Low-Power MEMS-Based Pierce Oscillator Using a 61-MHz Capacitive-Gap Disk Resonator
Low-Power MEMS-Based Pierce Oscillator Using a 61-MHz Capacitive-Gap Disk Resonator
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DOI：
10.1109/tuffc.2020.2969530
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发表时间：
2020-07-01
影响因子：
3.6
通讯作者：
Nguyen, Clark T. -C.
中科院分区：
文献类型：
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作者：
Naing, Thura Lin;Rocheleau, Tristan O.;Nguyen, Clark T. -C.
采用 0.35μm CMOS 技术构建的 61MHz 皮尔斯振荡器，参考多晶硅表面微机械加工的电容间隙换能酒杯盘谐振器，在 1kHz 偏移处实现了 -119dBc/Hz 的相位噪声标记，在远离载波偏移处实现了 -139dBc/Hz 的相位噪声标记。当分频至 13 MHz 时，这对应于距载波 1 kHz 偏移时的 -132 dBc/Hz 和远离载波时的 -152 dBc/Hz，足以满足移动电话参考振荡器应用的需要，使用单个 MEMS 谐振器，即无需阵列多个谐振器。实现这些标志的关键是基于皮尔斯的电路设计，该设计利用比宏观石英晶体小 100 倍的 MEMS 支持的输入到输出并联电容，以实现足够的负电阻来激发和维持振荡，同时仅消耗 78 μW 的功率，与之前的工作相比减少了大约 4.5 倍。将谐振器的偏置电压提高 1.25 V，进一步将功耗降低至 43 μW，而远距载波相位噪声仅降低了几分贝。该振荡器的 1kHz 偏移品质因数 (FOM) 为 -231dB，是迄今为止已发布的芯片级振荡器中最好的。完整的线性电路分析量化了谐振器输入到输出并联电容对功耗的影响，并预测通过减小电极到谐振器换能器间隙和焊盘尺寸来进一步降低功耗。这种基于 MEMS 的微型振荡器所展示的相位噪声和功耗非常有吸引力，可以作为低功耗“一劳永逸”自主传感器网络和嵌入式无线电的潜在推动者。
A 61-MHz Pierce oscillator constructed in 0.35-mu m CMOS technology and referenced to a polysilicon surface-micromachined capacitive-gap-transduced wine-glass disk resonator has achieved phase noise marks of - 119 dBc/Hz at 1-kHz offset and -139 dBc/Hz at far-fromcarrier offsets. When divided down to 13 MHz, this corresponds to -132 dBc/Hz at 1-kHz offset from the carrier and - 152 dBc/Hz far-from-carrier, sufficient for mobile phone reference oscillator applications, using a single MEMS resonator, i.e., without the need to array multiple resonators. Key to achieving these marks is a Pierce-based circuit design that harnesses a MEMS-enabled input-to-output shunt capacitance more than 100x smaller than exhibited by macroscopic quartz crystals to enable enough negative resistance to instigate and sustain oscillation while consuming only 78 mu W of power-a reduction of similar to 4.5x over previous work. Increasing the bias voltage of the resonator by 1.25 V further reduces power consumption to 43 mu W at the cost of only a few decibels in far-from-carrier phase noise. This oscillator achieves a 1-kHz-offset figure of merit (FOM) of -231 dB, which is now the best among published chip-scale oscillators to date. A complete linear circuit analysis quantifies the influence of resonator input-to-output shunt capacitance on power consumption and predicts further reductions in power consumption via reduction of electrode-to-resonator transducer gaps and bond pad sizes. The demonstrated phase noise and power consumption posted by this tiny MEMS-based oscillator are attractive as potential enablers for low-power "set-and-forget" autonomous sensor networks and embedded radios.