Enhancing Observability of Signal Composition and Error Signatures During Dynamic SEE Analog to Digital Device Testing

A novel approach to dynamic SEE ADC testing is presented. The benefits of this test scheme versus prior implemented techniques include the ability to observe ADC SEE errors that are in the form of phase shifts, single bit upsets, bursts of disrupted signal composition, and device clock loss

Accurate spectral test algorithms with relaxed instrumentation requirements

Spectral testing is widely used to test the dynamic linearity performance of Analog-to-Digital Converters (ADC) and waveform generators. Dynamic specifications for ADCs are very important in high speed applications such as digital communications, ultrasound imaging and instrumentation. With improvements in the performance of ADCs, it is becoming an expensive and challenging task to perform spectral testing using standard methods due to the requirement that the test instrumentation environment must satisfy several stringent conditions. In order to address these challenges and to decrease the test cost, in this dissertation, three new algorithms are proposed to perform accurate spectral testing of ADCs by relaxing three necessary conditions required for standard spectral testing methods. The testing is done using uniformly sampled points. The first method introduces a new fundamental identification and replacement (FIRE) method, which eliminates the requirement of coherent sampling when using the DFT for testing the spectral response of an ADC. The robustness and accuracy of the proposed FIRE method is verified using simulation and measurement results obtained with non-coherently sampled data. The second method, namely, the Fundamental Estimation, Removal and Residue Interpolation (FERARI) method, is proposed to eliminate the requirement of precise control over amplitude and frequency of the input signal to the ADC. This method can be used when the ADC output is both non-coherently sampled and clipped. Simulation and measurement results using the FERARI method with non-coherently sampled and clipped outputs of the ADC are used to validate this approach. A third spectral test method is proposed that simultaneously relaxes the conditions of using a spectrally pure input source and coherent sampling. Using this method, the spectral characteristics of a high resolution ADC can be accurately tested using a non-coherently sampled output obtained with a sinusoidal input signal that has significant and unknown levels of nonlinear distortion. Simulation results are presented that show the accuracy and robustness of the proposed method. Finally, the issue of metastability in comparators and Successive Approximation Register (SAR) ADCs is analyzed. The analysis of probability of metastability in SAR ADCs with and without using metastable detection circuits is provided. Using this analysis, it is shown that as the frequency of sampling clock increases, using a metastable detection circuit decreases the probability of metastability in SAR ADC

Relaxing the requirements for accurate spectral testing of data converters

Analog-to-digital converters (ADCs) are becoming increasing more common to be involved in many systems in integrated circuits. One of the difficulties being faced is to be able to accurately and cost-effectively test the continually higher performance ADCs. Part of this test is being able to assess the dynamic linearity of the ADC through dynamic spectral testing. The standard test method for ADCs can be difficult to implement accurately and cost effectively due to the stringent requirements. Three different algorithms are proposed that can be used to relax the test requirements in order to reduce the cost of the test equipment while still being able to maintain the test accuracy. The accuracy and robustness of these methods will be shown through simulation and measurement results. The first algorithm developed is relaxing the requirements on the linearity of the test signal and of the need to achieve coherent sampling. The standard test requires that the input signal linearity be about 20dB more pure than the ADC under test along with always maintaining coherent sampling. This algorithm will reduce the purity requirement by allowing the test signal to be much less pure than the ADC under test while also completely removing the need for coherent sampling. The second algorithm is focusing on adding the allowance of the signal to be clipped in addition to the claims of the first algorithm. The standard test requires the input signal to be near full range of the ADC under test without clipping. This algorithm allows for the signal to be clipped up to 1% while still ensuring accurate results. The last algorithm is performing spectral testing of the ADC using a DAC of equal or lower linear performance. If accurate estimates of the INL/DNL of the ADC using a lower performance DAC can be obtained using other algorithms under development, then pre-distortion codes can be added to the DAC to accurately test the dynamic spectral testing performance of the ADC

