Adaptive beam forming receiver

• US 20060073801A1
• Filed: 09/28/2005
• Published: 04/06/2006
• Est. Priority Date: 12/10/2003
• Status: Active Grant

• Current Assignee: Moltia, Inc., The Renda Trust
• Original Assignee: Motia, Inc.
• Inventors: Doong, Meng-Chang, Wang, James June-Ming
• Granted Patent: US 7,702,304 B2
• Time in Patent Office: Days
• US Class Current: 455/226.100
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention provides a method and system for operating a wireless communication system in which received signals from a plurality of antennas are weighted and combined with a beam forming operation to form an output signal. In an embodiment of the present invention, beamforming operations are performed with maximal ratio combining (MRC) and an interference nulling algorithm (INA). The INA receives an error signal which is 180° out of phase with a combination of the channels for individual antennas, referred to as the SUM channel. The error signal is determined by complex conjugate multiplication of the individual signals and a reference complex signal. The weight amplitude is controlled by weight normalization to provide faster convergence and prevent integrator overflow.

Claims

1. A method for operating a wireless communication system receiver comprising the steps of:

receiving a plurality of input signals;

generating weights to be applied to each of said input signals by a combination of maximal ratio combining (MRC) to align phases of said input signals to the same phase and to scale said input signals in proportion to a square root of a received signal-to-noise ratio and an interference nulling algorithm (INA) for generating said weights to align phases of said input signals to 180 degree opposite of a SUM channel and to scale said input signal in proportional to an envelop of said input signal;

applying weight normalization to said weights generated by said combination of maximal ratio combining (MRC) and an interference nulling algorithm (INA);

weighting said plurality of input signals with said weights generated by weight normalization; and

combining said weighted plurality of signals to form an output signal.

2. The method of claim 1 wherein said weight normalization is performed by the steps of:

scaling said weights generated by said combination of maximal ratio combining (MRC) and an interference nulling algorithm (INA) to a proper level for combining.

3. The method of claim 1 comprising:

four input signals wherein inputs to the weight normalization are WI_k and WQ_k, where k=1, 2, 3 and 4 and the weights generated from said weight normalization are

$\frac{{\mathrm{WI}}_k}{\sqrt{\underset{m=1}{\overset{4}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{WI}}_m^2+{\mathrm{WQ}}_m^2\right)}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{{\mathrm{WQ}}_k}{\sqrt{\underset{m=1}{\overset{4}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left({\mathrm{WI}}_m^2+{\mathrm{WQ}}_m^2\right)}},$

where k=1, 2, 3 and 4.

4. The method of claim 1 wherein said weights are generated as error signals and weight normalization is performed by the steps of:

transforming input voltages of each of said error signals into current;

squaring said current of each of said error signals;

normalizing said squared current of each of said error signals;

square rooting said normalized current of each of said error signals; and

transforming said square rooted current of each of said error signals into an output voltage of each of said error signals.

5. The method of claim 4 further comprising the step of:

correcting polarity of each of said error signals.

6. The method of claim 1 wherein said weight normalization is performed digitally using a clock delay.

7. The method of claim 6 wherein said weight normalization comprises a weight normalization loop and a weight accumulation loop.

8. The method of claim 7 wherein said accumulation loop is isolated from said normalization loop.

9. The method of claim 6 wherein an analog integrator is used in said normalization loop.

10. The method of claim 7 comprising means for preventing said integrator from overflow in said normalization loop.

11. The method of claim 1 further comprising the step of:

subtracting interference from said input signals before said step of weighting said plurality of input signals.

12. A method for operating a wireless communication system receiver comprising the steps of:

splitting a plurality of input signals into a first path and a second path;

generating first weights to be applied to said input signals of said first path for interference cancellation;

generating second weights to be applied to said input signals of said second path by a combination of maximal ratio combining (MRC) to align phases of said input signals to the same phase and to scale said input signals in proportion to a square root of a received signal-to-noise ratio and an interference nulling algorithm (INA) for generating said weights to align phases of said input signals to 180 degree opposite of a SUM channel and to scale said input signal in proportional to an envelop of said input signal;

applying weight normalization to said second weights generated by said combination of maximal ratio combining (MRC) and an interference nulling algorithm (INA) for generating second normalized weights; and

weighting said plurality of input signals with said first weights and said second normalized weights.

13. The method of claim 12 wherein said first weights are generated from said second weights combined with each of said input signal being added with a second signal from a combination of other of said input signals.

14. The method of claim 12 wherein a high level interference signal is cancelled in the receiver frontend.

15. The method of claim 13 comprising four input signals wherein said first weights are

$\begin{array}{c}W\end{array}$

 

⁢

1 i = W ⁢

 

⁢

1 ⁢

I i + j ⋆

W ⁢

 

⁢

1 ⁢

Q i = WCON i WCON 1 , i = 2 , 3 ⁢

 

⁢

or ⁢

 

⁢

4 W ⁢

 

⁢

2 i = W ⁢

 

⁢

2 ⁢

I i + j ⋆

W ⁢

 

⁢

2 ⁢

Q i = WCON i WCON 2 , i = 1 , 3 ⁢

 

⁢

or ⁢

 

⁢

4 W ⁢

 

⁢

3 i = W ⁢

 

⁢

3 ⁢

I i + j ⋆

W ⁢

 

⁢

3 ⁢

Q i = WCON i WCON 3 , i = 1 , 2 ⁢

 

⁢

or ⁢

 

⁢

4 W ⁢

 

⁢

4 i = W ⁢

 

⁢

4 ⁢

I i + j ⋆

W ⁢

 

⁢

4 ⁢

Q i = WCON i WCON 4 , i = 1 , 2 ⁢

 

⁢

or ⁢

 

⁢

3.

