適用於IEEE 802.15.6無線人體區域網路之人體通道接收機及ISM頻段低功耗射頻接收機設計

Abstract

本論文描述應用於無線人體區域網路(WBAN)之接收機積體電路設計，包含一個人 體通道傳輸(HBC)接收機以及一個ISM 頻段具低功耗操作之射頻無線接收機。人體通道接收機是一種採用人體低導電損耗以及低通道干擾特性為優點之新興WBAN 傳輸技術，而WBAN 實體層相關之標準規範是在2012 年制定為IEEE 802.15.6。人體上的電場強度會受到傳輸距離、電極和皮膚接觸品質等的影響，而造成人體通道之路徑損耗大範圍改變。此外，根據實測結果，訊號在非接觸式傳輸的情況下皮膚和電極介面的等效電容性會使路徑損耗大幅度增加。為解決此問題，本論文提出一具有雙模態操作之直接降頻式HBC接收機，並且以電磁傳輸理論建構人體通道等效RC 電路模型。系統子電路包含前端放大器、雙模態混頻器、主動低通濾波器、基頻電路以及溫度補償式本地振盪器。此接收機以標準0.18 μm CMOS 製程實現，量測結果顯示接收機在1.2 V 低電壓操作下之功率消耗為1.75 mW 並且適用於IEEE 802.15.6 HBC 實體層標準規範。HBC 接收機晶片面積為1.05 mm2，最大的電壓轉換增益為85.5 dB，在資料傳輸率為164 kbps 下最佳系統靈敏度達-90 dBm。此外，在人體實測上，文字訊號可成功的經過人體傳輸並以接收機解調回原始訊號。另一方面，除了前述介紹之HBC 接收機之外，本論文亦實現了一個ISM 頻段之低功耗無線接收機。另外，一種用於射頻前端電路之增益提升技術被提出使系統在不增加額外功耗的情況下有效的改善其靈敏度。此低功耗無線接收機採用開關式鍵入調變(OOK)並以標準0.18 μm CMOS 製程實現。整體接收機系統包括射頻前端電路、LC tank架構之本地源壓控振盪器、中頻放大器、以及OOK 解調器。此外，中頻放大器具有抑制自我混頻之特性，可使接收機系統之BER 下降至少一個等級。量測結果顯示在位元錯誤率(BER)為0.001下系統最佳靈敏度為-63dBm，藉由論文所提出之增益提升技術可使靈敏度改善4dB(100kbps之資料傳輸率)。整體的系統功耗在1.2 V 供應電壓下為383微瓦，亦可為無線接收機系統提供一較高能源效益之解決方案。

Design of receivers for wireless body area network (WBAN) is presented in this dissertation, which includes a human body communication (HBC) receiver and an ISM band low-power RF wireless receiver. HBC, a technique featuring low conduction loss and low interference by taking advantage of the nature of body composition, has emerged as one of the most promising techniques towards next-generation wireless body area network. The regulation of wireless body area network, IEEE 802.15.6, concerning the standard of physical layer has also been established in 2012. The intensity of electric field around body is affected by the transmission distance, quality of electrode-skin contact, and so on, which results in wide variance in path loss. In addition, according to the measurement results, the equivalent capacitance of electrode-skin interface increases path loss significantly when non-contact transmission happens. To solve the problems, a low-power receiver with dual-mode operation is proposed in this dissertation. In addition, equivalent RC circuitmodel of the human body was established by electromagnetic propagation theory. The sub-circuits of HBC receiver system include front end amplifier, dual mode active mixer, active LPF, baseband circuit, and temperature-compensated LO oscillator. The receiver has been implemented in a standard 0.18 μm CMOS process. Measurement shows the receiver is fully functional with power consumption below 1.75 mW under 1.2 V supply voltage and compatible with IEEE 802.15.6 HBC layer. The chip size is 1.05 mm2. Maximum voltage conversion gain can be 85.5 dB. Experimental sensitivity is up to -90 dBm under an information data rate of 164 kbps. It has been demonstrated that the receiver provides successful text file transmission through human body with the fabricated sensing electrodes. On the other hand, this dissertation proposes a gain-increasing method in the RF front-end to improve receiver sensitivity without increasing extra power consumption. An ISM band wireless receiver with OOK modulation was also implemented in TSMC 0.18 μm CMOS process. The receiver contains a RF front end, a LC-tank based LO VCO, an IF amplifier and an OOK demodulator. In addition, the IF amplifier employs a self-mixing elimination mechanism to improve the BER by more than one order of magnitude. Measurement results show a sensitivity of -63 dBm given a BER of 10-3. By using the gain-improving method, the sensitivity is improved by 4 dB (100 kbps data rate). Including the bias circuit, overall power consumption is less than 383 μW under 1.2 V supply, providing a high-energy efficiency solution for wireless radio.