Antenna apparatus and mobile communication device using the same

1. An antenna apparatus applicable for a wireless device operated in a frequency band, comprising:

an antenna unit comprising a first conductor having a first end for feeding signals and a second end; and

a ground plane providing a ground reference to the signals;

wherein there is a first distance between the first conductor and the ground plane, and the first distance is adjustable to improve the impedance matching of the antenna apparatus;

wherein the area of the first conductor is less than 1/64 square of operating wavelength of the antenna unit;

wherein there is an angle between the first conductor and the ground plane, and the angle is adjustable to improve impedance matching of the antenna apparatus; and

wherein the antenna unit has an input impedance having a real part and an imaginary part, the real part of the input impedance is adjustable by tuning the angle.

2. The antenna apparatus as claimed in claim 1 , wherein the length of the first conductor is shorter than ¼ the operating wavelength of the antenna unit.

3. The antenna apparatus as claimed in claim 1 , wherein the frequency bands is between 88˜108 MHz.

4. The antenna apparatus as claimed in claim 1 , wherein the first distance is shorter than or equal to 15 mm.

5. The antenna apparatus as claimed in claim 1 , wherein the first distance is shorter than or equal to 10 mm.

6. The antenna apparatus as claimed in claim 1 , wherein the antenna unit has an input impedance having a real part and an imaginary part, the real part of the input impedance is adjustable by changing the first distance.

7. The antenna apparatus as claimed in claim 6 , wherein the real part of the input impedance of the antenna unit decreases as the first distance decreases.

8. The antenna apparatus as claimed in claim 1 , wherein the antenna unit has an input impedance having a real part and an imaginary part, the antenna unit further comprises a second conductor extending from the second end of the first conductor, wherein the first conductor and the second conductor are on different planes, the second conductor and the ground plane are of a second distance, wherein the real part of the input impedance of the antenna unit is adjustable by changing the second distance.

9. The antenna apparatus as claimed in claim 8 , wherein the real part of the impedance of the antenna unit decreases as the second distance decreases.

10. The antenna apparatus as claimed in claim 1 , further comprising:

a reactive device coupled to the first end of the antenna unit, wherein the reactive device has inductive components or capacitive components to improve impedance matching of the antenna apparatus.

11. The antenna apparatus as claimed in claim 10 , wherein the antenna unit has an input impedance having a real part and an imaginary part, the imaginary part of the input impedance is adjustable by tuning the reactive device.

12. The antenna apparatus as claimed in claim 10 , wherein the reactive device further has resistance components.

13. The antenna apparatus as claimed in claim 1 , wherein the antenna unit is a monopole antenna with the second end open.

14. The antenna apparatus as claimed in claim 1 , wherein the first conductor of the antenna unit has a spiral pattern or meander line pattern. ,

15. The antenna apparatus as claimed in claim 1 , wherein the first conductor of the antenna unit is made of a metal trace printed on a supporting member, a metal line or metal sheet.

16. The antenna apparatus as claimed in claim 15 , wherein the supporting member comprises a multilayer structure and the metal trace is provided on at least one layer of the layer structure.

17. The antenna apparatus as claimed in claim 1 , wherein the second end of the antenna unit serves as a ground end electrically coupled to the ground plane.

18. The antenna apparatus as claimed in claim 1 , wherein the real part of the input impedance of the of the antenna unit decreases as the angle decreases.

19. The antenna apparatus as claimed in claim 1 , wherein the wireless device is a mobile phone.

20. An antenna unit applicable for a wireless device operated in a frequency band, wherein the wireless device has a circuit module and a ground plane, comprising:

a first conductor having a first end and a second end; and

a reactive device, coupled to the first end and the circuit module, for feeding signals from the circuit module to the first end of the first conductor, wherein the reactive device having inductive components or capacitive components;

wherein there is a first distance between the first conductor and the ground plane, the antenna unit has an input impedance having a real part and an imaginary part, the real part of the input impedance is adjustable by changing the first distance and the imaginary part of the input impedance is adjustable by tuning the reactive device;

wherein the length of the first conductor is shorter than ¼ the operating wavelength of the antenna unit;

wherein there is an angle between the first conductor and the ground plane; and

wherein the real part of the input impedance of the antenna unit is adjustable by changing the angle.

21. The antenna unit as claimed in claim 20 , wherein the frequency band is between 88˜108 MHz.

22. The antenna unit as claimed in claim 20 , wherein the first distance is shorter than or equal to 15 mm.

23. The antenna unit as claimed in claim 20 , further comprising:

a second conductor extending from the second end of the first conductor, wherein the first conductor and the second conductor are on different planes, the second conductor and the ground plane are of a second distance,

wherein the real part of the input impedance of the antenna unit is adjustable by changing the second distance.

24. The antenna unit as claimed in claim 20 , wherein the reactive device further has the resistance components.

25. The antenna unit as claimed in claim 20 , wherein the antenna unit is a monopole antenna with the second end open.

26. The antenna unit as claimed in claim 20 , wherein the first conductor of the antenna unit has a spiral pattern or meander line pattern.

27. The antenna unit as claimed in claim 20 , wherein the second end of the antenna unit serves as a ground end electrically coupled to the ground plane.

28. The antenna unit as claimed in claim 20 , wherein the wireless device is a mobile phone.