US5790591A — Spread spectrum transmitter and communications sy…

Claim 1

Independent Claim 98 words

A spread spectrum transmitter comprising: a shift register having a plurality of stages including a first stage, a plurality of taps connected to selected ones of said stages, a plurality of exclusive-OR gates connected to said taps, each exclusive-OR gate outputting a different spread spectrum code, said exclusive-OR gates thereby collectively outputting a plurality of spread spectrum codes, and means for selecting, in response to a data signal, one of said spread spectrum codes for transmission, said one selected spread spectrum code being fed back from said means for selecting into the first stage of said shift register.

Claim 2

Dependent Claim 98 words

A spread spectrum transmitter comprising: a shift register having a plurality of stages including a first stage, a plurality of taps connected to selected ones of said stages, a plurality of exclusive-OR gates connected to said taps, each exclusive-OR gate outputting a different spread spectrum code, said exclusive-OR gates thereby collectively outputting a plurality of spread spectrum codes, and means for selecting, in response to a data signal, one of said spread spectrum codes for transmission, said one selected spread spectrum code being fed back from said means for selecting into the first stage of said shift register.

Claim 3

Dependent Claim 30 words

The spread spectrum transmitter of claim 1 wherein said means for selecting comprises a plurality of logic gates each connected to a plurality of data bits from said data signal.

Claim 4

Dependent Claim 56 words

The spread spectrum transmitter of claim 1 further comprising a second means for selecting, in response to said data signal, a second spread spectrum code for transmission from among a second plurality of spread spectrum codes, and means for combining and simultaneously transmitting said first selected spread spectrum code and said second selected spread spectrum code.

Claim 5

Dependent Claim 87 words

The spread spectrum transmitter of claim 3 wherein said means for combining and simultaneously transmitting said first selected spread spectrum code and said second selected spread spectrum code comprises means for modulating said first selected spread spectrum code with a carrier signal and generating a first modulated signal thereby, means for modulating said second selected spread spectrum code with a phase offset version of said carrier signal and generating a second modulated signal thereby, and means for adding said first modulated signal and said second modulated signal.

Claim 6

Dependent Claim 25 words

The spread spectrum transmitter of claim 4 wherein said phase offset version of said carrier signal is 90 degrees phase offset from said carrier signal.

Claim 7

Dependent Claim 51 words

The spread spectrum transmitter of claim 3 wherein said means for combining and simultaneously transmitting said first selected spread spectrum code and said second selected spread spectrum code comprises means for modulating said first selected spread spectrum code and said second selected spread spectrum code using offset quadrature phase shift keying.

Claim 8

Dependent Claim 131 words

A spread spectrum transmitter for generating a plurality of spread spectrum codes, comprising: a shift register having a plurality of stages, a plurality of tap sets connected to selected ones of said stages, each tap set defining a different spread spectrum code, wherein each of said spread spectrum codes corresponds to a unique series of data bits, and whereby said shift register outputs one of said spread spectrum codes in response to selection of one of said tap sets, a data register coupled to a data stream, and a code selector connected to said data register whereby one of said tap sets is selected for transmission in response to the contents of said data register, said code selector being connected in feedback configuration to the first stage of said shift register.

Claim 9

Dependent Claim 131 words

A spread spectrum transmitter for generating a plurality of spread spectrum codes, comprising: a shift register having a plurality of stages, a plurality of tap sets connected to selected ones of said stages, each tap set defining a different spread spectrum code, wherein each of said spread spectrum codes corresponds to a unique series of data bits, and whereby said shift register outputs one of said spread spectrum codes in response to selection of one of said tap sets, a data register coupled to a data stream, and a code selector connected to said data register whereby one of said tap sets is selected for transmission in response to the contents of said data register, said code selector being connected in feedback configuration to the first stage of said shift register.

Claim 10

Dependent Claim 70 words

The spread spectrum transmitter of claim 7, wherein each tap set comprises a plurality of taps, said spread spectrum transmitter further comprising a plurality of exclusive-OR gates, one exclusive-OR gate for each tap set, wherein each tap from each of said tap sets is connected to an input of one of said exclusive-OR gates, and outputs from all of said exclusive-OR gates are connected as inputs to said code selector.

Claim 11

Dependent Claim 17 words

The spread spectrum transmitter of claim 7 wherein said code selector comprises a plurality of logic gates.

Claim 12

Dependent Claim 19 words

The spread spectrum transmitter of claim 7 wherein all of said spread spectrum codes have the same code length.

