Adjustable multi-band antenna

• US 20050128152A1
• Filed: 12/09/2004
• Published: 06/16/2005
• Est. Priority Date: 12/15/2003
• Status: Active Grant

• Current Assignee: Pulse Finland Oy (Yageo Corporation)
• Original Assignee: Filtronic LK Oy
• Inventors: Milosavljevic, Zlatoljub
• Granted Patent: US 7,468,700 B2
• Time in Patent Office: Days
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 21/30 Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
• CPC Class Codes: H01Q 9/0421 with a shorting wall or a shorting pin at one end of the element H01Q9/0414 takes precedence
• CPC Class Codes: H01Q 9/0442 with particular tuning means

Abstract

An adjustable multi-band planar antenna especially applicable in mobile terminals. A conductive element is placed in the structure of an antenna of PIFA type such that the conductive element has a significant electromagnetic coupling to the radiating plane. The parasitic element at issue is connected to a matching circuit (550) consisting of several reactive element. The parasitic element, the matching circuit and a line (540) between them constitute an adjusting circuit of the antenna. The circuit values of the matching circuit can be chosen from at least two alternatives. Alteration in the circuit values changes the coupling between the parasitic element and the ground, in which case an operation band of the antenna is displaced, because the electric length of the antenna'"'"'s part corresponding that band is changed, measured from the short-circuit point. Regarding the shiftable operation band, proper impedance matching and a proper efficiency can be arranged for the antenna.

Claims

1. An adjustable multi-band antenna comprising a ground plane, a radiating plane with a dielectric support part, and an adjusting circuit having a parasitic element of the radiating plane and a controllable part connected to the parasitic element, by which controllable part a coupling between the parasitic element and the ground plane can be changed to displace an operation band of the antenna, said controllable part being a reactive matching circuit, circuit values of which have been arranged to be chosen from at least two alternatives to implement said change in the coupling, and each alternative set of the circuit values comprises values of at least two reactive elements to optimize an impedance matching and efficiency of the antenna.

2. An antenna according to claim 1, wherein, to choose said circuit values, the matching circuit comprises a switch and at least two reactive circuits having different circuit values, one reactive circuit at a time being connected to said parasitic element depending on state of the switch.

3. An antenna according to claim 1, wherein, to choose said circuit values, the matching circuit comprises at least one capacitance diode, a control voltage of which is arranged to be chosen from at least two alternatives.

4. An antenna according to claim 2, each of said reactive circuits constituting a parallel circuit, one branch of which comprises a coil and another branch of which comprises a capacitor and a second coil in series.

5. An antenna according to claim 3, said matching circuit constituting a parallel circuit, one branch of which comprises a first capacitance diode and a first condenser in series, and another branch of which comprises a coil, a second capacitance diode and a second capacitor in series.

6. An antenna according to claim 1, having at least a lower operation band and an upper operation band, wherein said operation band to be displaced is the upper operation band.

7. An antenna according to claim 6, the matching circuit having a parallel resonance in range of the lower operation band, to limit influence of a change in said circuit values to the upper operation band.

8. An antenna according to claim 1, the parasitic element being a conductive strip being attached to said dielectric support part.

9. An antenna according to claim 1, the matching circuit being a LTCC circuit, from the point of its manufacturing technology.

10. A radio device having an adjustable multi-band antenna, which comprises a ground plane, a radiating plane with a dielectric support part, and an adjusting circuit having a parasitic element of the radiating plane and a controllable part connected to the parasitic element, by which controllable part a coupling between the parasitic element and the ground plane can be changed to displace an operation band of the antenna, said controllable part being a reactive matching circuit, circuit values of which have been arranged to be chosen from at least two alternatives to implement said change in the coupling, and each alternative set of circuit values comprises values of at least three reactive elements, to optimize an impedance matching and efficiency of the antenna.