Receiver Design for Close-In Phase Noise and Reciprocal Mixing Compensation

In many wireless communication systems, the receiver needs to be highly integrated, reconfigurable, and able to coexist in congested frequency bands in the presence of many strong interfering blockers. Although significant progress has been made in advanced receiver design, mitigating the effects of oscillator phase noise remains a major challenge. Phase noise degrades the desired signal in two ways – the close-in phase noise and reciprocal mixing distortion.

In the case of close-in phase noise distortion, the phase noise spectrum distorts the desired signal itself, while in the case of reciprocal mixing, the phase noise spectrum couples with nearby interfering blockers to corrupt the desired signal. While the topic of close-in phase noise distortion has been addressed in the literature, practical solutions to mitigating the effects of reciprocal mixing are nearly non-existent.

The general approach to minimizing the distortion from reciprocal mixing today is to suppress the blocking interferers themselves with sharp off-chip filters at the expense of increased complexity, form factor and cost as well as reduced reconfigurability. This project will jointly and seamlessly compensate for both the close-in phase noise and reciprocal mixing distortion without requiring training signals or knowledge of the interfering blockers.

The immediate impact of the proposed research is the introduction of a new approach to compensate for the effects of reciprocal mixing, which is a major problem in communication receiver design. Furthermore, as the concepts and techniques developed in the proposed research are general and broadly applicable to address other sources of circuit non-idealities, the proposed research is expected to have a major impact on how future receivers are designed.

The PI’s research activities are coupled with an educational plan that delineates how the research will help train both graduate and undergraduate students. The multi-disciplinary nature of the proposed research is expected to broaden the technical understanding of the students involved. The project includes participation of undergraduate students and the recruitment of students from underrepresented groups by leveraging programs at the PI’s institution.

The proposed approach employs an IF-receiver architecture with a modified local oscillator to provide the receiver front-end with the additional degrees of freedom necessary for the desired signal to span a different vector space than the subspace spanned by reciprocal mixing and close-in phase noise distortion. The phase noise induced distortion can then be removed by projecting to its null space which involves multiplying and summing of baseband samples to recover the desired signal.

Despite the simplicity of the proposed phase noise compensation approach, preliminary results suggest that the resulting performance improvements are significant. There are significant research issues at both the circuit and algorithmic levels that will be addressed to fully realize the benefits of the proposed compensation approach.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.