A terahertz mixer is one of terahertz key components and widely used on terahertz wireless communication, remote sensing, aerospace exploration, and biomedical system. The performance of the terahertz mixer has a great effect on the entire terahertz transceiver system performance. This paper proposes a 220 GHz broadband sub-harmonic mixer based on global design method (GDM), which is different from the traditional subdivision design method of which the mixer circuit is composed of functional unit circuits. Instead, the GDM adopts the overall performance of the mixer (conversion loss) as an optimization goal. The continuous structures of the circuit are described by ideal transmission line models and waveguide models, meanwhile, the S-parameters of the de-embedded model are used to describe the discontinuous structures. The measured single-sideband (SSB) conversion loss is basically consistent with the simulation results, which verifies the accuracy and reliability of the GDM. When local oscillator (LO) frequency is fixed at 110 GHz, the measured SSB conversion loss is less than 10 dB with the average value of 8.1 dB from 198 to 238 GHz. The minimum conversion loss of the mixer is 6.35 dB at 207 GHz. The measured double-sideband noise temperature of the mixer is less than 924 K at an intermediate frequency of 1.6 GHz. The GDM has the characteristics with a wide frequency band, small circuit size, simple structure, low LO power, and stable performance, and can also be applied to other terahertz components. INDEX TERMS Terahertz components, terahertz sub-harmonic mixer, subdivision design method, global design method.

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A low-barrier Schottky barrier diode based on the InGaAs/InP material system is designed and fabricated with a new non-destructive dry over-etching process. By using this diode, a high-sensitivity waveguide detector is proposed. The measured maximum responsivity is over 2000 mV/mW at 630 GHz. The measured noise effective power (NEP) is less than 35 pW/Hz0.5 at 570–630 GHz. The minimum NEP is 14 pW/Hz0.5 at 630 GHz. The proposed high-sensitivity waveguide detector has the characteristics of simple structure, compact size, low cost and high performance, and can be used in a variety of applications such as imaging, molecular spectroscopy and atmospheric remote sensing.