Hybrid Waveform-Based Efficient Chirp Demarcation and Clock-Free Synchronization in FMCW Radar Systems

Phase coherence is critical for accurate Doppler extraction in frequency-modulated continuous-wave (FMCW) radars. While integrated system-on-chip (SoC) solutions achieve this through shared clocking, discrete commercial-off-the-shelf (COTS) radar systems often lack inherent synchronization, leading to phase inconsistencies and Doppler errors. Existing solutions typically add hardware complexity, such as extra general-purpose input/output (GPIO) bits and ADC channels, for chirp demarcation. This work proposes a hybrid FMCW–CW waveform that embeds chirp transition information within the transmitted signal, enabling self-synchronized operation without external triggering. The approach ensures precise 2-D baseband matrix construction, eliminates phase inconsistencies, and preserves Doppler fidelity with reduced hardware overhead. A detailed mathematical framework, followed by simulation results and experimental validation using a radar-on-chip (RoC) based platform, is presented. The proposed method achieves accurate chirp segmentation and Doppler estimation without relying on auxiliary hardware. Discussion on various sequences of the proposed waveform for different applications and a methodology for adaptive selection are also presented. This low-cost, scalable solution enhances the adaptability of FMCW radar systems across diverse domains, including automotive safety, biomedical monitoring, surveillance, and uncrewed aerial vehicle (UAV) detection.