Design And Research Of OAM Signal Transmission Platform Based On Software Radio

With the fast growth of wireless communication technologies,the demand for capacity and speed of wireless communication system has been rising significantly.This brings the increasingly grave problem of resource scarcity and low efficiency in spectrum management,as well as the constraints of developing high-speed and high-bandwidth wireless communication in the future.Orbital Angular Momentum(OAM)is therefore introduced to alleviate this problem.OAM multiplexing is one of the emerging technique that takes the advantage of the orthogonality between the OAM of multiple electromagnetic waves under different quantum states,thereby effectively transmitting signals of the same frequency via a massive number of channels.In theory,the channel capacity and spectrum efficiency can be improved by investigating the transmission characteristics of OAM.As a result,it will also contribute to traffic improvements in wireless communication.This thesis mainly adopts the Software Defined Radio(SDR)as a research platform and experimental environment for OAM multiplexing transmission as well as suggesting its detailed practical plan.The thesis main content and innovations are divided in to the following three sections:In order to implement an SDR platform which is suitable for OAM multiplexing transmission investigation,at first,three hardware devices are set up and tested,including RTL-SDR,Para SDR and Universal Software Radio Peripheral(USRP).Hence,three types of platforms are successfully built by programming.Followed by an analysis and comparison,it concludes that an SDR based on USRP and GNU Radio is the most competent platform for OAM multiplexing transmission investigation in this case,considering the available open-source software packages and its wideband operation.In the second section,the OAM spin waves are generated based on radiation characteristics of single-feed circular microstrip phased array antenna,which is utilised as the radio frequency antenna for the SDR platform.Hence,both transmission and reception of the OAM audio signals are achieved using GNU Radio at the PC head end.Also,the signal transmission characteristics are tested under different Signal-to-Noise Ratio(SNR)in a transmission channel simulation.At last,it is tested in a real-channel environment,the transmission system can realize short-distance audio transmission and reception,which has proved the feasibility and steadiness of this audio transmission system.In the last section,the focus is to implement the transmission and reception of text data,thereby verifying the flexibility and programmability of the SDR platform based on OAM multiplexing.The system consists of four elements:signal transmitter,channel simulation,channel optimization,signal receiver and hence completing step-by-step the real-time transmission and receiving.It finally realises the short distance transmission of text data with integrity,proving the reliability and effectiveness of the above platform.