System and method for communicating data using constant amplitude equalized waveform

• US 7,508,884 B2
• Filed: 03/24/2005
• Issued: 03/24/2009
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: Harris Global Communications, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Wadsworth, Michael A., Nieto, John W., Furman, William N.
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Perilla; Jason M.
• Application Number:
  US11/088,510
• Publication Number:
  US 20060215786A1
• Time in Patent Office: 1,461 Days
• Field of Search: 375/229, 375/316, 375/295, 375/140, 375/302, 375/325, 375/329, 375/334, 375/335
• US Class Current: 375/295
• CPC Class Codes: H04L 27/2014 in which the phase changes in a piecewise linear manner during each symbol period, e.g. minimum shift keying, fast frequency shift keying H04L27/201 takes precedence
• CPC Class Codes: H04L 27/2017 in which the phase changes are non-linear, e.g. generalized and Gaussian minimum shift keying, tamed frequency modulation H04L27/201 takes precedence

Abstract

A system communicates data and includes an encoder for encoding communications data with a forward error correction code. A data randomizer randomizes the communications data with a random bit sequence and a combining circuit combines the communications data with known symbols into frames. A modulator maps the communications data into minimum shift keying or Gaussian minimum shift keying (MSK or GMSK) symbols based on a specific mapping algorithm to form a communications signal having an MSK or GMSK waveform over which the communications data can be transmitted.

Claims

1. A system for communicating data, which comprises:

a transmitter for transmitting a communications signal that carries communications data, and including an encoder for encoding the communications data with a forward error correction code, a single interleaver for interleaving the encoded communications data in a serial data stream, a data randomizer that extracts bits from the interleaver corresponding to the communications data and processes the extracted bits with a random bit sequence, a combining circuit for combining the communications data processed with the random bit sequence with known symbols into frames, and a modulator for mapping the framed communications data from the combining circuit into minimum shift keying or Gaussian minimum shift keying (MSK or GMSK) symbols based on a specific mapping algorithm without spread spectrum modulation to form a communications signal having a constant amplitude MSK or GMSK waveform over which the communications data can be transmitted; and

a receiver for receiving the communications signal from the transmitter, and including a filter that is matched to a main pulse of the MSK or GMSK waveform and a block or symbol equalizer for equalizing the communications signal, and further comprising a block or symbol equalizer and a clamping circuit operative for clamping received communications data symbols of the communications signal to a real symbol (+/−

1 ) or an imaginary symbol (+/−

j) such that odd communications data symbols are clamped to a one of the real symbols or the imaginary symbols and even communications data symbols are clamped to the other one of the real symbols or the imaginary symbols depending on the starting phase of MSK or GMSK.

2. A system according to claim 1, wherein said interleaver further comprises a block interleaver for interleaving the encoded communications data.

3. A system according to claim 2, wherein said data randomizer is operative for extracting bits from the interleaver after said block interleaver is full.

4. A system according to claim 1, wherein said encoder is operative for encoding the communications data with a rate 1/2 convolutional code.

5. A method for communicating data, which comprises:

at a transmitter, encoding communications data in an encoder with a forward error correction code;

interleaving in a single interleaver the encoded communications data;

extracting bits from the interleaver corresponding to the communications data and processing the extracted bits with a random bit sequence;

combining the communications data processed with the random bit sequence with known symbols into frames;

mapping the framed communications data from the combining circuit into minimum shift keying or Gaussian minimum shift keying (MSK or GMSK) symbols based on a specific mapping algorithm without spread spectrum modulation to form a communications signal having a constant amplitude MSK or GMSK waveform over which the communications data can be transmitted;

transmitting the communications signal to a receiver; and

receiving the communications signal with a matched filter of the receiver that is matched to a main pulse of the MSK or GMSK waveform and equalizing the communications signal within a block or symbol equalizer having a clamping circuit for clamping received communications data symbols of the communications signal to a real symbol (+/−

1) or an imaginary symbol (+/−

j) such that odd communications data symbols are clamped to a one of the real symbols or the imaginary symbols and even communications data symbols are clamped to the other one of the real symbols or the imaginary symbols depending on the starting phase of MSK or GMSK.

6. A method according to claim 5, which further comprises interleaving the encoded communications data in a block interleaver.

7. A method according to claim 6, which further comprises extracting bits from the interleaver for randomizing after the block interleaver is full.