Method and apparatus for linearizing a non-linear power amplifier

1. A method for linearizing a non-linear power amplifier, comprising:

performing an iteration algorithm by using a desired output signal of the non-linear power amplifier, to calculate an input signal of the non-linear power amplifier, wherein during iteration n+1, the input signal is adjusted to cancel out the difference between actual output signal and the desired output signal that measured during iteration n, n is an positive integer;

whereby with the calculated input signal of the non-linear power amplifier, the non-linear power amplifier is linearized;

wherein the iteration algorithm is given by:

pa_in

n

+

1

=

pa_in

n

-

alpha

×

(

pa_out

n

-

pa_out

⁢

_desired

G

n

)

,

wherein pa_out_desired is the desired output signal of the non-linear power amplifier pa_in a is the calculated input signal of the non-linear power amplifier for iteration n, pa_out n is a time aligned output signal of the non-linear power amplifier for iteration n, G n is a ain of the non-linear power amplifier for iteration n which can be calculated by pa_in n and pa_out n , is in a range from 0 to 1, and wherein pa_in 1 is the desired output signal of the non-linear power amplifier divided by an estimated gain of the non-linear power amplifier;

or

the iteration algorithm is given by:

pa_mdl

⁢

_in

⁢

_corr

n

,

i

=

pa_mdl

⁢

_in

n

,

i

-

alpha

×

(

pa_mdl

⁢

_out

n

,

i

-

S

n

G

n

,

i

)

,

wherein S n represents segment n and is composed of samples n*B−M to n+1*B−1 of the desired output signal of the non-linear power amplifier, pa_mdl_in n,i is an input signal of a forward model of the non-linear power amplifier for segment n and iteration i,pa_mdl_out n,i is an output signal of the forward model of the non-linear power amplifier for segment n and iteration i, G n,i is an gain of the forward model of the non-linear power amplifier for segment n and iteration i which can be calculated by pa_mdl_in n,i and pa_mdl_out n,i alpha is in a range from 0 to 1, and pa_mdl_in_corr n,i is an input correction signal for segment n and iteration i,

wherein pa_mdl_in n,1 is S n divided by an estimated gain of the forward model, pa_mdl_in n,i+1 is obtained by concatenating samples B to B+M−1 of pa_mdl_in n−1,end and samples M to B+M−1 of pa_mdl_in_corr n,i , pa_mdl_in n−1,end is an input signal of a forward model of the non-linear power amplifier for segment n−1 of a final iteration, and pa_mdl_in 0,end is 0,

whereby the input signal of the non-linear power amplifier is obtained by concatenating samples M to B+M−1 of the input signals of the forward model of the non-linear power amplifier of the last iteration for all segments,

wherein the forward model of the non-linear power amplifier is a zero delay and memory limited forward model, and an output of the forward model is related to a current input sample and previous M−1 samples of the forward model.

2. The method according to claim 1 , wherein the estimated gain of the non-linear power amplifier is specified by a manufacturer of the non-linear power amplifier.

3. The method according to claim 1 , wherein the estimated gain of the non-linear power amplifier is obtained by measuring the non-linear power amplifier when a low power signal is input into the non-linear power amplifier.

4. The method according to claim 1 , further comprising:

performing a simulation algorithm by using the calculated input signal of the non-linear power amplifier and a corresponding time aligned output signal of the non-linear power amplifier, to simulate an inverse model of the non-linear power amplifier,

whereby the power amplifier is linearized by using the simulated inverse model of the non-linear power amplifier.

5. An apparatus for linearizing a non-linear power amplifier, comprising:

a device for performing an iteration algorithm by using a desired output signal of the non-linear power amplifier, to calculate an input signal of the non-linear power amplifier, wherein during iteration n+1, the input signal is adjusted to cancel out the difference between actual output signal and the desired output signal that measured during iteration n, n is an positive integer;

whereby with the calculated input signal of the non-linear power amplifier, the non-linear power amplifier is linearized;

wherein the iteration algorithm is given by:

pa_in

n

+

1

=

pa_in

n

-

alpha

×

(

pa_out

n

-

pa_out

⁢

_desired

G

n

)

