A Packaged 54-to-69-GHz Wideband 2T2R FMCW Radar Transceiver Employing Cascaded-PLL Topology and PTAT-Enhanced Temperature Compensation in 40-nm CMOS
Chenyu Xu, Xiaofei Liao, Mengru Yang, Feifan Hong, Peijuan Ju, Wendi Chen, Pengfei Diao, Hao Gong, Xiang Liu, Xiaohu You, Dixian Zhao
Abstract
This article introduces a highly integrated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$</tex-math> </inline-formula> -band frequency-modulated-continuous-wave (FMCW) radar transceiver (TRX) in 40-nm bulk CMOS. It incorporates two identical transmitter (TX) and receiver (RX) channels, enabling not only traditional forward sensing but also full-360 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> detection. The FMCW synthesizer is based on a cascaded-phase-locked-loop (PLL) topology, enhancing chirp quality while reducing the necessity for complex off-chip components. Additionally, it generates extra clocks to ensure synchronized operation for the entire radar system. A proportional-to-absolute-temperature (PTAT)-enhanced temperature compensation (TC) technique is proposed to improve the temperature robustness at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$</tex-math> </inline-formula> -band. The impacts of clock synchronization and temperature insensitivity of the TRX on FMCW radar systems are also analyzed. For broadband, high-linearity, and low-noise operation within limited stages, RF front-ends are carefully designed, with the optimization strategy elaborated. Fabricated in a fan-out wafer-level chip-scale packaging (WLCSP), this TRX achieves a 3-dB bandwidth ranging from 54 to 69 GHz. The RX features a 67-dB tuning range of the conversion gain (CG) and a 10-dB noise figure (NF). The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_\text{SAT}$</tex-math> </inline-formula> of TX is 12.8 dBm. The PTAT-enhanced TC effectively minimizes variations in CG, NF, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_\text{SAT}$</tex-math> </inline-formula> , maintaining less than 2.1-, 2.9-, and 2.5-dB changes, respectively, from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 55 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> C to 105 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> C. The FMCW generator achieves a chirp rate of 468.5 MHz/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> s with a bandwidth of 7.2 GHz, demonstrating a minimal 0.019% chirp error.