超声波流量计自增益控制电路研究

为了改善超声波流量计中换能器由于长时间工作、老化而产生的信号强度衰减问题,设计了一种基于DSP和FPGA的超声波流量计自增益控制电路,通过实时监测和比较换能器的信号幅值大小,并结合驱动端增益控制和接收端增益控制的动态控制方法,使得换能器的信号幅值能够保持在基准幅值的90%以上,从而保证了超声波流量计的测量精度,延长了换能器的使用寿命。

基于AGC的等精度数字频率计设计

为了改善工业控制中对频率计的测量精度不高和测量带宽不大的问题,依据等精度测量技术,利用单片机STM32F103VET6、FPGA及自增益控制电路(AGC)设计了一款数字频率计,该频率计可以测量信号频率、周期、时间间隔以及占空比等参数.经实测表明,该频率计具有测量精度高、测量带宽大等优点,具有良好的实用价值.

画中画SDA9488X在视频技术中的应用

MICRONAS生产的画中画SDA9488X是随着数码技术和视频技术发展的迫切需要而产生的,比同类芯片更有优越性.讲述SDA9488X的特性、内部结构及其典型应用.

Design and implementation of digital closed-loop drive control system of a MEMS gyroscope

In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for the MEMS gyroscope in digital closed-loop control is proposed, which utilizes a digital phase-locked loop （PLL） in frequency control and an automatic gain control （AGC） method in amplitude control. A digital processing circuit with a field programmable gate array （FPGA） is designed and the experiments are carried out. The results indicate that when the temperature changes, the drive frequency can automatically track the resonant frequency of gyroscope in drive mode and that of the oscillating amplitude holds at a set value. And at room temperature, the relative deviation of the drive frequency is 0.624 ×10^-6 and the oscillating amplitude is 8.0 ×10^-6, which are 0. 094% and 18. 39% of the analog control program, respectively. Therefore, the control solution of the digital PLL in frequency and the AGC in amplitude is feasible.

Single-Stage Wide-Range CMOS VGA with Temperature Compensation and Linear-in-dB Gain Control

A novel wide-range CMOS variable gain amplifier （VGA） topology is presented. The proposed VGA is composed of a variable transconductor and a novel variable output resistor and can offer a high gain variation range of 80dB while using a single variable-gain stage. Temperature-compensation and decibel-linear gain characteristic are achieved by using a control circuit that provides a gain error lower than ±1.5dB over the full temperature and gain ranges. Realized in 0.25μm CMOS technology, a prototype of the proposed VGA provides a total gain range of 64.5dB with 55.6dB-linear range,a P-1dB varying from - 17.5 to 11.5dBm,and a 3dB-bandwith varying from 65 to 860MHz while dissipating 16.5mW from a 2.5V supply voltage.

A Novel Low Power ASK Receiver with AGC Loop

We report a low power ASK IF receiver for short-range wireless systems,which includes an AGC loop that compensates the channel attenuation and an ASK detector. A novel current-limited transconductor and feed-forward differential peak detector have been designed to maintain a high compression ratio and fast response for the AGC with lower power consumption. A storage unit with a zero and a feed-forward structure have been introduced into the peak detector to control the damping characteristic of the AGC loop. A rectifier and low-pass filter included in the ASK detector have been integrated into a more compact structure to further lower the power consumption. The simulation results show the feasibility of the proposed technique.

Design of 10 Gbit/s burst-mode transimpedance preamplifier for PON systems

A 10 Gbit/s burst-mode preamplifier is designed for passive optical networks （PONs）. To achieve a high dynamic range and fast response, the circuit is DC coupled, and a feed-back type peak detector is designed to perform auto-gaincontrol and threshold extraction. Regulated cascade （RGC） architecture is exploited as the input stage to reduce the input impedance of the circuit and isolate the large parasitic capacitance including the photodiode capacitance from the determination pole, thus increasing the bandwidth. This preamplifier is implemented using the low-cost 0. 13 ixm CMOS technology. The die area is 425 μm × 475 μm and the total power dissipation is 23.4 mW. The test results indicate that the preamplifier can work at a speed from 1.25 to 10.312 5 Gbit/s, providing a high transimpedance gain of 64.0 dBΩ and a low gain of 54. 6 dBl2 with a dynamic input range of over 22.9 dB. The equivalent input noise current is 23. 4 pA/ Hz1/2. The proposed burst amplifier satisfies related specifications defined in 10G-EPON and XG-PON standards.

