Long Slot mmWave Low-SLL Periodic-Modulated Leaky-Wave Antenna Based on Empty SIW

In this article, empty substrate integrated waveguides (ESIW) technology is applied to design long slot leaky-wave antennas (LWAs). First, a uniform-aperture structure is presented and its limitations on forming the beam are studied. Then, a sinusoidal curve is employed to modify the geometry of guided-wave structure which divides the slot into a number of segments, making a periodic aperture. After that, a method is proposed to regulate the guided waves inside the ESIW. To this end, a modulation function is derived to simultaneously determine the local amplitude and segment length of the physical sinusoidal curve at each individual points on the structure. This results in manipulating the phase constant
$(\beta)$
and leakage rate
$(\alpha)$
across the aperture which ultimately controls both the tilt angle and sidelobe-level (SLL) of the constructed beam. The slot is placed on the centerline of the broad wall of the ESIW to reduce the cross polarization. The structure is designed to operate at 35 GHz with SLL = −30 dB and a backward tilt angle of
$\theta _{m}=-20 ^\circ $
. Finally, the proposed LWA is simulated and a fabricated design is measured. A good agreement is observed between the theoretical, simulated, and measured performance of the antenna.