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arXiv 1703.01082physics.ins-dethep-ex
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基于环形振荡器的多通道游标时间数字转换器的FPGA实现:设计要点与构造方法

Towards implementing multi-channels, ring-oscillator-based, Vernier time-to-digital converter in FPGAs: key design points and construction method

Ke Cui, Xiangyu Li, Zongkai Liu, Rihong Zhu

摘要:

对于TOF正电子发射断层成像(TOF PET)探测器,时间-数字转换器(TDC)对于解决光子对的符合时间至关重要。最近,我们的团队报道了一种高效的TDC结构,称为基于环形振荡器(RO)的游标TDC使用进位链。该方法具有线性度误差小、资源消耗少等优点,具有很好的应用前景.然而,实现复杂度相当高,尤其是当移动到多通道TDC设计时,因为该方法需要对编译软件的初始拟合结果进行手动干预。在本文中,我们阐述了实现高性能的多通道TDC的这种同时保持最低的实现复杂度的关键点。此外,我们提出了一种高效的精细时间序列构建方法,称为周期差记录,它只需要最多31次调整试验,以获得目标TDC分辨率。为了验证本文提出的技术,我们建立了一个32通道TDC上的Stratix III FPGA芯片,并充分评估其性能。码密度测试结果表明,32个TDC通道的分辨率在23 ps ~ 37 ps之间,微分非线性(DNL)在-0.4 LSB ~ 0.4 LSB之间,积分非线性(INL)在-0.7 LSB ~ 0.7 LSB之间。本文的研究大大降低了基于RO的进位链TDC的设计难度,对实际应用具有重要的推动作用。

英文摘要:

For TOF positron emission tomography (TOF PET) detectors, time-to-digital converters (TDCs) are essential to resolve the coincidence time of the photon pairs. Recently, an efficient TDC structure called ring-oscillator-based (RO-based) Vernier TDC using carry chains was reported by our team. The method is very promising due to its low linearity error and low resource cost. However, the implementation complexity is rather high especially when moving to multi-channels TDC designs, since this method calls for a manual intervention to the initial fitting results of the compilation software. In this paper, we elaborate the key points toward implementing high performance multi-channels TDCs of this kind while keeping the least implementation complexity. Furthermore, we propose an efficient fine time interpolator construction method called the period difference recording which only needs at most 31 adjustment trials to obtain a targeted TDC resolution. To validate the techniques proposed in this paper, we built a 32-channels TDC on a Stratix III FPGA chip and fully evaluated its performance. Code density tests show that the obtained resolution results lie in the range of (23 ps ~ 37 ps), the differential nonlinearity (DNL) results lie in the range of (-0.4 LSB ~ 0.4 LSB) and the integral nonlinearity (INL) results lie in the range of (-0.7 LSB ~ 0.7 LSB) for each of the 32 TDC channels. This paper greatly eases the designing difficulty of the carry chain RO-based TDCs and can significantly propel their development in practical use.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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