- 學位論文
應用於生醫系統之低功率基於壓控振盪器三角積分調變器與四相位移鍵接收機設計
Design of a Low-Power VCO-Based Delta-Sigma Modulator and a QPSK Receiver for Biomedical Applications
摘要
在遠距健康照護系統中，可攜式監測裝置必須能以低功率消耗完成擷取生醫信號與無線資料傳輸以期達到長時照顧的目的。 第一部分即提出一個用於生醫信號擷取的小面積、極低功耗之基於壓控振盪器的三角積分調變器。壓控振盪器的非線性轉換通常會造成輸出的諧波失真並降低了無雜散動態範圍和信號對雜訊與失真比。此調變器使用單位元回授迴路與降低輸入振幅之方式來降低壓控振盪器的非理想效應。而為使調變器能有最大操作區域且避免信號轉換失真，壓控振盪器中心頻率需為取樣頻率的整數倍。因此，此處提出一個快速頻率校正之機制，利用閘控振盪器技巧來解決初始相位之不確定性之外，同時能在數百個週期內迅速達到振盪器中心頻率之校正。 第二部份則提出一個用於低功率無線資料傳輸的四相位移鍵接收機，其有效應用了在注入鎖定振盪器中相位轉振幅變化的特性。相較於基於柯斯塔迴路或鎖相迴路解調器之高電路複雜度，此一基於注入鎖定之差動四相位移鍵解調器僅使用一個振盪器與一個振幅區別電路，如此便可大幅減少功率消耗及晶片面積。模擬結果則驗證了利用注入鎖定振盪器完成差動四相位移鍵解調之可行性。
並列摘要
Portable monitoring devices in the remote healthcare system require a low power solution both in biomedical signal acquisition and wireless data transmission for continuous long-term caring. The first work presents an extremely low-power small-area VCO-based delta-sigma modulator (ΔƩM) for biomedical signal acquisition. The modulator nonlinearity induced by the VCO usually causes harmonic tones and deteriorates the SFDR/SNDR performance. This nonideal effect is mitigated by adopting the closed-loop architecture with 1-bit feedback. In addition, the signal swing at the VCO input is reduced to further suppress the nonlinearity. To maximize the operation range of the VCO-based ΔƩM and avoid signal distortion, the VCO center frequency should be an integer multiple of the sampling clock. An agile frequency calibration scheme is devised to correct the VCO free running frequency. The proposed calibration utilizes a gated VCO technique to remove the initial phase uncertainty and quickly correct the VCO center frequency in only hundreds of clock cycles. The second part proposes an energy-efficient QPSK receiver for low-power wireless data transmission. It leverages the characteristic of phase-to-amplitude conversion possessed by the injection-locking oscillator. Compared to Costas-loop-based and PLL-based demodulators with high circuit complexity, the injection-locking-based D-QPSK demodulator exploits only one oscillator and one envelope discrimination circuit, which significantly reduces the power dissipation and chip area. Simulation results manifest the effectiveness of injection-locking technique for D-QPSK demodulation.