Differential line driver employing predistortion
AssigneeLevel One Communications, Inc.
InventorsStefan M. Wurster, Daniel L. Ray
Life of this patent
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Abstract
A two terminal line driver employing predistortion is disclosed, for driving data over a lossy transmission line such as a twisted pair cable at speeds on upwards of 10 Mbit/s. The driver is designed for voltage output operation wherein fullstep and halfstep information is actively encoded into a voltage level provided for at the output terminals. The driver provides a fullstep voltage spanning the supply rails and a halfstep voltage having a selectable controlled amplitude of a predetermined value. Fat bits resulting from the biphase encoding format are predistorted by dropping the amplitude to a predetermined value, equalizing the relative power content.
Claims10
A differential line driver, powered between voltage supply rails, for driving a transmission line with predistorted data, comprising:
- a) a plurality of input terminals for receiving input signals containing data symbols, the input terminals being coupled to logic means for selecting a fullstep output voltage level in response to identical adjacent data symbols and for selecting a halfstep output voltage level in response to different adjacent data symbols, the fullstep output voltage level substantially spanning the supply rails and the halfstep output voltage level having a selectable value between the supply rails;
- b) differential driving means, having an input coupled to the logic means and responsive thereto and having a first and a second output terminal coupled to the transmission line, for impressing the halfstep and fullstep output voltage levels on the transmission line;
- and
- c) means, coupled to the differential driving means, for setting the halfstep output voltage level.
A line driver in a local area network comprising:
- a) input means for receiving data from an attachment unit interface (AUI) transmit receiver;
- b) means, coupled to the input means, for impressing a differential output voltage across a two terminal transformer, the output voltage substantially spanning from an upper logic rail to a lower logic rail;
- c) means for establishing a predetermined halfstep value;
- and
- d) means, coupled to the inputs means and responsive thereto, for detecting adjacent data bits having opposite values and for reducing the output voltage to the predetermined halfstep value.
In a line driver having a single pair of output terminals, a method for differentially driving predistorted data onto a transmission line comprising the steps of:
- a) receiving data symbols;
- b) selecting a fullstep output voltage level in response to receiving identical adjacent data symbols and selecting a halfstep output voltage level in response to receiving different adjacent data symbols;
- and
- c) differentially impressing the halfstep and the fullstep output voltage levels across the single pair of output terminals on to the transmission line.
A method for driving a local area network comprising the steps of:
- a) receiving data from an attachment unit interface (AUI) transmit receiver;
- b) impressing a differential output voltage across a two terminal transformer, the output voltage substantially spanning from an upper logic rail to a lower logic rail;
- c) establishing a predetermined halfstep value;
- and
- d) detecting adjacent data bits having opposite values and for reducing the output voltage to the predetermined halfstep value.
Dependencies are inferred from the claim text.