An Embedded Triband Shared-Aperture Antenna with Omnidirectional Radiation Pattern

This paper presents an integrated triband shared-aperture antenna which can be applied to communication and data links systems to make the radiation aperture more compact. The antenna is composed of three microstrip antennas operating in UHF, L and C band respectively. For each antenna, the TM
01
and TM
02
modes are excited for a circular microstrip patch to achieve omnidirectional radiation pattern. For the UHF band antenna, substrate material with a relatively large permittivity is utilized to lower the resonant frequency of the patch and thus to miniaturize the overall size of the antenna. Substrate material with relatively lower permittivity is utilized for L and C band antennas to enhance operating bandwidth. The three antennas are coaxial stacked and integrated together, and thus has the advantage of low-profile. Thanks to the low-profile of the antenna, the integrated antenna is then embedded in a circular cavity, enabling the exterior of the antenna assembly to be conformal with an outer surface of a platform. This method can be used to keep the low radar cross section performance of the platform. All the three antennas can be feed at the bottom of the cavity. For the UHF band antenna, the patch can be directly connected to the connector. For the L band antenna, the feed probe at the center of the patch is connected to a strip line which is sandwiched between UHF band and L band antennas, and then the strip line is connected to the connector at the bottom of the cavity through a via of the UHF band antenna, thus the feeding structure does not influence the radiation property of the UHF band antenna. The same kind of feeding structure is also utilized for C band antenna. The structure of the integrated antenna is given in detail, and the influence of the cavity on the VSWR and radiation pattern are investigated. Simulation results are also given to validate the proposed idea.