Abstract
Frequency multipliers and mixers based on Schottky barrier diodes (SBDs) are widely used in terahertz (THz) imaging applications. However, they still face obstacles, such as poor performance consistency caused by discrete flip-chip diodes, as well as low efficiency and large receiving noise temperature. It is very hard to meet the requirement of multiple channels in THz imaging array. In order to solve this problem, 12-μm-thick gallium arsenide (GaAs) monolithic integrated technology was adopted. In the process, the diode chip shared the same GaAs substrate with the transmission line, and the diode’s pads were seamlessly connected to the transmission line without using silver glue. A three-dimensional (3D) electromagnetic (EM) model of the diode chip was established in Ansys High Frequency Structure Simulator (HFSS) to accurately characterize the parasitic parameters. Based on the model, by quantitatively analyzing the influence of the surface channel width and the diode anode junction area on the best efficiency, the final parameters and dimensions of the diode were further optimized and determined. Finally, three 0.34 THz triplers and subharmonic mixers (SHMs) were manufactured, assembled, and measured for demonstration, all of which comprised a waveguide housing, a GaAs circuit integrated with diodes, and other external connectors. Experimental results show that all the triplers and SHMs had great performance consistency. Typically, when the input power was 100 mW, the output power of the THz tripler was greater than 1 mW in the frequency range of 324 GHz to 352 GHz, and a peak efficiency of 6.8% was achieved at 338 GHz. The THz SHM exhibited quite a low double sideband (DSB) noise temperature of 900~1500 K and a DSB conversion loss of 6.9~9 dB over the frequency range of 325~352 GHz. It is indicated that the GaAs monolithic integrated process, diodes modeling, and circuits simulation method in this paper provide an effective way to design THz frequency multiplier and mixer circuits.
Highlights
Over the past few decades, various terahertz (THz) technologies have been developed rapidly.Among them, THz imaging and sensing technology have broad application prospects in science and other fields, such as safety and security screening, process monitoring, non-contact material testing, radio astronomy, and earth observation [1,2,3,4,5,6,7,8,9]
Verifythe theeffectiveness effectivenessof of the the diode diode design method and simulation optimization method proposed in this article, three triplers and three mixers method and simulation optimization method proposed in this article, three triplers and three mixers were assembled and measured for the research on performance consistency
Taking THz active imaging array as the application background, 0.34 THz triplers, and mixers based on 12-μm-thick gallium arsenide (GaAs) monolithic integrated process and Schottky diode chips, are proposed in based on 12-μm-thick GaAs monolithic integrated process and Schottky diode chips, are proposed in this article
Summary
THz imaging and sensing technology have broad application prospects in science and other fields, such as safety and security screening, process monitoring, non-contact material testing, radio astronomy, and earth observation [1,2,3,4,5,6,7,8,9]. Sci. 2020, 10, 7924 systems based on all-solid-state electronics technology have been reported at the submillimeter and THz band [9,10,11,12,13,14,15]. Low-noise and broadband receivers are necessarily needed in THz imaging systems. These receivers are mainly based on Schottky diodes or III/V compound semiconductor transistors
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