Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Reexamination Certificate
2000-03-28
2002-01-08
Lam, Tuan T. (Department: 2816)
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
C327S034000, C327S037000
Reexamination Certificate
active
06337649
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates generally to analog to digital signal conversion and more particularly to a method and apparatus operable on the output of a comparator to provide increased accuracy in the face of noise.
2. Description of Related Art
As illustrated in
FIG. 1
, conversion of an analog signal to a digital pulse train normally employs a comparator
11
and various analog signal processing such as analog pre-filtering
13
combined with hysterisis
15
. Noise may be introduced at the input to the comparator
11
, as symbolically represented at adder
17
, or after analog pre-filtering, as symbolically represented at adder
19
. Errors in the output pulse train result when such noise-induced error exceeds any hysterisis processing and filtering contained in the comparator
11
. In cases where an extremely high pulse rate is required, such noise compromises the bandwidth and phase of the analog to digital conversion performed by the comparator
11
.
SUMMARY OF THE INVENTION
According to the invention, a pulse filter is provided which prevents a pulse having a width less than a specified time duration from propagating into the pulse train at the output of the comparator. The invention operates on the output of any comparator circuit and provides a minimum pulse width rejection of any pulse which may result from noise that sets or resets the comparator. This pulse width rejection can be programmable or designed directly into the hardware/software/firmware such that a pulse less than a specified time duration will not be allowed to propagate into the pulse train.
REFERENCES:
patent: 4775840 (1988-10-01), Ohmori et al.
patent: 5680265 (1997-10-01), Noguchi
patent: 5737140 (1998-04-01), Carr
patent: 5907299 (1999-05-01), Green et al.
patent: 6169765 (2001-01-01), Holcombe
patent: 6218870 (2001-04-01), Wilson
Becker Jeff
Curby Robert
McCammon George H.
Richmond Tim
Lam Tuan T.
Litton Systems Inc.
Price & Gess
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