Abstract. The presented "open" composite left-handed/right-handed (CRHLH) substrate integrated waveguide performs well as a low-profile leaky wave antenna. This design is distinguished due to the fact that it is derived from the approved equivalent circuit model of the H₁₀ rectangular hollow waveguide mode. The wave propagation behaviour is visualised by the dispersion diagram calculated by two different methods, infinite periodic full-wave simulation and Matrix-Pencil analysis of driven field solutions. The periodic configuration is also analysed in terms of the Bloch impedance. Although FR-4 serves as substrate the antenna features an efficiency of about 50% to 60%. The radiation performance demonstrates nearly backfire to almost endfire scanning capability of the antenna by mere frequency variation. Broadside radiation is possible due to the balanced state at 4 GHz.