Multirate, constant envelope, constant bandwidth, modulation, channelization and detection system based on orthogonal bipolar spreading vectors

• US 7,310,364 B2
• Filed: 04/23/2003
• Issued: 12/18/2007
• Est. Priority Date: 04/23/2003
• Status: Active Grant

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Linsky, Stuart T.
• Primary Examiner(s): Payne, David C.
• Assistant Examiner(s): File, Erin M.
• Application Number:
  US10/421,081
• Publication Number:
  US 20040213142A1
• Time in Patent Office: 1,700 Days
• Field of Search: 375/130, 375/141, 375/146, 375/147, 375/222, 375/265, 375/340
• US Class Current: 375/141
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04J 13/0048 Walsh

Abstract

A modulation channelization and demodulation system based on orthogonal bipolar spreading vectors is provided that permits a variable information rate to be transmitted without inducing envelope fluctuations and permits multiple access without requiring the transmitter amplifiers to support the combined information rate of all users. The modulation system uses the vectors of a Hadamard matrix to form communication channels. The information rate on any channel may be doubled by using half the vector length to transmit information. The vector that is not non-orthogonal-in-the-half to the rate-doubled vector is preferably deactivated. In the same fashion, higher information rates may be provided through truncation of the transmission vector and the elimination of the resultant non-orthogonal vectors. A multi-channel receiver including a Fast Hadamard Transform structure comprised of controllable modified logic cells for performing the multi-rate communication of the present invention is illustrated. A multi-channel transmitter for performing the present invention is also shown.

Claims

1. A multirate communication system comprising:

a set of orthogonal spreading modulation vectors, each vector 2^v chips in length, where v is any positive integer, each modulation vector supporting transfer of information at a first information rate;

each modulation vector additionally supporting the transfer of information at an information rate 2ⁿ times the first information rate, where n is any positive integer, with the exclusion of (2ⁿ−

1) vectors in said set not orthogonal to the first 2<sup>(v−

n)</sup> chips of said modulation vectors;

a transmitter for modulating and transmitting information over said set of modulation vectors; and

a receiver for receiving and demodulating information over said modulation vectors.

2. A multirate communication system comprising:

a set of orthogonal spreading modulation vectors, each vector being 2^v chips in length, where v is any positive integer, each modulation vector supporting the simultaneous transfer of information at variable rates of 2ⁿ times a first information rate, where the total information transfer rate for the set of orthogonal spreading modulation vectors is less than or equal to 2^v bits per vector epoch;

each modulation vector additionally supporting the transfer of information at an information rate 2ⁿ times the first information rate, where n is any positive integer, with the exclusion of (2ⁿ−

1) vectors in said set not orthogonal to the first 2<sup>(v−

n)</sup> chips of said modulation vectors;

a transmitter for modulating and transmitting information over said set of modulation vectors; and

a receiver for receiving and demodulating information over said modulation vectors.

3. A multirate communication system comprising:

a set of orthogonal spreading modulation vectors comprising a Hadamard matrix, each vector being 2^v chips in length, where v is any positive integer, each modulation vector supporting transfer of information at a first information rate;

each modulation vector additionally supporting the transfer of information at an information rate 2ⁿ times the first information rate, where n is any positive integer, with the exclusion of (2ⁿ−

1) vectors in said set not orthogonal to the first 2<sup>(v−

n)</sup> chips of said modulation vectors;

a transmitter for modulating and transmitting information over said set of modulation vectors; and

a receiver for receiving and demodulating information over said modulation vectors.

4. A method for transmitting information comprising:

forming a set of orthogonal spreading modulation vectors having a first length;

transmitting information at a first information rate using a first vector of said set of vectors having said first length;

transmitting information at a second information rate using a portion of a second vector of said set of vectors, said portion of said second vector being orthogonal to said first vector so that the information is transmitted at the first and second information rates using the same length orthogonal vectors;

refraining from transmitting using any vector in said set not orthogonal to said portion of said second vector; and

receiving and demodulating said information transmitted at said first and second information rates.

5. A method for transmitting information comprising:

forming a set of orthogonal spreading modulation vectors having a first length into a Hadamard matrix;

transmitting information at a first information rate using a first vector of said set of vectors having said first length;

transmitting information at a second information rate using a portion of a second vector of said set of vectors, said portion of said second vector being orthogonal to said first vector so that the information is transmitted at the first and second information rates using the same length orthogonal vectors;

refraining from transmitting using any vector in said set not orthogonal to said portion of said second vector; and

receiving and demodulating said information transmitted at said first and second information rates.

6. A multirate communication system comprising:

a set of orthogonal spreading modulation vectors, each vector being 2^v chips in length, where v is any positive integer, each modulation vector supporting transfer of information at a first information rate,

wherein at least one of said set of orthogonal spreading modulation vectors is variably truncated to support the transfer of information at any of v different rates over said at least one of said set of orthogonal spreading modulating vectors using orthogonal vectors having the same length;

a transmitter for modulating and transmitting information over said set of modulation vectors; and

a receiver for receiving and demodulating information over said modulation vectors.

7. A multirate communication system comprising:

a set of orthogonal spreading modulation vectors, each vector being 2^v chips in length, where v is any positive integer, each modulation vector supporting transfer of information at a first information rate;

each modulation vector additionally supporting the transfer of information at an information rate 2ⁿ times the first information rate, where n is any positive integer, by truncating the modulation vector to a length of 2<sup>v−

n)</sup> chips;

a transmitter for modulating and transmitting information over said set of modulation vectors; and

a receiver for receiving and demodulating information over said modulation vectors.