Research On Mixing Demodulation Technology For THz Direct Modulated Communication

Terahertz is considered an important way towards 6G communication.In recent years,both at home and abroad,terahertz communication system has been continuously explored and constructed.And relevant prototypes with high-speed communication capability of a certain distance have been developed.In terahertz communication system,modulation and demodulation is a very important part and mixer has a close relationship with it.In a communication system,a mixer can be used as either a transmitter or a receiver of a signal.In this thesis,fundamental and sub-harmonic mixers are developed for terahertz wireless communication system,involving multiple frequency bands such as 0.34 THz,0.22 THz,0.14 THz and 0.12 THz.Based on the further study of schottky diode modeling and mixing circuit simulation method,analyze the principle of the fundamental wave mixer and the harmonic mixer and formulate the corresponding research plan and implementation plan.Several mixers have been developed by using the planar schottky diode and Ga As reverse parallel diode and been applied in the terahertz wireless communication system.Major research work includes:(1)The design scheme and simulation method of the mixer are developed,and the practice of establishing the unit circuit model first and then discretizing it to optimize the overall performance is established.Based on this,a 340 GHz sub-harmonic mixer with low intermediate frequency output is developed to meet the demand of 0.34 THz communication system for low frequency conversion loss mixer.The measured optimal value of SSB conversion loss is 9.85 d B.(2)The fundamental mixer for 0.12 THz communication system is developed.First use of the fin line-suspended microstrip line structure to develop a 110 GHz fin-line fundamental wave mixer.Then to meet the requirements of the system,develop three 120 GHz fundamental wave mixer which are using low frequency signal as the driving source.Finally,the conversion loss of a 120 GHZ fundamental wave mixer is tested.The results show that the SSB conversion loss is less than 10 d B when the local oscillator frequency is fixed at 20 GHz and the minimum SSB conversion loss is 6.21 d B when the local oscillator frequency is fixed at 30 GHz.(3)Firstly,a 140 GHz sub-harmonic mixer is developed for a 0.14 THz wireless communication system.Secondly,two IQ mixers with center frequencies of 200 GHz and220GHz are designed.Finally,to meet the demand of a 0.34 THz direct modulation communication system,a high intermediate frequency output harmonic mixer is designed.And then use it to complete a short and medium distance communication experiment.The work of this part lays a solid foundation for the terahertz direct modulation communication system received by a mixer.