Analytical Study of Open-Stopband Suppression in Leaky-Wave Antennas

In the majority of leaky-wave antennas (LWAs), the lack of broadside radiation is due to the existence of an open-stopband (OSB) at broadside. In this letter, we present a study on the OSB suppression in LWAs. In particular, we start from a simple unit cell comprising a planar waveguide having alternating open and short sidewalls. The analytical and simulated band structures testify consistently that OSB suppression can indeed be realized by proper design, analytically studied using mode-matching, and further supported by full-wave simulations. An LWA is then implemented using the substrate integrated waveguide (SIW) technology, which provides interesting features such as a high directive beam with frequency scanning capabilities, and a simple feeding network, making it well suited for microwave applications. Phase and leakage constants are adjusted to yield a directive beam with beam scanning over a wide range of angles (from -30 degrees to 30 degrees). The presented 25-cell LWA has a wide impedance bandwidth of 20% around 15 GHz with high efficiency and operates with peak gains of about 9 dBi throughout the frequency scan range of 13.5-16.5 GHz. A prototype is fabricated using standard substrates, and measured results show an excellent agreement with the simulated results, validating the proposed concepts.