Technologies Of Terahertz Full-Duplex High-Rate Wireless Communication System Front Ends

Terahertz(THz)waves,which are in a special position between millimeter waves and light waves,are defined from 100 GHz to 10 THz.They have many advantages such as ultra-high bandwidth,high security,and strong directivity.With the explosive growth of global mobile data rates,the spectrum resources of traditional microwave and millimeter wave frequency bands are becoming more and more crowded.Therefore,it is urgent to develop new spectrum resources.Since the THz band has a large number of undeveloped spectrum resources,it has huge potential for ultra-high-rate wireless communication.Therefore,THz communication technology,as one of the key technologies of the 6G,has always been a hot research field and been extensively studied by scholars from all over the world.This dissertation focuses on solid-state THz full-duplex high-rate wireless communication technology,as well as the development of key circuits(THz filters,THz manifold-coupled multiplexers,THz quadrature modulator)in THz full-duplex real-time communication systems.Based on these circuits,the 210-GHz frequency division multiplexing wireless communication system was built,and the outdoor full-duplex wireless communication with a transmission distance over 1050 m was successfully realized.The main content of this dissertation includes the following four parts:(1)THz pseudoelliptic filter technology.The filter has the function of frequency selection in the communication system,which can avoid the influence of environmental noise and image signal.Low-loss,large-bandwidth,high-square-coefficient filters have always been a hot research topic for scholars domestic and overseas.In this dissertation,starting from the physical mechanism of introducing the transmission zero(TZ)by the dual-mode resonator,the THz pseudoelliptic filter is deeply studied.A 340-GHz pseudoelliptic waveguide filter based on TE₃₀₁ and TE₁₀₂ dual-mode resonators and extracted pole structure is firstly proposed.The insertion loss is better than 0.7 d B,3-d B relative bandwidth reaches 9.9%,30-d B coefficient is 0.87.Secondly,a 140-GHz pseudoelliptic waveguide filters based on TM₁₁₀and TE₁₀₁ dual-mode resonators is developed.The insertion loss of the proposed filter is better than 0.3 d B,3-d B relative bandwidth reaches 10%,the 30-d B coefficient is 0.81.The high performance of the filter is maintained while reducing the difficulty of device processing and improving design flexibility.(2)THz manifold-coupled multiplexer technology.The multiplexer is the core device in the frequency division multiplexing full-duplex communication system,which is mainly used for the separation and aggregation of different channel signals.Because of its complex design and difficult processing,relatively little research has been done in the past.In this dissertation,starting from the manifold-coupled multiplexer model establishment method,combined with the low-order distributed model and the full-wave electromagnetic(EM)model,an efficient and accurate design method suitable for the THz manifold-coupled multiplexer is proposed.Based on this method,a 220-GHz multiplexer is firstly proposed,which all channels are adopted Chebyshev bandpass filters.The measured results show that the insertion loss of four channels is better than 1.8 d B,the return loss of the common port is better than 15 d B,and the isolation between the transmission and reception channels is better than 60 d B.In order to improve spectrum utilization and realize broadband multiplexer,a 140 GHz triplexer based on the TM₁₂₀and TE₁₀₁ dual-mode resonator pseudoelliptic filter proposed in(1)is developed.The measured return loss is better than 15 d B,the relative bandwidth is greater than 20%,and the isolation between the three channels is better than 45 d B.(3)THz quadrature modulator.In the terahertz frequency band,the traditional superheterodyne system requires one or even multiple frequency conversions,which increases the system complexity and makes it difficult to achieve broadband high-speed data transmission due to the large IF bandwidth.However,in the I/Q direct modulation architecture,the baseband I and Q signals are directly frequency-converted through THz quadrature modulators,which can greatly simplify the system links and achieve broadband high-speed transmission.Therefore,this dissertation focuses on the THz quadrature modulator technology,starting from the physical mechanism of Schottky barrier diodes,based on the 3-D electromagnetic accurate model of mixing diodes,a 210-GHz quadrature modulator is developed using the"field-circuit"design method.The measured results show that in the frequency range of 190-230 GHz,the frequency conversion loss of the quadrature modulator I and Q channels is less than 16 d B,the optimal frequency conversion loss is 11.1 d B and 11.4 d B,respectively.The amplitude imbalance of the I and Q channels is less than 4d B.In addition,the image rejection of the quadrature modulator is also measured,which shows better than 9 d B in the IF range of1-18 GHz.(4)Terahertz full-duplex high-rate wireless communication technology.On the basis of key circuit breakthroughs and realization of the system prototype,the research on THz full-duplex high-speed wireless communication technology is carried out.A 100 Gbit/s THz wireless communication principal verification system and a 210 GHz full-duplex wireless communication system are built.The former uses the high-rate arbitrary waveform generator and high-speed oscilloscope.Based on the coherent demodulation method,the 16 QAM modulated signal transmission with a 100 Gbit/s data rate is realized over 2 m.The bit error rate of this system is less than 10^-7,thereby proving the potential of terahertz ultra-high-rate communication.Comprehensively considering factors such as working bandwidth,device performance,baseband data processing capability,etc.The uplink and downlink of the latter system are adopted the traditional superheterodyne architecture with 10 Git/s date rate and I/Q direct modulation architecture with 20 Gbit/s data rate,respectively.Successfully realized the high-definition video transmission demonstration over a distance of 1050 m.