A Fast and Precise Blind I/Q Mismatch Compensation for Image Rejection in Direct‐Conversion Receiver

In this paper, we propose a new digital blind in‐phase/quadrature‐phase (I/Q) mismatch compensation technique for image rejection in a direct‐conversion receiver (DCR). The proposed image‐rejection circuit adopts DC offset cancellation and a sign‐sign least mean squares (LMS) algorithm with a unique step size adaptation both for a fast and precise I/Q mismatch estimation. In addition, several performance‐optimizing design considerations related to accuracy, speed, and hardware simplicity are discussed. The implementation of the proposed circuit in an FPGA results in an image‐rejection ratio (IRR) of 65 dB, which is the best performance with modulated signals, along with an adaptation time of 0.9 seconds, which is a tenfold increase in the compensation speed as compared to previously reported circuits. The proposed technique will be a promising solution in the area of image rejection to increase both the speed and accuracy of future DCRs.     

（英）STI埋层的高光电流和低暗计数率单光子雪崩二极管

本文研究和分析了一种0.18-μm CMOS工艺单光子雪崩二极管（SPAD）,其结构能抑制过早的边缘击穿（PEB）,同时获得较大的光电流和低的暗计数率（DCR）。该SPAD由p-well/deep n-well的感光结,deep n-well向上扩散形成的区域和边缘Shallow Trench Isolation（STI）共同形成的保护环组成。通过测试确定了与光电流和暗率有关的STI层的大小。结果证明,在STI层与保护环之间的重叠区域为1-μm 时,SPAD的暗计数率和光电流最佳。此外,直径为10-μm的圆形SPAD器件的暗计数率为208Hz,且在波长为510nm时峰值光子探测概率为20.8%,此时具有低的暗计数率和高的探测效率以及宽的光谱响应特性。     

A LUT-based scheme for LNA linearization in direct RF sampling receivers

Direct RF sampling receiver – a fully digital receiver architecture – undoubtedly becomes a favored choice for HF/VHF as this approach inherently bypasses the legacy nonlinearities caused by analog components. In DRF-RF and wideband multichannel in general, LNA is still an indispensable component to ensure the receiver’s sensitivity. However, with the presence of multiple channels, the total RF power often surpasses the linear threshold that LNA and the amplified signal become severely distorted. This paper proposed a method for mitigating the LNA distortion using the look-up table (LUT) approach. Specifically, our receiver is designed with two modes of operation. In training mode, a built-in signal circuit generates a training signal for extracting the LNA characteristic and eventually reconstructs the inverse LNA nonlinear model in the form of a LUT memory. During the receiving mode, a linearization circuit reverses the distortion impact by matching the RF power level with the inverse nonlinear model pre-stored in the LUT. The effectiveness of the proposed distortion compensation method first is evaluated by a MATLAB simulation with a multi-channel DRF-RF model. The simulation results show that the proposed approach significantly improved the SNDR for the channel of interest. Furthermore, the model has been practically verified, where the actual distorted signals are sampled from a commercial LNA (ZFL-500LN+) by a customized FPGA board. Results from measurements show an improvement of $\sim$7 dB for SNDR and 27% for EVM in a strong distortion scenario of QPSK modulation signal.     

A Joint Scheme of AGC and Gain/Phase Mismatch Compensation for QPSK DCR

This paper presents a simple gain/phase blind compensation algorithm with an automatic gain control (AGC) function for the adoption of the AGC function and compensation for gain/phase imbalances in quadrature phase shift keying (QPSK) direct conversion receivers (DCRs). The AGC function is interactively operated with the compensation algorithm for gain/phase imbalances. By detecting the gain sum and difference values between the I‐channel and Q‐channel, the combined AGC and gain imbalance compensation algorithm provides a simpler DCR architecture.     

