New feeding networks and planar antenna designs for leaky-wave systems and communication applications

Abstract

The fast development in modern communication systems such as radars, medical imaging, sensors or satellites demands efficient and compact antenna designs that can satisfy the high data throughput and beam scanning requirements. This is commonly achieved by different means including electromechanical or mechanical steering, which sometimes are not the best option as additional cost, size or losses may be introduced. However, low-cost and compact structures can be obtained by using planar leaky-wave antennas, whose inherent high directivity and electrical beam steering capabilities have been realised to be a solution for the issues encoun tered by these systems. Nevertheless, there are several limitations that these antennas still need to overcome. One clear example is the lack of efficient and simple feeding networks for certain types of leaky-wave antennas that can reduce their performance and compactness. In turn, there are modern indoor applications, such as WiFi or radio frequency identification (RFID), where selective distributed communications are required but current leaky-wave antennas cannot efficiently provide or their use implies cost and weight constraints. In this thesis, planar configurations are presented to provide efficient and low profile solutions for leaky-wave antennas using concepts such as partial reflective surfaces or simple technologies as parallel-plate waveguides. It is also demonstrated that novel systems for two-dimensional (2D) or wideband beam scanning can also be obtained by the use of simple feeders including vertical electric dipoles. In addition, a broad-beam alternative to a non-selective and expensive beam scanning performance inside airplanes for RFID systems is introduced easing weight restrictions. These configurations represent an advancement for the state-of-the-art and are interesting alternatives to their non-planar counterparts. To support these designs, theoretical analysis, full-wave simulations and measurements are provided.