Research On Absorption Terahertz Solid-state Switch And High-speed Amplitude Control Device

Terahertz absorption-type solid-state switches and high-speed amplitude modulators are key components of terahertz communication system modules.However,currently,terahertz direct amplitude modulators are mainly designed using strong resonance principles,resulting in mostly reflective modulators.The high back-reflection loss of reflective modulators has an impact on the preceding devices.In response to the development requirements of terahertz communication systems,this thesis analyzes the theory of absorption-type terahertz solid-state switches.It designs absorption-type terahertz solid-state switches with dual-branch and multi-branch configurations for center frequencies of 140 GHz and 220 GHz,and verifies the feasibility of the device designs through experimental testing.Furthermore,due to the narrow modulation bandwidth and low modulation depth associated with the use of strong resonance methods,the performance and development of modulators are significantly constrained.To address this issue,this thesis also conducts research and analysis on terahertz amplitude modulators with ultra-high modulation depth and wide modulation bandwidth based on the principles of artificial surface plasmon resonance dispersion breaking and terahertz wave phase interference synthesis.The main research work and results of this thesis are as follows:1.The theoretical analysis of absorption-type terahertz solid-state switches is conducted,and the conditions for absorption are analyzed from the perspective of transfer matrix.The absorption theory is then extended from dual-branch to multi-branch,making the theory of absorption-type terahertz solid-state switches universal.Based on the theoretical analysis,the designs of dual-branch and multi-branch absorption-type terahertz switches are completed for the frequency ranges of 140 GHz and 220 GHz.The simulation results for the dual-branch absorption-type terahertz solid-state switch at 140 GHz show an insertion loss of 1.5 d B,a maximum switch ratio of 17 d B,and a bandwidth that simultaneously satisfies a standing wave ratio of less than 1.2,covering 20 GHz,with a standing wave ratio of less than 1.1 at the center frequency of 140 GHz.For the multibranch absorption-type terahertz solid-state switch at 220 GHz,the simulation results show a minimum insertion loss of 2 d B,a maximum switch ratio of 30 d B,and a standing wave ratio at the center frequency better than 1.1.The processed and assembled 220 GHz multi-branch absorption-type terahertz solid-state switch demonstrates experimental results of a minimum insertion loss of 7.8 d B,a maximum switch ratio of 12 d B within the frequency range of 170 GHz to 260 GHz,a bandwidth of 60 GHz with a standing wave ratio better than 1.5,and a minimum standing wave ratio of 1.1 between 200 GHz and 210 GHz.The dynamic test results achieve a single-tone modulation rate of 32 GHz and a modulation rate of 17 Gbps.2.To address the contradiction between modulation bandwidth and modulation depth caused by strong resonance,the following approaches are proposed:(1)Terahertz modulators based on spoof surface plasmon resonance dispersion coupling reconstruction.The simulation results show that the designed modulator structure exhibits considerably low insertion loss.The modulator has an insertion loss of 0.8 d B,0.55 d B,and 0.5 d B at140 GHz,220 GHz,and 340 GHz,respectively.The corresponding switch ratios are 32 d B,29 d B,and 17 d B,with low group delay differences.(2)Terahertz modulators based on two-channel terahertz phase interference synthesis.The simulation results show that within the frequency range of 180 GHz to 260 GHz,the modulator achieves a minimum insertion loss of 5 d B,a maximum isolation of 70 d B,and realizes a modulation depth of nearly 65 d B and a bandwidth of 80 GHz.