DUPLO Deliverable D2.2 Integration report of RF and antenna self-interference cancellation techniques

Full-duplex sets challenging requirements for wireless communication radios, in particular their capability to prevent receiver sensitivity degradation due to self-interference (transmit signals leaking into its own receiver). The DUPLO project mainly targets solutions for wireless radios to facilitate full-duplex operation in compact commercially attractive communication devices. This work package focusses on the design of small form-factor antenna structures and RF circuits which offer a substantial self-interference isolation or rejection and support integration with other solutions developed in the DUPLO project (e.g. baseband cancellation). Previously published techniques mainly rely on physical dimensions (i.e., antenna spacing) and/or require bulky components. Therefore, they are not applicable in the DUPLO project, as they hamper dense integration in compact radios. The previous deliverables of this workpackage [1, 2] and the JSAC publication [3] report and motivate the architecture selection, design and initial measurements of the first antenna and RF prototype, and presents a theoretical link budget calculation methodology to derive the system component design requirements. Current document evaluates these earlier achieved results and develops, designs and fabricates new prototypes to improve the performance or to investigate the elimination of potential show-stoppers. This document continues on the three designs presented in D2.1 [1, 3]. The first design covers a dual-polarized microstrip patch antenna, where a second prototype has been design and fabricated. This prototype offers improved bandwidth and has a smaller form factor compared to the first prototype. This second prototype has been designed based on parametric optimization and the measured performance has been reported. The second design covers a duplexer based on a tunable electrical balance circuit. Some severe limitations have been observed with the first electrical balance prototype in terms of bandwidth and linearity. To investigate if these limitations can be overcome, a second prototype has been designed and fabricated. This second prototype implements a highly linear balance network with multiple degrees of freedom to create multiple tunable isolation notches. The third design covers an active cancellation network operating on RF signals, capable of cancelling dynamically the self-interference. The performance of different cancellation networks, including components with variable gain, phase and time delay, with gain, are evaluated in combination with the antenna solution developed in this project. These designs have been well received by the scientific community as this work has been accepted for publication in several peer-reviewed IEEE conferences. Compared to state-of-the-art, the developed designs differ mainly in terms of form-factor and integration potential in compact or portable radio system devices. Disclaimer: This document reflects the contribution of the participants of the research project DUPLO. The European Union and its agencies are not liable or otherwise responsible for the contents of this document; its content reflects the view of its authors only. This document is provided without any warranty and does not constitute any commitment by any participant as to its content, and specifically excludes any warranty of correctness or fitness for a particular purpose. The user will use this document at the user's sole risk. DUPLO WP2 D2.2 2 / 76