High Speed Wireless Transmission Technology And Experimental Research For Sub-terahertz

With the rapid development of information technology(IT),6G communication,and artificial intelligence(AI),people's demand for information is growing,and higher and higher requirements are given on information transmission bandwidth and delay.Traditional microwave information transmission methods are facing severe challenges,the development of higher frequency bands has become an inevitable trend,and the sub-terahertz/terahertz frequency band has naturally become an important frequency band for high-speed wireless transmission.To solve the key problems faced in future application of sub-terahertz wireless transmission,related technology and experimental research on the long-distance sub-terahertz high-speed wireless transmission system are carried out,focusing on the system architecture,sub-terahertz high-efficiency solid source,channel characteristics,as well as technology verification.The main research contents are shown as follow:1)The system architecture: The traditional architecture ca nnot fully utilize the physical advantages of sub-terahertz/terahertz wave,and has the problems of low spectrum efficiency and large bandwidth occupancy.With the a rchitecture,it is hard to adapt to long-distance and high-speed applications at the same time.Confronted with these problems,different from the general OOK or ASK system in the world,a novel electronic sub-terahertz architecture of "high-order digital modulation and demodulation+ fundamental wave mixing + power amplification chain(cascaded solid-state amplification and electronic vacuum amplification)" architecture is proposed.The proposed architecture has high spectrum efficiency and small band width occupancy,and can achieve long distance and high-speed transmission simultaneously.The power device is easy to implement,and is convenient to form a high-power chain by cascading with electronic vacuum devices.Besides,digital signal processing technology can be used to achieve channel equalization and compensation.Thus can provide strong anti-interference ability.Using this architecture,it is the first time to realize the furthest reported transmission system on the sea surface at 140 GHz,with a transmission distance of 27 km.The measured results verified the feasibility,advancement,and high-speed transmission capability of the architecture.2)Key technology of sub-terahertz high-efficiency solid-state source: First,in response to the key problem of the synthesis efficiency of the sub-terahertz solid-state power combining source,a rad ial power divider/synthesis technology adapted to the sub-terahertz frequency band is proposed.Different from the conventional waveguide binary synthesis,the direct one-step synthesis is adopted.Theoretically,the synthesis loss is independent of the number of synthesis channels,and it is easy to realize large-scale channel number synthesis.At the same time,the synthesis ports are arranged in a circle without a separate isolation element,and have good amplitude,phase consistency and failure resistance,which effectively solves the efficiency problem in power synthesis.The test result shows: the loss of the 140 GHz 32-channel power divider/combiner in the 130?150GHz frequency band is 2.74 d B.The single synthesizer loss is 1.37 d B,and the synthesis efficiency is 72.9%.Secondly,to address the key issues of high-efficiency and high-power generation of the sub-terahertz solid-state frequency multiplying source,an integrated frequency amplification/frequency multiplication chain(FAMC)implementation tec hnology with a reliable DC power supply network is proposed.With the frequency multiplier,the input frequency is multiplied,synthesized,and amplified,and then used to drive the Schottky diode frequency multiplier,which minimizes the length and loss of the interconnection transmission line.Thus,a high-efficiency and high-power solid-state frequency multiplier is realized.The test result shows: at 110 GHz,the output power is greater than22 d Bm.The best output power is 23.2d Bm at around 104 GHz,and the corresponding efficiency is more than 20%.3)Sub-terahertz front-end channel characteristics: In the sub-terahertz frequency band above 100 GHz,the front-end channel characteristics have more prominent influence on the system transmission performance,and its influence still lacks corresponding experimental data support and quantitative analysis.The realistic sub-terahertz front-end channel's phase noise,intermodula tion signal,gain compression and other effects on the system performance are analyzed and experimented,and the key factors that affect the system's transmission error rate performance is obtained.Compared with the far-end phase noise and third-order intermodulation spurious products,the near-end phase noise of the sub-terahertz source and the transmission front-end gain compression is the key factors that affect the performance of the system transmission error rate.The filtering performance of the digital phase-locked loop at the receiving end can effectively reduce the impact of near-end phase noise and improve system transmission performance.4)Sub-terahertz wireless channel characteristics: The current understanding of the transmission characteristics of sub-terahertz high-speed channels is only limited to theoretical models,and there is still no experimental data at long distance(about ten kilometer)in real environments.Based on the long-distance transmission system,experimental research on transmission channel characteristics on the sea surface is carried out.Real atmospheric channel transmission characteristics data at about ten kilometers are obtained.An ITU theoretical model correction method is proposed and an accurate channel transmission model is established,effectively reducing the error on link budget estimation.