Outphasing transmitter systems and methods
View Patent ↗The present disclosure is directed to a system and method for performing the outphasing technique without using a combiner at the output of two power amplifiers to reduce loss and distortions.
1. A transmitter front-end, comprising:
a modulator configured to produce a first constant-envelope rectangular wave signal of amplitude A 0 and phase (θ−φ) and a second constant-envelope rectangular wave signal of amplitude A 0 and phase (θ+φ), where θ is a modulation angle and φ is an outphasing angle; and
a power amplifier configured to amplify a logical conjunction of the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal to provide an output signal, wherein the power amplifier comprises at least two series coupled switches configured to provide the logical conjunction of the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal.
2. The transmitter front-end of claim 1 , wherein the power amplifier is a class-D power amplifier.
3. The transmitter front-end of claim 1 , wherein the at least two series coupled switches comprise:
a first set of two series transistors coupled between ground and a first end of a primary winding of a balun; and
a second set of two series transistors coupled between ground and a second end of the primary winding of the balun.
4. The transmitter front-end of claim 3 , wherein gates of the first set of two series transistors are respectively coupled to the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal.
5. The transmitter front-end of claim 3 , wherein gates of the second set of two series transistors are respectively coupled to a complement of the first constant-envelope rectangular wave signal and a complement of the second constant-envelope rectangular wave signal.
6. The transmitter front-end of claim 1 , further comprising:
a calibration circuit configured to sweep φ over a range of values and measure amplitude A and phase Ψ of the output signal over the range of values for φ.
7. The transmitter front-end of claim 6 , wherein the calibration circuit is further configured to subtract, for a given value of φ, a value proportional to the measured value of Ψ at the given value of φ from the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal.
8. The transmitter front-end of claim 6 , wherein the calibration circuit is further configured to map φ to φ′ based on the measured value of A at φ′ corresponding to a desired value of A at φ.
9. A transmitter front-end, comprising:
a modulator configured to produce a first constant-envelope rectangular wave signal of amplitude A 0 and phase (θ−φ) and a second constant-envelope rectangular wave signal of amplitude A 0 and phase (θ+φ), where θ is a modulation angle and φ is an outphasing angle;
a power amplifier configured to amplify a logical conjunction of the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal to provide an output signal, wherein the power amplifier comprises at least two series coupled switches configured to provide the logical conjunction of the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal; and
a calibration circuit configured to calibrate an amplitude A and phase Ψ of the output signal by adjusting φ.
10. The transmitter front-end of claim 9 , wherein the power amplifier is a class-D power amplifier.
11. The transmitter front-end of claim 9 , wherein the at least two series coupled switches comprise:
a first set of two series transistors coupled between ground and a first end of a primary winding of a balun; and
a second set of two series transistors coupled between ground and a second end of the primary winding of the balun.
12. The transmitter front-end of claim 11 , wherein gates of the first set of two series transistors are respectively coupled to the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal.
13. The transmitter front-end of claim 11 , wherein gates of the second set of two series transistors are respectively coupled to a complement of the first constant-envelope rectangular wave signal and a complement of the second constant-envelope rectangular wave signal.
14. The transmitter front-end of claim 11 , wherein the calibration circuit is further configured to sweep φ over a range of values and measure A and Ψ over the range of values for φ.
15. The transmitter front-end of claim 14 , wherein the calibration circuit is further configured to subtract, for a given value of φ, a value proportional to the measured value of Ψ at the given value of φ from the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal.
16. The transmitter front-end of claim 14 , wherein the calibration circuit is further configured to map φ to φ′ based on the measured value of A at φ′ corresponding to a desired value of A at φ.
17. A method, comprising:
producing a first constant-envelope rectangular wave signal of amplitude A 0 and phase (θ−φ), where θ is a modulation angle and φ is an outphasing angle;
producing a second constant-envelope rectangular wave signal of amplitude A 0 and phase (θ+φ); and
amplifying, using a power amplifier, a logical conjunction of the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal to provide an output signal,
wherein the logical conjunction of the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal is provided by at least two series coupled switches of the power amplifier.
18. The method of claim 17 , further comprising:
sweeping φ over a range of values; and
measuring amplitude A and phase Ψ of the output signal over the range of values for φ.
19. The method of claim 18 , further comprising:
subtracting, for a given value of φ, a value proportional to the measured value of Ψ at the given value of φ from the first constant-envelope rectangular wave signal and the second constant-envelope rectangular wave signal.
20. The method of claim 18 , further comprising:
mapping φ to φ′ based on the measured value of A at φ′ corresponding to a desired value of A at φ.