Pulse or digital communications – Systems using alternating or pulsating current – Antinoise or distortion
Reexamination Certificate
1999-11-02
2001-02-06
Chin, Stephen (Department: 2734)
Pulse or digital communications
Systems using alternating or pulsating current
Antinoise or distortion
C375S296000, C455S114100
Reexamination Certificate
active
06185261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to distortion in transmitters. More particularly, the present invention relates to a method and a system for determining the nonlinear distortion of a transmitter included in a gigabit Ethernet transceiver.
2. Description of Related Art
Receivers that use digital signal processing modules, such as linear equalizers and cancellers, are particularly sensitive to nonlinear distortion that are present in the received signals. Severe nonlinear distortion would cause erroneous decoding of the received signals. The major contributor to the nonlinear distortion in a transmission channel is the corresponding transmitter.
In a Gigabit Ethernet communication system that conforms to the 1000BASE-T standard, two gigabit transceivers are connected via four twisted pairs of Category 5 copper cables and are in full-duplex bi-directional communication with each other. There are four constituent transceivers in each gigabit transceiver. The full-duplex bi-directional communication implies that each constituent transceiver is transmitting simultaneously on the same twisted pair of cable with a corresponding remote constituent transceiver. This simultaneous transmission would stress the analog components of the transmitter of a constituent transceiver. This stress would cause the transmitter to produce more nonlinear distortion. Thus, nonlinear distortion is an important problem in Gigabit Ethernet communication system.
In addition, the bi-directional nature of the Gigabit Ethernet communication system requires the use of echo cancellers in the gigabit transceivers. Since the echo cancellers are very sensitive to nonlinear distortion, nonlinear distortion must be kept, by design of the transmitters, at an acceptable level. The 1000BASE-T standard specifies that the peak nonlinear distortion of each constituent transceiver, when under test with no intervening cable, must be less than 10 millivolts.
Therefore, there is a need for techniques for determining nonlinear distortion of a transmitter, particularly, for a transmitter included in a constituent transceiver of a gigabit Ethernet transceiver.
SUMMARY OF THE INVENTION
The present invention provides a method for determining nonlinear distortion of a transmitter. A test symbol sequence is transmitted from the transmitter under test as an analog output signal. The analog output signal is sampled to produce a first sequence which represents the test symbol sequence as distorted by a linear distortion sequence and a nonlinear distortion sequence. The test symbol sequence is filtered via an adaptive filter to produce a second sequence such that the second sequence is approximately equal to the test symbol sequence as distorted by the linear distortion sequence. The second sequence is subtracted from the first sequence to produce an output sequence substantially equal to the nonlinear distortion sequence.
One embodiment of the invention provides a method for determining nonlinear distortion of a transmitter in the presence of a disturbing sinusoidal signal which simulates a signal transmitted from a remote transceiver in full duplex communication with the transceiver having the transmitter under test. A test symbol sequence is transmitted from the transmitter under test as an analog output signal. The analog output signal is sampled to produce a set of sampled data. A sinusoidal sequence is fitted to the sampled data. The sinusoidal sequence is subtracted from the sampled data to produce a first sequence, the first sequence representing the test symbol sequence as distorted by a linear distortion sequence and a nonlinear distortion sequence. The test symbol sequence is filtered via an adaptive filter to produce a second sequence such that the second sequence is approximately equal to the test symbol sequence as distorted by the linear distortion sequence. The filter coefficients are adapted based on the difference between the first and second sequences. The second sequence is subtracted from the first sequence to produce an output sequence substantially equal to the nonlinear distortion sequence.
REFERENCES:
patent: 4615038 (1986-09-01), Lim, et al.
patent: 4792915 (1988-12-01), Adams et al.
patent: 5247458 (1993-09-01), Cabot
patent: 5339054 (1994-08-01), Taguchi
patent: 6034993 (2000-03-01), Norrell et al.
patent: 6081158 (2000-06-01), Twitchell et al.
patent: 0 399 968 A1 (1990-11-01), None
K. Fischer, J. Cioffi, H. Thapar, “Modeling Thin-Film Storage Channels”, IEE Transactions on Magnetics, vol. 25, No. 5, Sep. 1989 (1989-09), pp. 4081-4083, XPOO2133753 Section 2.1 Nonlinear Distortion.
Bellanger M.B., “Gradient Adaptive Filters”, 1987, Marcel Dekker, US, New York, XP02133754, 4.1 The Gradient—LMS Algorithm. pp. 97-98.
Agazzi Oscar E.
Creigh John L.
Broadcom Corporation
Chin Stephen
Christie Parker & Hale LLP
Ha Dac V.
LandOfFree
Determination of transmitter distortion does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Determination of transmitter distortion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Determination of transmitter distortion will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2563941