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In the traditional signal subdivision system, it is usually necessary to compensate each kind of error separately, which will consume many hardware and computing resources and cause a significant output latency, especially in the filtering section and normalization section. In this paper, a non-linear Kalman filter-based sin-cos wave subdivision method is proposed. Compared with the traditional filtering methods, non-linear Kalman filter has higher dynamic response and can provide instantaneous phasor estimation. In addition, it can simultaneously achieve filtering, amplitude normalization, decoupling DC bias, harmonic suppression, and phase compensation functions, which significantly reduces the computational burden and facilitates the implementation on low-cost processors.
In this study, a non-linear Kalman filter-based signal segmentation system is implemented on an FPGA platform and verified on a six-degree-of-freedom grating ruler platform. The results show that the single-channel output delay is only 1.8us at a 50MHz clock, which has a very high real-time ability. When the frequency and amplitude of the input signal varies, the non-linear Kalman filter can track instantaneously and has high dynamic characteristics. Experimental results show the effectiveness of this method.
In this paper, the fluorescence quantum efficiency of 3 different samples at atmosphere was compared, and the electrospray ionization source was selected for its soft ionization characteristics. The ionization method did not spoil the fluorophore of the sample, and the drift tube of ion mobility spectrometry (IMS) was used for ions transport and desolvation. The ionization source was on the one side of the drift tube and the test point was on the other side. The paths of excited laser and emission light were orthogonal at the test point. Meanwhile, stable ions flowed through the drift tube. The emission light was captured by the camera, which was coupled with a long-wave pass filter. The test samples were Rhodamine 6G,Rhodamine B and amino copper indium sulfide quantum dots of the same mass fraction. The energy of excited laser was between 30 mW and 150 mW. Then the results showed that the emission intensity was proportional to the laser power in gas phase, and the sort of the fluorescence quantum efficiency was the quantum dots>Rhodamine 6G>Rhodamine B.
In this work, we tested the signal in different electric field intensity by a home-made ion mobility spectrometer, using silicon wafers the sample. The transportation of metal ions was match with the formula: Td = d/K • 1/E, when the electric field intensity is greater than 350v/cm. The relationship between signal intensity and collection angle (the angle between drift tube and the surface of the sample) was studied. With the increasing of the collection angle, signal intensity had a significant increase; while the variation of incident angle of the laser had no significant influence. The signal intensity had a 140% increase when the collection angle varied from 0 to 45 degree, while the angle between the drift tube and incident laser beam keeping the same as 90 degree. The position of ion gate in LA-IMS(Laser Ablation Ion Mobility Spectrometry) is different from the traditional ones for the kinetic energy of the ions is too big, if the distance between ion gate and sampling points less than 2.5cm the ion gate will not work, the ions could go through ion gate when it closed. The SNR had been improved by define the signal when the ion gate is closed as background signal, the signal noise including shock wave and electrical field perturbation produced during the interaction between laser beam and samples is eliminated when the signal that the ion gate opened minus the background signal.
Gaseous phase ion detection method based on laser-induced fluorescence for ion mobility spectrometer
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