Abstract: Two types of longitudinal slot antenna sparse arrays based on substrate integrated waveguide (SIW) technology are proposed and investigated. This design method could lead to an enhanced bandwidth and a lower requirement for fabrication accuracy, while preserving acceptable radiation properties. Moreover, it is easy to realize low side-lobe levels (SLL) performance due to the lower internal and external mutual couplings. The full wave simulation results show that the sparse designs are effective and feasible.