Apparatuses and methods for compensating phase fluctuations
The present disclosure relates to methods and apparatuses for compensating carrier or clock signal phase fluctuations. An apparatus comprises a digital phase locked loop ( 210 ) comprising a phase error output ( 214 ) for a phase error ( 216 ) between a reference signal ( 218 ) and an output signal ( 212 ) generated by the digital phase locked loop, and a phase rotator ( 220 ) coupled to the phase error output ( 214 ) and configured to rotate a phase of a data signal based on the phase error ( 216 ).
1. Apparatus for compensating phase fluctuations, comprising:
a digital phase locked loop comprising a phase error output for a phase error between a reference signal and an output signal generated by the digital phase locked loop;
filter circuitry coupled between the phase error output and a phase rotator and configured to separate the phase error from noise; and
the phase rotator coupled to the phase error output and configured to rotate a phase of a data signal based on the filtered phase error.
2. The apparatus of claim 1 , further comprising:
a signal combiner configured to combine the data signal with the output signal prior to or after rotating the phase of the data signal.
3. The apparatus of claim 1 , wherein the data signal a transmit signal.
4. The apparatus of claim 1 , wherein the data signal a receive signal.
5. The apparatus of claim 1 , wherein the data signal is a digital baseband signal.
6. The apparatus of claim 5 , wherein the digital baseband signal is a quadrature modulated signal or a polar modulated signal.
7. The apparatus of claim 5 , further comprising:
a signal combiner configured to combine a received RF signal with the output signal to generate the digital baseband signal.
8. The apparatus of claim 5 , further comprising:
a signal combiner configured to combine the digital baseband signal with the output signal to generate an RF transmit signal.
9. The apparatus of claim 1 , wherein the filter circuitry comprises a digital filter comprising filter coefficients based on phase error samples and/or phase error statistics.
10. The apparatus of claim 1 , wherein the filter circuitry comprises an adaptive digital filter comprising adaptive filter coefficients based on decision feedback.
11. The apparatus of claim 1 , wherein the filter circuitry comprises a non-causal filter.
12. The apparatus of claim 1 , wherein the filter circuitry comprises a low-pass filter.
13. The apparatus of claim 1 , wherein the filter circuitry comprises a linear filter, in particular a linear MMSE filter.
14. Transmitter circuitry, comprising:
a digital phase locked loop configured to generate a carrier signal and to determine a phase error between a reference signal and the carrier signal;
a digital non-causal linear filter coupled between the digital phase locked loop and a transmit data path and configured to generate smoothened phase error samples of the phase error; and
a phase rotator coupled between the digital phase locked loop and the transmit data path and configured to rotate a phase of a transmit signal based on the smoothened phase error samples.
15. The transmitter circuitry of claim 14 , further comprising:
a signal combiner configured to combine the transmit signal with the carrier signal to generate an RF transmit signal.
16. Receiver circuitry, comprising:
a digital phase locked loop configured to generate a carrier signal and to determine a phase error between a reference signal and the carrier signal;
a digital non-causal linear filter coupled between the digital phase locked loop and a receive data path and configured to generate smoothened phase error samples of the phase error; and
a phase rotator coupled between the digital phase locked loop and the receive data path and configured to rotate a phase of a receive signal based on the smoothened phase error samples.
17. The receiver circuitry of claim 16 , further comprising:
a signal combiner configured to combine a received RF signal with the carrier signal to generate the receive signal.
18. The receiver circuitry of claim 16 , wherein the digital non-causal linear filter is adaptive based on decision feedback of detected data samples.
19. Method for compensating phase fluctuations, comprising:
determining a phase error between a reference signal and an output signal generated by a digital phase locked loop and generating phase error samples;
filtering the phase error samples of the digital phase locked loop with a digital low pass filter; and
rotating a phase of a data signal based on the filtered phase error samples before or after combining the data signal with the output signal.
20. The method of claim 19 , wherein filtering comprises filtering the phase error samples with a non-causal filter.
21. The method of claim 19 , wherein rotating the phase of the data signal comprises rotating the phase of a quadrature modulated signal and/or a polar modulated signal.