A K-Band FMCW Frequency Synthesizer Using Q-Boosted Switched Inductor VCO in SiGe BiCMOS for 77 GHz Radar Applications

Zhe Chen,Lei Bao,Pinpin Yan,Yuanye Zheng,Debin Hou,Ji-Xin Chen,Zheying Hong

doi:10.3390/electronics9111933

Zhe Chen, Lei Bao + Show 5 more

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https://doi.org/10.3390/electronics9111933

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Journal: Electronics	Publication Date: Nov 17, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: Institute of Microelectronics, Southeast University

Abstract

In this article, a fractional-N phase-locked loop (PLL) with integrated chirp generation circuit block for a 76~81 GHz frequency-modulated continuous-wave (FMCW) radar system is presented. Thanks to the switched inductor voltage-controlled oscillator (VCO) topology, the linearity, phase noise, chirp bandwidth, and chirp rate of the FMCW synthesizer can be optimized for the short-range radar (SRR) and long-range radar (LRR) applications, with switch at ON/OFF states, respectively, according to different requirements and concerns. In this way, the proposed FMCW synthesizer shows improved phase noise for switch OFF-state, good for LRR applications, compared to the conventional single-varactor VCOs or cap-bank VCOs. The switch loss at ON-state is further decreased with the Q-boosting technique, which helps the FMCW synthesizer to simultaneously obtain a wide chirp bandwidth, steep modulation rates and good phase noise for SRR applications. The FMCW synthesizer is fabricated in 0.13 µm SiGe BiCMOS technology, occupies an area of 1.7 × 1.9 mm2, and consumes 330 mW from a 3.3 V voltage supply. Measured results show that the FMCW synthesizer can cover 25.3~27 GHz (with a frequency tripler to fully cover 76~81 GHz band), showing optimized phase noise, chirp bandwidth, linearity, and modulation rates performance. The measured K-band phase noise is −110.5 dBc/Hz for switch OFF-state, and −106 dBc/Hz for switch ON-state at 1 MHz offset. The normalized root mean square (RMS) frequency error is 518 kHz for chirp rate of ±14.6 MHz/μs and 1.44 MHz for chirp rate of ±39 MHz/μs for the 77 GHz band. Moreover, the integrated waveform generator offers fully programmability in chirp rate, duration and bandwidth, which supports multi-slope chirp generations. With a frequency tripler, the chip is well suited for the 76~81 GHz FMCW radar system.

Highlights

Miniaturized low-cost frequency-modulated continuous-wave (FMCW) radars are becoming dominant in a range of applications, including automotive, industrial and consumer electronics
The phase-frequency detector (PFD), charge pump (CP) and band gap (BG)/low dropout regulators (LDOs) are designed with thick-gate-oxide CMOS transistors, and the programmable divider, the FMCW waveform generator, 20-bit multistage noise shaping (MASH) 1-1-1 sigma-delta modulator (SDM), serial-peripheral interface (SPI) circuits are designed with thin-gate-oxide CMOS transistors, both offered by the 0.13 μm SiGe
The K-band FMCW frequency synthesizer chip is wire-bonded to the printed-circuit-board (PCB), on which the phase-locked loop (PLL)’s loop filter is implemented

Summary

Introduction

Miniaturized low-cost frequency-modulated continuous-wave (FMCW) radars are becoming dominant in a range of applications, including automotive, industrial and consumer electronics. For better measurement of close-proximity objects and their relative velocities, FMCW radars need to have both high bandwidth (to improve spatial resolution) and steep modulation rates (to push the beat tones to higher frequencies). The chirp linearity and phase noise are the primary determinants for long-range radar (LRR) applications (>200 m), for which 76 to 77 GHz is frequently the operational band. For the FMCW source, the linearity and phase noise requirements are more stringent for 76~77 GHz band, while chirp bandwidth and modulation rates are of more concern for the 77~81 GHz band [2,3,4,5]

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Conclusion