MULTIBAND LOOP ANTENNA AND PORTABLE RADIO COMMUNICATION DEVICE COMPRISING SUCH AN ANTENNA

1 . An antenna device for operation in at least two operational frequency bands, the antenna device comprising:

a loop element having a feeding end for connection to radio communication circuitry and a grounding end for connection to ground;

first filtering means connecting the grounding end to ground; and

switching means parallel with the first filtering means, wherein the switching means is configured to:

in a first state, connect the grounding end to ground parallel with the first filtering means to match the loop element to a first operational frequency band of the at least two operational frequency bands; and

in a second state, connect the grounding end to an open end parallel with the first filtering means to match the loop element to a second operational frequency band of the at least two operational frequency bands.

2 . The antenna device of claim 1 , wherein the first filtering means comprises a series inductor.

3 . The antenna device of claim 1 , further comprising second filtering means between the ground and the first state of the switching means.

4 . The antenna device of claim 3 , wherein the second filtering means comprises a series inductor to match the loop element to the first operational frequency band.

5 . The antenna device of claim 3 , wherein the second filtering means comprises a series capacitor for DC blocking.

6 . The antenna device of claim 1 , further comprising third filtering means between the switching means and the grounding end.

7 . The antenna device of claim 6 , wherein the third filtering means comprises a series capacitor for DC blocking.

8 . The antenna device of claim 1 , further comprising a parasitic capacitance parasitically connecting the second state of the switching means to ground.

9 . The antenna device of claim 1 , further comprising fourth filtering means connecting a third state of the switching means to ground, to match the loop element to a third frequency band.

10 . The antenna device of claim 9 , wherein the fourth filtering means comprises a series inductor.

11 . The antenna device of claim 1 , further comprising:

second filtering means between the ground and the first state of the switching means;

third filtering means between the switching means and the grounding end;

fourth filtering means connecting a third state of the switching means to ground, to match the loop element to a third frequency band; and

a parasitic capacitance parasitically connecting the second state of the switching means to ground.

12 . The antenna device of claim 11 , wherein:

the second filtering means comprises a series inductor to match the loop element to the first operational frequency band; and/or

the third filtering means comprises a series capacitor for DC blocking.

13 . The antenna device of claim 11 , wherein:

the parasitic capacitance is about 0.5 to 2 picofarads (pF); and/or

the loop element has an electrical length corresponding to λ for 1850 MHz; and/or

the first filtering means comprises a series inductor of about 13 nanoHenries (nH); and/or

the second filtering means comprises a series inductor of about 0 nH; and/or

the fourth filtering means comprises a series capacitor of about 2.7 pF; and/or

the switching means comprises a SP4T switch having one input and four outputs, one output for each of four states of the switch.

14 . The antenna device of claim 1 , further comprising DC blocking means arranged on the input and outputs of the switching means.

15 . The antenna device of claim 14 , wherein the DC blocking means comprise series capacitors of about 100 pF.

16 . The antenna device of claim 1 , wherein the antenna device is configured such that:

in the first state of the switching means, frequency band coverage of cellular operational frequency bands 850, 1800, 1900; and 2100 is provided; and

in the second state of the switching means, frequency band coverage of the LTE 700 is provided.

17 . A portable radio communication device comprising the antenna device of claim 1 .

18 . A portable radio communication device comprising an antenna device for operation in at least two operational frequency bands, the antenna device comprising:

a loop element having a feeding end for connection to radio communication circuitry and a grounding end for connection to ground;

first filtering means connecting the grounding end to ground;

switching means parallel with the first filtering means, wherein the switching means is configured to:

in a first state, connect the grounding end to ground parallel with the first filtering means to match the loop element to a first operational frequency band of the at least two operational frequency bands; and

in a second state, connect the grounding end to an open end parallel with the first filtering means to match the loop element to a second operational frequency band of the at least two operational frequency bands;

second filtering means between the ground and the first state of the switching means; and

DC blocking means arranged on the input and outputs of the switching means.

19 . The portable communication device of claim 18 , wherein:

the first filtering means comprises a series inductor.

the second filtering means comprises a series inductor to match the loop element to the first operational frequency band;

the DC blocking means comprise series capacitors; and

a parasitic capacitance parasitically connects the second state of the switching means to ground.

20 . The antenna device of claim 18 , wherein:

the loop element has an electrical length corresponding to λ for 1850 MHz; and/or

the switching means comprises a SP4T switch having one input and four outputs, one output for each of four states of the switch; and

the antenna device is configured such that:

in the first state of the switching means, frequency band coverage of cellular operational frequency bands 850, 1800, 1900; and 2100 is provided; and

in the second state of the switching means, frequency band coverage of the LTE 700 is provided.