specific layout and extra-shielding structures, such as fences of metallic vias and air cavities, are designed to reduce the unwanted coupling between antennas. In addition to the antennas, a cylindrical radome is introduced closely attached to the surface of the LTCC substrate. Since radome acts as a dielectric superstrate, its influence on radiation performance is also taken into consideration, especially for
${D}$
-band operation, where a ring-shaped cavity is introduced to suppress the detrimental propagation of surface waves inside radome and enhance the gain as a consequence of dielectric loading effect. Measured results agree well with simulation. Proposed triband antennas, working at three frequencies 3, 30.5, and 120 GHz, achieve broadside gains of 6.51, 9.74, and 13.36 dBi with −10 dB fractional impedance bandwidths of 15.3%, 6.1%, and 6.5%, respectively.