基于DCR标准的数字对讲系统设计

本文研究了DCR标准的信源编码算法——AMBE算法和信道编码算法——删除卷积码,采用AMBE3000声码器和数字专网移动通信专用芯片CMX7141设计了一款遵从DCR标准的数字对讲系统。并对所设计的DCR数字对讲机系统进行仿真和实验验证。实验结果表明：该系统在保证通信的有效性和可靠性的基础上,具有较高的语音通信质量。     

Crystallization-based optical resolution of 1,1′-binaphthalene-2,2′-dicarboxylic acid via 1-phenylethylamides: control by the molecular structure and dielectric property of solvent

In the recrystallization of a diastereomeric mixture of amides (RS_a,S)-1 formed from racemic 1,1′-binaphthalene-2,2′-dicarboxylic acid and (S)-1-phenylethylamine, either of the diastereomers crystallizes out as a diastereomerically pure form, depending on the solvent employed; sterically undemanding solvents, acetone, dichloromethane, and acetonitrile, afford crystals formulated as (S_a,S)-1·solvent with an exception of ethanol, which affords (R_a,S)-1·EtOH, while sterically bulkier solvents afford (R_a,S)-1 including no solvent. The stereoselectivity can be rationalized by the crystal structures. A dielectrically controlled resolution (DCR) can also be carried out by using mixed solvents, which contain, for example, 25 vol % of acetone and varying ratios of hexane and 1-propanol in total 75 vol %; (S_a,S)-1·acetone is deposited as crystals from the solvents with a dielectric constant (ε) range 8.9 ? ε ? 10.2, while (R_a,S)-1 is deposited from the solvents with 14.8 ? ε ? 20.3.     

高边缘击穿和扩展光谱的圆形单光子雪崩二极管

介绍了一种0. 18μm互补金属氧化物半导体(CMOS)技术的新型宽光谱荧光相关谱探测器,其为高边缘击穿、扩展光谱和低暗计数率的圆形单光子雪崩二极管(SPAD).该器件由p+/deep n-well结,p-well保护环和多晶硅保护环组成.通过Silvaco TCAD 3D器件仿真,直径为10μm的圆形p+/deep n-well SPAD器件具有较高边缘击穿特性.此外,p+/deep n-well结SPAD比p+/n-well结SPAD具有更长的波长响应和扩展光谱响应范围.该器件在0. 5 V过量偏压下,可在490～775 nm波长范围内实现超过40%的光子探测率.该圆形p+/deep n-well SPAD器件在25℃时具有较好雪崩击穿为15. 14 V,具有较低暗计数率为638 Hz.     

p-well/DNW单光子雪崩二极管保护环的最小化设计

随着CMOS工艺特征尺寸的不断减小,探测器本身的大小成为进一步缩小CMOS单光子雪崩二极管(SPAD)阵列的障碍。为了进一步缩小SPAD探测器的尺寸,基于0.18 μm CMOS 图像传感器(CIS)工艺对p-well/DNW(deep n-well)SPAD的保护环尺寸进行设计,并制造了不同保护环尺寸的SPAD器件。测试结果表明,保护环尺寸减小到0.4 μm仍然能有效防止器件发生过早边缘击穿(PEB),且保护环尺寸大于0.4 μm的SPAD器件雪崩击穿电压为16 V,并表现出良好的雪崩击穿特性。此外,保护环尺寸对p-well/DNW SPAD器件的暗计数(DCR)和光子探测概率(PDP)影响较小,直径为20 μm的SPAD器件,温度为25 ℃时暗计数率为638 Hz,且波长为530 nm时峰值光子探测概率为16%,具有低的暗计数率特性和宽的光谱响应特性。     

基于FPGA的100MHz近红外单光子探测器

为克服InGaAs/InP雪崩二极管(APD)光电探测器的后脉冲现象,本文提出了基于FPGA的单光子探测器(SPD)测量系统,其门控频率最高可达100MHz,门控宽度最窄可到1ns,死区时间设定为109ns,并且这些参数都易于调节且有助于减少后脉冲概率。实验结果表明:在以上门控条件并且制冷温度为218K时,探测器的有效门宽为0.79ns;在死区时间超过109ns时,后脉冲现象可忽略;最大光子探测效率(PDE)约为14%;在光子探测效率为10%时,暗计数率(DCR)约为2×10-5/ns;并具有小型化、易调节的特点。