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Evaluation of Mixed-Signal Noise Effects in Photon Counting X-Ray Image Sensor Readout Circuits
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (STC)
Responsible organisation
2006 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, no 1, 88-91 p.Article in journal (Refereed) Published
Abstract [en]

In readout electronics for photon counting pixel detectors, the tight integration between analog and digital blocks causes the readout electronics to be sensitive to on-chip noise coupling. This noise coupling can result in faulty luminance values in grayscale X-ray images, or as color distortions in a color X-ray imaging system. An exploration of simulating noise coupling in readout circuits is presented which enables the discovery of sensitive blocks at as early a stage as possible, in order to avoid costly design iterations. The photon counting readout system has been simulated for noise coupling in order to highlight the existing problems of noise coupling in X-ray imaging systems. The simulation results suggest that on-chip noise coupling should be considered and simulated in future readout electronics systems for X-ray detectors.

Place, publisher, year, edition, pages
2006. Vol. 563, no 1, 88-91 p.
Keyword [en]
Photon Counting, Pixel Detector, Noise Effects, Evaluation
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-3433DOI: 10.1016/j.nima.2006.01.098ISI: 000238764700022Scopus ID: 2-s2.0-33745000546Local ID: 3432OAI: oai:DiVA.org:miun-3433DiVA: diva2:28465
Conference
7th International Workshop on Radiation Imaging Detectors, Jul 04-07, 2005, Grenoble, France
Projects
STC - Sensible Things that Communicate
Note

7th International Workshop on Radiation Imaging Detectors, Jul 04-07, 2005, Grenoble, France

Available from: 2008-09-30 Created: 2009-01-07 Last updated: 2016-09-28Bibliographically approved
In thesis
1. Simulating Behavioral Level On-Chip Noise Coupling
Open this publication in new window or tab >>Simulating Behavioral Level On-Chip Noise Coupling
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, noise coupling simulation is introduced into the behavioral level. Methods andmodels for simulating on-chip noise coupling at the behavioral level in a design flow are presentedand verified for accuracy and validity. Today, designs of electronic systems are becoming denserand more and more mixed-signal systems such as System-on-Chip (SoC) are being devised. Thisraises problems when the electronics components start to interfere with each other. Often, digitalcomponents disturb analog components, introducing noise into the system causing degradation ofthe performance or even introducing errors into the functionality of the system.Today, these effects can only be simulated at a very late stage in the design process, causinglarge design iterations and increased costs if the designers are required to return and makealterations, which may have occurred at a very early stage in the process.This is why the focus of this work is centered on extracting noise coupling simulation modelsthat can be used at a very early design stage, such as at the behavioral level and then follow thedesign through the various design stages. To achieve this, SystemC is selected as a platform andimplementation example for the behavioral level models. SystemC supports design refinement,which means that when designs are being refined and are crossing the design levels, the noisecoupling models can also be refined to suit the current design.This new method of thinking in primarily mixed-signal designs is called Behavioral levelNoise Coupling (BeNoC) simulation and shows great promise in enabling a reduction in the costsof design iterations due to component cross-talk and simplifies the work for mixed-signal systemdesigners.

Abstract [sv]

