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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]

Multi-label classification is a branch of machine learning that can effectively reflect real-world problems. Among all the multi-label classification methods, stacked binary relevance (2BR) is a classic approach. Based on 2BR, a series of optimized algorithms have been derived. Although these algorithms have adapted complex optimizing processes and shown remarkable performance, their core concepts are rather similar, mainly involving restructuring the feature spaces of meta-classifiers. Existing research has rarely discussed that the use of inappropriate two-level predictions causes negative impacts on 2BR structures. In this study, we propose a 2BR-based label correction method named LabCor, which focuses on the identification and correction of unreliable two-level predictions. We first discuss the inner mechanism by which the 2BR-based algorithms obtain their two-level outputs and find a marker that can reflect the reliabilities of the samples predictions. Based on the mechanism, we then introduce a graph based output determination method that can use the training samples to generate dimensional decision patterns. The global label count distribution is also used to reflect the goal of classification problems. In the prediction phase, LabCor uses the decision patterns and label count constraints to identify and correct the misclassified labels. According to the evaluation results, the proposed method can effectively reduce the impact of troubling two-level predictions and yield superior or competitive performance versus well-established 2BR-based algorithms. [ABSTRACT FROM AUTHOR]

In this paper, a new terahertz solid-state frequency doubler design method named function-based harmonic impedance optimization method (FHIOM) is reported to improve the simulation iteration speed and accuracy of terahertz solid-state circuit design. Obtaining the matching impedance of the diode part in the optimal operating condition and realizing this impedance through the input-output matching structure are the two main steps in the design of the terahertz doubler. In this design method, harmonic impedance optimization and function-based impedance optimization are applied to quickly obtain the best input and output embedded impedance of the broadband frequency doubler device, which reduces the blindness of tentative optimization. This method innovatively estimates the impedance of the matching structure through the formula, which strengthens the connection between impedance optimization and matching structure realization. Based on the function-based harmonic impedance optimization method, a 220 GHz doubler is designed, processed, and measured. Measured results show that the doubler exhibits a bandwidth from 212 GHz to 230 GHz, with a conversion efficiency of above 15.0% a mean output power of 9.12 mW when supplied with up to 32 mW of input power. A 16 mW peak output power with a 16.4% efficiency was measured at 228 GHz when the input power was 97.55 mW. The frequency doubler design method presented in this work has the advantages of high efficiency and accuracy, which makes it very attractive for practical broadband terahertz applications. [ABSTRACT FROM AUTHOR]