Power- conserving drive-modulation method for envelope-elimination-and-restoration (EER) transmitters

• US 6,256,482 B1
• Filed: 04/04/1998
• Issued: 07/03/2001
• Est. Priority Date: 04/07/1997
• Status: Expired due to Term

• Current Assignee: Frederick H. Raab
• Original Assignee: Frederick H. Raab
• Inventors: Raab, Frederick H.
• Primary Examiner(s): Nguyen, Lee
• Assistant Examiner(s): Nguyen, Simon
• Application Number:
  US09/055,165
• Time in Patent Office: 1,186 Days
• Field of Search: 455/108, 455/93, 455/102, 455/127, 332/149, 332/159, 332/151, 330/200, 330/199, 330/136, 330/110
• US Class Current: 455/108
• CPC Class Codes: H03F 1/0227 using supply converters

Abstract

A method and a circuit for high-efficiency linear RF-power amplification over a wide range of amplitudes from zero to peak output includes a final RF-power amplifier operating at or near saturation, an RF driver amplifier, a high-level amplitude modulator for the final amplifier, preferably a high-level amplitude modulator for the driver amplifier, and a means for determining the supply-voltage input to the final amplifier and for controlling the amplitude of the drive. The means for determining the supply-voltage input and for controlling the amplitude acts so that the final amplifier drive varies from a minimum level to peak as the desired transmitter output varies from zero to peak. The transmitter is preferably of the envelope-elimination-and-restoration type or the envelope-tracking type.

Claims

1. A transmitter, comprising:

a) a first amplifier, said first amplifier having a signal input, a first supply-voltage input, and a first amplifier output;

b) a driver having a second supply-voltage input and a driver output; and

c) a final amplifier having a final amplifier input coupled to said driver output, said final amplifier having a drive level, an RF output, and a third supply-voltage input, and said first amplifier being coupled to said third supply-voltage input of said final amplifier for modulating said final amplifier, said transmitter being characterized in that;

said first amplifier is also coupled to said second supply-voltage input of said driver for modulating said driver, whereby said first amplifier performs as a first modulator and said transmitter being further characterized in that said drive level of said final amplifier is controlled by a DC offset voltage applied to said driver for setting said minimum drive level for ensuring linear modulation of said final amplifier.

2. A transmitter as recited in claim 1, wherein said transmitter is of the envelope-elimination-and-restoration type.

3. A transmitter as recited in claim 1, wherein said transmitter is of the envelope-tracking type.

4. A transmitter as recited in claim 1, further comprising a first filter for filtering said first amplifier output.

5. A transmitter as recited in claim 1, further comprising a second filter for filtering said final amplifier output.

6. A transmitter as in claim 1, wherein said first amplifier comprises an amplifier selected from the group consisting of Class S, Class G, pulse step, and split band amplifiers, and combinations thereof.

7. A transmitter as in claim 1, wherein said final amplifier comprises an amplifier selected from the group consisting of Class A, Class B, Class C, Class D, Class E, and Class F amplifiers, and combinations thereof.

8. A transmitter comprising:

a) a first modulator, said first modulator having a first signal input, a first supply-voltage input, and a first modulator output;

b) a second modulator separate from said first modulator, said second modulator having a second signal input, a second supply-voltage input, and a second modulator output;

c) a driver having a third supply-voltage input and a driver output, said second modulator output being coupled to said third supply-voltage input of said driver for modulating said driver; and

d) a final amplifier having a final amplifier input coupled to said driver output, said final amplifier having a drive level, an RF output, and a fourth supply-voltage input, said first modulator output being coupled to said fourth supply-voltage input of said final amplifier for modulating said final amplifier.

9. A transmitter as recited in claim 8, wherein said transmitter is of the envelope-elimination-and-restoration type.

10. A transmitter as recited in claim 8, wherein said transmitter is of the envelope-tracking type.

11. A transmitter as recited in claim 8, said final amplifier having a drive level, wherein said drive level of said final amplifier is controlled to maintain a minimum drive level for ensuring linear modulation of said final amplifier.

12. A transmitter as recited in claim 8, further comprising a first filter for filtering said first modulator output.

13. A transmitter as recited in claim 8, further comprising a second filter for filtering said final amplifier output.

14. A transmitter as recited in claim 8, further comprising a third filter for filtering said second modulator output.

15. A transmitter as in claim 8 wherein said first modulator comprises an amplifier selected from the group consisting of Class S, Class G, pulse step, and split band amplifiers, and combinations thereof.

16. A transmitter as in claim 8 wherein said second modulator comprises an amplifier selected from the group consisting of Class S, Class G, pulse step, and split band amplifiers, and combinations thereof.

17. A transmitter as in claim 8, further comprising an envelope detector whose envelope output is coupled to said signal input of said first modulator.

18. A transmitter as in claim 17 further comprising a summing circuit coupled between said envelope detector and said driver.

