Spread spectrum transmitter and communications system using multiple spreading codes

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.

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.

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.

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.