N-order noise shaper

1. An n-order noise shaper circuit with n≧3, wherein the n-order noise shaper circuit is arranged in a signal path of a transmitter and/or of a receiver of a mobile communication device, and is configured to receive a digital communication signal in a useful frequency band, comprising:

a signal processor circuit in a forward path of the noise shaper circuit; and

an n-order feedback filter circuit in a feedback path of the noise shaper circuit to thereby form a feedback loop, wherein the feedback filter circuit is configured to receive an error signal associated with the signal processor circuit and generate a correction signal, wherein the n-order feedback filter circuit comprises a transmission function H(z)=Σ i=1 n a i z −i+1 , wherein a i comprises polynomial coefficients thereof; and

a correction circuit configured to adjust the digital communication signal at an input of the signal processor circuit based on the correction signal generated by the n-order feedback filter circuit,

wherein a first set of polynomial coefficients of the n-order feedback filter circuit are optimized with respect to the useful frequency band,

wherein a second set of polynomial coefficients are optimized with respect to an optimization aim depending on an overall out of band noise and/or on a maximum out of band noise caused by the signal processor circuit, and

wherein the useful frequency band and a frequency band associated with the overall out of band noise and/or the maximum out of band noise are different.

2. The n-order noise shaper circuit according to claim 1 , wherein the first set of polynomial coefficients comprises a first polynomial coefficient a 1 and/or a second polynomial coefficient a 2 , and wherein the second set of polynomial coefficients comprises one or more further polynomial coefficients.

3. The n-order noise shaper circuit according to claim 1 , further comprising a comparison circuit in the feedback loop coupled to an input and an output of the signal processor circuit which is configured to generate the error signal which indicates a deviation of the digital communication signal input to the signal processor from an output signal of the signal processor circuit.

4. The n-order noise shaper circuit according to claim 1 , wherein the feedback loop is arranged between the output of the signal processor circuit and the correction circuit arranged at the input of the signal processor circuit.

5. The n-order noise shaper circuit according to claim 1 , wherein the feedback filter circuit comprises a feedback filter or a FIR-filter arranged within the feedback loop.

6. The n-order noise shaper circuit according to claim 5 , wherein a delay element is arranged between the feedback filter or the FIR-filter and the correction circuit or integrated into the feedback filter or the FIR-filter.

7. The n-order noise shaper circuit according to claim 1 , wherein the signal processor circuit comprises a quantizer, a digital to analog converter and/or a digital to time converter.

8. The n-order noise shaper circuit according to claim 1 , wherein the signal processor circuit comprises a quantizer coupled to a digital to analog converter at the output.

9. The n-order noise shaper circuit according to claim 1 , wherein the comparison circuit is coupled to the output of the signal processor circuit via an analog to digital converter if the signal processor circuit comprises a digital to analog converter and via a time to digital converter if the signal processor circuit comprises a digital to time converter.

10. The n-order noise shaper circuit according to claim 1 , wherein no lowpass filter is arranged at an output of the signal processor circuit.

11. The n-order noise shaper circuit according to claim 2 , wherein the first polynomial coefficient a 1 and/or the second polynomial coefficient a 2 are selected such that the transmission function H(z)=Σ i=1 n a i z −i+1 has a zero at the frequency of the useful band.

12. The n-order noise shaper circuit according to claim 2 , wherein the first polynomial coefficient a 1 and/or the second polynomial coefficient a 2 and the further polynomial coefficients are disjoint to each other.

13. The n-order noise shaper circuit according to claim 1 , wherein the transmission function H(z)=Σ i=1 n a i z −i+1 has an order of four or more.

14. A mobile communication device configured to perform a mobile communication in a signal path comprising a signal processor circuit of a transmitter and comprising an n-order feedback filter circuit that operates as a noise shaper in generating a correction signal in a feedback path that is employed by a correction circuit to adjust a digital communication signal input to the signal processor circuit in the signal path, wherein the n-order feedback filter circuit comprises a transmission function H(z)=Σ i=1 n a i z −i+1 , with n≧3,

wherein the first polynomial coefficient a 1 and/or the second polynomial coefficient a 2 are optimized with respect to a useful frequency band of the digital communication signal in the signal path,

wherein one or more further polynomial coefficients are optimized with respect to an optimization aim depending on an overall out of band noise and/or on a maximum out of band noise caused by the signal processor circuit,

wherein the signal processor circuit is coupled to a digital to analog converter or comprises a digital to analog converter in the signal path, and

wherein the useful frequency band and a frequency band associated with the overall out of band noise and/or the maximum out of band noise are different.

15. A non-transitory computer readable digital storage medium having stored thereon a computer program having a program code for performing, when running on a computer, a method for optimizing a transmission function H(z)=Σ i=1 n a i z −i+1 of a noise shaper with n≧3, comprising:

electing a first polynomial coefficient a 1 and/or a second polynomial coefficient a 2 with respect to a useful frequency band; and

electing one or more further polynomial coefficients with respect to an optimization aim depending on an overall out of band noise and/or on a maximum out of band noise,

wherein the useful frequency band and a frequency band associated with the overall out of band noise and/or the maximum out of band noise are different.