Method and apparatus for rotating a phase of a modulated signal

• US 7,106,782 B2
• Filed: 12/17/2002
• Issued: 09/12/2006
• Est. Priority Date: 09/17/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Black, Peter J., Howard, Michael A.
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US10/322,246
• Publication Number:
  US 20030123526A1
• Time in Patent Office: 1,365 Days
• Field of Search: 375/130, 375/146, 375/295, 375/296, 375/297, 455/114.3, 455/127.1, 455/127.2, 455/115.1, 455/126, 330/2
• US Class Current: 375/146
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 27/367 using predistortion

Abstract

Techniques to adjust the phase rotation of a modulated signal to compensate for the phase rotation introduced by circuit elements associated with the transmit signal path. In one implementation, at least one control signal is received, with each control signal being provided to adjust a particular characteristic (e.g., gain, bias current) of one or more circuit elements (e.g., VGA, PA) associated with the transmit signal path. The circuit elements can be located directly in, or operatively coupled to, the transmit signal path. A phase rotation corresponding to an operating state defined by the received control signal(s) is then determined, and the phase of the modulated signal is rotated by an amount related to the determined phase rotation. The phase rotation compensation can be performed at various locations along the transmit signal path by rotating either the data, the PN sequences used to spectrally spread the data, or the carrier signals used to modulate the data.

Claims

1. A method comprising:

determining a phase rotation of a modulated signal that is caused by an adjustment of a characteristic of a circuit element associated with a signal path of the modulated signal, based on a gain control signal and a bias control signal; and

performing a phase rotation compensation with respect to the modulated signal to compensate for the phase rotation caused by the adjustment of the characteristic of the circuit element, wherein the phase rotation compensation comprises rotating a phase of at least one of (a) a data signal, (b) a spreading sequence for spectrally spreading the data signal, and (c) a carrier signal for modulating the data signal, wherein performing the phase rotation compensation further comprises;

determining a direction and an amount of the phase rotation of the modulated signal, wherein the direction and amount are associated with the gain control signal and the bias control signal; and

rotating the phase of the modulated signal by an amount corresponding to the determined amount of the phase rotation in an opposite direction relative to the direction of the determined phase rotation.

2. The method of claim 1 wherein the gain control signal and the bias control signal are used to adjust one or more characteristics of the circuit element according to an operating state defined by the gain control signal and the bias control signal.

3. The method of claim 1 wherein rotating the phase of the modulated signal is performed using a complex multiplier.

4. The method of claim 1 wherein rotating the phase of the modulated signal is performed digitally.

5. The method of claim 1 wherein a time at which the phase rotation compensation is performed corresponds to a time of the adjustment.

6. The method of claim 5 wherein the time at which the phase rotation compensation is performed is aligned with the time of the adjustment such that phase discontinuity in the modulated signal is reduced when the adjustment occurs.

7. The method of claim 5 wherein the time at which the phase rotation compensation is performed is approximately the same as the time of the adjustment.

8. The method of claim 1 wherein performing comprises:

rotating phases of pseudo-random noise (PN) sequences used to spectrally spread data from which the modulated signal is generated.

9. The method of claim 8 wherein the pseudo-random noise (PN) sequences comprise pseudo-random noise (PN) sequences in accordance with IS-95-A standard.

10. The method of claim 1 wherein performing comprises:

rotating phases of data that are used to generate the modulated signal.

11. The method of claim 1 wherein performing comprises:

rotating phases of one or more carrier signals that are used to generate the modulated signal.

12. The method of claim 1 wherein each value of the gain control signal and the bias control signal corresponds to a particular phase rotation value.

13. The method of claim 12 wherein phase rotation values corresponding to values of the gain control signal and the bias control signal are stored in a look-up table and wherein determining the phase rotation is performed using the look-up table.

14. The method of claim 1 wherein rotating the phase of the modulated signal is performed in discrete increments.

15. The method of claim 1 wherein the circuit element is located directly in the signal path.

16. The method of claim 1 wherein the circuit element is operatively coupled to the signal path.

17. A method comprising:

determining a phase shift of a modulated signal caused by one or more circuit elements associated with a signal path of the modulated signal, based on a gain control signal and a bias control signal; and

performing a phase adjustment with respect to the modulated signal to compensate for the phase shift caused by the one or more circuit elements associated with the signal path, wherein the phase adjustment comprises adjusting a phase of at least one of (a) a data signal, (b) a spreading sequence for spectrally spreading the data signal, and (c) a carrier signal for modulating the data signal, wherein performing the phase adjustment further comprising;

determining a direction and an amount of the phase shift of the modulated signal, wherein the amount of the phase shift is associated with the gain control signal and the bias control signal; and

shifting the phase of the modulated signal by an amount corresponding to the determined amount of the phase shift in an opposite direction relative to the direction of the determined phase shift.

18. The method of claim 17 wherein the gain control signal and the bias control signal are used to adjust one or more characteristics of the one or more circuit elements according to an operating state defined by the gain control signal and the bias control signal.

19. A method comprising:

receiving at least one data stream and a pair of pseudo-random noise (PN) sequences;

spreading the at least one data stream with the pair of pseudo-random noise (PN) sequences to generate spread data;

modulating the spread data to generate a modulated signal;

conditioning the modulated signal with at least one circuit element to generate an output signal, based on a gain control signal and a bias control signal which are used to adjust one or more characteristics of the at least one circuit element;

compensating a phase rotation of the output signal which is caused by adjustment of the one or more characteristics of the at least one circuit element, based on the gain control signal and the bias control signal, wherein compensating the phase rotation comprises rotating a phase of at least one of (a) the pseudo-random noise (PN) sequences, (b) the spread data, and (c) one or more carrier signals that are used to modulate the spread data, wherein compensating the phase rotation further comprises;

determining a direction and an amount of the phase rotation of the modulated signal, wherein the direction and the amount are associated with the gain control signal and the bias control signal; and

rotating the phase of the modulated signal by an amount corresponding to the determined amount of the phase rotation in an opposite direction relative to the direction of the determined phase rotation.

20. An apparatus comprising:

a signal processor to receive a data stream and generate a modulated signal based on the data stream;

at least one circuit element coupled to the signal processor to condition the modulated signal based on a gain control signal and a bias control signal which are used to adjust one or more characteristics of the at least one circuit element, wherein the signal processor comprises;

a spreader to spread the data stream with pseudo-random noise (PN) sequences to generate spread data, and

a modulator to modulate the spread data with one or more carrier signals,

wherein a phase rotation of the modulated signal caused by adjustment of one or more characteristics of the at least one circuit element is determined and compensated based on the gain control signal and the bias control signal, and is further based on rotating a phase of at least one of (a) the pseudo-random noise (PN) sequences, (b) the spread data generated by the spreader, and (c) one or more carrier signals that are used to modulate the spread data, wherein the phase rotation is by an amount of the determined phase rotation and in an opposite direction relative to the direction of the determined phase rotation.

21. The apparatus of claim 20 wherein the phase rotation of the modulated signal caused by the adjustment of the one or more characteristics is determined using a look-up table that stores a set of phase rotation values each of which corresponds to a value of the gain control signal and the bias control signal.

22. The apparatus of claim 20 wherein the at least one circuit element comprises a variable gain element having a gain determined by the gain control signal.

23. The apparatus of claim 22 wherein the variable gain element is a variable gain amplifier (VGA).

24. The apparatus of claim 20 wherein the at least one circuit element comprises an active circuit element having a bias current determined by the bias control signal.

25. The apparatus of claim 24 wherein the active circuit element is a power amplifier (PA).