A pseudo differential Gm-C complex filter with frequency tuning for IEEE802.15.4 applications

This paper presents a CMOS G_m-C complex filter for a low-IF receiver of the IEEE802.15.4 standard.A pseudo differential OTA with reconfigurable common mode feedback and common mode feed-forward is proposed as well as the frequency tuning method based on a relaxation oscillator.A detailed analysis of non-ideality of the OTA and the frequency tuning method is elaborated.The analysis and measurement results have shown that the center frequency of the complex filter could be tuned accurately.The chip was fabricated in a standard 0.35μm CMOS process,with a single 3.3 V power supply.The filter consumes 2.1 mA current,has a measured in-band group delay ripple of less than 0.16μs and an IRR larger than 28 dB at 2 MHz apart,which could meet the requirements of the IEEE802.15.4 standard.     

Ultra-low-power capacitor-splitting switching algorithm with minus energy for SAR ADCs

In this letter, an ultra-low-power capacitor-splitting switching algorithm for successive approximation register analog-to-digital converters is proposed. To achieve low power, the first three bit cycles consume no power from the reference by introducing minus energy during the third bit cycle and proper switching algorithm. To further reduce the switching energy, only single-side capacitors are switched from the forth bit cycle. Besides, to add one bit, the dummy capacitor is realized by four unit capacitors and switched to generate the least significant bit. Compared to the Sanyal and Sun switching technique, the proposed capacitor switching method achieves 94.19% energy saving and 47.66% capacitor area reduction.     

频率综合器中低功耗高速多模分频器设计的“时间借用”方法

提出一种基于"时间借用"方法的相位切换型多模高速分频器,新型的相位切换控制策略有效地减少相位切换控制环路的延时,使得多模分频器在较低的电源电压下仍能在较高的输入频率下工作,同时获得最大可分频模数.本文设计的多模分频器采用0.35μm标准CMOS工艺流片.测试结果表明,该多模分频器能够在2.5V电源电压下对2.4GHz输入信号进行48到64分频,所消耗的最大功耗仅为4.85mW,与近来报道的CMOS多模分频器相比,进一步降低了功耗速度比.     

频率综合器中低功耗高速多模分频器设计的 "时间借用"方法

提出一种基于"时间借用"方法的相位切换型多模高速分频器,新型的相位切换控制策略有效地减少相位切换控制环路的延时,使得多模分频器在较低的电源电压下仍能在较高的输入频率下工作,同时获得最大可分频模数.本文设计的多模分频器采用0.35μm标准CMOS工艺流片.测试结果表明,该多模分频器能够在2.5V电源电压下对2.4GHz输入信号进行48到64分频,所消耗的最大功耗仅为4.85mW,与近来报道的CMOS多模分频器相比,进一步降低了功耗速度比.     

Effect of Intermediate Diaphragms on Decked Bulb-Tee Bridge System for Accelerated Construction

One of the promising systems for accelerated bridge construction is the use of the decked precast prestressed concrete girders or decked bulb-tee girders for the bridge superstructure. Using the calibrated three-dimensional finite-element models through field tests, a parametric study was conducted to determine the effect of intermediate diaphragms on the deflections and flexural strains of girders at the midspan as well as the live load forces in the longitudinal joint. The following diaphragm details were considered: different diaphragm types (steel and concrete), different diaphragm numbers between two adjacent girders, and different cross-sectional areas for steel diaphragms. Five bridge models with different diaphragm details were developed, and the short span length effect on the bridge behavior was also studied. It was found that as long as one intermediate diaphragm was provided between two adjacent girders at midspan, changing the diaphragm details did not affect the girder deflection, the girder strain, and the live load forces in the longitudinal joint significantly. The effect of diaphragms on the midspan deflection was more prominent in the short span bridge; however, the reduction in the maximum bending moment by the diaphragms was more significant in the long span bridge than in the short span bridge. Specific design recommendation is provided in this paper.     

