This letter presents a fractional-N frequency synthesizer with an ultrawideband continuously tuning range of 32.4% centered at 26.85- and 8.7-GHz chirp for frequency-modulated continuous-wave (FMCW) radars. The synthesizer uses a fractional-N 9-GHz charge-pump phase-locked loop (CPPLL) cascaded by an injection-locked frequency tripler (ILFT). A voltage-controlled oscillator (VCO) with transformer (TFM) coupling for an enhanced linear control voltage range, a better quality factor and good isolation from the load seen by the resonator, and a wide output voltage range charge-pump (CP) are used to achieve the ultrawideband CPPLL. The ILFT is implemented using a weakly coupled TFM for broadband locking range and 3-dB output power. The synthesizer is fabricated in the 40-nm CMOS technology and consumes 28.5 mW. The phase noise (PN) of the synthesizer at 27 GHz is −97.87 dBc/Hz at 1 MHz and the prototype is capable of generating a triangle or sawtooth chirp of 8.7-GHz modulation bandwidth with an rms FM error of 0.04% of BWchirp.

中文翻译：

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具有 8.7GHz 线性调频脉冲的 22.5-31.2GHz 连续调谐频率合成器，适用于 FMCW 应用

这封信介绍了一种分数 N 频率合成器，其超宽带连续调谐范围为 32.4%，以 26.85 GHz 和 8.7 GHz 啁啾为中心，用于调频连续波 (FMCW) 雷达。合成器使用由注入锁定频率三倍器 (ILFT) 级联的分数 N 9 GHz 电荷泵锁相环 (CPPLL)。带有变压器 (TFM) 耦合的压控振荡器 (VCO) 用于增强线性控制电压范围、更好的品质因数和与谐振器看到的负载的良好隔离，以及宽输出电压范围的电荷泵 (CP)用于实现超宽带CPPLL。ILFT 是使用弱耦合 TFM 实现的，用于宽带锁定范围和 3-dB 输出功率。合成器采用 40-nm CMOS 技术制造，功耗为 28.5 mW。