Reconfigurable directional coupler

1. A directional coupler, comprising:

a first port;

a second port;

a third port;

a fourth port;

a first inductive element coupled between the first port and the second port;

a second inductive element mutually coupled to the first inductive element;

a first switchable conductive path configured to be opened and closed, wherein the first switchable conductive path is coupled between a first location of the second inductive element and the third port;

a second switchable conductive path configured to be opened and closed, wherein the second switchable conductive path is coupled between a second location of the second inductive element and the third port;

a third switchable conductive path configured to be opened and closed; and

a first variable impedance device configured to provide a first variable impedance wherein:

the third switchable conductive path is coupled between the second location of the second inductive element and the fourth port; and

the first variable impedance device is coupled to the fourth port.

2. The directional coupler of claim 1 wherein:

the second inductive element includes a first end and a second end oppositely disposed with respect to the first end;

the first location of the second inductive element is the first end of the second inductive element; and

the second location of the second inductive element is the second end of the second inductive element.

3. The directional coupler of claim 1 wherein the first variable impedance device comprises:

a first variable resistive element configured to vary a first variable resistance of the first variable impedance; and

a first variable capacitive element configured to vary a first variable reactance of the first variable impedance.

4. The directional coupler of claim 3 wherein:

the first variable resistive element comprises a first programmable array of resistors; and

the first variable capacitive element comprises a first programmable array of capacitors.

5. The directional coupler of claim 1 further comprising a fifth port, a fourth switchable conductive path configured to be opened and closed, and a second variable impedance device configured to provide a second variable impedance wherein:

the fourth switchable conductive path is coupled between the first location of the second inductive element and the fifth port; and

the second variable impedance device is coupled to the fifth port.

6. The directional coupler of claim 5 wherein:

the first variable impedance device comprises:

a first variable resistive element configured to vary a first variable resistance of the first variable impedance;

a first variable capacitive element configured to vary a first variable reactance of the first variable impedance;

the second variable impedance device comprises:

a second variable resistive element configured to vary a second variable resistance of the second variable impedance; and

a second variable capacitive element configured to vary a second variable reactance of the second variable impedance.

7. The directional coupler of claim 6 wherein:

the first variable resistive element comprises a first programmable array of resistors;

the first variable capacitive element comprises a first programmable array of capacitors;

the second variable resistive element comprises a second programmable array of resistors; and

the second variable capacitive element comprises a second programmable array of capacitors.

8. The directional coupler of claim 1 wherein the first variable impedance device comprises:

a first variable resistive element configured to vary a first variable resistance of the first variable impedance; and

a first variable capacitive element configured to vary a first variable reactance of the first variable impedance.

9. The directional coupler of claim 8 wherein:

the first variable resistive element comprises a first programmable array of resistors; and

the first variable capacitive element comprises a first programmable array of capacitors.

10. Radio frequency (RF) front end circuitry comprising:

a directional coupler, comprising:

a first port;

a second port;

a third port;

a fourth port;

a first inductive element coupled between the first port and the second port;

a second inductive element mutually coupled to the first inductive element;

a first switchable conductive path configured to be opened and closed, wherein the first switchable conductive path is coupled between a first location of the second inductive element and the third port;

a second switchable conductive path configured to be opened and closed, wherein the second switchable conductive path is coupled between a second location of the second inductive element and the third port;

a third switchable conductive path configured to be opened and closed; and

a first variable impedance device configured to provide a first variable impedance wherein:

the third switchable conductive path is coupled between the second location of the second inductive element and the fourth port; and

the first variable impedance device is coupled to the fourth port; and

control circuitry operable in a first directivity mode and a second directivity mode, wherein the control circuitry is configured to:

close the first switchable conductive path in the first directivity mode;

open the second switchable conductive path in the first directivity mode;

close the second switchable conductive path in the second directivity mode; and

open the first switchable conductive path in the second directivity mode.

11. The RF front end circuitry of claim 10 wherein the directional coupler has a directivity and the directional coupler is configured to:

provide the directivity in a first signal direction from the first port to the second port when the first switchable conductive path is closed and the second switchable conductive path is opened; and

provide the directivity in a second signal direction from the second port to the first port when the first switchable conductive path is opened and the second switchable conductive path is closed.

12. The RF front end circuitry of claim 11 wherein:

the second inductive element includes a first end and a second end oppositely disposed with respect to the first end;

the first location of the second inductive element is the first end of the second inductive element; and

the second location of the second inductive element is the second end of the second inductive element.

13. The RF front end circuitry of claim 11 wherein the first directivity mode is a forward power directivity mode and the second directivity mode is a reverse power directivity mode.

14. The RF front end circuitry of claim 11 wherein the directional coupler further comprises a fifth port, a fourth switchable conductive path configured to be opened and closed, and a second variable impedance device configured to provide a second variable impedance wherein:

the fourth switchable conductive path is coupled between the first location of the second inductive element and the fifth port; and

the second variable impedance device is coupled to the fifth port.

15. The RF front end circuitry of claim 14 wherein the control circuitry is further configured to:

close the third switchable conductive path in the first directivity mode;

open the fourth switchable conductive path in the first directivity mode;

close the fourth switchable conductive path in the second directivity mode; and

open the third switchable conductive path in the second directivity mode.

16. The RF front end circuitry of claim 15 wherein the control circuitry is further configured to:

adjust the first variable impedance of the first variable impedance device in the first directivity mode so as to increase the directivity of the directional coupler in the first signal direction; and

adjust the second variable impedance of the second variable impedance device in the second directivity mode so as to increase the directivity of the directional coupler in the second signal direction.

17. The RF front end circuitry of claim 16 wherein the control circuitry is further configured to:

obtain an operating frequency parameter than indicates an RF operating frequency;

adjust the first variable impedance of the first variable impedance device in the first directivity mode by being configured to set the first variable impedance as a function of the operating frequency parameter so that the first variable impedance substantially matches a first port impedance at the fourth port; and

adjust the second variable impedance of the second variable impedance device in the second directivity mode by being configured to set the second variable impedance as a function of the operating frequency parameter so that the second variable impedance substantially matches a second port impedance at the fifth port.

18. The RF front end circuitry of claim 17 wherein the control circuitry is further configured to:

obtain a Voltage Standing Wave Ratio (VSWR) VSWR parameter that indicates a VSWR;

set the first variable impedance in the first directivity mode as the function of the operating frequency parameter and of the VSWR parameter so that the first variable impedance substantially matches the first port impedance at the fourth port; and

set the second variable impedance in the second directivity mode as the function of the operating frequency parameter and of the VSWR parameter so that the second variable impedance substantially matches the second port impedance at the fifth port.