Research On Terahertz Mixer Based On Holistic And Semi-holistic Design Methods

The terahertz mixer is the core component of the terahertz transceiver system,and an important part in the research of terahertz technology.In the terahertz band,sources with high power and high performance are scarce and expensive.The subharmonic mixer can effectively solve this problem,and the required local oscillator frequency is only half of the RF frequency.Therefore,this paper mainly focuses on the research of THz subharmonic mixer and design method.The terahertz mixers reported in recent years at home and abroad are studied at first in this paper,providing a foundation for subsequent design.The principle of designing mixer with Schottky diodes and the modeling of Schottky diodes in terahertz frequency band are introduced in detail,with an emphasis on combining the diode's intrinsic model with parasitic effect.A 220 GHz subharmonic mixer is developed by holistic design method after comparing the advantages and disadvantages of traditional partial design method and holistic design method.Based on the two methods,a 560 GHz subharmonic mixer is designed by the semi-holistic design method.In this paper,the holistic design method is adopted for the 220 GHz subharmonic mixer to satisfy both the up-conversion and down-conversion simulation,thus obtaining the simulated results satisfying both the RF bandwidth and the LO bandwidth.Simulation results: During up-conversion simulation,the conversion loss is better than 7.3dB,and a wide frequency band is required for the local oscillator.The return loss simulation result is between 100 GHz and 120 GHz,which is better than 8.6dB.The conversion loss is better than 9 dB during down-conversion simulation.RF return loss is better than 10 dB within the RF 200-240 GHz.The measurement results show that when the intermediate frequency is in the range of 20 GHz,the single-side band conversion loss of the corresponding RF frequency point is basically less than 10 dB.When the local oscillator frequency is fixed at 108 GHz,the measurement results: the conversion loss is less than 9dB within the RF 203-230 GHz frequency range;an optimal value of 7.1dB is obtained at 218 GHz.The operating frequency of the local oscillator is wide,and it can work normally in 104GHz-120 GHz.On this basis,the semi-holistic design method is adopted for the 560 GHz subharmonic mixer.The simulation results show that when the local oscillator frequency is 280 GHz and the local oscillator power is 3mW,the single-side band conversion loss of the mixer is less than 9.2dB within the RF 540-580 GHz frequency range.The optimal conversion loss value is 7.28 dB at 566 GHz.