Mobile wireless communications device having frequency selective grounding and related method

1. A mobile wireless communications device, comprising:

a portable housing having a metallic front housing configured as a peripheral side wall and forming a metallic ring;

at least one circuit board carried by the portable housing and forming a chassis ground plane wherein the metallic ring is peripheral to and surrounds the circuit board;

a wireless communication circuit carried by a circuit board;

an antenna circuit carried by a circuit board and connected to the wireless communication circuit; and

a frequency selective grounding circuit positioned at a selected grounding location between the chassis grounding plane and metallic ring at a location where the current changes direction and forming a harmonic trap that responds to a specific range of frequencies.

2. The mobile wireless communications device according to claim 1 , wherein a respective frequency selective grounding circuit operates at a specific range of frequencies.

3. The mobile wireless communications device according to claim 1 , wherein a respective frequency selective grounding circuit comprises at least one of a series resonator and parallel resonator having a value depending on bandwidth requirements.

4. The mobile wireless communications device according to claim 3 , and further comprising a series resonator that resonates at high frequencies.

5. The mobile wireless communications device according to claim 1 , wherein a grounding location is specific to the frequency of operation.

6. The mobile wireless communications device according to claim 1 , wherein a frequency selective grounding circuit has a programmable frequency response for grounding.

7. The mobile wireless communications device according to claim 6 , wherein a frequency selective grounding circuit comprises a variable matching device.

8. The mobile wireless communications device according to claim 1 , wherein said antenna comprises a planar inverted F antenna.

9. The mobile wireless communications device according to claim 1 , wherein said wireless communications circuit comprises a cellular communications circuit.

10. The mobile wireless communications device according to claim 1 , and further comprising a display and user input device both carried by the portable housing and connected to said wireless communication circuit.

11. A mobile wireless communications device, comprising:

a portable housing having a metallic front housing configured as a peripheral side wall and forming a metallic ring;

at least one circuit board carried by the portable housing and forming a chassis ground plane wherein the metallic ring is peripheral to and surrounds the circuit board;

a wireless communication circuit carried by a circuit board;

an antenna circuit carried by a circuit board and connected to the wireless communication circuit; and

a frequency selective grounding circuit positioned at a selected grounding location between the chassis grounding plane and metallic ring at a location where the current changes direction and forming a harmonic trap that responds to a specific range of frequencies, wherein the frequency selective grounding circuit comprises a variable matching device in which the frequency response of grounding is programmed.

12. The mobile wireless communications device according to claim 11 , wherein a respective variable matching device is programmed to operate at a specific range of frequencies.

13. The mobile wireless communications device according to claim 11 , wherein a variable matching device is configured to change the impedance at a grounding location.

14. The mobile wireless communications device according to claim 11 , wherein a grounding location is specific to the frequency of operation.

15. The mobile wireless communications device according to claim 11 , wherein said antenna comprises a planar inverted F antenna.

16. The mobile wireless communications device according to claim 11 , wherein said wireless communications circuit comprises a cellular communications circuit.

17. The mobile wireless communications device according to claim 11 , and further comprising a display and user input device both carried by the portable housing and connected to said wireless communication circuit.

18. A method of operating a mobile wireless communications device, wherein the device comprises a portable housing having a metallic front housing configured as a peripheral side wall and forming a metallic ring of the portable housing, at least one circuit board carried by the portable housing and forming a chassis ground plane wherein the metallic ring is peripheral to and surrounds the circuit board, a wireless communication circuit carried by a circuit board, and an antenna circuit carried by a circuit board and connected to the wireless communication circuit; and

forming harmonic traps by positioning a frequency selective grounding circuit between a selected grounding location at the chassis grounding plane and metallic ring at a location where the current changes direction that responds to a specific range of frequencies.

19. The method according to claim 18 , and further comprising operating a respective frequency selective grounding circuit at a specific range of frequencies.

20. The method according to claim 18 , wherein a respective frequency selective grounding circuit comprises at least one of a series resonator and parallel resonator having a value depending on bandwidth requirements.

21. The method according to claim 18 , and wherein a frequency selective grounding circuit comprises a series resonator that resonates at high frequencies.

22. The method according to claim 18 , wherein a grounding location is specific to the frequency of operation.

23. The method according to claim 18 , wherein said frequency selective grounding circuit has a programmable frequency response for grounding.

24. The method according to claim 18 , wherein a frequency selective grounding circuit comprises a variable matching device.