通信工程专业英语(本) Lesson 12 Analog to Digital Converters 第12课 模数转换器 邓 磊 denglei@dgut.edu.cn https://leideng.github.io/communication-english/ (Some pictures are from the Internet) 东莞理工学院 电子工程与智能化学院 2017.10.30
Outline Technical Contents Technical Terms Structures and Sentences Flash ADC 闪式模数转换器 Over-Sampling to Achieve Processing Gain 过采样实现“处理增益” Sigma-Delta ADC Technical Terms Structures and Sentences
Introduction to ADC ADC is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal.
Technical Contents: Flash ADC Pros. Easy to implement High-speed conversion Cons. Need resistors if there are N encoding bits Large size Power hungry
FFT of Typical 12-Bit Flash ADC Samples The input analog signal is a pure sine wave. Theoretical SNR 6.02N+1.76=74dB Practical SNR 104dB
Technical Contents: Over-Sampling to Achieve Processing Gain Over-sampling and then filter out part of the noise band The increased SNR is called processing gain (处理增益)
Technical Contents: Sigma-Delta ADC Block diagram of
Technical Contents: Sigma-Delta ADC Noise shaping
Technique Terms comparator n. 比较器 resolution n. 分辨率 cellular adj. 使用蜂窝技术的 cell n. 蜂窝 decimation n. 抽取，降采样 accuracy n. 精度 interpolation n. 插值
Technique Terms sampling rate 采样率 reference voltage 参考电压 power consumption 功耗；能耗 full scale 满量程 processing gain 处理增益 analog interfacing 模拟接口 block diagram 框图 FFT abbr. Fast Fourier Transform 快速傅里叶变换
Structures and Sentences Analog-to-digital converters (ADC) come in almost as many flavors as ice creams, and at least as much care is needed in choosing the former as is required with the latter. ADC类型像冰淇淋口味一样多，挑选时至少要像挑选冰淇淋一样细心。
Structures and Sentences The flash converter operates by simultaneously presenting the input signal to a bank of 2^N-1 comparators, whose reference voltages are set by a resistor chain to exactly correspond to all of the possible sample levels which can be represented by the converter. 闪式ADC将输入信号同时传给2^N-1个比较器。这些比较器的参考电压由一列电阻设定，以使其值正好对应于转换器所能代表的全部采样值。
Structures and Sentences If we were to now digitally filter this sampled signal, we could remove approximately ¾ of the noise, increasing the SNR by a factor of 4 or 6 dB. 假如我们现在对采样后的信号做数字滤波，我们就可以去掉约3/4的噪声，从而讲信噪比提高4-6dB。
Thank You!