在物聯網的願景中，每個物品都有通過部署無線感測器連接到網路的潛力。然而，這些物聯網設備在功耗預算方面面臨嚴重的限制，其中一些甚至需要依賴無電池的能量收集解決方案。隨著物聯網概念的迅速發展，無線感測節點必須具備低功耗、高效率和小型化的特性。本論文探討了物聯網應用中超低功耗振盪器和無線發射機的關鍵挑戰。研究聚焦於三項主要成果，而每項成果都為無線系統的進步做出貢獻。
第一項成果介紹了基於雙斬波穩定技術的晶片上鎖頻振盪器。這項創新旨在透過減輕對溫度敏感的非理想效應來提高頻率穩定性。該原型採用180 nm CMOS製程實現，有效面積為0.3 mm2。測量結果顯示在工作頻率為250 kHz運行的鎖頻振盪器實現了27.1 ppm/°C的溫度穩定性和2.73 ppm的長期穩定性，並且功耗僅為293 nW。與無斬波穩定技術相比，低頻閃爍雜訊的抑制使其長期穩定性提高了16倍。
第二項成果展示了專為低功耗和低相位雜訊應用而設計的Colpitts電壓控制振盪器，利用轉導增強和電流重用技術來提高電流效率。該原型採用0.18 μm CMOS製程實現，在2.34至2.55 GHz工作頻率範圍下表現出8.6%的調諧範圍。此振盪器的功耗為1.4 mW，並在1 MHz頻率偏移處實現了卓越的−122.85 dBc/Hz的相位雜訊。
第三項成果提出了一個在419-445 MHz頻段中運作的超低功耗多通道多模式無線發射機。該發射機採用多相注入鎖定和倍頻技術，並由低頻相位旋轉型的頻率合成器實現對多通道和FSK調變的支援。透過N路徑濾波器和雙級注入鎖定環形振盪器，此架構有效衰減了合成器量化雜訊所造成的遠端相位雜訊。相位調變是透過調整振盪器自由運行頻率和注入頻率之間的偏移頻率以控制其穩態相位偏移來實現。最後，利用具有高能效的電流模式D類邊緣組合功率放大器實現5倍頻率放大以生成所需的載波頻率。該原型採用90 nm CMOS製程製造，在0.75 V電源電壓下提供−7 dBm的輸出功率，功耗僅為870 μW。此發射器支援OOK、FSK和QPSK調製的多功能性，實現了11 pJ/bit的高能效和23%的全局效率。
總而言之，這項研究應對了超低功耗振盪器和無線發射機的關鍵挑戰，並提出了有助於物聯網應用發展的創新解決方案。這些成果凸顯了增強無線系統穩定性、效率和多功能性的潛力，為未來的發展鋪平了道路。

In the vision of the Internet of Things (IoT), every object has the potential to be internet-connected through the deployment of wireless sensors. Nevertheless, these IoT devices face severe constraints in terms of power budgets, with some relying on battery-less energy harvesting solutions. With the rapid development of the IoT concept, wireless sensor nodes must possess characteristics such as low power consumption, high efficiency, and compact form factors. This dissertation addresses key challenges in ultralow-power oscillators and wireless transmitters for Internet of Things (IoT) applications. The research focuses on three major achievements, each contributing to the advancement of wireless systems.
The first achievement introduces a frequency-locked on-chip oscillator based on a double chopper stabilization technique. This innovation aims to improve frequency stability by mitigating temperature-sensitive nonidealities. Implemented in a 180-nm CMOS process with an active area of 0.3 mm2, the prototype demonstrates significant improvements. The frequency-locked oscillator, operating at 250 kHz, achieves temperature stability of 27.1 ppm/°C and long-term stability of 2.73 ppm, with a power consumption of only 293 nW. The suppression of low-frequency flicker noise results in a 16X improvement in long-term stability compared to the non-chopper technique.
The second achievement presents a Colpitts voltage-controlled oscillator (VCO) designed for low-power and low-phase-noise applications. The VCO utilizes gm-enhanced and current-reuse techniques to enhance current efficiency. Implemented in a 0.18 μm CMOS process, the prototype operates in the frequency range of 2.34 to 2.55 GHz with an 8.6% tuning range. With a 1.4 mW power consumption, the VCO attains a remarkable phase noise of –122.85 dBc/Hz at a 1 MHz frequency offset.
The third achievement proposes an ultralow-power multichannel multimode wireless transmitter operating in the 419-445 MHz frequency band. The transmitter employs multiphase injection locking and frequency multiplication techniques, supported by a low-frequency phase-rotation-based frequency synthesizer for multiple channels and FSK modulation. Through an N-path filter and a two-stage injection-locked ring oscillator, the far-out phase noise induced by the quantization noise of the synthesizer is effectively attenuated. Phase modulation is accomplished by adjusting the offset frequency between the free-running frequency of the oscillator and the injected frequency. Finally, a current mode class-D edge-combining power amplifier is utilized for 5X frequency multiplication for generating the necessary carrier frequency. Manufactured using a 90 nm CMOS process, the transmitter delivers a −7 dBm output power, consuming only 870 μW from a 0.75 V supply voltage. It demonstrates versatility with OOK, FSK, and QPSK modulation, attaining notable energy efficiency at 11 pJ/bit and a 23% global efficiency.
In summary, this research addresses critical challenges in ultralow-power oscillators and wireless transmitters, presenting innovative solutions that contribute to the advancement of IoT applications. The achievements underscore the potential for enhanced stability, efficiency, and versatility in wireless systems, paving the way for future developments in the field.

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