Analysis and Design of Wideband Planar 2-D Leaky-Wave Antennas
Rapid development in wireless communication systems at microwave and millimeter-wave frequencies increases the demand for more efficient wideband and high-gain electromagnetic radiator capable of supporting the high-speed data transfer and mitigate the free-space path loss. Fabry-Pérot cavity (FPC) antennas are a potential candidate as radiators since they exhibit useful radiation characteristics, such as high-directivity of broadside beam with high radiation efficiency from a low-profile structure, and feature simplicity of design and low-cost fabrication. This two-dimensional (2-D) class of leaky-wave antennas (LWAs) are conventionally constructed with a thin frequency selective surface (FSS) (metallic patches or holes in a metallic screen), forming a partially reflected surface (PRS), placed half of a wavelength from a ground plane and excited with a single source.
This dissertation focuses on the modal and radiation analysis of FPC antennas formed by an electrically thick PRS (single or multiple metal-dielectric layers) optimized for wideband radiation. A novel set of formulas is analytically derived, which relates the leaky-wave parameters (phase and attenuation constants of the traverse complex wavenumber) to the PRS reflection coefficient and input admittance. Additionally, we derived a new leaky-wave based power formula that is capable of describing the far-field behavior for any FPC antenna formed by an arbitrary thick PRS. The formulas are validated with different examples of wideband FPC antennas constructed using single-layer and multiple-layers of PRS structures. Moreover, we show how to efficiently radiate circularly polarized (CP) waves from a wideband FPC antenna excited by a single CP source. Furthermore, a study was carried out to further enhance the broadside gain with a sparse array implemented as a primary excitation source.
Additionally, we have investigated the radiation performance of an extremely thin (100th of a wavelength) 2-D leaky-wave antenna constructed from a high impedance surface (HIS) directly excited to work as an antenna. Physical insight is provided by analyzing the radiation mechanism of this class of HIS antennas and prove that radiation is in part related to a TM-like leaky-wave supported by the structure in the vicinity of its magnetic resonance. Wideband broadside radiation, in addition to a beam steering capability, was demonstrated. Finally, a HIS antenna with a differential feeding network was designed and fabricated for K-band wireless systems.