Antenna device and radio communication terminal

1. An antenna device comprising:

a first antenna element configured to resonate in a first frequency band;

a first matching circuit that impedance matches a first radio frequency circuit with the first antenna element;

a second antenna element configured to resonate in a second frequency band;

a second matching circuit that impedance matches a second radio frequency circuit with the second antenna element;

a first band-pass circuit connected to the second antenna element at one end and connected to the second matching circuit at the other end, and having a passband covering the second frequency band; and

a second band-pass circuit connected to the second antenna element at one end and grounded at the other end, and having a passband covering the first frequency band so the second antenna element serves as a parasitic element for the first antenna element.

2. The antenna device of claim 1 , wherein

the second band-pass circuit shunts signals in the first passband to ground while blocking signals in the second passband.

3. The antenna device of claim 1 , wherein

said antenna device operates said first antenna element and said second antenna elements simultaneously, with said second antenna element serving as a parasitic element without including a switch.

4. The antenna device of claim 1 , wherein,

said first band-pass circuit blocks signals in the first frequency band, but passes signals in the second frequency band.

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

a third band-pass circuit that interconnects said first impedance matching circuit with said first antenna element, and having a passband that blocks signals in the second frequency band but passes signals in the first frequency band.

6. The antenna device of claim 5 , further comprising:

a fourth band-pass circuit connected to the first antenna element at one end and grounded at the other end, and having a passband covering the second frequency band so the first antenna element serves as a parasitic element for the second antenna element.

7. The antenna device of claim 1 , wherein said first passband includes 800 MHz.

8. The antenna device of claim 1 , wherein said second passband includes at least one of 1.5 GHz and 2 GHz.

9. The antenna device of claim 1 , wherein said antenna device being included in a mobile communications device that supports at least two of 3G, GPS, and Bluetooth communications.

10. An antenna device comprising:

a first antenna element configured to resonate in a first frequency band;

a first matching circuit that impedance matches a first radio frequency circuit with the first antenna element and a third band-pass circuit;

a second antenna element configured to resonate in a second frequency band;

a second matching circuit that impedance matches a second radio frequency circuit with the second antenna element and a first band-pass circuit;

the first band-pass circuit connected to the second antenna element at one end and connected to the second matching circuit at the other end, and having a passband covering the second frequency band;

a second band-pass circuit connected to the second antenna element at one end and grounded at the other end, and having a passband covering the first frequency band so the second antenna element serves as a parasitic element for the first antenna element; and

the third band-pass circuit that interconnects said first impedance matching circuit with said first antenna element, and having a passband that blocks signals in the second frequency band but passes signals in the first frequency band.

11. The antenna device of claim 10 , further comprising:

a fourth band-pass circuit connected to the first antenna element at one end and grounded at the other end, and having a passband covering the second frequency band so the first antenna element serves as a parasitic element for the second antenna element.

12. The antenna device of claim 11 , wherein said antenna device being included in a mobile communications device that supports at least two of 3G, GPS, and Bluetooth communications.

13. The antenna device of claim 10 , wherein said first passband includes 800 MHz.

14. The antenna device of claim 10 , wherein said second passband includes at least one of 1.5 GHz and 2 GHz.

15. An antenna device comprising:

a first antenna element configured to resonate in a first frequency band;

a second antenna element configured to resonate in a second frequency band;

a matching circuit that impedance matches a radio frequency circuit with the first antenna element and with a combination of the second antenna element and a third band-pass circuit;

a first band-pass circuit connected to the first antenna element at one end and connected to ground at the other end, and having a passband covering the second frequency band; and

a second band-pass circuit connected to the first antenna element and the matching circuit at the other end, and having a passband covering the first frequency band;

the third band-pass circuit that interconnects said second antenna element and said matching circuit and has a passband that covers the second frequency band; and

a fourth band-pass circuit that is connected between the second antenna element and ground, and having a passband that covers the first frequency band.

16. The antenna device of claim 15 , wherein said antenna device being included in a mobile communications device that supports at least two of 3G, GPS, and Bluetooth communications.

17. The antenna device of claim 16 , wherein said first passband includes 800 MHz.

18. The antenna device of claim 16 , wherein said second passband includes at least one of 1.5 GHz and 2 GHz.