基于双线性调频的光载太赫兹通感信号产生与传输分析

Generation and Transmission Analysis of Optical Terahertz Communication Sensing Signals Based on Dual Linear Frequency Modulation

提出一种基于双线性调频(DLFM)的光载太赫兹通感一体化信号产生、传输与接收方案。通信调制格式采用概率整形(PS)64QAM,一体化信号产生采用时分复用(TDM)技术。理论分析了基于DLFM的一体化信号产生与感知原理,分析了信号带宽和持续时间对感知分辨率的影响;仿真分析了不同传输距离下系统的通信与感知性能界限。结果表明:在255 GHz频段,当无线传输距离为10 m、通感信号时宽比为3∶5时,通信与感知性能达到平衡,此时通信速率为31 Gbit/s,距离分辨率为7.5 mm,速度分辨率约为114 m/s,测距精度约为7 mm,测速精度约为15 m/s。基于PS64QAM-DLFM的一体化系统在完成高速率通信的同时,能够实现对高速移动目标距离的准确测量,解决了距离和速度联合测量时的模糊问题,为6G通感一体化提出了一种可行的方案。

Objective With the increasing frequency of mobile communication systems and wide application of large-scale antennas,mobile communication systems and radar systems have similarities in many aspects, including spectrum utilization, MIMO transmission, and beamforming technology. The integration of perception and communication will be an important direction in the development of 6G technology, and high-rate communication and high-precision perception is a key 6G technology. The terahertz frequency band(0.1-10 THz) is rich in resources, which can support ultra-high rate wireless communication and precision perception. With its inherent characteristics of large bandwidth and parallel processing, it can break through the bottleneck of the electronic bandwidth of the terahertz system. The existing integrated terahertz communication and sensing system can not provide simultaneous measurement of distance and speed, and the range offset can not be eliminated in the single frequency modulation slope linear frequency modulation(LFM) radar, without the ability to provide the simultaneous measurement of distance and speed independently. Thus, further research is needed on the integration system of terahertz communication and perception. Combining photonics technology to design an integrated signal of high-speed communication and high-performance perception is a development direction in the integration of terahertz communication and perception.Methods To solve the above problems, we propose a bilinear frequency modulated optical terahertz communication and sensing integrated signal. The carrier frequency is 255 GHz, the communication modulation format is probabilistic shaping 64-order orthogonal amplitude modulation(PS64QAM), and the sensing signal is a dual linear frequency modulation(DLFM) signal, with the integrated signal generated by time division multiplexing(TDM) technology. The generation,transmission, and reception of terahertz signals are carried out by MATLAB and VPI co-simulation. Additionally, digital signal processing is employed to recover and extract information from communication perception signals.Results and Discussions PS64QAM-DLFM terahertz communication and sensing integrated signals are generated by TDM technology and photon-assisted technology, and the performance of communication and sensing can be flexibly controlled by adjusting the time-width ratio of communication and sensing signals. In the 255 GHz band, when the wireless transmission distance is 10 m and the time-to-width ratio of the all-sensing signal is 3∶5, a balance is struck between the communication and sensing performance. The communication rate is 31 Gbit/s, the distance resolution is 7.5 mm, and the speed resolution is about 114 m/s, with a ranging accuracy of about 7 mm and speed measurement accuracy of about 15 m/s. As shown in Fig. 12 and Table 2, with the continuously rising distance and speed, ranging and velocity measurement errors become increasingly larger. As shown in Fig. 11, the system can achieve a centimeter-level ranging function under moving targets, which is not available in the existing optical terahertz communication and sensing integrated system.Conclusions The proposed integrated signal can complete simultaneous communication distance and speed measurement.Compared with the existing optical terahertz communication and sensing integrated systems, the integrated signal communication terminal can achieve low-error performance thanks to probability shaping technology. In terms of perception, DLFM technology solves the fuzzy problem of the joint distance and speed measurement, and can still accurately detect the target distance in high-speed moving conditions. This proves that the integrated signal has the ability of high-speed communication and high-resolution radar ranging and velocity measurement, with broad application prospects in the future 6G communication.