Cancelling Co-Channel Interference in Extremely Broadband Receivers

Modern 6G transceivers operate in the sub-THz band (100-300 GHz). Due to the high operating frequencies, baseband processing becomes particularly challenging. 6G systems propose using these frequency bands to achieve higher data capacity, but handling multi-GHz wide baseband signals presents a technical challenge. The purpose of this work is to investigate the interference mechanisms in a complex-IF downconversion receiver that selects distinct channels, often referred to as Component Carriers (CC) for independent processing. It is anticipated that the majority of receivers in the future will have similar architectures, because state-of-the-art analog-to-digital converters cannot process signals above 2-3 GHz bandwidth. Hence, the wide baseband must be divided into multiple component carriers, each will be processed separately in the digital domain. The receiver example in this work consists of eight component carriers and the bandwidth is up to 8 GHz. Interference due to image frequencies and harmonic mixing was studied using a MATLAB-based mathematical model. The results were verified through circuit-level simulations using passive Metal–Oxide–Semiconductor (MOS) mixers implemented in 130-nm SiGe BiCMOS technology, provided by the Leibniz Institute for High Performance Microelectronics (IHP) Solutions GmbH. Analog and digital mitigation techniques are described. Simulation results are provided for cancellation of harmonic mixing effects and cancellation of image frequency components in the digital domain. Image Rejection Ratio (IRR) improvement of about 10 dB was observed (from 25.5 dB to 35.6 dB), which is sufficient to detect the signal.