Method to mitigate undesired oscillator frequency modulation effects in-side a synthesizer due to interference signals and synthesizer circuit

1. A transmitter circuit comprising:

a synthesizer circuit adapted to generate a local oscillator carrier signal for a baseband signal, the synthesizer circuit comprising:

a controlled oscillator comprising a phase locked loop and an oscillator, wherein the controlled oscillator is configured to generate the local oscillator signal based on a correction signal; and

a pulling compensation circuit configured to generate the correction signal for a present output of the phase locked loop based on an information on an error of the local oscillator signal, an information on the baseband signal and a preceding correction signal for a preceding output of the phase locked loop; and

a mixer circuit configured to mix a signal based on the baseband signal and the local oscillator signal to generate a radio frequency signal.

2. The synthesizer circuit of claim 1 , wherein the pulling compensation circuit is further configured to generate the correction signal based on an iterative approximation algorithm.

3. The synthesizer circuit of claim 1 , wherein the pulling compensation circuit is configured to generate the correction signal using a Least Mean Square or a Least Square approximation.

4. The synthesizer circuit of claim 1 , wherein the correction signal comprises a gain component and a phase component.

5. The synthesizer circuit of claim 4 , wherein the pulling compensation circuit generates the correction signal using a first approximation rule for the gain component and a second approximation rule for the phase component.

6. The synthesizer circuit of claim 4 , wherein the pulling compensation circuit generates the correction signal using the expression:

g·A papd k ·sin(k·α papd (n)+φ), wherein k is an integer factor, g represents the gain component, φ represents the phase component, and α papd and A papd k represent an information on a present sample of the baseband signal.

7. The synthesizer circuit of claim 6 , wherein the integer factor k represents an order of a harmonic of a radio frequency generated by a power amplifier that causes a degradation of the local oscillator signal.

8. The synthesizer circuit of claim 4 , wherein the pulling compensation circuit is configured to use the preceding correction signal as a substitute for the correction signal when generating the correction signal.

9. The synthesizer circuit of claim 1 , further comprising a predistortion circuit configured to generate an information on a present sample of the baseband signal using the present sample of the baseband signal.

10. The synthesizer circuit of claim 1 , further comprising a frequency divider configured to generate a carrier signal to drive a mixer circuit by dividing a frequency of the local oscillator signal by a division factor.

11. The synthesizer circuit of claim 1 , wherein the pulling compensation circuit is configured to use an information on a present sample of the baseband signal as the information on the baseband signal.

12. A transmitter circuit, comprising:

a synthesizer circuit, the synthesizer circuit comprising:

a controlled oscillator comprising a phase locked loop and an oscillator, wherein the controlled oscillator is configured to generate a local oscillator signal based on a correction signal; and

a pulling compensation circuit configured to generate the correction signal for a present output of the phase locked loop based on an information on an error of the local oscillator signal, an information on the baseband signal and a preceding correction signal for a preceding output of the phase locked loop;

a frequency divider configured to generate a carrier signal by dividing a frequency of the local oscillator signal by a division factor; and

a mixer circuit configured to mix a signal based on the baseband signal and the carrier signal to generate a radio frequency signal.

13. The transmitter circuit of claim 12 , further comprising an amplifier configured to amplify the radio frequency signal.

14. The transmitter circuit of claim 13 , further comprising a predistortion circuit, wherein the predistortion circuit is configured to estimate a nonlinearity of the amplifier.

15. The transmitter circuit of claim 14 , wherein the predistortion circuit is configured to estimate a nonlinearity of the amplifier for a harmonic of the radio frequency signal of an order n.

16. The transmitter circuit of claim 15 , wherein n is equal to the division factor.

17. The transmitter circuit of claim 16 , wherein the division factor is 2 or 4.

18. The transmitter circuit of claim 12 , wherein the pulling compensation circuit is configured to generate the correction signal such that a degradation of a phase noise of the local oscillator signal which is caused by an amplifier using the local oscillator signal is reduced or minimized.

19. A method for generating a radio frequency signal based on a local oscillator signal for a baseband signal, the method comprising:

generating the local oscillator signal by a phase locked loop and an oscillator based on a correction signal; and

generating the correction signal for a present output of the phase locked loop based on an information on an error of the local oscillator signal, an information on a present sample of the baseband signal and a preceding correction signal for a preceding output of the phase locked loop; and

mixing a signal based on the baseband signal and the local oscillator signal to generate the radio frequency signal.

20. The method of claim 19 , comprising generating the correction signal using an iterative approximation algorithm.

21. The method of claim 19 , comprising generating the correction signal using a Least Mean Square or a Least Square approximation algorithm.

22. The method of claim 19 , wherein the correction signal comprises a gain component and a phase component.

23. The method of claim 22 , comprising:

using a first approximation rule for a present estimate of the gain component g est (n) according to: g est (n)=g est (n−1)−μ gain ·g gradient (n), wherein g est (n−1) is a preceding estimate of the gain component; and

using a second approximation rule for a present estimate of the phase component φ est (n) according to: φ est (n)=φ est (n−1)−μ φ ·φ gradient (n), wherein φ est (n−1) is a preceding estimate of the phase component;

wherein g gradient is calculated according to:

g

gradient

⁡

(

n

)

=

∂

e

2

∂

g

=

2

·

e

·

A

papd

k

·

(

k

·

α

papd

⁡

(

n

)

+

φ

est

)

*

TF

⁢

⁢

1

⁢

(

n

)

 and

wherein φ gradient is calculated according to:

φ

gradient

⁡

(

n

)

=

∂

e

2

⁡

(

n

)

∂

φ

=

2

·

e

⁡

(

n

)

·

g

est

⁡

(

n

-

1

)

·

A

papd

k

⁡

(

n

)

·

cos

⁡

(

k

·

α

papd

⁡

(

n

)

+

φ

est

⁡

(

n

-

1

)

)

*

TF

⁢

⁢

1

⁢

(

n

)

,

wherein α papd and A papd k represent the information on a present sample of the baseband signal, e represents a present error of the local oscillator signal, k being the order of a harmonic causing the degradation and TF1 represents a Transfer function of the phase lock loop.

24. A mobile telecommunications device comprising a transmitter circuit, the transmitter circuit comprising:

a synthesizer circuit comprising:

a controlled oscillator comprising a phase locked loop and an oscillator, wherein the controlled oscillator is configured to generate a local oscillator signal based on a correction signal; and

a pulling compensation circuit configured to generate the correction signal for a present output of the phase locked loop based on an information on an error of the local oscillator signal, an information on a baseband signal and a preceding correction signal for a preceding output of the phase locked loop; and

a mixer circuit configured to mix a signal based on the baseband signal and the local oscillator signal to generate a radio frequency signal.