Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By amplitude
Reexamination Certificate
1999-09-15
2001-01-23
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By amplitude
C327S074000
Reexamination Certificate
active
06177815
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to signal detectors, and more particularly, to a high bandwidth mean absolute value signal detector with hysteresis and tunability.
DESCRIPTION OF THE RELATED ART
A signal detector is used in the receiver section of an optical connection to indicate a loss of signal to the host system. As technology advances, demands are high for a signal detector that can operate with low power supply voltage, high bandwidth, better noise rejection, wide tuning range, temperature independence, and hysteresis.
Most parts now in the industry are striving for low power supply voltage which drives the demand for a 3.3v signal detector. High bandwidth is required to satisfy the 1.25 Gbit Ethernet requirement. Better noise rejection is needed to provide less chance for the output of the signal detector to chattered, thus providing a more reliable signal detector output. Due to the wide variations of the SNR of the preamp, a wide tuning range is needed to keep the threshold above the noise floor. Temperature independence is needed to insure a constant threshold regardless of present temperature. Hysterisis is needed to reduce the chance of chatter.
A need exists for an improved signal detector. It is desirable to provide an improved high bandwidth mean absolute value signal detector with hysteresis and tunability.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide an improved signal detector. Other objects of the invention are to provide such signal detector with hysteresis and tunability; to provide such signal detector substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, an improved signal detector is provided. The signal detector includes a linear amplifier receiving the input signal and providing an amplified signal. A full-wave rectifier is coupled to the linear amplifier and provides a rectified signal. A low-pass filter is coupled to the full-wave rectifier receiving the rectified signal and providing a comparing signal. A high threshold reference and a low threshold reference respectively is applied to a first comparator and a second comparator, each receiving the comparing signal. The first comparator and the second comparator respectively provide a first compared signal and a second compared signal.
In accordance with features of the invention, a reference path providing the high threshold reference and the low threshold reference includes a linear amplifier, a full-wave rectifier and a low-pass filter providing the high threshold reference. The linear amplifier, full-wave rectifier and low-pass filter in the reference path is matched with the signal path. A linear charge pump is connected at its input to the linear amplifier and connected at its output to a low-pass filter to provide the low threshold reference.
REFERENCES:
patent: 3797305 (1974-03-01), Ginns Haskell
patent: 5498985 (1996-03-01), Parle et al.
patent: 5856750 (1999-01-01), Koseki
Baumgartner Steven John
Ngo Anh Duy
Siljenberg David Warren
Cunningham Terry D.
International Business Machines - Corporation
Nguyen Long
Pennington Joan
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