Comparison of active dual-gate and passive mixers for terahertz applications
The authors propose four versions of a dual‐gate active down‐conversion mixer for H-band applications. The mixer operates at a local oscillator (LO) frequency of 240 GHz. Itis designed for maximum conversion gain and a large bandwidth of at least 50 GHz from 220 to 270 GHz. Furthermore, the mixer is .optimised to operate at low LO power levels beneath 0 dBm. This renders power hungry LO buffer stages redundant. Hereby, the necessary chip size and the overall power consumption of fully integrated receiver scan be drastically reduced. Four different versions of the downconverter were designed. Firstly, the layout of the transistors was changed from a conventional multi‐transistor cell design to a mixer topology within the multi‐finger transistor cell. Secondly, two on‐chip solutions to decouple the drain voltage from the intermediate frequency (IF) signal were realised to facilitate zero‐IF conversion: a resistive and an active load. The results are presented and the advantages and disadvantages of the four versions for the usage in terahertz applications are thoroughly analysed. Finally, the active dual‐gate mixers are compared to a state‐of‐the‐art resistive mixer for H‐band with regard to conversion gain, bandwidth, linearity, noise figure and chip size.