High Speed Electronics Design for TDI Detector

摘要

In the high resolution imaging, MTF performance will be low at high spatial frequencies. So for target detection and recognition, the radiometric performance has to be high enough. The radiometric performance is mainly dominated by signal energy collected by the sensor and various noise sources. Methods like step and stare and Time Delay and Integration (TDI) detectors are used improving radiometry. Previous high resolution Indian missions like Cartosat-2 have used step and stare method for better SNR. The sensor used is linear CCD detector. TDI detectors are under consideration for future missions. The camera electronics design for these detectors is different from that for a linear detector in terms of requirement of large number of clocks and bias lines, high speed of operation and synchronization with respect to satellite ground track velocity. This calls for design of new customized electronics to cater to these requirements.rnThis paper describes the design, implementation and test results of camera electronics designed based on tri-array TDI detector. The detector device has three arrays, each having 5200 pixels and 32 stages of integration. It can operate upto line rate of 8kHz and video rate of 11 MHz per port. Camera electronics consists of detector bias generator, clock drivers, timing and synchronization logic and video processor. The design uses state-of-the-art devices with low power and compact size. The main highlights of the design are low noise bias generation, high speed clock drivers with capacitive drive, 4-port video processing with 10-bit digitization and total data rate of 440Mbps. The design is implemented on a development card and the functionality is checked after interfacing with the detector. The electronics design meets the detector functional requirements. The radiometric performance is photon-noise limited.