19. A transmitter as in claim 18, wherein said summing circuit comprises:

i) a variable gain control device;

ii) a summing device, said variable gain control device being coupled between said envelope detector and said summing device; and

iii) a variable DC bias control device coupled to said summing device for controlling said drive level of said final amplifier to maintain a minimum drive level for ensuring linear modulation of said final amplifier.

20. A transmitter having a signal input, said transmitter comprising:

a) an envelope detector for forming an envelope signal;

b) a delay module, said signal input being coupled to both said envelope detector and said delay module;

c) a limiter coupled to said delay module;

d) a first modulator, said first modulator having a first supply-voltage input and a first modulator output;

e) a second modulator separate from said first modulator, said second modulator having a second supply-voltage input and a second modulator output, said envelope detector being coupled to both said first and second modulators;

f) a local oscillator and a mixer coupled to said limiter for providing a delayed phase-modulated signal;

g) a driver accepting said delayed phase-modulated signal, said driver having a third supply-voltage input and a driver output, said second modulator output being coupled to said third supply-voltage input of said driver for modulating said driver; and

h) a final amplifier having a final amplifier input coupled to said driver output, said final amplifier having a drive level, an RF output, and a fourth supply-voltage input, said first modulator output being coupled to said fourth supply-voltage input of said final amplifier for modulating said final amplifier.

21. A transmitter as recited in claim 20, wherein said signal input of said transmitter is provided by a modulator producing an analog RF signal at the desired frequency of said RF output of said final amplifier or at a suitable intermediate frequency.

22. A transmitter as recited in claim 20, wherein said drive level of said final amplifier is controlled to maintain a minimum drive level for ensuring linear modulation of said final amplifier.

23. A transmitter as in claim 20 further comprising a summing circuit coupled between said envelope detector and said driver.

24. A transmitter as in claim 23, wherein said summing circuit comprises:

i) a variable gain control device;

ii) a summing device, said variable gain control device being coupled between said envelope detector and said summing device; and

iii) a variable DC bias control device coupled to said summing device for controlling said drive level of said final amplifier to maintain a minimum drive level for ensuring linear modulation of said final amplifier.

25. A transmitter having an RF signal input, said transmitter comprising:

a) a modulator, said modulator having an envelope signal input, a first supply-voltage input, and a modulator output;

b) a driver having a driver input, a second supply-voltage input, and a driver output;

c) an envelope detector operating on said signal input of said transmitter and whose envelope output is coupled to said envelope signal input of said modulator;

d) a final amplifier having a final amplifier input coupled to said driver output, said final amplifier having a drive level, an RF output, and a third supply-voltage input, said modulator output being coupled to said third supply-voltage input of said final amplifier for modulating said final amplifier; and

e) a first variable gain control device operating on said RF signal input and coupled to said driver input.

26. A transmitter as recited in claim 25, further comprising:

f) a delay module operating on said signal input of said transmitter;

g) a limiter coupled to said delay module; and

h) a local oscillator and a mixer coupled to said limiter for providing a delayed phase-modulated signal.

27. A transmitter as recited in claim 25, further comprising a summing circuit coupled between said envelope detector and said first variable gain control device.

28. A transmitter as recited in claim 27, wherein said summing circuit comprises:

i) a second variable gain control device;

ii) a summing device, said second variable gain control device being coupled between said envelope detector and said summing device; and

iii) a variable DC bias control device coupled to said summing device for controlling said drive level of said final amplifier to maintain a minimum drive level for ensuring linear modulation of said final amplifier.

29. A transmitter as recited in claim 25, wherein said RF signal input of said transmitter is provided by a modulator producing an analog RF signal at the desired frequency of said RF output of said final amplifier or at a suitable intermediate frequency.

30. A transmitter having a baseband or other input, comprising:

a) a first modulator, said first modulator having a first signal input, a first supply-voltage input, and a first modulator output;

b) a second modulator separate from said first modulator, said second modulator having a second signal input, a second supply-voltage input, and a second modulator output;

c) a driver having a third supply-voltage input and a driver output, said second modulator output being coupled to said third supply-voltage input of said driver for modulating said driver;

d) a digital signal processor and digital-to-analog converter circuit, said digital signal processor operating on said baseband or other input of the transmitter and said circuit having a first analog or digital envelope output coupled to said first modulator, and a second analog or digital output coupled to said second modulator, said second analog or digital output including both gain and DC-offset adjustments to said envelope; and

e) a final amplifier having a final amplifier input coupled to said driver output, said final amplifier having a drive level, an RF output, and a fourth supply-voltage input, said first modulator output being coupled to said fourth supply-voltage input of said final amplifier for modulating said final amplifier.

31. A transmitter as in claim 30, further comprising:

a quadrature modulator circuit coupled between said digital signal processor and digital-to-analog converter circuit and said driver.

32. A transmitter as in claim 30, further comprising:

i) a quadrature modulator circuit;

ii) a frequency source; and

iii) a mixer, said quadrature modulator circuit being coupled between said digital signal processor and digital-to-analog converter circuit and said mixer;

said frequency source being coupled to said mixer, and said mixer being coupled to said driver input.