Gated multi-cycle integration (GMCI) for focal plane array (FPA) applications.

摘要

In this thesis, the model and the theory of gated multi-cycle integration (GMCI) were first developed specifically for focal plane array dealing with repetitive or modulated image. The operational modes of GMCI include gated integration (GI), phase sensitive integration (PSI), multi-point summation, multi-point subtraction, multi-sample averaging and some of their combinations. Thus, the analytic theory of GMCI somehow unifies the theories of gated integration, phase sensitive detection, multiple summation and average. PSI works with background and/or dark current subtraction. As a result, the storage well of a pixel is mainly used for signal integration even if there exists a strong background. Thus, the signal-to noise ratio, the dynamic range, the sensitivity of the detection and the noise equivalent temperature are greatly improved. For a storage well of 106 electrons, the sensitivity of the FPA operated at PSI mode could be improved by 3 orders. In addition, the transmission windows of PSI peak at odd harmonics of the modulation frequency, and therefore, the detector's 1/f and other low frequency noise can be attenuated.; A switched capacitor integrator was designed and fabricated with HP-0.5μm CMOS processing to demonstrate the feasibility of GMCI. The primary experimental results showed that the minimum detectable signal could be 5 orders less than the background, which is impossible for the conventional readout methods employed by current staring FPAs. The fixed patterns associated with switching charge injection, feedthrough, offset voltage of operational amplifier were addressed and suppressed by taking the differentia of two sampled voltages that correspond to signal integrations with 180° phase difference while keeping the same fixed pattern. GMCI, operated at PSI with multiple averages, is expected to become a powerful method in dealing with repetitive weak image swamped by strong background.