Apparatus, method and computer program for error compensation

1. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code,

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to

generate transfer function values of in-phase and quadrature channels;

determine compensation coefficients based on the generated transfer function values of the in-phase and quadrature channels; and

generate compensated frequency domain symbols for at least one frequency pair by using the compensation coefficients for compensating for frequency dependent distortion of a base band circuit.

2. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to generate the transfer function values by measuring a test signal.

3. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to generate the compensated frequency domain symbols for a single frequency component located between the at least one frequency pair.

4. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to determine compensation coefficients by using at least one of an amplitude response of the in-phase channel, a phase response of the in-phase channel, an amplitude response of the quadrature channel, a phase response of the quadrature channel, a base band frequency component, a base band phase difference between the in-phase and quadrature channels, a phase error between oscillator signals, and a gain difference between the in-phase and quadrature channels.

5. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to determine the compensation coefficients by using at least one of a gain at a frequency of a direct current component of the in-phase channel, and a gain at a frequency of a direct current component of the quadrature channel.

6. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to determine the compensation coefficients by comparing differences between the generated transfer function values of the in-phase and quadrature channels.

7. The apparatus according to claim 1 , wherein the apparatus is a transmitter.

8. The apparatus according to claim 1 , wherein the apparatus is a chip set.

9. A method, comprising:

generating transfer function values of in-phase and quadrature channels;

determining compensation coefficients based on the generated transfer function values of the in-phase and quadrature channels; and

generating compensated frequency domain symbols for at least one frequency pair by using the compensation coefficients for compensating for frequency dependent distortion of a base band circuit.

10. The method of claim 9 , further comprising:

generating the transfer function values by measuring a test signal.

11. The method of claim 9 , further comprising:

generating the compensated frequency domain symbols for a single frequency component located between the at least one frequency pair.

12. The method of claim 9 , further comprising:

determining the compensation coefficients by using at least one of a real part of a negative frequency component, an imaginary part of the negative frequency component, a real part of a positive frequency component, an imaginary part of the positive frequency component, a base band frequency component, a base band phase difference between in-phase and quadrature signals, a phase error between oscillator signals, and a gain difference between in-phase and quadrature signals.

13. The method of claim 9 , further comprising:

determining the compensation coefficients by using at least one of a real part of a frequency component at a frequency of a direct current component, and an imaginary part of a frequency component at a frequency of a direct current component.

14. The method of claim 9 , further comprising:

determining the compensation coefficients by comparing differences between the generated transfer function values of the in-phase and quadrature channels.

15. A computer program product, embodied on a non-transitory computer-readable storage medium, encoding a computer program of instructions for executing a computer process, the process comprising:

generating transfer function values of in-phase and quadrature channels;

determining compensation coefficients on a basis of the generated transfer function values of the in-phase and quadrature channels; and

generating compensated frequency domain symbols for at least one frequency pair by using the compensation coefficients for compensating for frequency dependent distortion of a base band circuit.

16. The computer program product of claim 15 , further comprising:

generating the transfer function values by measuring a test signal.

17. The computer program product of claim 15 , further comprising:

generating the compensated frequency domain symbols for a single frequency component located between the at least one frequency pair.

18. The computer program product of claim 15 , further comprising:

determining the compensation coefficients by using at least one of a real part of a negative frequency component, an imaginary part of the negative frequency component, a real part of a positive frequency component, an imaginary part of the positive frequency component, a base band frequency component, a base band phase difference between in-phase and quadrature signals, a phase error between oscillator signals, and a gain difference between in-phase and quadrature signals.

19. The computer program product of claim 15 , further comprising:

determining the compensation coefficients by using at least one of a real part of a frequency component at a frequency of a direct current component, and an imaginary part of a frequency component at a frequency of a direct current component.

20. The computer program of claim 15 , further comprising:

determining the compensation coefficients by comparing differences between the generated transfer function values of the in-phase and quadrature channels.

21. An apparatus, comprising:

processing means for

generating transfer function values of in-phase and quadrature channels;

determining compensation coefficients on a basis of the generated transfer function values of in-phase and quadrature channels; and

generating compensated frequency domain symbols for at least one frequency pair by using the compensation coefficients for compensating for frequency dependent distortion of a base band circuit.

22. The apparatus of claim 21 , wherein the processing means is further for generating the transfer function values by measuring a test signal.

23. The apparatus of claim 21 , wherein the processing means is further for generating the compensated frequency domain symbols for a single frequency component located between the at least one frequency pair.

24. The apparatus of claim 21 , wherein the processing is further for determining the compensation coefficients by using at least one of an amplitude response of an in-phase channel, a phase response of the in-phase channel, an amplitude response of a quadrature channel, a phase response of the quadrature channel, a base band frequency component, a base band phase difference between in-phase and quadrature channels, a phase error between oscillator signals, and a gain difference between in-phase and quadrature channels.

25. The apparatus of claim 21 , wherein the processing means is further for determining the compensation coefficients by using at least one of a gain at a frequency of a direct current component of the in-phase channel and a gain at a frequency of a direct current component of the quadrature channel.

26. The apparatus of claim 21 , wherein the processing means is further for determining the compensation coefficients by comparing differences between the generated transfer function values of the in-phase and quadrature channels.

27. The apparatus according to claim 21 , wherein the apparatus comprises a transmitter.

28. The apparatus according to claim 21 , wherein the apparatus comprises a chip set.