In this paper, a more realistic cognitive radio network is proposed which considers several secondary links, some secondary relays, and one primary link. In the network, there are two steps of transmission from secondary sources to secondary destinations. At the first step, when primary link is idle, all of the secondary sources simultaneously broadcast their information to the relays. At the second step, the relays that successfully decode the information employ a new cooperative beamforming method and forward them to the secondary destination without causing harmful interference to the primary destination irrespective of whether primary link is idle or not. It is assumed that the channel state information between relays and primary destination isn’t perfectly known at the relays and they have erroneous estimation of the channel. The proposed cooperative beamforming method can maximize the received signal power at the secondary destination subject to keep received interference plus noise power at the primary destination under the predefined threshold. Results of simulations confirm validity of the method and improved performance compared to Zero-Forcing beamforming. The proposed cooperative beamforming can remain the interference plus noise power at the primary destination below the threshold even if the error in channel estimation is maximum.