OPTIMAL SWITCHING FREQUENCY FOR ENVELOPE TRACKING POWER SUPPLY

• US 20130194979A1
• Filed: 01/30/2013
• Published: 08/01/2013
• Est. Priority Date: 01/31/2012
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Levesque, Chris
• Granted Patent: US 9,065,505 B2
• Time in Patent Office: Days
• US Class Current: 370/278
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence

Abstract

A radio frequency (RF) communications system, which includes an RF power amplifier (PA) and an envelope tracking power supply, is disclosed. The RF communications system processes RF signals associated with at least a first RF communications band, which has a first bandwidth. The RF PA receives and amplifies an RF input signal to provide an RF transmit signal using an envelope power supply signal. The envelope tracking power supply provides the envelope power supply signal, which has switching ripple based on a programmable switching frequency. The programmable switching frequency is selected to be greater that the first bandwidth.

Claims

1. A radio frequency (RF) communications system adapted to process RF signals associated with at least a first RF communications band and comprising:

an RF power amplifier (PA) adapted to receive and amplify an RF input signal to provide an RF transmit signal using an envelope power supply signal; and

an envelope tracking power supply adapted to provide the envelope power supply signal, such that;

the first RF communications band has a first bandwidth;

the envelope power supply signal has switching ripple based on a programmable switching frequency; and

the programmable switching frequency is selected to be greater than the first bandwidth.

2. The RF communications system of claim 1 wherein the programmable switching frequency is further selected, such that the programmable switching frequency is high enough to allow the envelope power supply signal to at least partially envelope track the RF transmit signal.

3. The RF communications system of claim 1 wherein the envelope tracking power supply comprises frequency synthesis circuitry adapted to provide a switching clock signal having the programmable switching frequency.

4. The RF communications system of claim 3 wherein control circuitry is adapted to select the programmable switching frequency.

5. The RF communications system of claim 4 further comprising the control circuitry.

6. The RF communications system of claim 1 wherein:

a first guard band is adjacent to the first RF communications band, such that frequencies in the first guard band are greater than frequencies in the first RF communications band;

a first guard band-based bandwidth spans the first RF communications band and the first guard band; and

the programmable switching frequency is further selected to be greater than the first guard band-based bandwidth.

7. The RF communications system of claim 1 wherein the RF communications system is further adapted to process RF signals associated with the first RF communications band and a second RF communications band.

8. The RF communications system of claim 7 wherein a frequency gap is between the first RF communications band and the second RF communications band.

9. The RF communications system of claim 8 wherein a second bandwidth spans the first RF communications band and the frequency gap, such that the programmable switching frequency is further selected to be less than the second bandwidth.

10. The RF communications system of claim 8 wherein:

a third bandwidth spans the first RF communications band, the frequency gap, and the second RF communications band; and

the programmable switching frequency is further selected, such that a second harmonic of the programmable switching frequency is greater than the third bandwidth.

11. The RF communications system of claim 8 wherein:

a first guard band is adjacent to the first RF communications band and overlaps the frequency gap;

a first guard band-based bandwidth spans the first RF communications band and the first guard band; and

the programmable switching frequency is further selected to be greater than the first guard band-based bandwidth.

12. The RF communications system of claim 11 wherein:

a second guard band is adjacent to the second RF communications band and overlaps the frequency gap;

a second guard band-based bandwidth spans the first RF communications band and a portion of the frequency gap that does not overlap the second guard band; and

the programmable switching frequency is further selected to be less than the second guard band-based bandwidth.

13. The RF communications system of claim 12 wherein:

a third guard band is adjacent to the second RF communications band and opposite from the second guard band;

a third guard band-based bandwidth spans the first RF communications band, the frequency gap, the second RF communications band, and the third guard band; and

the programmable switching frequency is further selected, such that a second harmonic of the programmable switching frequency is greater than the third guard band-based bandwidth.

14. The RF communications system of claim 7 wherein the first RF communications band is a 3^rd Generation Partnership Project (3GPP) cellular communications band and the second RF communications band is a 3GPP cellular communications band.

15. The RF communications system of claim 14 wherein the first RF communications band is a long term evolution (LTE) cellular communications band and the second RF communications band is an LTE cellular communications band.

16. The RF communications system of claim 1 wherein the first RF communications band is a 3^rd Generation Partnership Project (3GPP) cellular communications band.

17. The RF communications system of claim 1 further comprising RF front-end circuitry adapted to receive and forward an RF receive signal, such that the RF receive signal is associated with the first RF communications band.

18. The RF communications system of claim 17 wherein the RF transmit signal is associated with the first RF communications band, such that the first RF communications band is a time division duplex (TDD) communications band.

19. The RF communications system of claim 17 wherein the RF communications system is further adapted to process RF signals associated with the first RF communications band and a second RF communications band, such that the RF transmit signal is associated with the second RF communications band.

20. The RF communications system of claim 19 wherein the first RF communications band is a frequency division duplex (FDD) receive band and the second RF communications band is an FDD transmit band.

21. The RF communications system of claim 1 wherein the RF transmit signal is associated with the first RF communications band.

22. The RF communications system of claim 21 further comprising RF front-end circuitry adapted to receive and forward an RF receive signal, wherein the RF communications system is further adapted to process RF signals associated with the first RF communications band and a second RF communications band, such that the RF receive signal is associated with the second RF communications band.

23. The RF communications system of claim 22 wherein the first RF communications band is a frequency division duplex (FDD) transmit band and the second RF communications band is an FDD receive band.

24. A method comprising:

processing radio frequency (RF) signals associated with at least a first RF communications band

receiving and amplifying an RF input signal to provide an RF transmit signal using an envelope power supply signal; and

providing the envelope power supply signal, such that;

the first RF communications band has a first bandwidth;

the envelope power supply signal has switching ripple based on a programmable switching frequency; and

the programmable switching frequency is selected to be greater than the first bandwidth.