Passive redundant digital data receiver with schmitt-trigger
AssigneeHewlett-Packard Development Company, L.P.
InventorsKarl Joseph Bois, David W. Quint, Randy K. Rannow
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Abstract
A passive coupling structure constructed using printed circuit board traces is used to separate the low and high frequency components of an incoming digital signal. The low and high frequency components of the signal are sent to separate receivers on an integrated circuit. The low frequency receiver may be a conventional level based receiver. The high frequency receiver is a Schmitt-trigger with hysteresis around a DC level or two comparators with separate reference voltages. The outputs of these receivers are combined to produce a receiver output that has increased reliability and noise immunity.
Claims12
A digital signal receiver, comprising:
- a passive coupling structure having a signal input, a low frequency component output, and a high frequency component output;
- a level based receiver having a first input connected to said low frequency component output and a first output;
- a Schmitt-trigger having a second input connected said high frequency component output and a second output and wherein said high frequency component output is biased to a DC voltage level that is between a first and a second trip point of said Schmitt-trigger;
- and,
- a logic block receiving said first and second output that changes a receiver output when said first and second output both change to the same logic level.
A redundant digital receiver, comprising:
- a level based receiver coupled to the low frequency output of a passive coupling structure comprised of two parallel circuit lines;
- a Schmitt-trigger receiver having a high and a low trip points that is coupled to the high frequency output of said passive coupling structure;
- at least one resistor that sets a DC bias on said high frequency output wherein said DC bias is between said high and low trip points of said Schmitt-trigger receiver;
- and,
- a logic block that receives a level based output from said level based receiver and
- an edge based output from said Schmitt-trigger and combines those outputs to change the state of a receiver output only when both said level based and said edge based outputs indicate that a state change on an input signal to said passive coupling structure has occurred.
A method of receiving digital signals, comprising:
- splitting an input signal into a high frequency component and a low frequency component;
- detecting a state of said low frequency component using a level based receiver to produce a level based output;
- detecting an occurrence of an edge on said high frequency component using a Schmitt-trigger to produce an edge based output;
- combining said level based and said edge based output to set the state of a receiver output when both said level based and said edge based output indicate that a state change on said input signal has occurred.
Dependencies are inferred from the claim text.