Title:  Adaptive Distortion Mitigation for Frequency-Selective Limiters for Improved Robustness to Interference

Committee:

Dr. Steve Kenney, ECE, Advisor

Dr. Benjamin Yang, ECE

Dr. Richard Causey, ECE

Dr. Azadeh Ansari, ECE

Dr. Rick Trebino, Physics

Abstract: The objective of this doctoral dissertation is to improve robustness to interference in a radio receiver application by developing advanced digital signal processing techniques for a frequency-selective limiter (FSL), a commercially available passive magnetic device that automatically and selectively attenuates signals above a threshold level. These innovations can improve its spectral selectivity as an automatically tuned notch filter or cancel associated distortion to increase spectral efficiencies when using FSLs to mitigate interference and extend receiver dynamic range in dense spectral environments. Two methods of distortion mitigation are investigated: 1) model-based post-distortion correction and 2) an adaptive feed-forward distortion cancellation architecture that does not rely on predictive models for FSLs. A proof-of-concept prototype is reported, including benchtop post-processing demonstrations that show effective distortion mitigation for various combinations of single-frequency tones, single-carrier QPSK waveforms, and LTE waveforms, in terms of suppression of out-of-band spectral distortion, including spectral regrowth, cross-modulation and intermodulation distortion, as well as in-band performance improvements in terms of EVM and BER, thus demonstrating the potential for increased receiver robustness to interference in conjunction with an FSL.