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Fu W.-Y.,Huaqiao University | Fu W.-Y.,Xiamen Key Laboratory of ASIC System | Ling C.-D.,Huaqiao University | Ling C.-D.,Xiamen Key Laboratory of ASIC System
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2013

Based on the linearity theory of transconductance amplifier and mathematical analysis, a method of improving linearity is presented. In this method, the mathematical analysis and simulation experiments proved that linearity of double ended input transconductor is better than single ended input transconductor. When one end input signal is 4/3 of the other end input signal and plus 1, the transconductor linear distortion can be minimized. A new transconductor is proposed according to the optimization measure. The simulation results show that the spurious free dynamic range of the transconductor is 60.25 dB, and noise-floor reach up to -100 dB.

Fu W.-Y.,Huaqiao University | Fu W.-Y.,Xiamen Key Laboratory of ASIC System | Ling C.-D.,Huaqiao University | Ling C.-D.,Xiamen Key Laboratory of ASIC System
Xitong Fangzhen Xuebao / Journal of System Simulation | Year: 2012

Based on stochastic process theory of Brownian bridge motion, a new type of integral nonlinearity (INL) and differential nonlinearity errors (DNL) and the DAC section of the mathematical model was proposed, which compared with the Monte Carlo simulation methods Comparison of validation. The results show that both the results do not differ more than 0.5%, but the simulation time less than 2000% for the Monte Carlo simulation. INL and DNL is the same trend compared with the segment s: (N-s) for low weight of coded binary DAC. When the s: (N-s) <1/2, INL and DNL are small; when s: (N-s) ≥ 1/2, INL and DNL increased slightly compared with the lower segment. Consider as chip area, it chooses s = [N/2] is better. The model could be used for high-speed video decoding and related fields.

Fu W.,Huaqiao University | Fu W.,Xiamen Key Laboratory of ASIC System | Ling C.,Huaqiao University | Ling C.,Xiamen Key Laboratory of ASIC System | And 4 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

Measurement of soil moisture is important for water management in crop cultivation, design of irrigation schedule and development of agricultural automation. Harmonic distortion of soil moisture sensor is high so that the measurement of soil moisture content by using those sensors has a large deviation. Therefore, a new design of soil moisture sensor based on differential signal was proposed in this study. The sensor consisted of six parts, which were circuit based on differential signal, correcting circuit, waveform generator, microcontroller unit, power conversion module and electrode module. Since the output signal of senor electrode had harmonic distortion due to the nonlinear factors of soil, a new circuit scheme was proposed using integrated time-based timer to design differential signal control circuit. The relationship between soil resistance and signal period was analyzed by mathematical models. The soil moisture could be obtained by constructing the hardware structure of sensor and measuring the signal period on microprogrammed control unit (MCU) controller in terms of the relationship. The two ends of input waveform in differential signal control circuit were with equal amplitude and phase difference of 180o. Thus these electrodes were almost equal to differential signal. Energy of even order harmonic distortion reduced, while odd order harmonic distortion energy increased at the same time. Moreover, considering the probability of mismatch to electric characteristic parameters, the variance ratio of period of signal in the output was less than the proposed circuit. To verify harmonic distortion of the proposed sensor, frequency spectrum was obtained by utilizing the software of electronic design automation for the proposed sensor with two ends of input-output and classical sensor with a single end of input-output. Total harmonic distortion of traditional circuit for a single end of input-output was 47.40% where the voltage amplitude of two-order harmonic and three-order harmonic was as high as 0.325 and 0.516V, respectively. In contrast, differential signal control circuit could be applied to improve harmonic distraction where the voltage amplitude of two-order harmonic was 0.097 V and that of three-order harmonic was 1.161 V, respectively. Experiment on the proposed sensor was organized as follows. Firstly, the sensor was calibrated by utilizing two types of soils including loam and sandy soil. Secondly, the sensor was evaluated in the soil samples with different soil moisture content. The result showed that the total harmonic distortion of this sensor of output signal was lower than traditional one. The maximum absolute error of soil moisture was less than 4.89% and the error of soil resistance was less than 2% when soil moisture was between 5% and 30%. The absolute error of soil resistance was less than 10% in the condition that soil moisture was in the interval of 30% and 47%. The study provides an effective method for design of soil moisture sensors. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.

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