Detection of EFM stream component widths

Details Detection of EFM stream component widths Detection of EFM stream component widths

1999-10-15

2003-12-02

Chin, Stephen (Department: 2734)

Pulse or digital communications

Receivers

Particular pulse demodulator or detector

C375S340000, C375S341000, C375S238000, C375S239000

Reexamination Certificate

active

06658068

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to detection of “mark” and “space” widths in an incoming digital signal stream.
BACKGROUND OF THE INVENTION
When a digital signal stream is being received, the temporal width of each mark values (high states or “1”) and the temporal width of each space value (low state or “0”) can vary within an acceptable range, or may sometimes have a width outside the acceptable range, such as w
1
≦w≦w
2
. Where a mark width or a space width lies within the corresponding acceptable range, a digital signal processing device can recognize and properly process that mark or space. However, a mark width (or space width) that is too large or too small, and thus lies outside an acceptable range, must be promptly detected.
What is needed is a system and method for examining a stream of digital signal marks and spaces sequentially and for quickly recognizing a mark or a space (referred to as a digital signal stream “component”) that has a width w that is smaller than a first value w
1
, or that is greater than a second value w
2
, and for promptly associating an indicium with this component that indicates that the width of this component lies outside the corresponding acceptable range.
SUMMARY OF THE INVENTION
These needs are met by the invention, which provides a system and method for off-line examination of mark widths and space widths and for association of a selected indicium with every stream component having a width w that lies outside a permissible range, such as w
1
≦w≦w
2
. This examination process requires only a small, constant time delay, related to the relative sizes of the width values w
1
and w
2
, so that processing of the resulting (compensated) digital signal occurs uninterrupted, apart from this small, constant time delay. The digital signal stream is divided into groups of consecutive marks and consecutive spaces, and each group of consecutive marks or consecutive spaces is examined in turn. This allows the width examination process within each group to proceed without requiring separate and time-consuming identification of each incoming signal component as a mark or a space.


REFERENCES:
patent: 3562494 (1971-02-01), Schmidt
patent: 4287596 (1981-09-01), Chari
patent: 4687321 (1987-08-01), Itoh
patent: 5933458 (1999-08-01), Leurent et al.

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