Adaptive configurable class-A/class-B transmit DAC for transceiver emission and power consumption control

• US 6,594,304 B2
• Filed: 04/18/2002
• Issued: 07/15/2003
• Est. Priority Date: 10/30/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Chan, Kevin T.
• Primary Examiner(s): Ghayour, Mohammad H.
• Assistant Examiner(s): AL BESHRAWI, TONY
• Application Number:
  US10/124,967
• Publication Number:
  US 20020154684A1
• Time in Patent Office: 453 Days
• Field of Search: 375/220, 375/222, 375/257, 375/219
• US Class Current: 375/220
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04L 12/10 Current supply arrangements
• CPC Class Codes: H04L 25/0276 Arrangements for coupling common mode signals
• CPC Class Codes: H04L 25/0282 Provision for current-mode coupling
• CPC Class Codes: H04L 25/0286 Provision of wave shaping within the driver wave shaping per se H04L25/03834
• CPC Class Codes: H04L 25/03834 using pulse shaping
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
• CPC Class Codes: H04L 25/14 Channel dividing arrangements , i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver

Abstract

A power efficient and reduced electromagnetic interference (EMI) emissions transmitter for unshielded twisted pair (UTP) data communication applications. Transmit data is processed by a digital filter. The digital filter output data is converted to a current-mode analog waveform by a digital-to-analog converter (DAC). The digital filter is integrated with the DAC binary decoder in a memory device such as a ROM with time multiplexed output. DAC line driver cells are adaptively configurable to operate in either a class-A or a class-B mode depending on the desired operational modality. A discrete-time analog filter is integrated with the DAC line driver to provide additional EMI emissions suppression. An adaptive electronic transmission signal cancellation circuit separates transmit data from receive data in a bidirectional communication system operating in full duplex mode. For a multi-transmitter system, timing circuitry staggers the time base of each transmitter to reduce the aggregate EMI emissions of the multi-transmitter system.

Claims

1. A method for reducing electromagnetic emissions in a data transmission system including a plurality of receivers for receiving respective receive signals from a plurality of transmission channels and a plurality of transmitters, each electrically coupled to a respective receiver, for driving the plurality of transmission channels with a respective transmit signal, said method comprising the steps of:

integrating, in a memory device, a digital filter for pulse shaping digital data and a DAC decoder for generating synchronized DAC control signals;

controlling an output DAC by the DAC decoder;

creating a current-mode differential output signal responsive to the digital input data, wherein the output circuit is configurable by a selection circuit to operate in a first mode sensitive to a first metric and a second mode sensitive to a second metric;

generating control signals to produce a portion of the current-mode differential output signal for a duration of a first time segment and to produce the full current-mode differential output signal for a duration of a second time segment; and

generating a plurality of timing references staggered in time by a time duration which is a function of a transmission data rate and the number of the transmitters in the system to drive the respective outputs of each of the plurality of transmitters.

2. The method of claim 1, wherein the data transmission system includes M transmitters, a data sampling is Fi, and the plurality of timing references are staggered in time by 1/(Fi*M).

3. The method of claim 1, further comprising the step of developing a cancellation signal and asserting the cancellation signal on an input path of each receiver to prevent a transmit signal from being asserted to the respective input path of each receiver.