Claim 13

Dependent Claim 26 words

The spread spectrum transmitter of claim 7 wherein at least one of said spread spectrum codes comprises a selected portion of a longer spread spectrum code.

Claim 14

Dependent Claim 17 words

The spread spectrum transmitter of claim 11 wherein said longer spread spectrum code is a non-maximal code.

Claim 15

Dependent Claim 113 words

A spread spectrum transmitter comprising: a shift register having a plurality of stages, a plurality of tap sets coupled to selected ones of said stages, each tap set defining a spreading code from among a plurality of spreading codes, means for periodically selecting one of said spreading codes at a time in response to a data stream, and means for generating, in response to each selected spreading code, a code portion of the selected spreading code, said code portion having a code length L, wherein L is less than or equal to the code length of the shortest of said spreading codes, wherein said code portion is fed back into said shift resister.

Claim 16

Dependent Claim 113 words

A spread spectrum transmitter comprising: a shift register having a plurality of stages, a plurality of tap sets coupled to selected ones of said stages, each tap set defining a spreading code from among a plurality of spreading codes, means for periodically selecting one of said spreading codes at a time in response to a data stream, and means for generating, in response to each selected spreading code, a code portion of the selected spreading code, said code portion having a code length L, wherein L is less than or equal to the code length of the shortest of said spreading codes, wherein said code portion is fed back into said shift resister.

Claim 17

Dependent Claim 23 words

The spread spectrum transmitter of claim 13 wherein said code portion corresponds to a unique sequence of data bits in said data stream.

Claim 18

Dependent Claim 29 words

The spread spectrum transmitter of claim 13 wherein each of said spreading codes corresponds to a different data symbol, each data symbol comprising a unique sequence of data bits.

Claim 19

Dependent Claim 17 words

The spread spectrum transmitter of claim 13 wherein at least one of said spreading codes is non-maximal.

Claim 20

Dependent Claim 49 words

The spread spectrum transmitter of claim 13 whereby a plurality of code portions are generated in response to said periodically selected spreading codes, wherein the cross-correlation between any two of said code portions generated from different ones of said spreading codes is less than a designated maximum cross-correlation value.

Claim 21

Dependent Claim 63 words

The spread spectrum transmitter of claim 13 wherein said spread spectrum transmitter communicates with a receiver, said receiver comprising a receive shift register coupled to an incoming signal containing said code portion, and having receive tap locations matching said code portion, and means for combining said incoming signal with outputs from each of said receive tap locations, and generating a correlation signal thereby.

Claim 22

Dependent Claim 25 words

The spread spectrum transmitter of claim 18 wherein said correlation signal comprises a series of consecutive correlation bits of uniform polarity and of predetermined length.

Claim 23

Dependent Claim 72 words

The spread spectrum transmitter of claim 17 further comprising a carrier signal generator outputting a carrier signal, a first modulator connected to said carrier signal and said first code portion, a second modulator connected to a second one of said code portions and to a phase offset version of said carrier signal, a summer having two inputs, one input connected to said first modulator and another input connected to said second modulator.

Claim 24

Dependent Claim 26 words

The spread spectrum transmitter of claim 20 wherein said phase offset version of said carrier signal is 90 degrees offset in phase from said carrier signal.

Claim 25

Dependent Claim 42 words

The spread spectrum transmitter of claim 20 wherein said spread spectrum transmitter communicates with a receiver, said receiver comprising means for receiving a signal containing an output of said summer and simultaneously detecting said first code portion and said second code portion.

Claim 26

Dependent Claim 14 words

The spread spectrum transmitter of claim 22 wherein said receiver comprises a best-2-of-M detector.

Claim 27

Dependent Claim 199 words

A spread spectrum transmitter for generating a plurality of spread spectrum codes, comprising: a shift register having a plurality of stages, a plurality of tap sets connected to selected ones of said stages, each tap set defining a different spread spectrum code, wherein each of said spread spectrum codes corresponds to a unique series of data bits, and whereby said shift register outputs one of said spread spectrum codes in response to selection of one of said tap sets, a first data register coupled to a data stream, said first data register serially receiving said data stream, a second data register coupled to said first data register, said second data register periodically receiving the contents of said first data register in parallel, said first data register being clocked by a first data clock, and said second data register being clocked by a second data clock, wherein the rate of said first data clock is an integral multiple of the rate of said second data clock, and a code selector connected to said second data register, whereby an output of one of said tap sets is selected for transmission, said output being coupled to the input of said shift register.