,

wherein pa_out_desired is the desired output signal of the non-linear power amplifier, pa_in a is the calculated input signal of the non-linear power amplifier for iteration n, pa_out n is a time aligned output signal of the non-linear power amplifier for iteration n, G n is a gain of the non-linear power amplifier for iteration n which can be calculated by pa_in n and pa_out n , and alpha is in a range from 0 to 1, and wherein pa_in 1 is the desired output signal of the non-linear power amplifier divided by an estimated gain of the non-linear power amplifier;

or

the iteration algorithm is given by:

pa_mdl

⁢

_in

⁢

_corr

n

,

i

=

pa_mdl

⁢

_in

n

,

i

-

alpha

×

(

pa_mdl

⁢

_out

n

,

i

-

S

n

G

n

,

i

)

,

wherein S n represents segment n and is composed of samples n*B−M to n+1*B−1 of the desired output signal of the non-linear power amplifier, pa_mdl_in n,i is an input signal of a forward model of the non-linear power amplifier for segment n and iteration i, pa_mdl_out n,i is an output signal of the forward model of the non-linear power amplifier for segment n and iteration i, G n,i is an gain of the forward model of the non-linear power amplifier for segment n and iteration i which can be calculated by pa_mdl_in n,i and pa_mdl_out n,i , alpha is in a range from 0 to 1, and pa_mdl_in_corr n,i is an input correction signal for segment n and iteration i,

wherein pa_mdl_in n,1 is S n divided by an estimated gain of the forward model, pa_mdl_in n,i+1 is obtained by concatenating samples B to B+M−1 of pa_mdl_in n−1,end and samples M to B+M−1 of pa_mdl_in_corr n,i , pa_mdl_in n−1,end is an input signal of a forward model of the non-linear power amplifier for segment n−1 of a final iteration, and pa_mdl_in 0,end is 0,

whereby the input signal of the non-linear power amplifier is obtained by concatenating samples M to B+M−1 of the input signals of the forward model of the non-linear power amplifier of the last iteration for all segments,

wherein the forward model of the non-linear power amplifier is a zero delay and memory limited forward model, and an output of the forward model is related to a current input sample and previous M−1 samples of the forward model.

6. The apparatus according to claim 5 , wherein the estimated gain of the non-linear power amplifier is specified by a manufacturer of the non-linear power amplifier.

7. The apparatus according to claim 5 , wherein the estimated gain of the non-linear power amplifier is obtained by measuring the non-linear power amplifier when a low power signal is input into the non-linear power amplifier.

8. The apparatus according to claim 5 , further comprising:

an electronic signal generator for repeatedly generating a signal which is the calculated input signal of the non-linear power amplifier;

a signal capturing device for capturing an output signal of the non-linear power amplifier, such that at least one period of the signal being generated by the electronic signal generator is captured; and

a filter for filtering out frequencies that can not be generated by the electronic signal generator and can not be captured by the signal capturing device from a signal of subtracting pa_out_desired from pa_out n .

9. The apparatus according to claim 8 , bandwidths of the electronic signal generator and the signal capturing device are related to the non-linear power amplifier.

10. The apparatus according to claim 8 , the signal capturing device is configured to capture the output signal of the non-linear power amplifier for iteration n more than one times, whereby an averaged result of more than one captures is taken as pa_out n .

11. The apparatus according to claim 8 , further comprising:

an inverse model of the signal capturing device for post-processing the output signal of the non-linear power amplifier captured by the signal capturing device, whereby a linearity of the signal capturing device can be improved.

12. The apparatus according to claim 5 , further comprising:

a simulator for performing a simulation algorithm by using the calculated input signal of the non-linear power amplifier and a corresponding time aligned output signal of the non-linear power amplifier, to simulate an inverse model of the non-linear power amplifier,

whereby the power amplifier is linearized by using the simulated inverse model of the non-linear power amplifier.

13. An apparatus for linearizing a non-linear power amplifier, comprising:

a device for performing an iteration algorithm by using a desired output signal of the non-linear power amplifier, to calculate an input signal of the non-linear power amplifier, wherein during iteration n+1, the input signal is adjusted to cancel out the difference between actual output signal and the desired output signal that measured during iteration n, n is an positive integer;

whereby with the calculated input signal of the non-linear power amplifier, the non-linear power amplifier is linearized; and

a simulator for performing a simulation algorithm by using the calculated input signal of the non-linear power amplifier and a corresponding time aligned output signal of the non-linear power amplifier, to simulate an inverse model of the non-linear power amplifier,

whereby the power amplifier is linearized by using the simulated inverse model of the non-linear power amplifier.