Interference reduction between RF communications bands

1. Circuitry comprising:

radio frequency (RF) power amplifier (PA) circuitry comprising a quadrature RF PA and adapted to:

receive and amplify an RF input signal using the quadrature RF PA to provide an RF output signal using an envelope power supply signal;

operate in one of a normal RF spectral emissions mode and a reduced RF spectral emissions mode, wherein a quadrature balance of the quadrature RF PA is better in the reduced RF spectral emissions mode than in the normal RF spectral emissions mode;

when reduced RF spectral emissions are required, operate in the reduced RF spectral emissions mode, such that the quadrature RF PA has higher PA linearity in the reduced RF spectral emissions mode than during the normal RF spectral emissions mode; and

when reduced RF spectral emissions are not required, operate in the normal RF spectral emissions mode; and

a PA envelope power supply adapted to provide the envelope power supply signal.

2. The circuitry of claim 1 wherein when the reduced RF spectral emissions are not required, the RF PA circuitry is further adapted to operate in the normal RF spectral emissions mode.

3. The circuitry of claim 1 wherein at a given RF output power, during the reduced RF spectral emissions mode, RF spectral emissions of the RF output signal are less than during the normal RF spectral emissions mode.

4. The circuitry of claim 1 wherein:

the RF output signal falls within one of a plurality of RF communications bands;

the plurality of RF communications bands comprises a first RF communications band, which is about adjacent to a second RF communications band; and

when the one of the plurality of RF communications bands is the first RF communications band, reduced RF spectral emissions are required.

5. The circuitry of claim 1 wherein:

the RF output signal falls within one of a plurality of RF communications bands;

the plurality of RF communications bands comprises a first RF communications band, which is about adjacent to a second RF communications band; and

when the one of the plurality of RF communications bands is the first RF communications band and an RF output power from the quadrature RF PA is higher than an RF output power threshold, reduced RF spectral emissions are required.

6. The circuitry of claim 5 wherein the first RF communications band is a cellular communications band and the second RF communications band is a non-cellular communications band.

7. The circuitry of claim 6 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 Public Safety Band.

8. The circuitry of claim 7 wherein a frequency range of the first RF communications band is between about 777 megahertz and about 787 megahertz, and a frequency range of the second RF communications band is between about 788 megahertz and about 798 megahertz.

9. The circuitry of claim 1 wherein at a given RF output power, during the reduced RF spectral emission mode, a magnitude of the envelope power supply signal is higher than during the normal RF spectral emissions mode.

10. The circuitry of claim 1 wherein:

the quadrature RF PA comprises a quadrature final stage; and

during the reduced RF spectral emissions mode, a bias level of the quadrature final stage is different than during the normal RF spectral emissions mode to improve a quadrature balance of the quadrature final stage.

11. The circuitry of claim 10 wherein:

the quadrature RF PA comprises a quadrature driver stage; and

during the reduced RF spectral emissions mode, a bias level of the quadrature driver stage is different than during the normal RF spectral emissions mode to improve a quadrature balance of the quadrature driver stage.

12. The circuitry of claim 1 wherein:

the quadrature RF PA comprises a quadrature driver stage; and

during the reduced RF spectral emissions mode, a bias level of the quadrature driver stage is different than during the normal RF spectral emissions mode to improve a quadrature balance of the quadrature driver stage.

13. The circuitry of claim 1 wherein the RF PA circuitry is hardwired to select the reduced RF spectral emissions mode.

14. The circuitry of claim 1 wherein the RF PA circuitry comprises:

the quadrature RF PA adapted to receive and amplify the RF input signal to provide the RF output signal using the envelope power supply signal;

PA control circuitry adapted to select the one of the normal RF spectral emissions mode and the reduced RF spectral emissions mode; and

PA bias circuitry coupled between the PA control circuitry and the quadrature RF PA.

15. The circuitry of claim 14 wherein:

the RF PA circuitry further comprises a PA-digital communications interface (PA-DCI) coupled between a digital communications bus and the PA control circuitry; and

the PA control circuitry is further adapted to receive information via the digital communications bus and select the one of the normal RF spectral emissions mode and the reduced RF spectral emissions mode based on the information.

16. The circuitry of claim 15 wherein:

the RF output signal falls within one of a plurality of RF communications bands; and

the information identifies the one of the plurality of RF communications bands.

17. The circuitry of claim 16 wherein the information is indicative of an RF output power from the quadrature RF PA.

18. The circuitry of claim 16 wherein the information is indicative of a magnitude of the envelope power supply signal.

19. A method comprising:

receiving and amplifying a radio frequency (RF) input signal using a quadrature RF power amplifier (PA) to provide an RF output signal using an envelope power supply signal;

operating in one of a normal RF spectral emissions mode and a reduced RF spectral emissions mode;

when reduced RF spectral emissions are required, operating in the reduced RF spectral emissions mode, wherein a quadrature balance of the quadrature RF PA is better in the reduced spectral emissions mode than in the normal RF spectral emissions mode;

when reduced RF spectral emissions are not required, operating in the normal RF spectral emissions mode; and

providing the envelope power supply signal.