Spread spectrum communication and synchronization

• US 7,933,315 B2
• Filed: 08/15/2006
• Issued: 04/26/2011
• Est. Priority Date: 08/15/2006
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Li, Yunchu, Schafferer, Bernd, Engel, Gil
• Primary Examiner(s): BAYARD, EMMANUEL
• Application Number:
  US11/504,270
• Publication Number:
  US 20080043819A1
• Time in Patent Office: 1,715 Days
• Field of Search: 375/130, 375/133, 375/141, 375/142, 375/150, 375/152, 375/347, 375/349
• US Class Current: 375/150
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A method for generating a data signal for synchronizing one or more electrically coupled digital receivers is disclosed. A data signal having a data rate is modulated with a pseudo-noise (PN) code having a data rate greater than the data rate of the data signal. The modulated data signal is demodulated by a receiver using the PN code. A correlation value is generated and is compared to a predetermined value to indicate phase synchronization. If the receiver is in phase synchronization with the transmitter, the received demodulated data signal is passed.

Claims

1. A method for determining temporal synchronization of a plurality of electrically-coupled digital receivers, the method comprising:

receiving at an input of a single modulator circuit a data signal having a data rate;

modulating the data signal with a pseudo-noise code wherein the pseudo-noise code has a data rate that is greater than the data rate of the data signal;

communicating the modulated signal from the single modulator circuit to the plurality of digital receivers through a wireline connection;

receiving at the plurality of digital receivers the modulated data signal;

for each digital receiver;

generating a correlation values using the modulated data signal and the pseudo-noise code; and

comparing the correlation values to a predetermined value to determine if the data signal is temporally synchronized.

2. The method of claim 1, wherein the pseudo-noise code when auto-correlated has a maximum peak at a single time shift.

3. The method of claim 1, further comprising:

passing the correlation values which represent the demodulated data signal if comparing indicates temporal synchronization.

4. The method of claim 1, further comprising sending an out-of-synchronization signal if comparing indicates out-of-synchronization.

5. The method of claim 1, further comprising:

if comparing indicates out-of-synchronization, repeatedly shifting the pseudo-noise code, demodulating the modulated data signal with the shifted pseudo-noise code, generating a correlation value of the data signal, and comparing the correlation value to the predetermined value until the comparison indicates synchronization.

6. The method of claim 1, wherein the predetermined value is such that comparing indicates synchronization when a predetermined number of bit errors occur during a predetermined interval in the modulated data signal.

7. The method of claim 5, wherein if the pseudo-noise code has been shifted through all bits of the code and no comparison indicates synchronization, sending a data error signal.

8. A system for temporally synchronizing data signals between electrically coupled digital systems, comprising:

a transmitter including an input for receiving a digital data signal having a data rate, a modulator for modulating the digital data signal with a pseudo-noise code having a data rate greater than the digital data signal, and an output for communicating the modulated digital data signal; and

a plurality of receivers electrically coupled through a wireline connection to the transmitter, each receiver having an input for receiving the modulated digital data signal, a demodulator for generating at least one correlation value using the pseudo-nouse code and the modulated digital data signal, a comparator for comparing the al least one correlation value to a predetermined value to determine temporal synchronization, and an output for passing the the at least one correlation value that represents the demodulated digital data signal.

9. The system of claim 8, wherein the pseudo-noise code has an auto-correlation function having a maximum peak at one time shift.

10. The system of claim 8, operated to pass the correlation value that represents the demodulated digital data signal if comparing the correlation value to the predetermined value indicates synchronization.

11. The system of claim 8, operated to send an out-of-synchronization signal if comparing the correlation value to the predetermined value indicates out-of -synchronization.

12. The system of claim 8, wherein the predetermined value is such that comparing the correlation value to the predetermined value indicates synchronization when a predetermined number of bit errors occur during a predetermined interval in the modulated data signal.

13. The system of claim 8, further operated such that if comparing the correlation value to the predetermined value indicates out-of-synchronization, repeatedly shifting the pseudo-noise code, demodulating the modulated data signal with the shifted pseudo-noise code, generating a correlation value of the data signal, and comparing the correlation value to the threshold value until the comparison indicates synchronization.

14. A method for determining if a data signal is temporally synchronized, the method comprising:

at a plurality of receivers in a wireline system;

receiving a data signal modulated with a pseudo-noise code and having a data rate from a modulator within the wireline system;

generating a correlation signal using the modulated data signal and the pseudo-noise code; and

comparing the correlation signal to a predetermined value for determining if the demodulated data signal is temporally synchronized.

15. The method according to claim 14 wherein the pseudo-noise code has a data rate that is greater than the data rate of the received data signal.

16. The method according to claim 14, wherein the predetermined value is such that comparing will determine that the correlation value that is representative of the demodulated data signal is synchronized even if there is a transmission error during one period of the pseudo-noise code.

17. The method according to claim 14, wherein the predetermined value is such that comparing will determine that the demodulated data signal is synchronized even if there is a transmission error during multiple periods of the pseudo-noise code.

18. The method according to claim 14 wherein if comparing determines that the demodulated data signal is not synchronized, repeatedly shifting the pseudo-noise code, demodulating the modulated data signal with the shifted pseudo-noise code, generating a correlation signal, and comparing the correlation signal with the predetermined value until comparing determines that the demodulated signal is temporally synchronized.

19. The method according to claim 18, wherein if all shifted versions of the pseudo-noise code are used and comparing determines that the demodulated signal is not synchronized, outputting an error signal.

20. The method according to claim 18 wherein a new portion of the received data signal is used during demodulating with each shifted version of the pseudo-noise code.