Method and system for using PSK sync word for fine tuning frequency adjustment
In RF transceivers, a method and system for using phase shift key (PSK) sync word for fine tuning frequency adjustment are provided. One aspect of the invention provides for adjusting a local oscillator frequency in a radio frequency (RF) receiver when a residual DC offset remains after a coarse frequency offset adjustment if performed. The fine adjustment may be necessary because of the synchronization required with a PSK-based modulated portion of a Bluetooth packet. A residual phase shift detected in a sync sequence portion of the Bluetooth packet may be utilized to determine a residual or fine frequency adjustment. This approach may allow an RF receiver to operate, in some instances, without the need for an equalizer. In this regard, the power consumed by the RF receiver may be minimized and/or the overall cost of the RF receiver may be reduced.
1. A method for signal processing, the method comprising:
generating a coarse frequency adjustment for adjusting a receiver frequency based on a DC offset estimate of a Bluetooth packet;
adjusting said receiver frequency based on said generated coarse frequency adjustment;
generating a fine frequency adjustment based on a sampling instant estimate; and
correcting said adjusted receiver frequency based on said generated fine frequency adjustment.
2. The method according to claim 1 , further comprising monitoring a header portion of said Bluetooth packet to determine whether said generated DC offset estimate is outside a threshold value range.
3. The method according to claim 1 , further comprising generating said fine frequency adjustment by determining a phase difference between a last symbol and a sixth symbol of a sync sequence portion of said Bluetooth packet.
4. The method according to claim 1 , further comprising determining said sampling instant estimate by correlating contents of a sync sequence portion of said Bluetooth packet with expected contents of said sync sequence portion.
5. The method according to claim 4 , further comprising correlating said contents of said sync sequence portion of said Bluetooth packet after said adjustment of said receiver frequency based on said coarse frequency adjustment.
6. The method according to claim 1 , further comprising estimating said coarse frequency adjustment for said receiver frequency during a frequency shift key (FSK) portion of said Bluetooth packet.
7. The method according to claim 1 , further comprising generating a coarse frequency adjustment signal to increase said receiver frequency.
8. The method according to claim 1 , further comprising generating a coarse frequency adjustment signal to decrease said receiver frequency.
9. The method according to claim 1 , further comprising generating a fine frequency adjustment signal to increase said receiver frequency.
10. The method according to claim 1 , further comprising generating a fine frequency adjustment signal to decrease said receiver frequency.
11. The method according to claim 1 , further comprising generating said DC offset estimate via DC offset slicing.
12. A system for signal processing, the system comprising:
a modem that generates a coarse frequency adjustment for adjusting a receiver frequency based on a DC offset estimate generated via DC offset slicing of a Bluetooth packet;
said modem adjusts said receiver frequency based on said generated coarse frequency adjustment;
said modem generates a fine frequency adjustment based on a sampling instant estimate; and
said modem corrects said adjusted receiver frequency based on said generated fine frequency adjustment.
13. The system according to claim 12 , wherein said modem monitors a header portion of said Bluetooth packet to determine whether said generated DC offset estimate is outside a threshold value range.
14. The system according to claim 12 , wherein said modem generates said fine frequency adjustment by determining a phase difference between a last symbol and a sixth symbol of a sync sequence portion of said Bluetooth packet.
15. The system according to claim 12 , wherein said modem determines said sampling instant estimate by correlating contents of a sync sequence portion of said Bluetooth packet with expected contents of said sync sequence portion.
16. The system according to claim 15 , wherein said modem correlates of said contents of said sync sequence portion of said Bluetooth packet after said adjustment of said receiver frequency based on said coarse frequency adjustment.
17. The method according to claim 12 , wherein said modem estimates said coarse frequency adjustment for said receiver frequency during a frequency shift key (FSK) portion of said Bluetooth packet.
18. The system according to claim 12 , wherein said modem generates a coarse frequency adjustment signal to increase said receiver frequency.
19. The system according to claim 12 , wherein said modem generates a coarse frequency adjustment signal to decrease said receiver frequency.
20. The system according to claim 12 , wherein said modem generates a fine frequency adjustment signal to increase said receiver frequency.
21. The system according to claim 12 , wherein said modem generates a fine frequency adjustment signal to decrease said receiver frequency.
22. The system according to claim 12 , wherein said modem generates said DC offset estimate via DC offset slicing.