Apparatuses and methods for generating a radio frequency signal, a modulator, a controller for a modulator, and a method for controlling a modulator

1. An apparatus for generating a radio frequency signal, comprising:

a modulator configured to generate the radio frequency signal based on an input signal; and

a controller configured to control the modulator to generate the radio frequency signal using polar modulation, if the input signal has a first characteristic,

wherein the controller is configured to control the modulator to generate the radio frequency signal using quadrature modulation, if the input signal has a different second characteristic

wherein the first characteristic indicates that a sample of the input signal is located in a first region of a constellation diagram, and wherein the second characteristic indicates that the sample is located in a different second region of the constellation diagram.

2. The apparatus of claim 1 , wherein the constellation diagram is spanned by a first axis representing an in-phase component and an orthogonal second axis representing a quadrature component.

3. The apparatus of claim 2 , wherein the first region comprises the first axis and the second axis of the constellation diagram.

4. The apparatus of claim 3 , wherein, in the second region, a maximum distance of the sample to the origin of the constellation diagram is smaller than a first threshold value.

5. The apparatus of claim 4 , wherein, apart from the first axis and the second axis, a minimum distance of the sample to the origin of the constellation diagram is greater than the first threshold value in the first region.

6. The apparatus of claim 1 , wherein the second region corresponds to instantaneous frequencies of the radio frequency signal having a frequency deviation from a desired carrier frequency of the radio frequency signal that is greater than a second threshold value.

7. The apparatus of claim 6 , wherein the first region corresponds to instantaneous frequencies of the radio frequency signal having a frequency deviation from the desired carrier frequency of the radio frequency signal that is smaller than the second threshold value.

8. An apparatus for generating a radio frequency signal, comprising:

a modulator configured to generate the radio frequency signal based on a plurality of samples; and

a control unit configured to control the modulator to generate the radio frequency signal using quadrature modulation for a first sequence of the samples,

wherein the control unit is configured to control the modulator to generate the radio frequency signal using polar modulation for a second sequence of the samples, the second sequence of the samples directly succeeding the first sequence of the samples,

wherein the control unit is configured to calculate a phase of the last sample of the first sequence, and

wherein the control unit is configured to calculate a carrier frequency of the radio frequency signal for the first sequence based on the phase of the last sample of the first sequence.

9. The apparatus of claim 8 , wherein a deviation of a desired carrier frequency of the radio frequency signal to a calculated instantaneous frequency of the radio frequency signal for each sample of the second sequence is smaller than a threshold value.

10. The apparatus of claim 9 , wherein the deviation of the desired carrier frequency of the radio frequency signal to the calculated instantaneous frequency of the radio frequency signal for each sample of the first sequence is greater than the threshold value.

11. The apparatus of claim 8 , wherein the control unit is configured to calculate a required transmission time for transmitting the samples of the first sequence, the first sample of the second sequence and the last sample of a third sequence of the samples, wherein the third sequence directly precedes the first sequence, and wherein the modulator is configured to generate the radio frequency signal using polar modulation for the third sequence of the samples.

12. The apparatus of claim 11 , wherein the modulator is configured to use a first local oscillator signal for generating the radio frequency signal for the third sequence of the samples, and wherein the control unit is configured to calculate the required transmission time for the case that the modulator uses the first local oscillator signal for generating the radio frequency signal for the second sequence of the samples, and to calculate the required transmission time for at least one further case where the modulator uses a second local oscillator signal for generating the radio frequency signal for the second sequence of the samples, wherein the second local oscillator signal has a phase offset relative to the first local oscillator signal.

13. The apparatus of claim 12 , wherein the phase offset is one of 90°, 180° and 270°.

14. The apparatus of claim 12 , wherein the control unit is configured to calculate the carrier frequency of the radio frequency signal for the first sequence based on the required transmission time that is closest to a reference transmission time and the number of samples transmitted in the required transmission time, the reference transmission time corresponding to a desired carrier frequency of the radio frequency signal.

15. The apparatus of claim 14 , wherein the modulator is configured to use the local oscillator signal that corresponds to the required transmission time that is closest to the reference transmission time for generating the radio frequency signal for the second sequence of the samples.

16. A method for generating a radio frequency signal, comprising:

generating the radio frequency signal based on an input signal using a modulator;

controlling the modulator to generate the radio frequency signal using polar modulation, if the input signal has a first characteristic; and

controlling the modulator to generate the radio frequency signal using quadrature modulation, if the input signal has a different second characteristic,

wherein the first characteristic indicates that a sample of the input signal is located in a first region of a constellation diagram, and wherein the second characteristic indicates that the sample is located in a different second region of the constellation diagram.

17. The method of claim 16 , wherein the constellation diagram is spanned by a first axis representing an in-phase component and an orthogonal second axis representing a quadrature component.

18. The method of claim 17 , wherein the first region comprises the first axis and the second axis of the constellation diagram.

19. The method of claim 18 , wherein, in the second region, a maximum distance of the sample to the origin of the constellation diagram is smaller than a first threshold value.

20. The method of claim 19 , wherein, apart from the first axis and the second axis, a minimum distance of the sample to the origin of the constellation diagram is greater than the first threshold value in the first region.

21. A method for generating a radio frequency signal, comprising:

generating the radio frequency signal based on a plurality of samples using a modulator;

controlling the modulator to generate the radio frequency signal using quadrature modulation for a first sequence of the samples;

controlling the modulator to generate the radio frequency signal using polar modulation for a second sequence of the samples, the second sequence of the samples directly succeeding the first sequence of the samples;

calculating a phase of the last sample of the first sequence; and

calculating a carrier frequency of the radio frequency signal for the first sequence based on the phase of the last sample of the first sequence.

22. The method of claim 21 , wherein calculating a phase of the last sample of the first sequence comprises calculating a required transmission time for transmitting the samples of the first sequence, the first sample of the second sequence and the last sample of a third sequence of the samples, wherein the third sequence directly precedes the first sequence, and wherein the modulator is configured to generate the radio frequency signal using polar modulation for the third sequence of the samples.

23. The method of claim 22 , wherein a first local oscillator signal is used by the modulator for generating the radio frequency signal for the third sequence of the samples, and wherein calculating the phase of the last sample of the first sequence comprises calculating the required transmission time for the case that the modulator uses the first local oscillator signal for generating the radio frequency signal for the second sequence of the samples, and calculating the required transmission time for at least one further case where the modulator uses a second local oscillator signal for generating the radio frequency signal for the second sequence of the samples, wherein the second local oscillator signal has a phase offset relative to the first local oscillator signal.