16. A system for operating a wireless communication system receiver comprising:

means for receiving a plurality of input signals;

means for generating weights to be applied to each of said input signals by a combination of maximal ratio combining (MRC) to align phases of said input signals to the same phase and to scale said input signals in proportion to a square root of a received signal-to-noise ratio and an interference nulling algorithm (INA) for generating said weights to align phases of said input signals to 180 degree opposite of a SUM channel and to scale said input signal in proportional to an envelop of said input signal;

means for applying weight normalization to said weights generated by said combination of maximal ratio combining (MRC) and an interference nulling algorithm (INA);

means for weighting said plurality of input signals with said weights generated by weight normalization; and

means for combining said weighted plurality of signals to form an output signal.

17. The system of claim 16 wherein said weight normalization is performed by:

means for summing said weights generated by said combination of maximal ratio combining (MRC) and an interference nulling algorithm (INA); and

means for scaling the weights to a proper level for combining.

18. The system of claim 16 comprising:

four input signals wherein inputs to the weight normalization are WI_k and WQ_k, where k=1, 2, 3 and 4; and

outputs from said weight normalization are

$\frac{{\mathrm{WI}}_k}{\sqrt{\underset{m=1}{\overset{4}{\sum <br><br>}}<br><br>\left({\mathrm{WI}}_m^2+{\mathrm{WQ}}_m^2\right)}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{{\mathrm{WQ}}_k}{\sqrt{\underset{m=1}{\overset{4}{\sum <br><br>}}<br><br>\left({\mathrm{WI}}_m^2+{\mathrm{WQ}}_m^2\right)}},$

where k=1, 2, 3 and 4.

19. The system of claim 16 wherein said weights are generated as error signals and weight normalization is performed by:

means for transforming input voltages of each of said error signals into current;

means for squaring said current of each of said error signals;

means for normalizing said squared current of each of said error signals;

means for square rooting said normalized current of each of said error signals; and

means for transforming said square rooted current of each of said error signals into an output voltage of each of said error signals.

20. The system of claim 19 further comprising:

means for correcting polarization of each of said error signal.

21. The system of claim 20 wherein said weight normalization is performed digitally using a clock delay.

22. The system of claim 21 wherein said weight normalization comprises a weight normalization loop and a weight accumulation loop.

23. The system of claim 22 wherein said accumulation loop is isolated from said normalization loop.

24. The system of claim 22 wherein an analog integrator is used in the said normalization loop.

25. The system of claim 22 further comprising:

means for preventing said analog integrator from overflow in said normalization loop.

26. The system of claim 16 further comprising:

means for subtracting interference from said input signals before weighting said plurality of input signals.

27. A system for operating a wireless communication system receiver comprising:

means for splitting a plurality of input signals into a first path and a second path;

means for generating first weights to be applied to said input signals of said first path;

means for generating second weights to be applied to said input signals of said second path by a combination of maximal ratio combining (MRC) to align phases of said input signals to the same phase and to scale said input signals in proportion to a square root of a received signal-to-noise ratio and an interference nulling algorithm (INA) for generating said weights to align phases of said input signals to 180 degree opposite of a SUM channel and to scale said input signal in proportional to an envelop of said input signal;

means for applying weight normalization to said weights generated by said combination of maximal ratio combining (MRC) and an interference nulling algorithm (INA) for generating second normalized weights; and

means for weighting said plurality of input signals with said weights generated by weight normalization.

28. The system of claim 27 wherein said first weights are generated from said second weights combined with each of said input signal being added with a second signal from a combination of other of said input signals.

29. The system of claim 27 wherein high level interference signal is cancelled in the receiver frontend.

30. The system of claim 28 comprising four input signals wherein said first weights are

$\begin{array}{cc}{\mathrm{W1}}_i={\mathrm{W1I}}_i+j*{\mathrm{W1Q}}_i=\frac{{\mathrm{WCON}}_i}{{\mathrm{WCON}}_1},& i=2,3\end{array}$

 

⁢

or ⁢

 

⁢

4 W2 i = W2I i + j * W2Q i = WCON i WCON 2 , i = 1 , 3 ⁢

 

⁢

or ⁢

 

⁢

4 W3 i = W3I i + j * W3Q i = WCON i WCON 3 , i = 1 , 2 ⁢

 

⁢

or ⁢

 

⁢

4 W4 i = W4I i + j * W4Q i = WCON i WCON 4 , i = 1 , 2 ⁢

 

⁢

or ⁢

 

⁢

3.