Self-interference cancellation: The future of FDD in mobile devices скачать в хорошем качестве

Self-interference cancellation: The future of FDD in mobile devices

Leo Laughlin, (Co-founder & CTO, Forefront RF) presenting at Interlligent UK's 2024 RF Design Seminar. Today’s mobile devices rely on fixed frequency filter, such as surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters, for frequency division duplex (FDD) operation. These are used to prevent self-interference, wherein the relatively high-powered transmit signal to the receiver, preventing reception of receive signals. SAW and BAW filters provide the high selectivity needed to attenuate self-interference in FDD systems, which typically operate with narrow duplex separation frequencies. A drawback of this approach is that these filters are fixed to a specific frequency band, meaning that multiple duplexer components, and switches for bands selection, are needed to support multi-band operation. This architecture leads to increased size, cost, and RF front-end losses, as the number of supported bands increases. Self-interference cancellation is a fundamentally different approach, in which a copy of the transmitted signal is processed to create a cancellation signal, which is then injected into the receive signal path to cancel self-interference. Self-interference cancellation can replace SAW and BAW filters with a frequency tunable FDD RF front-end architecture, replacing multiple components with a single circuit and thereby reducing the size of the RF front-end. This presentation provided an overview of self-interference cancellation technology, and discussed the pros and cons of different approaches to implementing self-interference cancellation in the context of mobile devices.