摘要
本論文主題為設計一個符合2.4-GHz之工業/科學/醫療頻段之應用的數位頻率轉換器(DFC)。數位頻率轉換器是直接將輸入的數位頻率控制碼轉換成週期性的類比訊號輸出，使得輸出類比訊號的頻率與輸入數位控制碼的數值有正比的關係。由於不採用回授控制迴路而直接採用開路控制，此數位頻率轉換器可達到相當快速的頻率切換，對於某些無線應用，像是高傳輸速率之頻率調變無線發射器來說，這是十分重要且不容忽視的。 提出的設計架構包含了一個數位控制震盪器(DCO)、一個高速閘控漣波計數器以及一個數位控制電路用來校準電容以及頻率。使用數位控制震盪器做為基礎，可避免吵雜的類比控制，進而達到穩定且精準的頻率訊號輸出。數位到頻率的轉換是利用建立一個輸入頻率數位碼對數位控制震盪器控制碼的對照表來實現。考慮到硬體的複雜度以及製程變異，提出兩個演算法分別採用片段式線性近似法以及非二進制權重的切換電容陣列來達成轉換輸出頻率的最小誤差。 此設計利用台灣積體電路公司的互補式金氧(CMOS) 0.18微米製程實現，整個晶片面積為1 x 1 平方微米。經由量測結果，震盪頻率輸出範圍為2.34 ~ 2.59 GHz，相位雜訊在偏離中心載波頻率500 KHz低於-102 dBc/Hz。有效頻率解析度為7位元，且在供應電壓為1.8伏特的情形下，功率消耗為13微瓦特。
並列摘要
In this thesis, a digital-to-frequency converter (DFC) designed for 2.4 GHz ISM-band applications is proposed. The DFC directly produces an analog periodic output signal which frequency is proportional to the input digital code. Since there is no feedback control loop, the converter can achieve very fast frequency-switching which is important for some wireless applications, for example: high data-rate FSK transmitters. The proposed design consists of a digitally controlled oscillator (DCO), a high speed gated ripple counter, and a digital control circuit for capacitance and frequency calibration. The DCO-based design provides stable and precise output frequency by avoiding noisy analog control. The digital-to-frequency conversion is realized by transfer the input frequency code to the capacitor control code of the DCO. Considering hardware complexity and process variations, two transfer algorithms for piecewise linear approximation and non-binary-weighted switched-capacitor arrays are proposed to minimize output frequency error. This design is implemented in TSMC 0.18 µm 1P6M CMOS process and the chip area is 1 x 1 mm2. According to the measurement results, the oscillation frequency is 2.34 ~ 2.59 GHz with 255 MHz tuning range, and the phase noise is less than -102 dBc/Hz at 500 kHz offset. The effective frequency resolution is 7 bits and the total power consumption is 13 mW under 1.8 V supply voltage.