The purpose of Cognitive Radio (CR) technology is to improve the spectrum utilization by allowing the secondary users (SU) to transmit data over the spectrum that the primary user (PU) is temporarily absent. In addition to recognizing the available spectrum hole, the SU shall properly select the channel to avoid congestion with other SU on the same channel so that the throughput can be maximized. Although secondary users may not fairly and uniformly choose the available channels in distributed spectrum selection environment, the radio resource can still be effectively utilized if SU can detect the congestion and can properly adjust the spectrum usage actively. This paper proposes a chip-based distributed spectrum adjustment (SA) framework to improve the system throughput. The proposed framework consists of the decision policy of spectrum adjustment and the channel competition and handoff procedure. In the proposed framework, each SU adjusts its channel according to the predicted congestion status and its channel conditions. Furthermore, the proposed chip based concept fairly decides the handoff of SUs. Exhaustive simulations conduct to show that the proposed scheme achieves better system throughput and fair spectrum handoff among SUs.