Small animal Positron Emission Tomography (PET)is dedicated to small animal imaging, which requires high position and energy precision, as well as good flexibility and efficiency of the electronics. This paper presents the design of a digital signal processing logic for a marmoset brain PET system based on LYSO crystal arrays, SiPMs, and the resistive network readout method. We implement 32-channel signal processing in a single Xilinx Artix-7 Field-Programmable Gate Array (FPGA). The logic is designed to support four online modes which are regular data processing mode, flood map construction mode, energy spectrum construction mode, and raw data mode. Several functions are integrated, including two-dimensional (2D) raw position calculation, crystal locating, events filtering, and synchronization detection. Furthermore, a series of online corrections is also integrated, such as photon peak correction to 511 keV and time measurement result correction with crystal granularity. A Gigabit Ethernet interface is utilized for data transfer, Look-Up Tables (LUTs) configuration, and command issuing. The pipeline logic works at 125 MHz with a signal processing capability beyond the required data rate of 1,000,000 events/s/channel. A series of initial tests are conducted. The results indicate that the logic design meets the application requirement.
In the process of non-intrusive load monitoring, the first step is to find the switching on/off events as accurate as possible. However, there are extensive disturbances in the recorded data, due to the voltage fluctuations, electrical noise and etc, resulting in either false detection or event missing. To solve this problem, a new event detection technique is proposed in this paper. This technique uses median filter algorithm and the proposed ripple mitigation algorithm to effectively remove the unexpected disturbances and extract the real signal of switching on/off events. The proposed algorithms are very easy to implement in the low cost devices. The lab data and BLUED data tests show more than 90% accurate rate of event detection.
Position Emission Tomography (PET) is an advanced clinical diagnostic imaging technique for nuclear medicine. Small animal PET is increasingly uesd for studying the animal model of disease, new drugs and new therapies. A prototype of Singles Processing Unit (SPU) for a small animal PET system was designed to obtain the time, energy, and position information. The energy and position is actually calculated through high precison charge measurement, which is based on amplification, shaping, A/D conversion and area calculation in digital signal processing domian. Analysis and simulations were also conducted to optimize the key parameters in system design. Initial tests indicate that the charge and time precision is better than 3‰ FWHM and 350 ps FWHM respectively, while the position resolution is better than 3.5‰ FWHM. Commination tests of the SPU prototype with the PET detector indicate that the system time precision is better than 2.5 ns, while the flood map and energy spectra concored well with the expected.
For application to cascaded multi-level inverter, three phase-difference SVM (PD-SVM) schemes based on left and right bridge vectors are proposed firstly. For these three schemes, equivalent SPWM components are deduced, and unipolarity or bipolarity of output waveforms is analyzed. Use sampling time staggered SVM (STS-SVM) for reference, improved PD-SVM-STS PD-SVM can be applied to cascaded medium-voltage variable speed driver (MV-VSD). The mechanism of eliminating two sorts of CMV by one of improved PD-SVM schemes-STS 2π/3 PD-SVM is analyzed in detail. Through the simulation results in the end, this modulation scheme can effectively eliminate CMV without reducing the utilization of the dc voltage excessively in contrast with conventional 3d-order harmonic injection SPWM.Presently, two approaches are mainly considered to restrict CMV, including:• Appending passive or active filters [5], [6]The disadvantages of this approach attribute to significantly increase size, cost, and hardly applied in highvoltage and large-power systems.• Improving modulation techniqueBased on SVM and SPWM separately, two improved modulation schemes for three-level NPC, are proposed to eliminate CMV in [4]. The basic idea about improved SVM is only to select zero-CMV
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