A Hexa-Polarization Reconfigurable Fixed-Frequency Beam-Scanning Leaky-Wave Antenna for Millimeter-Wave Application

In this letter, a hexa-polarization reconfigurable fixed-frequency beam scanning leaky-wave antenna (LWA) operating in the millimeter-wave band is developed. Two parallel gap waveguides (GWs) are used as the basic transmission structure, and wide serrated ridges are adopted to produce quasi-TEM mode and slow-wave transmission in the GWs. A square patch array excited by the GWs is designed to generate radiation with desired polarization. A control structure loaded with a PIN diode is applied to tune the working state of each patch unit. Then, based on the holographic theory, the hologram on the antenna aperture can be manipulated by controlling the states of all the patch elements. In this way, six polarizations can be obtained (±45° linear polarizations, horizontal polarization, vertical polarization, left-hand circular polarization and right-hand circular polarization), and independent fixed-frequency beam scanning for each polarization can be achieved. In the measurement, a beam-scanning range of 100° is realized for each polarization state, and the property of two circular polarizations is also verified by the measured axial ratios. Therefore, this LWA shows potential in millimeter-wave applications that demand polarization agility and fixed-frequency beam scanning.