超外差结构GPS接收机射频前端电路仿真研究

设计了一种GPS接收机射频前端电路,采用三级混频器抑制镜像信号,并进行优化滤波。基于ATF54143设计了适用于接收机前端电路的低噪声放大器,采用源极串接负反馈的方法提高电路稳定性并利用ADS软件进行仿真。构建了基于GPS L1波段(1575.24 MHz)卫星信号射频接收前端仿真平台,利用自动增益控制元件调整输出信号,实现大动态范围。对射频前端电路整体的增益、灵敏度、三阶截断点等指标进行了测试,讨论了电路三阶互调失真特性与噪声系数的关系。仿真结果表明,设计的低噪声放大器稳定性好,噪声系数低,射频前端电路具有良好的线性度与较大的动态范围,对实现多射频链路数字中频接收机大动态范围稳定接收提供了一个有效的解决方案。

Design of a 6.25 Gbps backplane SerDes with adaptive decision feedback equalization

A 6.25 Gbps SerDes core used in the high signed based on the OIF-CEI-02.0 standard. To speed backplane communication receiver has been decounteract the serious Inter-Syrmbol-Interference （ISI）, the core employed a half-rate four-tap decision feedback equalizer （DFE）. The equalizer used the Signsign least mean-squared （SS-LMS） algorithm to realize the coefficient adaptation. An automatic gain control （AGC） amplifier with the sign least mean-squared （S-LMS） algorithm has been used to compensate the transmission media loss. To recover the clock signal from the input data serial and provide for the DFE and AGC, a bang-bang clock recovery （BB-CR） is adopted. A third order phase loop loek （PLL） model was proposed to predict characteristics of the BB-CR. The core has been verified by behavioral modeling in MATLAB. The results indicate that the core can meet the specifications of the backplane receiver. The DFE recovered data over a 34＂ FR-4 backplane has a peak-to-peak jitter of 17 ps, a horizontal eye opening of 0.87 UI, and a vertical eye opening of 500 mVpp.

Digital AGC Based on Coherent Adjustment Cycle for DSSS Receiver

In order to meet the requirements for zero value stability of direct sequence spread spectrum(DSSS) signal processing in high dynamic scenario,digital automatic gain control(AGC) is employed to regulate power.However,conventional AGC causes degradation in the synchronization performance of DSSS receiver.Based on the theoretical analysis of the influence of digital AGC on DSSS signal synchronization,this paper proposes a new AGC algorithm,which is applicable to multi-channel digital DSSS signal receiver.By making power adjustment cycle and synchronization cycle coherent with each other adaptively,the influence of digital AGC on subsequent synchronization processing has been eliminated.Theoretical analysis,simulation results and experimental data verify the validity of the proposed algorithm.By virtue of the proposed algorithm,the influence of digital AGC on DSSS signal synchronization is eliminated.This algorithm applies to an aerospace engineering project successfully.

CMOS Automatic Gain Control Circuit with DC Offset Cancellation for FM/cw Ladar

This paper presented an automatic gain control （AGC） circuit suitable for FM/cw ladar. The proposed architecture was based on two-stage variable gain amplifier （VGA） chain with a novel DC offset canceller circuit, which contained an improved Gilbert cell and a Gm-C feedback loop. To keep the VGA with a linearity in dB characteristic, an improved exponential gain control circuit was introduced. The AGC was implemented in 0.18 gm standard CMOS process. Simulation and measurement results verified that its gain ranged from -20 dB to 30 dB, and band- width ranged from 100 kHz to 10 MHz. Its power consumption was 19.8 mW under a voltage supply of 3.3 V.

Clinical observation of capecitabine plus oxaliplatin in treatment of 68 cases with advanced gastric cancer

Objective:The aim of this study was to evaluate the response rate,time to progression(TTP),overall survival,and safety of the combination of capecitabine plus oxaliplatin in treatment of advanced gastric cancer(AGC).Methods:All the patients with advanced gastric cancer who were not received any prior chemotherapy or radiotherapy were treated with combination of capecitabine(1250 mg/m2 twice daily,days 1-14) plus oxaliplatin(130 mg/m2 as a 2-h intravenous infusion on day 1) every 3 weeks.Results:Two cases of complete response(CR) and 34 cases of partial response(PR) were confirmed,giving an overall response rate of 52.9%,of the 68 patients with advanced gastric cancer.The median TTP and overall survival for all patients were 7.3 and 11.9 months,respectively.Grade 3 leukopenia,thrombocytopenia,nausea/vomiting,and diarrhea were observed in 3,5,1,and 4 patients,respectively.Yet,no grade 4 toxicity was observed.Conclusion:Capecitabine/ oxaliplatin combination chemotherapy is active in patients with advanced gastric cancer.

