An electronically tunable half-mode substrate integrated waveguide leaky-wave antenna

In this paper, a new type of leaky-wave antenna (LWA) is proposed using half-mode substrate integrated waveguide (HMSIW) as the base structure. The HMSIW allows easy implementation of shunt tuning elements, which in turn enables changes in the dispersion characteristic of the LWA. By incorporating series and shunt tuning capacitors, i.e. varactor diodes, the LWA is able to scan from backward to forward angles at a fixed frequency. Since the structure is periodic in nature, Floquet analysis of its unit cell is used as the basis for the initial design to obtain estimated angles of the maximum beam and Bloch impedance. The antenna is also designed to minimize the number of shunt tuning components required to implement the desired scanning. From numerical simulations, the HMSIW LWA demonstrates scanning angles between -33° and +56° at 8.2 GHz over the capacitance range of 0.1-0.4 pF. The return loss is found to be larger than 5 dB in most cases. Finally, the proposed design is evaluated experimentally using unit cell prototypes.