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US 4,498,141 AGranted
High speed correlation circuit and method
AssigneeAmpex Corporation
InventorJ. Carl Cooper
Life of this patent
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Abstract
High speed serial data bits of a data stream are received, stored, shifted and compared in parallel to bit contents of a known correlation word. For each bit match a known signal change is provided on a common terminal. High speed current or voltage changes on the common terminal are proportional to the number of matching bits and are monitored to detect presence of the correlation word in the received data stream. The circuit has minimum number of components and built-in temperature compensation.
Claims31
A high speed correlation circuit for detecting a known digital correlation word in a serial data stream, comprising:
- a first means coupled to receive and store consecutive bits of said serial data stream and to shift said stored bits by one bit position in succession when a new bit is received thereby, said first means being coupled to store information related to respective bit contents of said known correlation word and to detect a match at corresponding bit positions between said stored data bits and said known correlation word bits, respectively, said first means having a plurality of parallel outputs each coupled to provide an output signal of a predetermined magnitude in response to one said match, respectively;
- a plurality of current setting second means each having an input coupled to one said output of said first means and each having an output coupled to provide a known amount of current, said respective outputs of said second means being coupled to a common terminal to provide an output signal having a magnitude proportionally changing with the number of matches obtained by said first means;
- and
- a third means coupled to maintain said common terminal at a predetermined constant voltage level.
1 more element
A high speed correlation circuit for detecting presence of a known digital correlation word in a serial data stream, comprising:
- a serial-to-parallel shift register means having an input coupled to receive and store consecutive bits of said serial data stream and to shift said stored bits by one bit position in succession when a new bit is received thereby, said shift register means having a plurality of parallel outputs each containing one bit stored in said shift register means;
- a presettable memory means coupled to store respective bits of said known correlation word, said memory means having a plurality of parallel outputs each containing one bit stored in said memory means;
- a plurality of logic gates each having a first input coupled to one parallel output of said shift register means and a second input coupled to a corresponding parallel output of said memory means, each logic gate having an output coupled to provide an output signal of a first known logic signal level when matching bits are obtained at its respective inputs and output signal of a second known logic signal level when its input bits do not match, respectively;
- a plurality of resistors each having a first terminal coupled to an output of one said logic gate, the other terminals of said resistors being coupled to a common terminal, each said resistor having a value selected to apply an appreciable amount of current to said common terminal when one of said first or said second known logic signal level is provided by said logic gate;
- means coupled to maintain said common terminal at a predetermined constant voltage level to obtain a substantially linearly changing current thereon with the number of bit matches obtained by said logic gates;
- a current-to-voltage converter means coupled to said common terminal for substantially linearly converting said current changes thereon to corresponding voltage changes;
- and
- means coupled to an output of said current-to-voltage converter means for detecting a known voltage magnitude obtained on said common terminal in response to a predetermined number of matching bits obtained by said plurality of logic gates.
5 more elements
A high speed correlation circuit for detecting presence of a known digital correlation word in a serial data stream comprising:
- a first means coupled to receive and store consecutive bits of said serial data stream and to shift said stored bits by one bit position in succession when a new bit is received thereby, said first means being coupled to store information related to respective bit contents of said known correlation word and to detect a match at corresponding bit positions between said stored data bits and said known correlation word bits, respectively, said first means having a plurality of parallel outputs each coupled to provide an output signal of a predetermined level in response to one said match, respectively;
- a plurality of resistors, each having a first terminal coupled to one said parallel output of said first means, respectively, respective second terminals of said resistors being coupled to a common terminal;
- a transistor means having an emitter coupled to a first voltage supply via said common terminal and a first series resistor, a collector coupled to a second voltage supply via a second series resistor and a base coupled to a reference voltage source providing a voltage corresponding to a predetermined constant voltage level to be maintained on said common terminal;
- and
- negative feedback means coupled between the emitter and base of said transistor means to maintain said predetermined constant voltage level on said common terminal.
2 more elements
A high speed correlation method for detecting a known digital correlation word in a serial data stream, comprising the steps of:
- receiving and storing consecutive bits of the serial data stream and shifting said stored bits by one bit position in succession when a new bit is received;
- storing information related to respective bit contents of said known correlation word;
- matching simultaneously respective bits pertaining to corresponding bit positions of said stored serial data and said correlation word, respectively and providing an output signal of a predetermined level in response to each obtained match;
- providing for each said output signal level a predetermined corresponding current value;
- summing said current values at a current summing point to obtain a current whose magnitude changes proportionally with the number of obtained bit matches;
- and
- maintaining said current summing point at a predetermined constant voltage level to obtain a proportionally changing current with the number of obtained bit matches.
4 more elements
A correlation circuit, comprising:
- a first means coupled to receive and store consecutive bits of a serial data stream, said first means being further coupled to store information related to bit contents of a known correlation word, and to compare said stored serial data bits with said known correlation word, said first means having a plurality of outputs, each coupled to provide an output signal of a known magnitude for each match obtained between a stored serial data bit and known correlation word bit;
- a plurality of current setting second means each having an input coupled to one said output of said first means and each having an output, said respective outputs of said second means being coupled to a common terminal;
- and
- a third means coupled to maintain said common terminal at a predetermined constant voltage level.
1 more element
A high speed correlation circuit, comprising;
- a first means coupled to receive and store consecutive bits of a serial data stream, said first means being further coupled to store information related to bit contents of a known correlation word, and to compare said stored serial data bits with said known correlation word, said first means having a plurality of outputs, each coupled to provide an output signal of a known magnitude for each match obtained between a stored serial data bit and known correlation word bit;
- a plurality of second current setting resistor means each having an first terminal coupled to one said output of said first means, said resistor means having their respective second terminals interconnected to a common e terminal, each resistor means applying a known amount of current to said common terminal in response to said output signal obtained at said output of the first means connected to said resistor means;
- a third means coupled to said common terminal for substantially linearly inverting said current on said common terminal to a voltage;
- a fourth means coupled to provide a reference voltage corresponding to a known magnitude of said converted voltage corresponding to a predetermined number of matches obtained by said first means;
- a fifth means coupled to compare said converted voltage with said reference voltage and to provide responsively a control signal;
- and
- a sixth means coupled to said common terminal for maintaining thereon a predetermined constant voltage.
4 more elements
Dependencies are inferred from the claim text.