TAPPED CCD DELAY LINE WITH NON-DESTRUCTIVE CHARGE SENSING USING FLOATING DIFFUSIONS

摘要

A CCD delay line may be tapped using a floating-diffusion electrometer at the tap. Charge sensing is made non-destructive by not resetting the floating diffusion to a reset drain after charge sensing. The resulting charge integration on the floating diffusion causes a smearing of the samples described by successive charge packets. The smearing is in the baseband frequencies of the sample frequency spectrum, but does not appreciably affect the subspectra surrounding harmonics of the delay line clock rate. Consequently, smear-free response to the floating-gate electrometer output signals can be obtained by synchronously detecting them at a harmonic of the delay line clock rate. Using floating-diffusion electrometers, rather than floating-gate electrometers, to sense charge packet amplitudes at taps along a CCD delay line lowers the noise in the output response of output-weighted, charge-coupled-devive transversal fiters. Additionally, it simplifies the filter by eliminating the need for reset transistors and the bussing associated with them.