A Study of \Delta\Sigma -CDS Algorithm for X-Ray CCD Applications

• Published in: IEEE transactions on nuclear science 2019-02, Vol.66 (2), p.597-608
• Main Authors: Lu, Bo, Chen, Yong, Zhou, Yumei, Cao, Xiaofei, Wang, Yanchao, Yu, Qian, Wang, Kerou, Yi, Ting, Hong, Zhiliang
• Format: Article
• Language: English
• Subjects: Charge coupled devices; differential cascade-of-integrator (DCoI); Filtering algorithms; Frequency-domain analysis; Modulation; Prototypes; readout integrated circuit (ROIC); Time-domain analysis; truncated cascaded-integrator-comb (TCIC); X-ray charge-coupled device (CCD); X-ray imaging; ΔΣ-correlated double sampling (CDS)
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2019.2892623

Correlated double sampling (CDS) circuits are essential to processing the X-ray charge-coupled devices (CCDs) that have been used in the modern X-ray astronomical field. For spectroscopy observations, the energy resolution is of decisive importance. In this paper, a comprehensive study of the CDS algorithm based on the incremental \Delta \Sigma technique, named \Delta \Sigma -CDS algorithm hereafter, is studied. Theoretical and practical aspects for modulations and demodulations for applications with different pixel rates (PRs) are discussed. The concepts of differential cascade-of-integrator filter and truncated cascaded-integrator-comb filter are extensively investigated from both the time-domain and frequency-domain analyses. The operating principles, prototype design, and experimental results are addressed. As a prototype for 100-kHz PR, a readout integrated circuit (ROIC) is designed. When tested with the target X-ray CCD-CCD236 using a 1~\mu Ci 55 Fe radioisotope, the ROIC achieves an energy resolution characterized by the full-width-at-half-maximum as 132.4 ± 2.4 eV at 5.9 keV, which is very close to the 121-eV limit of CCD236.