RF transmitter, integrated circuit device, wireless communication unit and method therefor

1. A radio frequency (RF) transmitter comprising:

at least one digital signal processing module comprising:

at least one noise shaping component and at least one digital pre-distortion component, wherein the at least one noise shaping component is arranged to:

receive at least one complex input signal,

receive at least one feedback signal from the at least one digital pre-distortion component,

apply noise-shaping to the at least one complex input signal based at least partly on the at least one feedback signal, and

output at least one noise shaped complex input signal; and

wherein the at least one digital pre-distortion component is arranged to:

receive the at least one noise-shaped complex input signal comprising information to be transmitted over an RF interface,

perform two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase digital pre-distortion control word and a further, quadrature digital pre-distortion control word, and

output the in-phase and quadrature digital pre-distortion control words; and

at least one power amplifier module comprising a digital power amplifier (DPA) having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells, wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one noise-shaped complex input signal, and wherein two-dimensional non-uniform mapping comprises a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells, wherein each of the switch-mode power cells is arranged to:

receive the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module, and

generate the analog RF signal for transmission over the RF interface based at least partly on the in-phase and quadrature digital pre-distortion control words.

2. The RF transmitter of claim 1 wherein the at least one digital pre-distortion component is arranged to:

identify a closest matching predefined vector for the received noise-shaped complex input signal within the pre-distortion profile; and

map the identified closest matching predefined vector to a set of digital control words to be output.

3. The RF transmitter of claim 1 wherein the at least one noise shaping component and the at least one digital pre-distortion component form at least part of a delta sigma modulator.

4. The RF transmitter of claim 1 wherein the at least one digital signal processing module comprises an up-sampling component arranged to perform up-sampling of the received at least one complex input signal thereby increasing a sample rate of the received at least one complex input signal to an input data rate of the DPA.

5. The RF transmitter of claim 1 wherein:

the first array of switch-mode power cells is arranged to receive at least a part of the first, in-phase digital control word and to generate a first, in-phase, component of the analog RF signal based at least partly on the first, in-phase, digital control word; and

the at least one further array of switch-mode power cells is arranged to receive the at least one further, quadrature, digital control word and to generate at least one further, quadrature, component of the analog RF signal based at least partly on the at least one further, quadrature, digital control word.

6. The RF transmitter of claim 5 wherein the first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells are further arranged to receive respective carrier frequency signals, and to generate the respective in-phase and quadrature components of the analog RF signal further based at least partly on the received carrier frequency signals.

7. The RF transmitter of claim 6 wherein the at least one power amplifier module comprises

a first, in-phase, phase selector arranged to receive a carrier frequency signal and a first, in-phase, sign signal, and to output a first, in-phase, carrier frequency signal for the first, in-phase, array of switch-mode power cells; and

at least one further, quadrature, phase selector arranged to receive the carrier frequency signal and at least one further, quadrature, sign signal, and to output at least one further, quadrature, carrier frequency signal for the at least one further, quadrature, array of switch-mode power cells.

8. The RF transmitter of claim 1 wherein the at least one power amplifier module comprises a magnitude and sign generator module arranged to:

directly receive the digital pre-distortion control words output by the digital signal processing module; and

generate from each digital pre-distortion control word a magnitude control word comprising a magnitude component of the respective digital pre-distortion control word, and a sign signal comprising a sign component of the respective digital pre-distortion control word.

9. The RF transmitter of claim 1 wherein each array of switch-mode power cells comprises a plurality of inverse Class D structure switch-mode power cells.

10. An integrated circuit device comprising:

at least one digital signal processing module comprising:

at least one noise shaping component and at least one digital pre-distortion component, wherein the at least one noise shaping component is arranged to:

receive at least one complex input signal,

receive at least one feedback signal from the at least one digital pre-distortion component,

apply noise-shaping to the at least one complex input signal based at least partly on the at least one feedback signal, and

output at least one noise-shaped complex input signal; and

wherein the at least one digital pre-distortion component is arranged to:

receive at least one noise-shaped complex input signal comprising information to be transmitted over a radio frequency (RF) interface,

perform two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase digital pre-distortion control word and at least one further, quadrature digital pre-distortion control word, and

an output port arranged to output the in-phase and quadrature digital pre-distortion control words to at least one power amplifier module comprising a digital power amplifier, DPA, having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells, wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one complex input signal, and wherein two-dimensional non-uniform mapping comprising a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells, wherein each of the switch-mode power cells is arranged to receive the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module,

such that a combined output of the switch-mode power cells produces the analog RF signal for transmission based at least partly on the in-phase and quadrature digital pre-distortion control words.

