Low power long range transmitter

Patent metadata

Field	Value
Publication number	US-9252834-B2
Application number	US-201414170170-A
Country	US
Kind code	B2
Filing date	Jan 31, 2014
Priority date	Feb 5, 2013
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

A transmitter device arranged to encode a set of digital input data into a succession of modulated chirps, whereby said digital input data are encoded according to a Gray code into codewords ( 320, 321, 322 ) having a plurality of bits, and having an interleaver that distributes the bits (C 00 , . . . C nn ) of each codeword into a series of digital modulation values (S 0 , . . . S 7 ), at different bit positions, and to synthesize a series of modulated chirps whose cyclical shifts are determined by the modulation values. A special frame structure is defined in order to ensure high robustness, and variable bit-rate flexibility.

First claim

The invention claimed is:

1. A transmitter device comprising:
an encoder operatively arranged for encoding digital message according to a Gray code into codewords having a plurality of bits;
an interleaver arranged for interleaving the bits of each of said codewords into a series of digital modulation values, at different bit positions; and
a modulator arranged for synthesizing a series of modulated chirps whose instantaneous frequencies vary according to one of a plurality of a functions that are cyclical shifts of one base chirp function, wherein said modulator embeds the series of modulated chirps in data frames, said data frames having a preamble with unmodulated chirps, and frame synchronization symbols having a predetermined modulation value.

2. The transmitter of claim 1 , wherein the interleaver is diagonal and distributes the bits of each codeword at cyclically increasing positions inside successive modulation values.

3. The transmitter of claim 1 , comprising a generator of correction codes, whereby each codeword includes data bits and error correction bits.

4. The transmitter of claim 1 , wherein the preamble further includes frequency synchronization symbols that are complex conjugate of the base chirp function.

5. The transmitter of claim 1 , wherein the preamble further includes a silence.

6. The transmitter of claim 5 , wherein the silence is followed by base unmodulated symbols for fine frequency and/or time synchronization.

7. The transmitter of claim 1 , wherein part of the chirps are modulated with a reduced set of cyclic shifts.

8. A method of transmitting a digital message, the method comprising: encoding the digital message according to a Gray code into codewords having a plurality of bits, interleaving the bits of each of said codewords into a series of digital modulation values, at different bit positions, synthesizing a series of modulated chirps whose instantaneous frequencies vary according to one of a plurality of a functions that are cyclical shifts of one base chirp function, and embedding said modulated chirps in data frames having a preamble with unmodulated chirps, whose instantaneous frequency vary according to the base chirp function, and frame synchronization symbols having a predetermined modulation value.

9. The method of claim 8 wherein a phase of said series of modulated chirps is essentially continuous.

10. The method of claim 8 , wherein said interleaving distributes the bits of each of said codewords at cyclically increasing positions inside successive modulation values.

11. The method of claim 8 , comprising inserting in the message correction codes, whereby each codeword includes data bits and error correction bits.

12. The method of claim 8 , comprising inserting in said preamble frequency synchronisation symbols that are complex conjugate of the unmodulated symbols.

13. The method of claim 8 , comprising inserting in said preamble a silence.

14. The method of claim 13 , comprising following said silence is followed with unmodulated symbols.

15. The method of claim 8 , comprising modulating part of the chirps with a reduced set of cyclic shifts.

Assignees

• Seller Olivier B A
• Sornin Nicolas
• Semtech Corp

Inventors

• Seller Olivier B A
• Sornin Nicolas

Classifications

• H04B2001/6912

  using chirp · CPC title

• H04B1/69

  Spread spectrum techniques · CPC title

• H03M13/2721 Primary

  the interleaver involves a diagonal direction, e.g. by using an interleaving matrix with read-out in a diagonal direction · CPC title

• H03M13/276

  Interleaving address generation · CPC title

• H03M5/14

  Code representation, e.g. transition, for a given bit cell depending on the information in one or more adjacent bit cells, e.g. delay modulation code, double density code · CPC title