Accurate and robust spectral testing with relaxed instrumentation requirements

Spectral testing has been widely used to characterize the dynamic performances of the electrical signals and devices, such as Analog-to-Digital Converters (ADCs) for many decades. One of the difficulties faced is to accurately and cost-effectively test the continually higher performance devices. Standard test methods can be difficult to implement accurately and cost effectively, due to stringent requirements. To relax these necessary conditions and to reduce test costs, while achieving accurate spectral test results, several new algorithms are developed to perform accurate spectral and linearity test without requiring precise, expensive instruments. In this dissertation, three classes of methods for overcoming the above difficulties are presented. The first class of methods targeted the accurate, single-tone spectral testing. The first method targets the non-coherent sampling issue on spectral testing, especially when the non-coherently sampled signal has large distortions. The second method resolves simultaneous amplitude and frequency drift with non-coherent sampling. The third method achieves accurate linearity results for DAC-ADC co-testing, and generates high-purity sine wave using the nonlinear DAC in the system via pre-distortion. The fourth method targets ultra-pure sine wave generation with two nonlinear DACs, two simple filters, and a nonlinear ADC. These proposed methods are validated by both simulation and measurement results, and have demonstrated their high accuracy and robustness against various test conditions. The second class of methods deals with the accurate multi-tone spectral testing. The first method in this class resolves the non-coherent sampling issue in multi-tone spectral testing. The second method in this class introduces another proposed method to deal with multi-tone impure sources in spectral testing. The third method generates the multi-tone sine wave with minimum peak-to-average power ratio, which can be implemented in many applications, such as spectral testing and signal analysis. Similarly, simulation and measurement results validate the functionality and robustness of these proposed methods. Finally, the third class introduces two proposed methods to accurately test linearity characteristics of high-performance ADCs using low purity sinusoidal or ramp stimulus in the presence of flicker noise. Extensive simulation results have verified their effectiveness to reduce flicker noise influence and achieve accurate linearity results

Accurate spectral testing without accurate instrumentation

Analog-to-digital converters (ADCs) are becoming increasingly common in many systems in integrated circuits. Spectral testing is widely used to test the dynamic linearity performance of ADCs and waveform generators. With improvements in the performance of ADCs, it is becoming an expensive and challenging task to perform spectral testing using standard methods because of the requirement that the test instrumentation environment must satisfy several stringent conditions. In order to address these challenges and to decrease the test cost, in this dissertation, four new algorithms are proposed to perform accurate spectral testing of ADCs by relaxing three conditions required for standard spectral testing methods. The first method developed is relaxing the requirements on precise control of coherent sampling and input signal amplitude. The efficiency and accuracy of this method is similar to the straightforward FFT, but it can simultaneously handle amplitude clipping and noncoherent sampling. By replacing a noncoherent and clipped fundamental with a coherent and unclipped one, correct spectral specifications can be obtained. Both simulation and measurement results validated the proposed method. The second algorithm can simultaneously perform the linearity test and the spectral test with only one-time data acquisition. Targeted for realizing the cotest of linearity and spectral performance under noncoherent sampling and amplitude clipping, a new accurate method for identifying the noncoherent and clipped fundamental is introduced. The residue after removing the identified fundamental from raw data is used to obtain the linearity and spectral characterizations. Simulation and measurement results against the standard test methods collaborate to validate the accuracy and robustness of the new solution. The third method proposes an efficient and accurate jitter estimation method based on one frequency measurement. Applying a simple mathematical processing to the ADC output in time domain, the RMS of jitter and noise power are obtained. Furthermore, prior information of harmonics need not be known before the processing. The algorithm is robust enough that nonharmonic spurs do not affect the estimation result. Using the proposed algorithm, specifications of the ADC under test can be obtained without the jitter effect. Simulation results of ADCs with different resolutions show the functionality and accuracy of the method. The last method is developed to accurately estimate the SNR with sampling clock jitter. This method does not require a precise sampling clock and thus reduces the test cost. The ADC output sequence is separated into two segments. By analyzing the difference of the two segments, the RMS of jitter and the noise power are estimated, and then the SNR is obtained. Simulation and measurement results against the standard test methods collaborate to validate the accuracy and robustness of the new solution

Estimação da Velocidade do Motor de Indução através do Algoritmo de Aproximação Senoidal na Corrente do Estator.

A informação da velocidade rotórica é muito importante em aplicações industriais como controle da velocidade, posição, torque, estimação de eficiência, análise preditiva entre outras. Sensores de velocidade, como tacômetros e encoders possuem alguns problemas, como dificuldade de instalação em motores já em operação. Com isso, a estimação da velocidade através de parâmetros disponíveis, como corrente e tensão, surge como alternativa, solucionando os problemas dos sensores físicos além de ser menos invasivo. O trabalho visa a estimar a velocidade de motores de indução trifásico (com 2 e 4 pólos) através dos sinais da corrente do estator de forma a atingir características de exatidão, precisão e tempo de atualização similares a de um tacômetro tradicional (de contato ou óptico). O trabalho propõe o aprimoramento de um método para a estimação da velocidade do motor utilizando o Algoritmo de Aproximação Senoidal para estimar os harmônicos de passagem de ranhuras (slot harmonics). O algoritmo é usado como alternativa à FFT (Fast Fourier Transform) e Estimação Espectral para a estimação de frequências relacionadas a velocidade, proporcionando maior exatidão, precisão, menor tempo computacional e diminuindo o tempo de atualização. O método utiliza uma robusta técnica de reamostragem para encontrar os harmônicos de passagem de ranhura, com isso a estimação da velocidade mantém a exatidão sobre diversas condições. Por fim são apresentados dois experimentos com dois motores diferentes, sob diversas condições de velocidade e carga. O método proposto é comparado com outras duas técnicas, uma proposta por Hurst e usada como base para esse trabalho e outra baseada na estimação através da FFT