Mechanically Scanned Leaky-Wave Pillbox K-Band Antenna With Dual Radiating Layers Using Variable Permittivity Substrate and Nonuniform Patches

A low-profile, high-gain leaky-wave pillbox K-band antenna with mechanical beam scanning is presented. The antenna consists of three layers: one feeding network layer and two radiating layers. A substrate-integrated waveguide wide-angle H-plane horn feed is connected to a one-dimensional reflector using vias rows, forming a closed pillbox reflector to prevent parasitic wave leakage. A simple coaxial feeding port is used to reduce the antenna’s complexity and cost. The middle substrate disk, made from two half-disk substrates with permittivities ${\varepsilon}_{r1}{=}2.55$ and ${\varepsilon}_{r2}{=}2.20$ , forms the bottom of the radiating structure and is separated from the top substrate layer with periodic leaky-wave radiating elements. Rotating the middle layer by 180° changes the leaky wave’s propagation, and thus shifts the beam direction. The top radiating layer has four sets of patches with different spacings in the disk’s four quadrants. Beam scanning is achieved by rotating the disk to activate each quadrant and thus shift the beam to four distinct elevation angles. Combining the rotation states of the two layers allows wide beam scanning in the elevation direction at eight different angles. Beam scanning in the azimuth direction can be realized using a rotary joint. The design was verified using the transverse resonance method and full wave simulations. A prototype with a size of $340\times 320\times 5{\mathrm {mm}}^{3}$ was built and tested in the 19.5 – 20.5 GHz frequency band, showing a beam scanning range of $0- 43^{\circ }$ , a realized gain of 25.7 dBi, −4 dB crossover levels, −27 dB cross-polarization level, and side lobe levels below −10 dB.