Investigation of local oscillator isolation in a 300 GHz wireless link

This paper presents the measurement and analysis of local oscillator isolation in an analog frontend based on monolithic microwave integrated circuits (MMICs) at a carrier frequency of 300 GHz. The transmit-receive wireless system uses a single-balanced resistive mixer with in-phase and quadrature channels that provides a very good isolation of the local oscillator. The dependency of the isolation on the baseband input is presented. The isolation obtained when a signal is transmitted only on the in-phase channel is higher than in the case of the signal transmitted on the quadrature channel. The paper presents the measurement method and a theoretical analysis which confirms the experimental observations.