| PhD Viva

Name of the Speaker: Mr. Ramasamy PL (EE15D204)
Guide: Dr. Sankaran Aniruddhan
Online meeting link: https://meet.google.com/rnv-iaat-oas
Date/Time: 20th June 2025 (Friday), 2:00 PM
Title: Analysis and Design of RF Canceller for Self-Interference Cancellation in Full-duplex Radios.

Abstract :

In-band Full-Duplex (IBFD) is a promising technology for future 6G and next-generation wireless communication standards. It can potentially double data throughput at the physical (PHY) layer and offers greater spectral efficiency compared to conventional Time-Division Duplexing (TDD) and Frequency-Division Duplexing (FDD) methods. However, a major challenge in implementing IBFD is the strong self-interference (SI) from the transmitter to the receiver. This issue is mitigated using advanced self-interference cancellation (SIC) techniques in both the RF and baseband domains.

In the first part of this talk, we present a theoretical analysis of the fundamental limitations in RF cancellation. We model the residual signal that remains after conventional active cancellation. Based on this analysis, we introduce the concept of a Spectral-Shaper (SS) circuit, which adapts to the characteristics of the residual signal and enhances SIC in higher-order canceller stages. We outline the generic architecture of a multi-stage SS-based RF canceller and highlight the advantages of distributing cancellation frequencies. A closed-form expression for this distribution is also provided.

In the second part, we present the design and implementation details of the RF front-end for an IBFD transceiver that integrates a two-stage SS-based RF canceller. The prototype successfully suppressed a +27 dBm transmit signal by more than 73 dB over a 20 MHz channel at 2.45 GHz. Measurement results under various real-world scenarios are discussed, and our scheme is compared with existing state-of-the-art solutions.

Finally, we present over-the-air (OTA) measurements conducted using the prototype canceller, which successfully demonstrated IBFD operation. The talk concludes with a summary of the key findings of this research and highlights potential directions for future work.