I denna avhandling introduceras brussimulering i mikrochip på en beteendenivå. Metoderoch modeller för brussimulering i chip presenteras och verifieras för noggrannhet och funktionalitetpå en beteendenivå i designflödet. I dagsläget blir elektroniska system tätare och tätare på chippenoch fler och fler system görs med både analog och digital elektronik såsom System-on-Chip (SoC).Detta skapar problem när komponenter börjar störa varandra. Oftast är det digitala komponentersom stör de analoga, vilket introducerar brus i systemet som reducerar prestanda eller till och medinför fel i funktionen hos systemet.Idag kan dessa effekter simuleras i ett mycket sent skede i designflödet, betyder att om felupptäcks måste designern kanske gå tillbaka många steg i flödet. Detta kostar mycket tid ochpengar.Därför ligger fokus i detta arbete på att extrahera brussimuleringsmodeller som kananvändas i ett tidigt skede såsom på beteendenivå och sedan följa designen genom senare skeden idesignflödet. För att realisera detta har SystemC valts som en plattform och som ettimplementationsexempel för beteendenivåmodellerna. SystemC har stöd för förfining av designervilket betyder att ett system kan börja beskrivas på en hög nivå för att sedan förfinas för att nå lägrenivåer. Detta gör det möjligt för brusmodellerna att också förfinas i takt med systemdesignen.Detta nya sätt att tänka på i designprocessen av i huvudsak analog/digital-integreradesystem kallas Behavioral level Noise Coupling (BeNoC) simulering och bådar gott för att reducerakostnader för designiterationer på grund av brus mellan komponenter, och gör arbetet enklare föranalog/digital- (mixed-signal) designers.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2007. 151 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 25
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-8057 (URN)978-91-85317-54-7 (ISBN)
Public defence
2007-05-30, O102, Holmgatan 10, Sundsvall, 10:00 (English)
Opponent
Supervisors
Available from: 2009-01-12 Created: 2009-01-07 Last updated: 2011-02-06Bibliographically approved
2. Architecture and circuit design of photon counting readout for X-ray imaging sensors
Open this publication in new window or tab >>Architecture and circuit design of photon counting readout for X-ray imaging sensors
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Hybrid pixel array detectors for X-ray imaging are based on different technologies for sensor and readout electronics. The readout electronics are based on standard CMOS technologies that are experiencing continuously rapid improvements by means of down-scaling the feature sizes, which in turn lead to higher transistor densities, lower power consumption, and faster circuits. For pixel-array imaging sensors the improvements in CMOS technology opens up new possibilities of integrating more functionality in the pixels for local processing of the sensor data. However, new issues related to the tight integration of both analog and digital processing circuits within the small area of a pixel must also be evaluated.

The advantages of down-scaling the CMOS technology can be utilized to increase the spatial resolution by reducing the pixel sizes. Recent research indicates however that the bottleneck in reaching further spatial resolution in X-ray imaging sensors may not be limited by the circuit area occupied by the functions necessary in the pixels, but are instead related to problems associated with charge-sharing of charges generated by the sensor which are distributed over a neighbourhood of pixels and will limit the spatial resolution and lead to a distortion of the energy spectrum. In this thesis a mechanism to be implemented in the readout circuits is proposed in order to suppress the charge-sharing effects. The proposed architecture and its circuit implementation are evaluated with respect to circuit complexity (area) and power consumption. For a photon-counting pixel it is demonstrated that the complete pixel, with charge-sharing suppression mechanism, can be implemented using 300 transistors with an idle power consumption of 2.7μW in a 120nm CMOS technology operating with a 1.2V power supply.

The improvements in CMOS technology can also be used for increasing the range of applications for X-ray imaging sensors. In this thesis, an architecture is proposed for multiple energy discrimination, called color X-ray imaging. The proposed solution is the result of balancing the circuit complexity and the image quality. The method is based on color sub-sampling with intensity biasing. For three-level energy discrimination, that corresponds to color imaging systems for visible light with R, G, and B color components, the increase in circuit complexity will be only 20% higher than that for the Bayer method but results in significantly better image quality.

As the circuit complexity in the digital processing within each pixel is increased, the digitally induced noise may play an increasingly important role for the signal-to-noise ratio in the measurements. In this thesis an initial study is conducted regarding how the digital switching noise affects the analog amplifiers in the photon-counting pixel.

Place, publisher, year, edition, pages
Sundsvall: Mittuniversitetet, 2007. 80 p.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 22
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-9327 (URN)
Presentation
(English)
Opponent
Supervisors
Available from: 2009-07-10 Created: 2009-07-10 Last updated: 2011-02-06Bibliographically approved

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Lundgren, JanAbdalla, SulimanO'Nils, MattiasOelmann, Bengt
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Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Electrical Engineering, Electronic Engineering, Information Engineering

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