A Self-Adapted Two-Point Modulation Type-II Digital PLL for Fast Chirp Rate and Wide Chirp-Bandwidth FMCW Signal Generation

• Published in: IEEE journal of solid-state circuits Vol. 57; no. 4; pp. 1162 - 1174
• Main Authors: Deng, Wei, Chen, Zipeng, Jia, Haikun, Yan, Angxiao, Sun, Shiyan, Chen, Guopei, Wang, Zhihua, Chi, Baoyong
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bandwidth; Bandwidths; Chirp; CMOS; Complementary metal–oxide–semiconductor (CMOS); digital phased-locked loop (PLL); Error detection; fast chirp; Frequency modulation; frequency-modulated continuous wave (FMCW); millimeter-wave (mm-wave); Modulation; Phase locked loops; PLL; Power consumption; self-adapted; Signal generation; Steady-state; two-point modulation (TPM); Voltage-controlled oscillators
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2021.3129900

Different from the conventional two-point modulation (TPM) type-II phase-locked loops (PLLs) requiring non-trivial gain calibrations and TPM type-III PLLs with loop stability concern and limited chirp rate, a self-adapting gain mismatch TPM type-II digital PLL is proposed in this article. It directly detects frequency error as its input signal, allowing frequency ramp tracking with zero steady-state frequency error using a type-II PLL. In addition, the maximum trackable slope in the case of the proposed TPM type-II PLL is intrinsically larger than that of the conventional TPM type-III PLL. A polarity navigator is embedded in the digital loop filter to improve the linearity at the chirp turning-around points (TAPs). Fabricated in a 28-nm complementary metal-oxide-semiconductor (CMOS) technology, the proposed PLL consumes 23 mW from a 1-V power supply and occupies 0.31 mm 2 . The measurement results indicate that the proposed PLL can generate a precise triangular chirp with 2.27-GHz bandwidth (BW) and 18.2-<inline-formula> <tex-math notation="LaTeX">\mu \text{s} </tex-math></inline-formula> period at 12.5 GHz. To the best knowledge of the authors, this work demonstrates the widest normalized Chirp-bandwidth and the fastest chirp rate simultaneously.