Research On Blind Detection Of Terahertz Wideband Signals

Since the fourth industrial revolution(information revolution),the generation of modern electronic information technology has caused a new round of technological change,which has made a qualitative leap in the modern social and economic structure.With the establishment of 5th Generation Mobile Networks(5G)standard,many countries have proposed the target of making 5G commercial and civilian by 2020.With the settling of 5G standard,countries have started to research the next generation of communication.Terahertz wireless communication has attracted worldwide attention due to its available bandwidth,good direction,high security,and strong anti-interference ability.Terahertz technology has been studied in civil and military fields in various countries.The function of blind signal detection technology is to detect and estimate the received signal in non-cooperative communication.It is an indispensable and critical technology for the spectrum monitoring and management in the civil field and for the electronic warfare in the military field.In order to prepare for the full application of terahertz wireless communication in the future,this thesis studies the blind detection of wideband signals in the terahertz background.This thesis first investigates and introduces the basic theory of signal blind detection technology,introduces the time and frequency domain characteristics of commonly used modulated signals,and elaborates the common methods and theories of signal carrier frequency estimation and modulation type recognition.Then,the performance requirements of terahertz wideband blind detection system are analyzed,and the main functions of terahertz wideband blind detection system are determined.This system uses FFT coarse estimation and CZT spectral thinning algorithm as the core algorithms of carrier frequency estimation and applies mean-shift clustering algorithm to modulation type recognition.The principle of the algorithm is described in detail,and the simulation is carried out.The spectral resolution of the carrier frequency estimation algorithm is 0.25 Hz,the maximum absolute error is not more than 200 Hz when the signal-to-noise ratio is 20 dB.The modulation recognition algorithm can effectively recognize BPSK,QPSK,8PSK,16 QAM,32QAM and 64 QAM signals at 20 dB signal-to-noise ratio.The results show that the performance of the algorithm meets the requirements of the system.The hardware part of the system takes the wideband receiving circuit and the data transmission platform of the FPGA as the core and completes the reception and transmission of terahertz signals.Thus,the architecture of the whole terahertz wideband blind detection system is planned.Finally,this thesis builds a terahertz wideband blind detection system and its test platform and completes the hardware implementation of the system.The detailed process of carrier frequency estimation and modulation identification for terahertz wideband modulation signal is mainly described.The two functions are experimented on the test platform and their functional tests are completed.Then the performance test is carried out for the target signal.The test results show that the system can detect the target signal blindly in 2s and output the result.The maximum error of carrier frequency estimation is not more than 300 Hz in the detection bandwidth range from 0.210 THz to 0.230 THz,and the BPSK,QPSK,8PSK,16 QAM,32QAM and 64 QAM signals can be classified accurately.