• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2646-2651
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• 2021

A rectangular-shaped PET system with an adjustable gantry (AGPET) has been developed for imaging small animals. The AGPET system employs a new depth of interaction (DOI) method using a depth dependent reflector patterns and a new digital time pickoff method based on the pulse reconstruction method. To evaluate the performance of the AGPET, timing resolution, intrinsic spatial resolution and point source images were acquired. The timing resolution and intrinsic spatial resolution were measured using two detector modules and Na-22 gamma source. The PET images were acquired in two field of view (FOV) sizes, 30 mm and 90 mm, to demonstrate the characteristic of the AGPET. As a result of in the experiment results, the timing resolution was 0.9 ns using the pulse reconstruction method based on the bi-exponential model. The intrinsic spatial resolution was an average of 1.7 mm and the spatial resolution of PET images after DOI correction was 2.08 mm and 2.25 mm at the centers of 30 mm and 90 mm FOV, respectively. The results show that the proposed AGPET system provided higher sensitivity and resolution for small animal imaging.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.8
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• pp.47-55
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• 2010

In this paper, a timing register architecture using demultiplexer and counter is proposed to reduce the area of the high resolution SAR type analog to digital converter. The area and digital power consumption of the conventional timing register based on the shift register is drastically increased, as the resolution is increased. On the other hand, the proposed architecture results in reduction of the area and the power consumption of the error correction logic of the SAR ADC. This chip is implemented with 0.18 um CMOS process. The area is reduced by 5.4 times and the digital power consumption is minimized compared with the conventional one. The 12 bits SAR ADC shows ENOB of 11 bits, power consumption of 2 mW, and conversion speed of 1 MSPS. The die area is $1 mm{\times}1mm$.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.50-56
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• 1999

This paper presents a new technique for generating precise clock delays. The technique can obtain finer timing resolution less than the gate delay of the delay chain by locking in multiple clock period. Using this technique, a 250ps of timing resolution could be achieved from a 750ps delay of the single delay stage in a DLL(Delay Locked Loop) structure. The delay chain of the proposed circuit is locked on three times of the clock period and a finer delay resolution than the absolute gate delay is achieved and verified through the simulation.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.432-438
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• 2019

In the study of nuclear structure, the fast timing technique can be used to measure the lifetime of excited states. In the paper, we have developed a new fast timing system, which is made up of two $LaBr_3:Ce$ detectors and a set of waveform sampling system. The sampling system based on domino ring sampler version 4 chip (DRS4) can digitize and store the waveform information of detector signal, with a smaller volume and higher timing accuracy, and the waveform data are performed by means of digital waveform analysis methods. The coincidence time resolution of the fast timing system for two annihilation 511 keV ${\gamma}$ photon is 200ps (FWHM), the energy resolution is 3.5%@511 keV, and the energy linear response in the large dynamic range is perfect. Meanwhile, to verify the fast timing performance of the system, the $^{152}Gd-2_1^+$ state form ${\beta}^+$ decay of $^{152}Eu$ source is measured. The measured lifetime is $45.3({\pm}5.0)ps$, very close to the value of the National Nuclear Data Center (NNDC: $46.2({\pm}3.9)ps$). The experimental results indicate that the fast timing system is capable of measuring the lifetime of dozens of ps. Therefore, the system can be widely used in the research of the fast timing technology.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.1
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• pp.23-31
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• 2020

It is essential to estimate the vehicle localization for an autonomous safety driving. In particular, since LIDAR provides precise scan data, many studies carried out to estimate the vehicle localization using LIDAR and pre-generated map. The road marking always exists on the road because of provides driving information. Therefore, it is often used for map information. In this paper, we propose to generate the Gaussian mixture map based on road-marking information and localization method using this map. Generally, the probability distributions map stores the single Gaussian distribution for each grid. However, single resolution probability distributions map cannot express complex shapes when grid resolution is large. In addition, when grid resolution is small, map size is bigger and process time is longer. Therefore, it is difficult to apply the road marking. On the other hand, Gaussian mixture distribution can effectively express the road marking by several probability distributions. In this paper, we generate Gaussian mixture map and perform vehicle localization using Gaussian mixture map. Localization performance is analyzed through the experimental result.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.223-224
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• 2007

