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In this paper, a novel full waveguide matching method (FWMM) is proposed to improve design efficiency and verify the feasibility of full waveguide matching for terahertz frequency doubler. In the proposed method, the frequency doubler is divided into three parts: packaging diode, input matching waveguide, and output matching waveguide, each of which realizes different functions. The most important diode embedding impedance matching part is transferred from the microstrip to the input and output matching waveguide. The impedance matching of the waveguide is realized by the structure called quasi-coupled resonator. These quasi-coupled resonators are implemented by inserting irises at the broadside of the waveguide and function as a capacitive load for the circuit. Using this method, a compact and efficient frequency doubler was designed and characterized. Measured results show that the peak efficiency of the doubler is 25.8% at 215 GHz with 50 mW input power. The good output performance of the 220 GHz doubler verifies the effectiveness of the proposed full waveguide matching method. [ABSTRACT FROM AUTHOR]

This paper summarizes the development of novel Schottky-diode-based terahertz frequency multipliers. The basic structure and manufacturing process of planar Schottky barrier diodes (SBDs) are reviewed, along with other diode structures that have been proposed in the literature. A numerical modeling method for the novel diodes in the context of terahertz frequency multipliers is presented, which includes 3D electromagnetic (EM) modeling, electro-thermal modeling and modeling of physical non-ideal effects. Furthermore, a general design methodology for developing terahertz frequency multipliers is introduced, involving a sub-division design method (SDM), a global design method (GDM) and a half-sub-division and half-global design method (HS-HGDM). These methods are summarized and compared for 110 GHz and 220 GHz frequency multipliers in the context of communication and imaging applications. Laboratory measurements of these multipliers show good agreement with numerical simulations. Finally, several classic terahertz remote sensing systems are reviewed, and a 220 GHz remote sensing system established using novel frequency multipliers for security inspection purposes is presented along with associated imaging results. [ABSTRACT FROM AUTHOR]

This paper describes the design and demonstration of a 135–190 GHz self-biased broadband frequency doubler based on planar Schottky diodes. Unlike traditional bias schemes, the diodes are biased in resistive mode by a self-bias resistor; thus, no additional bias voltage is needed for the doubler. The Schottky diodes in this verification are micron-scaled devices with an anode area of 6.6 μm2 and an epitaxial layer thickness of 0.26 μm. For accurate design of the doubler, the 3D-EM model of the Schottky diode is built up to extract the parasitic parameters induced by the diode package when frequency rises up to the terahertz band. In order to implement broadband working, input waveguide steps, output suspended microstrip steps, and output probe with bias filter are all used as matching elements for impedance matching. Measured results show that the doubler exhibits a 3 dB bandwidth of 34% from 135 GHz to 190 GHz, with a conversion efficiency of above 4% when supplied with 100 mW of input power. A 17.8 mW peak output power with a 10.2% efficiency was measured at 166 GHz when the input power was 174 mW. The measured results agree well with the simulated results, which indicates that the self-bias scheme for Schottky diode-based frequency multipliers is feasible and effective. [ABSTRACT FROM AUTHOR]