Apparatus, system, and method for digital base modulation of power amplifier in polar transmitter

1. A multi-mode polar transmitter comprising:

a filter configured to receive a polar modulated signal and to provide an amplitude signal;

a first amplifier;

a second amplifier; and

a switch to be coupled to said filter and configured to selectively provide one of said first and second amplifiers the amplitude signal;

each amplifier including a bias interface circuit comprising

a first substrate comprising a first material and a second substrate comprising a second material different from the first material,

a first transistor on said first substrate and having a control terminal configured to receive a bias current, and a first conduction terminal configured to provide a power supply signal, and

a second transistor on said second substrate and having

a control terminal to be coupled to the first conduction terminal of said first transistor and being configured to receive the amplitude signal, a phase modulated carrier signal, and the power supply signal, and

a first conduction terminal configured to provide a combined waveform of the amplitude signal, the phase modulated carrier signal, and the power supply signal.

2. The multi-mode polar transmitter of claim 1 further comprising a correction circuit configured to pre-distort the amplitude signal for reducing non-linearity of said second transistor.

3. The multi-mode polar transmitter of claim 2 wherein said correction circuit is configured to pre-distort the phase modulated carrier signal for reducing non-linearity of said second transistor.

4. The multi-mode polar transmitter of claim 1 further comprising a digital-to-analog converter (DAC) having an output to be coupled to said filter and configured to receive the polar modulated signal and digital segment control data.

5. The multi-mode polar transmitter of claim 1 wherein a voltage on the first conduction terminal of said second transistor is changed based an output power of said second transistor.

6. The multi-mode polar transmitter of claim 1 wherein said first amplifier comprises a high band amplifier.

7. The multi-mode polar transmitter of claim 1 wherein said second amplifier comprises a low band amplifier.

8. A multi-mode polar transmitter comprising:

a filter configured to receive a polar modulated signal and to provide an amplitude signal;

a high band amplifier;

a low band amplifier;

a switch to be coupled to said filter and configured to selectively provide one of said high band and low band amplifiers the amplitude signal; and

a digital-to-analog converter (DAC) having an output to be coupled to said filter and configured to receive the polar modulated signal and digital segment control data;

each amplifier including a bias interface circuit comprising

a first substrate comprising a first material and a second substrate comprising a second material different from the first material,

a first transistor on said first substrate and having a control terminal configured to receive a bias current, and a first conduction terminal configured to provide a power supply signal, and

a second transistor on said second substrate and having

a control terminal to be coupled to the first conduction terminal of said first transistor and being configured to receive the amplitude signal, a phase modulated carrier signal, and the power supply signal, and

a first conduction terminal configured to provide a combined waveform of the amplitude signal, the phase modulated carrier signal, and the power supply signal.

9. The multi-mode polar transmitter of claim 8 further comprising a correction circuit configured to pre-distort the amplitude signal for reducing non-linearity of said second transistor.

10. The multi-mode polar transmitter of claim 9 wherein said correction circuit is configured to pre-distort the phase modulated carrier signal for reducing non-linearity of said second transistor.

11. The multi-mode polar transmitter of claim 8 wherein a voltage on the first conduction terminal of said second transistor is changed based an output power of said second transistor.

12. A method of operating a multi-mode polar transmitter receiving a polar modulated signal, the method comprising:

using a switch coupled to selectively provide one of first and second amplifiers an amplitude signal based upon the polar modulated signal;

receiving a bias current at a control terminal of a first transistor in a bias interface circuit of each amplifier, the first transistor being on a first substrate comprising a first material;

providing a power supply signal at a first conduction terminal of the first transistor;

receiving the amplitude signal, a phase modulated carrier signal, and the power supply signal at a control terminal of a second transistor, the control terminal of the second transistor being coupled to the first conduction terminal of the first transistor, the second transistor being on a second substrate comprising a second material different from the first material;

providing a combined waveform of the amplitude signal, the phase modulated carrier signal, and the power supply signal at a first conduction terminal of the second transistor; and

transmitting the combined waveform.

13. The method of claim 12 further comprising pre-distorting the amplitude signal for reducing non-linearity of the second transistor.

14. The method of claim 12 further comprising receiving with a digital-to-analog converter (DAC) the polar modulated signal and digital segment control data.

15. The method of claim 12 further comprising pre-distorting the phase modulated carrier signal for reducing non-linearity of the second transistor.

16. The method of claim 12 further comprising changing a voltage on the first conduction terminal of the second transistor based an output power of the second transistor.