This paper proposes a simple antenna switching and a relay technique for cognitive radios using adaptive array antenna to effectively reduce the interference from the primary system. While the adaptive array antenna can create null towards the direction of primary system, the created antenna pattern can result in non-optimized pattern between cognitive nodes. In order to solve such a problem, this paper first introduces a simple antenna pattern switching. With this technique, each cognitive radio node is equipped with three antennas and each node tries to select the antenna configuration resulting in the best antenna pattern for each link. Furthermore, we propose a combination between the above simple antenna switching and the interference-induced multi-hop transmission where the multi-hop transmission is utilized when a link in the network suffers from the low transmission quality due to the created antenna pattern. Our numerical results show that the proposed techniques can significantly improve the achievable data rate in cognitive networks.