一种适用于IEEE802.15.4协议的带频率调谐的伪差分Gm-C复数滤波器

本文针对IEEE802.15.4协议的低中频接收机,提出一种CMOS Gm-C复数滤波器。该滤波器采用具有可重构共模反馈和共模前馈功能的伪差分OTA结构。文章还提出一种基于松弛振荡器的频率调谐方法,并对OTA的非线性和频率调谐方法进行了详细分析,分析及测试结果均表明该滤波器能够实现精确调谐的功能。芯片采用标准0.35μm CMOS工艺制作,测试结果显示,滤波器消耗电流2.1mA,带内群延时波动小于0.16μs,2MHz频偏处IRR大于28dB,可以满足IEEE802.15.4协议的要求。     

MEMS陀螺漂移误差建模与滤波

MEMS陀螺漂移误差直接影响光电稳定跟踪平台伺服机构的控制精度.针对MEMS陀螺随机漂移误差慢时变、弱非线性、难以准确补偿的特点,基于随机序列时序分析法的基本原理,对预处理后的MEMS陀螺漂移残差信号进行建模,并根据模型对残差信号进行Kalman滤波.结果显示滤波前后信号的方差提高了1到2个数量级,表明有效抑制了漂移误差,提高了MEMS陀螺的精度.     

Improved Longitudinal Joint Details in Decked Bulb Tees for Accelerated Bridge Construction: Fatigue Evaluation

This companion paper focuses on an investigation of improved continuous longitudinal joint details for decked precast prestressed concrete girder bridge systems. Precast concrete girders with an integral deck, which are cast and prestressed with the girder, provide benefits of rapid construction along with improved structural performance and durability. Despite these advantages, the use of this type of construction has been limited to isolated regions of the United States. One of the issues limiting more widespread use is the perceived problem with durability of longitudinal joints used to connect adjacent girders. Four full-scale slabs connected by No. 16 (#5) headed reinforcement detail using a 152 mm (6 in.) lap length were fabricated and tested. An analytical parametric study was conducted to provide a database of maximum forces in the longitudinal joint. These maximum forces are then used to determine the loading demand necessary in the slab testing due to the service live load. Static and fatigue tests under four-point pure-flexural loading, as well as three-point flexural-shear loading, were conducted. Test results were evaluated based on flexural capacity, curvature behavior, cracking, deflection, and steel strain. Based on these test results, the improved longitudinal joint detail is a viable connection system that transfers the forces between the adjacent decked bulb tee girders.     

基于MOEMS的微型数字太阳敏感器

结合CMOS APS图像传感器与MEMS工艺的优势,研制了一种适用于微纳卫星的两轴数字太阳敏感器,在保证测量精度的同时,减小了系统的体积与功耗.其光学系统由CMOS APS图像传感器和MEMS工艺制作的孔阵列结构光学引入器组成,提高了敏感器的分辨率,扩大了有效视场的范围.利用太阳模拟器对数字太阳敏感器进行了测试标定,结果表明,在120°圆锥全视场范围以内,1σ精度优于0.035°.     

Simplified full-depth precast concrete deck panel systems for accelerated bridge construction

A simplified full-depth precast concrete deck panel system for accelerating bridge construction (ABC) is introduced and a finite element analysis (FEA) is conducted to investigate the static and dynamic responses of this conceptual deck system. The FEA results are compared to those of the traditional full-depth precast concrete deck panel system. The comparison results show that the mechanical behavior of the new deck system is different from that of the traditional deck system. The concrete decks in the new system act as two-way slabs, instead of the one-way slab in the traditional system. Meanwhile, the connections in both the longitudinal and transverse directions may need to accommodate the negative moments. Compared to those in the traditional system, the longitudinal nominal stress at middle span increases a lot in the new deck system and the effective flange width varies significantly. In addition, the dynamic results show that the impact factor is influenced by the spacing of connections. Finally, some design concerns of the new deck system are proposed.