Switched-mode AGC circuits with internally created reset module for burst-mode unbalanced data optical receiver

This paper presents an innovative switched-mode auto gain control （AGC） circuit with internally created reset module for DC-10Mb/s burst-mode unbalanced （BMU） optical data transmission. Conventional AGC circuit is inappropriate for BMU data transmission because it is based on average level detection and requires considerable time to settle on a predefined gain. Therefore, we adopt a fast switched-mode AGC based on peak level detection. After the gain is adjusted, the peak level detectors need to re-detect the peak level of the input signal. Thus, we develop an internally created reset module. This AGC with reset module exhibits a fast operation and achieves an adjusted stable gain within one-bit, avoiding any bit loss up to 10Mb/s data rate. During power-up, the peak level detectors possibly hold an uncertain level resulting in the bit-errors. We propose a power-up reset circuit to solve this problem. Designed in a 0.5μm CMOS technology, the circuit achieves an optical sensitivity of better than -30dBm and a wide dynamic range of over 30dB with a power dissipation of only 30 mW from a 5V supply.

Transition Stage Control of Tail Sitter Aircraft Based on Guardian Maps

To deal with the high nonlinearities and strong couplings in the transition stage of tailsitter aircraft,an adaptive gainscheduling controller is proposed by combining the guardian maps theory and H∞control theory.This method is applied to track the flightpath angle of the transition stage of tailsitter aircraft,and compared with the linear quadratic regulator(LQR)method based on traditional gain scheduling.Simulation results show that the controller based on the guardian maps theory can autonomously schedule the appropriate control parameters and accomplish the stable transition.Besides,the proposed method shows better tracking performance than the LQR method based on traditional gain scheduling.

Using Adaptive Gain Scheduling LQR Method Control of Arm Driven Inverted Pendulum System Based on PIC18F4431

The arm driven inverted pendulum system is a highly nonlinear model, muhivariable and absolutely unstable dynamic system so it is very difficult to obtain exact mathematical model and balance the inverted pendulum with variable position of the ann. To solve this problem, this paper presents a mathematical model for arm driven inverted pendulum in mid-position configuration and an adaptive gain scheduling linear quadratic regulator control method for the stabilizing the inverted pendulum. The proposed controllers for arm driven inverted pendulum are simulated using MATLAB-SIMULINK and implemented on an experiment system using PIC 18F4431 mieroeontroller. The result of experiment system shows the control performance to be very good in a wide range stabilization of the arm position.

Acquisition algorithm assisted by AGC control voltage for DSSS signals

An appropriate acquisition configuration in terms of signal quality can optimize the acquisition performance. In view of this, a new approach of acquisition assisted by the control voltage of automatic gain control(AGC) is proposed. This approach judges the signal power according to the AGC control voltage and switches the working modes correspondingly and adaptively. Non-coherent accumulation times and the detection threshold are reconfigured according to the working mode. Theoretical derivation and verification by simulation in typical situations are provided, and the algorithm is shown to be superior in terms of the mean acquisition time, especially in strong signal scenarios compared with the conventional algorithm.

STABILIZATION OF THE QUADRUPLE INVERTED PENDULUM BY VARIABLE UNIVERSE ADAPTIVE FUZZY CONTROLLER BASED ON VARIABLE GAIN H_∞ REGULATOR

In this paper, the variable universe adaptive fuzzy controller based on variable gain Ha regulator （VGH∞R） is designed to stabilize a quadruple inverted pendulum. The VGH∞R is a novel robust gain-scheduling approach. By utilizing VGH∞R technique, a more precise real-time feedback gain matrix, which is changing with states, is obtained, Via the variable gain matrix 10 state variables of quadruple inverted pendulum are transformed into a kind of synthesis error （E） and synthesis rate of change of error （EC） at sampling time. Therefore, the dimension of the multivariable system is reduced and the variable universe adaptive fuzzy controller is built. Experiments illustrate the effectiveness of the proposed control scheme.