The Research And Design Of Cognitive Radio R F Receiver

With the development of wireless communication technology, the available spectrum resources are becoming more and more insufficient, and the contradiction between the enlarging need and the low utilization of spectrum resources is becoming more and more outstanding. With the premise of not affecting authorized users, cognitive radio(CR) realizes the dynamic spectrum sharing and improves the utilization of spectrum by using “spectrum hole” in the electromagnetic environment.Cognitive radio requires that the RF receiver should fully consider the special demand of CR network in hardware design, and provide sufficient functional flexibility. Therefore, it is necessary to carry out a research on RF receiver which meets the need of CR.The research of this dissertation is mainly divided into the following three aspects:(1) This dissertation analyses the three typical structures of RF receivers and compares their advantages and disadvantages, then proposes a system scheme of CR receivers based on the CR standard IEEE 802.22.(2) The hardware design of the proposed CR RF receiver has been completed. By using two variable gain amplifiers HMC681LP5 and a digital attenuator HMC624ALP4 E to implement an automatic gain controlled(AGC) loop, the receiver gets good gain-conctrol ability. By using a power detector AD8314 as a buffer between RF signal and sampling signal, the AGC loop gets good closed-loop stability. By using a direct frequency synthesis(DDS) AD9958 and a phase-locked loop(PLL) ADF4360-7 to implement a DDS+PLL local oscillator(LO) module,the receiver gets good LO module with fast frequency shifting ability and low output phase noise.(3) The system performance of RF receiver has been tested. This receiver is able to work in 14 channels between 694 MHz to 806 MHz, and the avaible receiving power ranges from-95 d Bm to-10 d Bm. The controlled gain ranges from-30 d B~60d B, with a controlled step 0.5d B. The test results verified the feasibility of the proposed system scheme.