To develop nuclear measurement system with characteristics including both re-configuration and multi-functions, we proposed a field programmable gate array (FPGA) technique to implement TDC which is more suitable for high energy Physics system. In TDC scheme, the timing resolution is more important than the count rates of channel. In order to manage pico-second resolution TDC, we used the delay components of FPGA, utilized the place and route (P&R) delay difference, and then got two ring oscillators. By setting P&R area constraints, we generated two precise ring oscillators with slightly different frequencies. Finally, we evaluated that the period difference of these two ring oscillators was about 60 pico-seconds, timing resolution of TDC.

• Journal of Radiation Protection and Research
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• v.35 no.2
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• pp.69-76
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• 2010

Prototype double-scattering Compton camera, which consists of three gamma-ray detectors, that is, two double-sided silicon strip detectors (DSSDs) as scatterer detectors and a NaI(Tl) scintillation detector as an absorber detector, could provide high imaging resolution with a compact system. In the present study, the energy resolution and the timing resolution of component detectors were measured, and the parameters affecting the energy resolution of the DSSD were examined in terms of equivalent noise charge (ENC). The energy resolutions of the DSSD-1 and DSSD-2 were, in average, $25.2keV{\pm}0.8keV$ FWHM and $31.8keV{\pm}4.6keV$ FWHM at the 59.5 keV peak of $^{241}Am$, respectively. The timing resolutions of the DSSD and NaI(Tl) scintillation detector were 57.25 ns FWHM and 7.98 ns FWHM, respectively. In addition, the Compton image was obtained for a point-like $^{137}Cs$ gamma source with double-scattering Compton camera. From the present experiment, the imaging resolution of 8.4 mm FWHM (angular resolution of $8.1^{\circ}$ FWHM), and the imaging sensitivity of $1.5{\times}10^{-7}$ (intrinsic efficiency of $1.9{\times}10^{-6}$) were obtained.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.319-327
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• 2003

We consider the problem of low-sampling rate high-resolution channel estimation and timing for digital ultrawideband (UWB) receivers. We extend some of our recent results in sampling of certain classes of parametric non-bandlimited signals and develop a frequency domain method for channel estimation and synchronization in ultra-wideband systems, which uses sub-Nyquist uniform sampling and well-studied computational procedures. In particular, the proposed method can be used for identification of more realistic channel models, where different propagation paths undergo different frequency-selective fading. Moreover, we show that it is possible to obtain high-resolution estimates of all relevant channel parameters by sampling a received signal below the traditional Nyquist rate. Our approach leads to faster acquisition compared to current digital solutions, allows for slower A/D converters, and potentially reduces power consumption of digital UWB receivers significantly.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.16-21
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• 2006

This paper shows a vernier delay technique for generating precise multiphase clocks using PLL structure. The proposed technique can achieve the finer timing resolution less than the gate delay of the delay chain in VCO. Using this technique, 62.5ps of timing resolution can be achieved if the reference clock rate is set at 1GHz using 0.18um CMOS technology. Jitter of 14ps peak-to-peak was measured.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.90-99
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• 1994

Picosecond time-correlated single photon counting system and time-resolved luminescence spectrometer were constructed, employing a mode-locked picosecond laser, fast electronics, and microchannel plate tube. It has been shown that the instrument response function critically depends on laser pulse shape, timing jitter and walk of the electronics, and characteristics of detector and amplifier. Correcting time dispersion in the optical system, the best instrument response function obtained appears to be 25 ps, which made it possible to measure the luminescence lifetime with less than 10 ps resolution in the picosecond to microsecond range. range.