| Due to the advances in semiconductor integrated circuit technology,the terahertz frequency band has been studied extensively.The terahertz superheterodyne transceiver system has immense potential in fields such as communication,radar,materials science,security,biomedicine,earth science,and astronomical exploration.A typical terahertz transceiver system comprises the following core components: frequency multipliers,mixers,amplifiers,and filters.Therefore,research on key technologies such as Schottky diode modelling,frequency multiplying,mixing,filtering,and integration is of great theoretical and practical significance for the development of high-performance terahertz solid-state source and wireless transceiver systems.In this dissertation,the Schottky barrier diode is employed for studying the Schottky diode multi-physics thermal model and physical electrothermal model,terahertz frequency multiplying technology,terahertz harmonic mixing technology,terahertz waveguide filtering technology and related integrated technology.The research is outlined as follows:(1)Research on Schottky barrier diode electrothermal model.The Schottky barrier varactors intended for terahertz frequency multipliers must satisfy the stringent requirements for input drive power,and address the problem of internal self-heating of the diode encountered in practical applications.Therefore,the heat transfer in solids and the electromagnetic heating multi-physics were used to establish the thermal models for Ga As Schottky barrier four-anode and six-anode varactors,respectively.The temperature distribution,current distribution,and the impact of dissipation power,ambient temperature,and substrate on the temperature of the Schottky diode were studied,and the thermal resistance of the diode is extracted.Variations in the temperature-dependent intrinsic and extrinsic parameters of the Schottky barrier diode under different operating states affect the diode current-voltage(I-V)and frequency conversion characteristics.To solve this problem,the diode simulation program with integrated circuit emphasis(SPICE)electro-thermal model and single-port symbolically defined devices(SDD)electro-thermal model of Schottky diode were established based on the temperature-dependent saturation current and series resistance.Next,by employing the thermal resistance extracted from the diode's thermal model,the Schottky diode physical SDD self-consistent electro-thermal model I was established based on the four-port SDD model.Furthermore,the temperature-dependent Ga As electron mobility was used to modify the saturation current,and the Schottky diode physical SDD self-consistent electro-thermal model II was established.Then,the effect of temperature,dissipation power,thermal resistance,saturation current,and series resistance on the characteristics of diode I-V was studied.Compared with the traditional SPICE model which ignores the self-heating effect,the Schottky diode SDD self-consistent electro-thermal models exhibit clear signs of current saturation.The Schottky diode electro-thermal model established in this dissertation demonstrates excellent generalization ability,thereby providing guidance not only for the structural optimization and reliability design of the Schottky diode but also for the study of terahertz frequency multipliers while considering the self-heating effect.(2)Research on design methodology for terahertz frequency conversion circuits.The subdivision design method(SDM),global design method(GDM),and half-subdivision and half-global design method(HS-HGDM)were studied from various perspectives including the design principle,examples,design flow,advantages,and disadvantages.Compared with the SDM,the terahertz mixers and frequency multipliers designed using the HS-HGDM are characterized by large optimization space and flexible circuit topology.Compared with GDM,the terahertz mixers and frequency multipliers designed using the HS-HGDM have improved the circuit convergence,stability,and versatility,and are less vulnerable to problems such as zero trap and multi-values.In this dissertation,the universality of the SDM and the uniqueness of the GDM were unified,and four types of the HS-HGDM based on a single passive structure were proposed for the design of terahertz mixers.Compared to the HS-HGDM with double passive structures,the HS-HGDM method developed in this study offers advantages such as flexible design,large optimization space,and simple circuit topology.Research on the design methods of terahertz frequency conversion circuits lays the foundation for realizing high-performance terahertz mixers and frequency multipliers,and also provides the method guidance for following 220 GHz and 500 GHz sub-harmonic mixers.(3)Research on terahertz frequency multipliers while considering the self-heating effect.The parameters of the traditional diode SPICE model,such as saturation current,series resistance,and ideal factor,are assumed as constants for the design of terahertz frequency multipliers and mixers,ignoring the influence of the self-heating effect on the terahertz frequency conversion circuit.To solve this problem,three terahertz frequency multipliers were studied using the self-built Schottky diode physical SPICE electro-thermal model and SDD electro-thermal model.Compared with the traditional diode SPICE model with constant parameters,the simulation results for the terahertz frequency multipliers with the diode physical SPICE and SDD electro-thermal model were closer to the measurement results.The self-built Schottky diode physical SPICE electro-thermal model and SDD self-consistent electro-thermal model were experimentally studied to verify the versatility,accuracy,and validity,serving as the model foundation for the design of high-performance terahertz frequency multipliers.(4)Research on terahertz harmonic mixers and harmonic mixers with integrated waveguide filters.By using Ga As Schottky diodes,two 220 GHz subharmonic mixers with the GDM and the single passive HS-HGDM were designed,fabricated,and experimentally studied.In the 220 GHz subharmonic mixer developed using the GDM,the measured single sideband(SSB)conversion loss in the RF frequency band of199-238 GHz was 7.84-12.4 d B with a LO frequency of 108 GHz.In the 220 GHz subharmonic mixer developed using the single passive HS-HGDM,the measured SSB conversion loss in the RF band of 200-240 GHz was 6.61-8.12 d B with an IF frequency of 1.8 GHz.The comparison between the hybrid integrated 220 GHz subharmonic mixers based on Schottky diode developed using different design methods revealed that the overall performance of the 200-240 GHz subharmonic mixer using the single passive HS-HGDM is comparable to that of similar mixers reported in the literature.To improve the integration of the terahertz superheterodyne system,a 500 GHz subharmonic mixer was designed based on the single passive HS-HGDM.In the RF frequency band of 473-519 GHz,the optimal measured SSB conversion loss was 13.4d B with a LO frequency of 250 GHz.A 250 GHz and a 500 GHz waveguide filter were integrated into the LO port and RF port of a 500 GHz subharmonic mixer,respectively.In the IF band of 0-20 GHz,the measured DSB conversion loss was 10.1-11.5 d B with a LO frequency of 250 GHz.The 500 GHz subharmonic mixer integrated with waveguide filters exhibited excellent performance and high integration,it performed well in the LO frequency band of 241-260 GHz. |
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