應用於音頻之二階具預先偵測3位元37位階動態量化器之三角積分調變器設計與實現

Abstract

在當今製程的進步下，積體電路設計已進入奈米時代。拜科技所賜，可攜式行動通訊已成為目前生活的必需品，所以低功率高效能電路的設計越來越重要。 以低功率高效能為目標，在眾多類比數位轉換器中，最屬三角積分調變器對類比電路元件的非理想特性較不敏感。且當今消費者對產品的需求，所以使得三角積分調變器非常適合用於高解析度的應用。

本篇論文中，提出一個具有動態量化功能的三角積分調變器架構，使3位元的量化器可以達到37個位階的量化功能。在此架構中，利用預先偵測的電路技術，適時調整量化器的可量化範圍，以增加可量化的階數，並大幅減少高位元量化下所需的元件數。藉由此技術，三角積分調變器不僅可以降低功率與面積的消耗，還可以大幅提升類比數位信號轉換的解析度。在TSMC 0.18 mm 1P6M標準CMOS製程下，此預先偵測動態量化之三角積分調變器在1.8 V的供應電壓，以及25 kHz的頻寬範圍內，測得的信號雜訊失真比為101.2 dB，動態範圍為102dB，功率消耗為1.68 mW。晶片面積不包含PAD的大小為3.06 mm2。

另外也提出了一個具雜訊移頻動態元件匹配電路用以處理數位至類比路徑所產生的雜訊。傳統上在處理此雜訊會使用動態元件匹配電路來完成，但無法像三角積分調變器在處理量化雜訊一樣具有雜訊移頻的方式把量化雜訊推至高頻。所提出的想法能使DAC路徑所產生的雜訊具有雜訊移頻的能力，降低雜訊在低頻的能量，使得系統訊號雜訊比的表現較好。In this paper, a high-resolution delta-sigma modulator with a pre-detective dynamic quantizer is proposed. A 37-level quantization can be achieved by using only a 3-bit quantizer in the proposed dynamic quantizer. In the proposed structure, a signal detector is added at the input of the presented modulator to pre-detect the magnitude of the sampled input and switch the dynamic quantizer to the corresponding quantization range. With the proposed technique, the quantization level can be greatly increased, and the number of comparators will hence be substantially reduced for a high-level quantization. The resulting resolution of delta-sigma modulators can thus be significantly promoted without consuming much power and area. The proposed delta-sigma modulator is implemented in a TSMC 0.18 μm 1P6M CMOS process. The signal-to-noise plus distortion ratio is 101.2 dB and dynamic range is 102 dB in a signal band of 25 kHz. The power consumption is 1.68 mW at a 1.8 V supply voltage.

A dynamic element matching with noise shaping technique in delta-sigma modulator is proposed. The proposed structure can shape the feedback noise to high frequency just like the delta sigma modulator shape the quantization noise. The architecture can substantially reduce the in-band noise and get much better performance.