Simple antenna structure enabling the simultaneous excitation of two different polarisation and radiation modes

A simple antenna structure able to simultaneously generate two different polarisation and radiation modes is proposed. In addition to a good impedance matching all over multiple bands, antennas based on the proposed geometry can exhibit a linearly polarised omnidirectional radiation pattern at lower frequencies, allowing the communication in any azimuthal direction, and a circularly polarised directive diagram at higher frequencies that enables links for satellite-based applications. These characteristics together with a low-profile, a light weight and a robust and easy-to-realise structure make the antenna an effective candidate for integration into vehicles. The antenna multimode radiation mechanism is explained in detail. In order to demonstrate its effectiveness, the proposed structure is applied to the design of two different antennas for practical applications. The performances of these antennas are assessed by means of numerical simulations and validated through experimental measurements.