Digitally Assisted RF-Analog Self Interference Cancellation for Wideband Full-Duplex Radios

Abstract

The ever-increasing demand for more data from users is pushing the development of alternative wireless technologies to improve upon network capacity. Full-Duplex radios provide an exciting opportunity to theoretically double the available spectral efficiency of wireless networks by simultaneously transmitting and receiving signals in the same frequency band.The main challenge that is presented in the implementation of a full-duplex radio is the high power transmitter leaking to the sensitive receiver chain and masking the desired receive signal to be decoded. This transmitter leakage is referred to as self interference and it is required that this self interference signal be cancelled below the receiver noise floor to achieve the full benefits of a full-duplex radio. Cancellation of the self interference signal is realized through several techniques, categorized as passive suppression, digital cancellation, and analog cancellation. These methods all have their challenges in achieving the full amount of cancellation necessary and therefore all three techniques are typically employed in the system.In this thesis, a novel digitally assisted radio frequency (RF) analog self interference canceller is proposed to suppress the self interference signal before the receiver chain for wide modulation bandwidth signals. This canceller augments minimum complexity RFanalog interference cancellation hardware that uses an RF vector multiplier in combination with a flexible digital rational function finite impulse response filter. The simple topology reduces the number of impairments added to the system through the analog components and identifies the parameters of the proposed filter in a deterministic and single iteration algorithm.The hardware proof-of-concept prototype is built using off-the-shelf RF-analog components and demonstrates excellent cancellation performance. Using four TX test signals with modulation bandwidths of 20 MHz, 40 MHz, 80 MHz, and 120 MHz, the self interference canceller achieves a minimum of 50 dB, 47 dB, 42 dB, and 40 dB of cancellation respectively. This thesis reviews the previously proposed self interference cancellation topologies, system non-idealities that provide challenges for full-duplex implementation, and the realization of the proposed RF-analog self interference canceller.iii Acknowledgements I would like to thank my supervisor, Dr. Slim Boumaiza, for giving me guidance, advice, and confidence throughout my Masters process. He has taught me how to properly conduct research, approach problems and allowed me to pursue a topic that suited my interests. The entire Emerging Radio Systems Group (EmRG) consists of intelligent, kind and helpful members who I have also learned a lot from and enjoyed working with.I would also like to acknowledge my incredible family and friends who have offered continuous love and support throughout this lengthy Masters process.Finally, I would like to dedicate this thesis to my husband, Michael, for his love, patience, and calming influence while pushing ...

A Mixed-Signal Circuit Technique for Cancellation of Interferers Modulated by LO Phase-Noise in 4G/5G CA Transceivers

“…A variety of different modulated spur mitigation techniques have been proposed in literature. They can be categorized into passive suppression techniques and cancellation architectures that can be divided into analog, digital and MS approaches [7].…”

“…This is beneficial with regards to compression effects and intermodulation distortion (IMD) components appearing in the RX baseband (BB). Although high levels of suppression can be reached, published analog architectures suffer from a trade-off between implementation complexity and cancellation performance [7], [13].…”

“…Mixed-signal cancellation (MSC) combines the simplicity of analog cancellation and the reliability of digital cancellation [7], [16]- [21]. In [17] an MS architecture is proposed as shown in Fig.…”

Full-Duplex Wireless Transceiver Self-Interference Cancellation Through FD-SOI Buried-Gate Signaling

“…However, solely digital SI cancellation techniques require huge dynamic range of RX and analog-to-digital converter (ADC). To mitigate this problem, various analog-domain solutions which cancel the SI earlier in RX chain have been implemented in conjunction with digital domain cancellation [2], [5]- [9].…”

“…Ideally, in order to reduce the dynamic range requirements of later RX stages, SI should be canceled as early as possible in RX chain. This has resulted in various analog SI cancellation techniques where cancellation is performed at the input of RX chain [2], [5]- [9]. However, SI cancellation at RX input comes at the penalty of increased noise figure (NF) due to additional SI cancellation circuitry.…”