Claim 28

Dependent Claim 199 words

A spread spectrum transmitter for generating a plurality of spread spectrum codes, comprising: a shift register having a plurality of stages, a plurality of tap sets connected to selected ones of said stages, each tap set defining a different spread spectrum code, wherein each of said spread spectrum codes corresponds to a unique series of data bits, and whereby said shift register outputs one of said spread spectrum codes in response to selection of one of said tap sets, a first data register coupled to a data stream, said first data register serially receiving said data stream, a second data register coupled to said first data register, said second data register periodically receiving the contents of said first data register in parallel, said first data register being clocked by a first data clock, and said second data register being clocked by a second data clock, wherein the rate of said first data clock is an integral multiple of the rate of said second data clock, and a code selector connected to said second data register, whereby an output of one of said tap sets is selected for transmission, said output being coupled to the input of said shift register.

Claim 29

Dependent Claim 17 words

The spread spectrum transmitter of claim 24 wherein said code selector comprises a plurality of logic gates.

Claim 30

Dependent Claim 26 words

The spread spectrum transmitter of claim 24 wherein at least one of said spread spectrum codes comprises a selected portion of a longer spread spectrum code.

Claim 31

Dependent Claim 17 words

The spread spectrum transmitter of claim 26 wherein said longer spread spectrum code is a non-maximal code.

Claim 32

Dependent Claim 24 words

The spread spectrum transmitter of claim 24 wherein said integral multiple corresponds to a number of serial register stages in said second data register.

Claim 33

Dependent Claim 89 words

The spread spectrum transmitter of claim 1, wherein said spread spectrum transmitter communicates with a receiver, said receiver comprising: a receive shift register connected to a signal received from said spread spectrum transmitter, said receive shift register comprising a plurality of receive stages; a plurality of taps connected to receive stages corresponding in location to the taps connected to the stages of the shift register in said spread spectrum transmitter; and a modulo-two adder connected to each of said plurality of taps, said modulo-two adder outputting a correlation signal.

Claim 34

Dependent Claim 24 words

The spread spectrum transmitter of claim 29, wherein each exclusive-OR gate of said spread spectrum transmitter is connected to exactly two of said taps.

Claim 35

Dependent Claim 87 words

The spread spectrum transmitter of claim 7, wherein said spread spectrum transmitter communicates with a receiver, said receiver comprising: a receive shift register connected to a signal received from said spread spectrum transmitter, said receive shift register comprising a plurality of receive stages; a tap set connected to receive stages in the same locations as the tap set connected to the stages of the shift register in said spread spectrum transmitter; and a modulo-two adder connected to said tap set, said modulo-two adder outputting a correlation signal.

Claim 36

Dependent Claim 87 words

The spread spectrum transmitter of claim 24, wherein said spread spectrum transmitter communicates with a receiver, said receiver comprising: a receive shift register connected to a signal received from said spread spectrum transmitter, said receive shift register comprising a plurality of receive stages; a tap set connected to receive stages in the same locations as the tap set connected to the stages of the shift register in said spread spectrum transmitter; and a modulo-two adder connected to said tap set, said modulo-two adder outputting a correlation signal.

Claim 37

Independent Claim 106 words

A method for transmitting a spread spectrum signal, comprising the steps of: serially clocking a data stream into a first data register; transferring in parallel the contents of said first register into a second data register; simultaneously generating a plurality of spread spectrum codes by serially clocking a shift register and, for each spread spectrum code being simultaneously generating, modulo-two adding the contents of at least two stages of said shift register; periodically selecting for transmission one of said spread spectrum codes according to the contents of said second data register; and feeding back said selected one of said spread spectrum codes into said shift register.

Claim 38

Independent Claim 106 words

A method for transmitting a spread spectrum signal, comprising the steps of: serially clocking a data stream into a first data register; transferring in parallel the contents of said first register into a second data register; simultaneously generating a plurality of spread spectrum codes by serially clocking a shift register and, for each spread spectrum code being simultaneously generating, modulo-two adding the contents of at least two stages of said shift register; periodically selecting for transmission one of said spread spectrum codes according to the contents of said second data register; and feeding back said selected one of said spread spectrum codes into said shift register.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2001-08-03	2002-02-02	2002-08-04	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2005-08-03	2006-02-02	2006-08-04	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2009-08-03	2010-02-02	2010-08-04	$7700.00	Window Closed / Lapsed

Spread spectrum transmitter and communications system using multiple spreading codes

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