Compensation of the IQ phase asymmetry in quadrature modulation and demodulation methods
View Patent ↗A simplified compensation matrix is set up for the compensation of phase errors between the I and the Q component in data transmission systems with quadrature modulation or demodulation. This simplified compensation matrix permits a previously determined phase error Δφ to be used as the basis for replacing two of the multipliers required in the conventional circuit configurations by relatively simple shift registers ( 4, 5 ) for a multiplication by 1 or by a constant.
1. A method for the compensation of the phase asymmetry between the inphase (I) and the quadrature (Q) components in the case of quadrature modulation or demodulation, comprising the steps of:
determining the phase error Δφ between the uncompensated I and Q components,
obtaining a compensated I component by subtracting from the I component, which is uncompensated, unaltered or multiplied by a constant, the product of the Q component and an error term which is proportional to tan(Δφ/2), and
obtaining a compensated Q component by subtracting from the Q component, which is uncompensated, unaltered or multiplied by a constant, the product of the I component and the error term.
2. The method according to claim 1 , wherein
the error term is equal to tan(Δφ/2)×2 N , wherein N being a natural number, and
the uncompensated I component is multiplied by 2 N when calculating the compensated I component, and
the uncompensated Q component is multiplied by 2 N when calculating the compensated Q component.
3. The method according to claim 1 , wherein
to calculate a vector of the compensated components, a vector of the uncompensated components is multiplied by the compensation matrix
[
1
-
tan
(
Δ
φ
2
)
-
tan
(
Δ
φ
2
)
1
]
.
4. The method according to claim 1 , wherein
a plurality of iterations of the method are passed through,
the number of the iterations being prescribed, or
iterations are passed through until the phase error undershoots a prescribed limit.
5. The method according to claim 1 , wherein
the method is used in a radio signal receiver with an analogue quadrature stage, in particular a directly mixing radio signal receiver.
6. The method according to claim 1 , wherein
the method is used in a radio signal receiver in which a quadrature modulation method is employed.
7. A device for the compensation of the phase asymmetry between the inphase (I) and the quadrature (Q) components in the case of quadrature modulation or demodulation, comprising:
two inputs for uncompensated I and Q components and two outputs for compensated I and Q components,
a calculation unit for calculating an phase error Δφ from the compensated or the uncompensated I and Q components and outputting an error term,
a first multiplier, connected to the calculation unit, for the multiplication of the uncompensated Q component by the error term, generating a first multiplication value,
a second multiplier, connected to the calculation unit, for the multiplication of the uncompensated I component by the error term, generating a second multiplication value,
a first adder, which can be fed the uncompensated I component, which is unaltered or multiplied by a constant, and which adder is fed with the first multiplication value, and
a second adder, which can be fed the uncompensated Q component, which is unaltered or multiplied by a constant, and which adder is fed with the second multiplication value wherein
the error term is equal to tan(Δφ/2)×2 N , and the device further comprises:
a third multiplier for a multiplication of the I component by the factor 2 N before feeding to the first adder, and
a fourth multiplier for a multiplication of the Q component by the factor 2 N before feeding to the second adder.
8. The device according to claim 7 , wherein
the third and/or the fourth multiplier are formed by shift registers which are driven in such a way that bit words fed are shifted by N bit positions in the direction of the most significant bit position.
9. The device according to claim 7 , further comprising:
a third adder following the first adder for adding a constant and a first divider following the third adder for dividing an output of the third adder by a factor 2 N , and
a fourth adder following the second adder for adding a constant and a second divider following the fourth adder for dividing an output of the fourth adder by a factor 2 N .
10. The device according to claim 9 , wherein
the first and/or the second divider are formed by shift registers which are driven in such a way that bit words fed are shifted by N bit positions in the direction of the least significant bit position.
11. A method for the compensation of the phase asymmetry between the inphase (I) and the quadrature (Q) components in the case of quadrature modulation or demodulation, comprising the steps of:
determining the phase error Δφ between the uncompensated I and Q components,
obtaining a compensated I component by subtracting from the I component, which is uncompensated, unaltered or multiplied by a constant, the product of the Q component and an error term dependent on the phase error Δφ, and
obtaining a compensated Q component by subtracting from the Q component, which is uncompensated, unaltered or multiplied by a constant, the product of the I component and the error term, wherein
to calculate a vector of the compensated components, a vector of the uncompensated components is multiplied by the compensation matrix
[
1
-
tan
(
Δ
φ
2
)
-
tan
(
Δ
φ
2
)
1
]
.
12. The method according to claim 11 , wherein
a plurality of iterations of the method are passed through,
the number of the iterations being prescribed, or
iterations are passed through until the phase error undershoots a prescribed limit.
13. The method according to claim 11 , wherein
the method is used in a radio signal receiver with an analogue quadrature stage, in particular a directly mixing radio signal receiver.
14. The method according to claim 11 , wherein
the method is used in a radio signal receiver in which a quadrature modulation method is employed.
15. A method for the compensation of the phase asymmetry between the inphase (I) and the quadrature (Q) components in the case of quadrature modulation or demodulation, comprising the steps of:
determining the phase error Δφ between the uncompensated I and Q components,
obtaining a compensated I component by subtracting from the I component, which is uncompensated, unaltered or multiplied by a constant, the product of the Q component and an error term dependent on the phase error Δφ, and
obtaining a compensated Q component by subtracting from the Q component, which is uncompensated, unaltered or multiplied by a constant, the product of the I component and the error term, wherein
a plurality of iterations of the method are passed through, wherein the number of the iterations is prescribed, or iterations are passed through until the phase error undershoots a prescribed limit.
16. The method according to claim 15 , wherein
the error term is proportional to tan(Δφ/2).
17. The method according to claim 16 , wherein
the error term is equal to tan(Δφ/2)×2 N , wherein N being a natural number, and
the uncompensated I component is multiplied by 2 N when calculating the compensated I component, and
the uncompensated Q component is multiplied by 2 N when calculating the compensated Q component.
18. A method for the compensation of the phase asymmetry between the inphase (I) and the quadrature (Q) components in the case of quadrature modulation or demodulation, comprising the steps of:
determining the phase error Δφ between the uncompensated I and Q components,
obtaining a compensated I component by subtracting from the I component, which is uncompensated, unaltered or multiplied by a constant, the product of the Q component and an error term dependent on the phase error Δφ, and
obtaining a compensated Q component by subtracting from the Q component, which is uncompensated, unaltered or multiplied by a constant, the product of the I component and the error term, wherein
the method is used in a radio signal receiver with an analogue quadrature stage, in particular a directly mixing radio signal receiver or in a radio signal receiver in which a quadrature modulation method is employed.
19. The method according to claim 18 , wherein
the error term is proportional to tan(Δφ/2).
20. The method according to claim 19 , wherein
the error term is equal to tan(Δφ/2)×2 N , wherein N being a natural number, and
the uncompensated I component is multiplied by 2 N when calculating the compensated I component, and
the uncompensated Q component is multiplied by 2 N when calculating the compensated Q component.