A 500-GHz+ GaAs-Based Subharmonic Mixer Utilizing Terahertz Thin-Film Monolithic Integrated Circuit Technology

A Schottky barrier diode (SBD) based on GaAs thin-film substrate is designed and manufactured. The effective method for extracting intrinsic and parasitic parameters is discussed in detail through the development of an equivalent model, which facilitates the correction of diode measured results and performance optimization. Then, an innovative high-frequency equivalent model of suspended microstrip line (SML) is proposed first and an equivalent conductivity is introduced. Based on the corrected intrinsic parameters of SBD as well as the SML equivalent conductivity, a subharmonic mixer chip is designed, manufactured, and measured. A minimum dual-sideband (DSB) conversion loss (CL) of 8.23 dB can be obtained in upconversion measurement, as well as a radio frequency (RF) bandwidth up to 80 GHz. In addition, a minimum single-sideband (SSB) CL of 10.2 dB can be obtained in the downconversion measurement. Furthermore, an intermediate frequency (IF) bandwidth above 20 GHz can be obtained at the fixed local oscillator (LO) frequency of 260 GHz. The excellent up/downconversion measured results indicate that the mixer chip has important applications in terahertz communication and imaging systems.