Substrate integrated waveguide leaky wave antenna with low cross polarization in X-Ku band

In this article, a balanced symmetrical low cross polarization (X-pol) substrate integrated waveguide (SIW) based leaky wave antenna (LWA) is presented. The unit cell of the LWA consists of transverse and longitudinal slots, which provide series and shunt resonant elements, essentially required to radiate at broadside direction efficiently. The radiating slots are arranged in a way such that the unit cell is symmetrical around the centerline so as to achieve the low X-pol levels. Moreover, the shape of the longitudinal slots are changed and optimized to match the unit cell impedance to the characteristic impedance of the SIW. Parametric constraints of the radiating slots are studied for achieving the continuous beam scanning and the best low X-pol in the presented LWA. The final presented LWA is capable of continuous beam scanning from -28 degrees to +30 degrees within a frequency range of 9.5-15.2 GHz including broadside at 12.2 GHz. Moreover, the X-pol levels are better than -40 dB all over the scanning frequency range. Finally, the antenna prototype is fabricated and tested. Simulated and measured results are in good agreement. The maximum gain of the antenna measured is 13.8 dB.