Design of an Image Frequency Rejection Mixer for the Terahertz Band

This chapter presents the analysis and design of a simply balanced mixer with image frequency rejection in the frequency band above 100 GHz. This circuit is designed for down-conversion using Pseudomorphic High Electron Mobility Transistors (PHEMT) from the PH15 process of the United Monolithic Semiconductors (UMS) foundry. It is designed using Monolithic Microwave-Integrated Circuit (MMIC) technology. The proposed mixer operates with a lower LO power, making it easy to implement in this frequency range. We used the charge injection and series shunt methods to find a compromise between gain, noise figure, linearity, and image rejection ratio. The downconverting mixer with charge injection technology has a high-conversion gain of between 15 and 25 dB, a low-noise figure of around 5.3 dB, good RF-IF isolation and an image frequency rejection ratio of over 35 dB at the frequency band 135 GHz to 145 GHz, as demonstrated using the Advanced Design System tool.