A clock-less coherent ultrawideband detector for active-reflector-based ranging with high interference rejection

Abstract

This paper introduces a clock-less coherent ultrawideband (UWB) detector tailored for active-reflector-based ranging systems, specifically engineered for robust performance in high-interference environments. Conventional impulse-radio UWB (IR-UWB) ranging systems often face challenges with various interference sources, which can degrade their precision. Non-coherent detectors, while offering design simplicity, typically exhibit lower sensitivity and greater susceptibility to interference. Conversely, existing coherent detectors, though inherently more robust, often introduce complexities related to precise clock synchronization and overall system cost. This research addresses these limitations by evolving a previously developed non-coherent two-way ranging system through the design and implementation of a novel coherent UWB detector. The proposed architecture enhances interference resilience by employing binary phase shift keying (BPSK) combined with pulse position modulation (PPM) for sync word encoding, a more robust alternative to on-off keying (OOK) based methods. A critical innovation lies in the sync word detector circuit, which features a configurable 4-bit sync word, tunable delay lines, and dual comparators, enabling high selectivity for the intended UWB signal. Fabricated using 65 nm CMOS technology, the proposed detector maintains comparable timing accuracy to its non-coherent predecessor while demonstrating markedly superior rejection capabilities against single-tone interference (STI), narrowband interference (NBI), and co-channel UWB interference. These empirical results underscore the detector’s suitability for demanding applications that require dependable ranging performance amidst pervasive radio frequency interference.