Pulse or digital communications – Transceivers
Reexamination Certificate
1998-04-01
2002-04-09
Vo, Don N. (Department: 2631)
Pulse or digital communications
Transceivers
C375S285000, C375S297000, C375S345000
Reexamination Certificate
active
06370187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates data communications systems and, more particularly, to power management for data communications systems.
2. Description of the Related Art
Today, it is very common that computer systems use modems and telephone lines to connect to other computer systems. Most of these modems provide fixed power level transmissions onto the telephone lines. Power supply voltage rails supplied to the modem are also normally set to accommodate the highest power. As a result, the power dissipation by the modem is normally fixed at a high amount.
In the case of high performance modems, such as digital subscriber line (DSL) modems, the power dissipation by the modems are also often fixed. Specifically, power supply voltage rails are set to accommodate the highest power, bias currents for line driver devices are constant, and transformer turn ratios are fixed. In such modems, the power dissipation is thus often fixed.
Recently, there have been some attempts to make minor improvements to the transmit power consumption of high performance modems. Such attempts at improving power dissipation were directed at controlling drive currents to driver circuitry. For example, often these approaches control the voltage level applied to the driver circuitry. With the driver circuitry having a fixed gain, the drive current levels supplied to a load on the telephone lines are thus reduced when the voltage level is reduced. Consequently, this recent approach does lead to some reduction in transmit power levels and system power dissipation.
FIG. 1
discussed below is an example of the recent attempts to improve power dissipation by controlling drive currents levels of the driver circuitry.
FIG. 1
is a block diagram of a conventional high performance modem
100
. The conventional high performance modem
100
, for example, a DSL type modem. The conventional high performance modem
100
includes a modem signal processor
102
, an analog front-end
104
, a power amplification unit
106
and a line interface
108
. The conventional high performance modem
100
performs both transmission and reception of data. Digital data (DATA) to be transmitted is received at the modem signal processor
102
. Also, digital data (DATA) that has been received is obtained from the modem signal processor
102
.
During transmission of data, the modem signal processor
102
performs various signal processing operations to modulate the data to be transmitted onto one or more carriers as well as to perform various filtering operations. The resulting digital data is then forwarded to the analog front-end
104
over a data bus (DATA BUS)
110
. The analog front-end
104
converts the incoming digital data into analog signals, and outputs the analog signals as complimentary transmit signals. The complimentary transmit signals include transmit positive signals (TXP) and transmit negative signals (TXN). The complimentary transmit analog signals (TXP and TXN) are then supplied to the power amplification unit
106
. The power amplification unit
106
includes power amplifiers that amplify the complimentary transmit analog signals (TXP and TXN). The amplified signals are then supplied to the line interface
108
that couples the amplified complimentary analog transmit signals to a subscriber line
112
(e.g., telephone line).
During reception of data, the conventional high performance modem
100
receives incoming analog signals from the subscriber line
112
. The incoming analog signals are received by the line interface
108
which supplies complimentary received analog signals to the power amplification unit
106
. The power amplification unit
106
produces received analog signals (RX) by amplifying the difference between the complimentary received analog signals. The received analog signals (RX) are then supplied to the analog front-end
104
where they are converted into digital receive signals and forwarded to the modem signal processor
102
over the data bus DATA BUS)
110
. Thereafter, the modem signal processor
102
processes the received digital signals by demodulating the signal to recover the data originally transmitted.
In the conventional high performance modem
100
, namely, a DSL type modem, the modem signal processor
102
includes circuitry or processing capabilities to determine whether transmit power should be increased or decreased given an amount of line impairments (e.g., noise, distortion, attenuation, etc.) that has been detected. The modem signal processor
102
is able to inform the analog front-end
104
via a control bus
114
as to whether the power level (i.e., drive current) used on the transmit analog signals (TXP and TXN) should be increased or decreased. In effect, the control bus
114
, in this case, operates to control the drive current used by the analog front-end
104
in producing the transmit analog signals (TXP and TXN), which to a limited extent causes the transmit signals placed on the subscriber line
112
to carry more power or less power.
Additional details on DSL type modems can be found, for example, in U.S. Pat. Nos. 5,479,447; 5,596,604; 5,623,513; and 5,627,863, which are hereby incorporated by reference. Also particular details on an Asymmetric Digital Subscriber Line (ADSL) type modem can be found in American National Standards Institute (ANSI) published standard ANSI T1.413-1995, which are hereby incorporated by reference.
One problem of the convention approaches is that they do not yield sufficient control over power dissipation of modems. While the conventional high performance modem
100
illustrated in
FIG. 1
provides some control over power dissipation, the degree with which these conventional approaches are able to control the power dissipation is minimal and therefore unsatisfactory. By better controlling power dissipation, many advantages can be achieved, including less energy consumption and less interference to other nearby modems.
Thus, there is a need for improved control over power dissipation by modems, in particular, high performance modems.
SUMMARY OF THE INVENTION
Broadly speaking, the invention relates to a high performance data communications system (e.g., modem, transceiver, etc.) that has improved control over power dissipation. In particular, the invention allows a data communications system to adaptively control its power dissipation so as to provide substantially improved control over the power dissipation than conventionally possible.
The invention can be implemented in numerous ways, including as an apparatus, system or method. Several embodiments of the invention are discussed below.
As data communications system for transmitting and receiving data over a link, an embodiment of the invention includes: a transmitter/receiver unit that receives digital data to be transmitted and produces modulated analog signals on one or more carriers for transmission over the link, and that receives incoming analog signals over the link and produces demodulated analog signals, and the transmitter/receiver unit includes a power controller that determines a power level setting and produces a bias current in accordance with the power level setting; and an amplifier stage operatively coupled between the link and the transmitter/receiver unit, the amplifier stage amplifies the incoming analog signals received over the link, and amplifies the modulated analog signals for transmission over the link based on at least the bias current produced in accordance with the power level setting. As an example, the data communications system provides power management by controlling the bias current supplied to the amplifier stage, such that as the power level setting is lowered, power consumption of the data communications system is reduced because the bias current is lowered.
Additionally, the power controller can optionally also produce a voltage control signal in accordance with the power level setting, and then provide power management by controlling not only the bias current supplied to the amplifier stage but a
Brady III W. James
Moore J. Dennis
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
Vo Don N.
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