Multiband Tunable Antenna

• US 20070216590A1
• Filed: 01/25/2007
• Published: 09/20/2007
• Est. Priority Date: 01/25/2006
• Status: Active Grant

• Current Assignee: SkyCross Co., Ltd.
• Original Assignee: SkyCross, Inc.
• Inventors: Montgomery, Mark, Tornatta, Paul, Caimi, Frank
• Granted Patent: US 7,616,163 B2
• Time in Patent Office: Days
• US Class Current: 343/745
• CPC Class Codes: H01Q 1/2258 used with computer equipment
• CPC Class Codes: H01Q 9/0442 with particular tuning means
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

One embodiment of the invention relates to an antenna providing a tunable resonant frequency within a low frequency band and further providing a high resonant frequency, the antenna comprises a first radiating structure of a first effective electrical length, a second radiating structure of a second effective electrical length having a fractional integer relationship to a wavelength related to the high resonant frequency and a variable reactance element connecting the first and the second radiating structures, wherein varying a reactance of the variable reactance element tunes the antenna within the low frequency band.

Claims

1. An antenna providing a tunable resonant frequency within a low frequency band and further providing a high resonant frequency, the antenna comprising:

a first radiating structure of a first effective electrical length;

a second radiating structure of a second effective electrical length having a fractional integer relationship to a wavelength related to the high resonant frequency; and

a variable reactance element connecting the first and the second radiating structures, wherein varying a reactance of the variable reactance element tunes the antenna within the low frequency band.

2. The antenna of claim 1 wherein the first effective electrical length has a fractional integer relationship to the high resonant frequency approximately equal to the fractional integer relationship of the second effective length.

3. The antenna of claim 1 wherein the second effective length is about one-half of the wavelength of the high resonant frequency.

4. The antenna of claim 1 responsive to a signal representing a desired operating frequency for the antenna, wherein the reactance of the variable reactance element is responsive to the desired operating frequency.

5. The antenna of claim 4 wherein the variable reactance element comprises a variable capacitor responsive to the signal for controlling a capacitance presented by the variable capacitor.

6. The antenna of claim 5 wherein the variable capacitor comprises a varactor diode, and wherein the signal controls a reverse DC bias applied to the varactor diode to control the capacitance presented by the varactor diode.

7. The antenna of claim 4 operative with a communications device providing a digital signal representing an operating frequency of the communications device, the antenna further comprising an element for converting the digital signal to an analog signal, the analog signal for affecting the reactance of the variable reactance element.

8. The antenna of claim 7 wherein the variable reactance element comprises a varactor diode, and wherein a reverse DC bias applied to the varactor diode for affecting the capacitance thereof is responsive to the analog signal.

9. The antenna of claim 1 wherein the first radiating structure comprises first and second meanderline conductive segments connected by a conductive bridging segment.

10. The antenna of claim 1 wherein the second radiating structure comprises a planar conductive element.

11. The antenna of claim 1 wherein the low frequency band comprises frequencies between about 470 MHz and 860 MHz, and wherein the high resonant frequency is about 1675 MHz.

12. The antenna of claim 1 wherein the variable reactance element comprises one or both of a controllably variable capacitance and a controllably variable inductance.

13. The antenna of claim 1 wherein the first radiating structure comprises an inverted F antenna structure.

14. The antenna of claim 1 further comprising a proximate ground plane.

15. The antenna of claim 14 further comprising a reactive element connected between the second radiating structure and the ground plane.

16. The antenna of claim 15 wherein the reactive element comprises a variable capacitor.

17. The antenna of claim 1 wherein the first effective electrical length and the second effective length are each about a half wavelength at the high resonant frequency.

18. An antenna providing a tunable first resonant frequency within a low frequency band and further providing a second resonant frequency at a high frequency, the antenna comprising:

a first and a second radiating structure;

a variable reactance element electrically connecting the first and the second radiating structures, wherein controllably varying a reactance of the variable reactance element tunes the antenna within the low frequency band; and

wherein at the second resonant frequency the first radiating structure is a primary radiating structure, and wherein a combination of the first and the second radiating structures, as determined by a reactance of the variable reactance element, provide the tunable first resonant frequency within the low frequency band.

19. The antenna of claim 18 the second radiating element having an effective electrical length of one-half of a wavelength of the high resonant frequency.

20. The antenna of claim 19 the first radiating element having an effective electrical length of one-half of a wavelength of the high resonant frequency.

21. The antenna of claim 18 responsive to a signal representing a desired operating frequency for the antenna, wherein the reactance of the variable reactance element is responsive to the signal representing the desired operating frequency.

22. The antenna of claim 18 wherein the first radiating structure comprises first and second meanderline conductive segments connected by a conductive bridging segment.

23. The antenna of claim 18 wherein the second radiating structure comprises a planar conductive element.

24. The antenna of claim 18 wherein the low frequency band comprises frequencies between about 470 MHz and 860 MHz, and wherein the second resonant frequency is about 1675 MHz.

25. An antenna providing a low resonant frequency and a high resonant frequency, the antenna comprising:

a first radiating structure of a first effective electrical length;

a second radiating structure of a second effective electrical length having a fractional integer relationship to a wavelength related to the high resonant frequency; and

a reactance element electrically connecting the first and the second radiating structures, wherein a reactance of the reactance element determined the low resonant frequency.

26. The antenna of claim 25 wherein the first effective electrical length has a fractional integer relationship to the high resonant frequency.

27. The antenna of claim 25 wherein the first and second effective lengths have the same fractional integer relationship to the high resonant frequency.

28. The antenna of claim 25 wherein the fractional relationship comprises an effective electrical length of one-half of the wavelength of the high resonant frequency.

29. The antenna of claim 25 wherein the first radiating structure comprises first and second meanderline conductive segments connected by a conductive bridging segment.

30. The antenna of claim 25 wherein the second radiating structure comprises a planar conductive element.

31. An antenna providing a tunable resonant frequency within a low frequency band and further providing a high resonant frequency, the antenna comprising:

a first and a second radiating structure; and

a plurality of switchably controllable reactance elements disposed between the first and the second radiating structures, wherein one or more of the plurality of switchably controllable reactance elements are connected between the first and the second radiating structures to vary a reactance between the first and the second radiating structures and thereby tune the antenna within the low frequency band.

32. The antenna of claim 31 wherein an effective electrical length of the first and the second radiating structures have the same fractional integer relationship to a wavelength of the high resonant frequency.

33. The antenna of claim 31 wherein an effective electrical length of the second radiating structure is one-half of a wavelength of the high resonant frequency.

34. The antenna of claim 31 responsive to a signal representing a desired operating frequency for the antenna, wherein one or more of the plurality of switchably controllable reactance elements is responsive to the signal to tune the antenna within the low frequency band.

35. The antenna of claim 34 wherein each one of the plurality of switchably controllable reactance elements comprises a serial configuration of a switch element and a capacitor, and wherein one or more of the switches are configured to a closed state responsive to the signal.

36. The antenna of claim 31 wherein the first radiating structure comprises first and second meanderline conductive segments connected by a conductive bridging segment.

37. The antenna of claim 31 wherein the second radiating structure comprises a planar conductive element.

38. A method for designing an antenna tunable over a low frequency band and further presenting a high resonant frequency, the method comprising:

producing a first radiating structure having a first effective electrical length having a fractional integer relationship to the high resonant frequency;

producing a second radiating structure having a second effective electrical length approximately equivalent to the first effective electrical length; and

determining a reactance range for a reactive element connecting the first and the second radiating structures, wherein changing the reactance within the reactance range tunes the antenna resonance to include the low frequency band.