Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Reexamination Certificate
1999-08-27
2001-08-28
Williams, Howard L. (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
C375S219000
Reexamination Certificate
active
06281829
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to analog front-end architecture. More specifically, the invention is related to an analog front-end integrated circuit, which solves problems associated with high-speed data communications by utilizing a combination of analog preprocessing and digital post-processing.
BACKGROUND OF THE INVENTION
With the advancement of technology, and the need for instantaneous information, the ability to transfer digital information from one location to another, such as from a central office (CO) to a customer premises (CP) has become more and more important. Allowing for increasing data transmission rates has, in fact, become a requirement, as opposed to an option.
In a digital subscriber line system (DSL), data is transmitted from a CO to a CP via a transmission line, such as a two-wire pair, and transmitted from the CP to the CO as well, either simultaneously or at different sessions. The same transmission line might be utilized for data transfer by both sides or the transmission to and from the CO might occur on two separate lines. The CO is basically comprised of a digital signal processor (DSP) which receives information from a data source and sends information to an analog front-end (AFE). The AFE interfaces between an analog line, such as the two-wire pair, and the DSP and functions to convert digital data, from the DSP, into a continuous time analog signal.
The analog signal is delivered, via a line driver, which is separate from the AFE, in accordance with the amount of power required to drive the amplified analog signal through the two-wire pair to the CP. A hybrid, which is located at both the CP and CO, is used to de-couple the received signal from the transmitted signal, by subtracting the transmitted signal from the sum of the transmitted and received signals. The AFE then converts the received analog signal into a digital signal, which is then transmitted to a DSP. Finally, the digital information is transmitted to the data source specified to receive such information.
As an important part of the abovementioned system responsible for proper transmission and reception of data in a broadband network, the AFE performs multiple functions in addition to converting a digital signal into a continuous time analog signal. However, the functionality of the AFE is particular to the specific DSL application considered, wherein factors such as signal bandwidth, data reach, signal quality, power budget, line power, and different applicable standards determine the optimum AFE. Unfortunately, due to the vast number of DSL applications available, including, but not limited to, HDSL, ADSL, MSDSL,
2
B
1
Q HDSL and RADSL, it has been necessary to purchase separate individual AFEs to perform the functions necessary for each individual DSL application enumerated. Therefore, as an example, if a broadband network were to function on HDSL and ADSL applications, two separate AFEs would have to be purchased and implemented, specifically, one for HDSL applications, and one for ADSL.
Considering the many flavors of each DSL application, this problem becomes even more apparent. Limiting to only ADSL, currently there are eight main flavors on the market including DMT and CAP, light and heavy, FDM and echo canceled. For each one of these, the optimum solution is different on the CP and CO, so ideally 16 different AFEs are needed simply to cover the ADSL market. This necessity for separate AFEs has led to excessive cost in maintaining an adaptable CO or CP.
SUMMARY OF THE INVENTION
In light of the foregoing, the invention is an AFE, having an internal hybrid and line driver, that accommodates all DSL applications in a power efficient manner, by switching specific blocks on and off within the AFE, and configuring these blocks optimally for a given DSL application.
In general, one embodiment of the invention provides for an AFE, having a line driver and hybrid provided therein, which provides numerous functions, in order to provide a close to optimum solution for all DSL applications. The functions provided for by the AFE include; programmable hybrid attenuation; onboard amplifiers for driving external transmit and receive filters; a line driver with programmable drive and gain; programmable RC-filters capable of calibration via an internal loop-back under digital control; programmable switched-capacitor (SC) filter for tracking the over sampling rate used by a digital signal processor; internal testing functions; a high frequency boost circuit; a dual input peak detector; selectable data rates; and a programmable data interface. The AFE allows for the exclusive use of specific blocks within the AFE which are used in the performance of functions necessary to be applied by the AFE for the particular DSL application addressed, thereby not using unnecessary blocks and saving power.
The invention has numerous advantages, a few of which are delineated hereafter as examples. Note that the embodiments of the invention, which are described herein, possess one or more, but not necessarily all, of the advantages set out hereafter.
One advantage of the invention is that it provides a low cost solution to providing an AFE, which will function on all DSL applications.
Another advantage is that, while it provides a single AFE for all DSL applications, it does not use large amounts of power since specific unused blocks of the AFE may be turned off when not in use.
Another advantage is that it compensates for the effect of process variations by calibration under digital control.
REFERENCES:
patent: 4972436 (1990-11-01), Halim et al.
patent: 5457456 (1995-10-01), Norsworthy
patent: 5512898 (1996-04-01), Norsworthy et al.
patent: 6067316 (2000-05-01), Amrany et al.
Amrany Daniel
George Sam Olu
Keller Peter D.
Larsen Frode
Lin Jung-lung
Globespan, Inc.
Thomas Kayden Horstemeyer & Risley
Williams Howard L.
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