11. The integrated circuit device of claim 10 wherein the at least one digital pre-distortion component is arranged to:

identify a closest matching predefined vector for the received noise-shaped complex input signal within the pre-distortion profile; and

map the identified closest matching predefined vector to a set of digital control words to be output.

12. The integrated circuit device of claim 10 wherein:

the first array of switch-mode power cells is arranged to receive at least a part of the first, in-phase digital control word and to generate a first, in-phase, component of the analog RF signal based at least partly on the first, in-phase, digital control word; and

the at least one further array of switch-mode power cells is arranged to receive the at least one further, quadrature, digital control word and to generate at least one further, quadrature, component of the analog RF signal based at least partly on the at least one further, quadrature, digital control word.

13. The integrated circuit device of claim 10 wherein the at least one power amplifier module comprises a magnitude and sign generator module arranged to:

directly receive the digital pre-distortion control words output by the digital signal processing module; and

generate from each digital pre-distortion control word a magnitude control word comprising a magnitude component of the respective digital pre-distortion control word, and a sign signal comprising a sign component of the respective digital pre-distortion control word.

14. A wireless communication unit comprising a radio frequency (RF) transmitter comprising:

at least one digital signal processing module comprising:

at least one digital signal processing module comprising:

at least one noise shaping component and at least one digital pre-distortion component, wherein the at least one noise shaping component is arranged to:

receive at least one complex input signal,

receive at least one feedback signal from the at least one digital pre-distortion component,

apply noise-shaping to the at least one complex input signal based at least partly on the at least one feedback signal, and

output at least one noise shaped complex input signal; and

wherein the at least one digital pre-distortion component is arranged to:

receive the at least one noise-shaped complex input signal comprising information to be transmitted over an RF interface,

perform two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase digital control pre-distortion word and a further quadrature digital pre-distortion control word, and

output the in-phase and quadrature digital pre-distortion control words; and

at least one power amplifier module comprising a digital power amplifier, DPA, having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells,

wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one complex input signal, and wherein two-dimensional non-uniform mapping comprises a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells, wherein each of the switch-mode power cells is arranged to:

receive the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module,

such that a combined output of the switch-mode power cells produces the analog RF signal for transmission over the RF interface based at least partly on the in-phase and quadrature digital pre-distortion control words.

15. A method of generating a radio frequency signal for transmission over a radio frequency (RF) interface, the method comprising:

receiving at least one complex input signal comprising information to be transmitted over the RF interface;

receiving at least one feedback signal from at least one digital pre-distortion component;

applying noise shaping to the at least one complex input signal based at least partly on the at least one feedback signal; and

outputting at least one noise-shaped complex input signal;

performing two-dimensional non-uniform mapping of the at least one received noise-shaped complex input signal to a first, in-phase, digital pre-distortion control word and at least one further, quadrature, digital pre-distortion control word;

providing the in-phase and quadrature digital pre-distortion control words to at least one power amplifier module comprising a digital power amplifier, DPA, having a first, in-phase, array of switch-mode power cells and at least one further, quadrature, array of switch-mode power cells;

wherein the first, in-phase digital pre-distortion control word and further, quadrature digital pre-distortion control word are arranged to drive the at least one power amplifier module to output an analog RF signal that represents the at least one complex input signal, and wherein two-dimensional non-uniform mapping comprises a pre-distortion profile that is generated at least partly according to an input/output relationship of the arrays of the switch mode power cells of the DPA to compensate non-linearities of the switch-mode power cells;

receiving the in-phase and quadrature digital pre-distortion control words output by the at least one digital signal processing module, and

combining an output of the switch-mode power cells;

producing the analog RF signal for transmission over the RF interface from the combined output of the switch-mode power cells based at least partly on the in-phase and quadrature digital pre-distortion control words.

16. The method of claim 15 further comprising:

identifying a closest matching predefined vector for the received complex input signal within the pre-distortion profile; and

mapping the identified closest matching predefined vector to a set of digital control words to be output.

17. The method of claim 15 further comprising:

performing up-sampling of the received at least one complex input signal thereby increasing a sample rate of the received at least one complex input signal to an input data rate of the at least one power amplifier module.

18. The method of claim 15 wherein the step of generating an analog RF signal comprises:

the first array of switch-mode power cells receiving at least a part of the first, in-phase digital control word and generating a first, in-phase, component of the analog RF signal based at least partly on the first, in-phase, digital control word; and

the at least one further array of switch-mode power cells receiving the at least one further, quadrature, digital control word and generating at least one further, quadrature, component of the analog RF signal based at least partly on the at least one further, quadrature, digital control word.

19. The method of claim 15 further comprising:

directly receiving the digital pre-distortion control words; and

generating from each digital pre-distortion control word a magnitude control word comprising a magnitude component of the respective digital pre-distortion control word, and a sign signal comprising a sign component of the respective digital pre-distortion control word.