Research On RF Module Of A Cognitive Radio

Cognitive Radio(CR) is a smart wireless communications technology that is self-adaptive to outside environment and is based on the software defined radio. It can cognize the surrounding wireless environment by the wireless communications equipment , then adjust some operating parameters to adapt the environment, consequently can improve spectrum utilization and ease the strain on the resources of the spectrum. The CR technology creates a new way to ultimately resolve the problem caused by increasingly rising radio communication services and limited spectrum resources.Beginning from the study background of the CR technology, this paper proposes a RF transceiver modules that can be used in cognitive radio system to meet its demand for wireless communication devices. The module contained a RF transmitter and a RF receiver,which could send and receive data. TDD mode was used in the transceiver, which worked at GSM frequency band. The frequency synthesizer was based on the chip Si4133.The transmitters transformed the IF signal from the baseband board to designated frequency and transmitted out on the two-step transformation frequency mode. The double-conversion was used in the receiver,after the first downconversion the circuit was divided into two independent branch.The signal in one branch was used for the detection and analysis of the frequency spectrum and the other one was used for data reception in the baseband board. All the work of design and debug of the RF module had been completed. The test results showed that the functions of the RF module were realized, including the spectrum detection and the data communication.