Method and apparatus for reducing the low frequency cut-off of a wideband meander line loaded antenna

• US 20020175872A1
• Filed: 04/16/2002
• Published: 11/28/2002
• Est. Priority Date: 05/14/2001
• Status: Active Grant

• Current Assignee: Achilles Technology Management Co Ii, Inc.
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Apostolos, John T.
• Granted Patent: US 6,731,247 B2
• Time in Patent Office: Days
• US Class Current: 343/749
• CPC Class Codes: H01Q 9/32 Vertical arrangement of element H01Q9/40 takes precedence
• CPC Class Codes: H01Q 9/38 with counterpoise with counterpoise comprising elongated elements coplanar with the active element H01Q9/44
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface
• CPC Class Codes: H01Q 9/42 with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Abstract

A wideband meander line loaded antenna is provided with a capacitive feed to lower the reactance of the meander line antenna such that at lower frequencies the antenna reactance goes negative to cancel out the reactance of the meander line and distributed capacitance. The resultant lowering of the low frequency cut-off for the antenna permits the antenna to be used, for instance, in cellular phone applications in which not only are the cellular frequencies accommodated by the antenna, but also PCS and GPS frequencies as well. With the capacitive, feed the low frequency cut-off is lowered by as much as 30% over standard meander line loaded antennas.

Claims

1. A method for reducing the low-frequency cut-off of a wideband meander line loaded antenna comprising the step of:

providing the antenna with a capacitive feed.

2. The method of claim 1, wherein the capacitive feed lowers the reactance of the meander line antenna such that at lower frequencies the antenna reactance goes negative to cancel out the reactance of the meander line and the associated distributed capacitance.

3. A wide bandwidth low cut-off frequency meander line loaded antenna, comprising;

a ground plane plate;

a signal source having one side connected to said ground plane plate;

a top plate spaced from said ground plane plate and having an edge;

an upstanding plate coupled at one end to the other of the sides of said signal source and having an opposed end in spaced adjacency to said end of said top plate to provide a capacitive coupling thereto; and

,

a meander line having one end connected to said edge of said top plate and extending in spaced adjacency along the underside of said top plate and having a looped back portion having an end connected to said ground plane plate.

4. The antenna of claim 3, and further including a capacitance increasing plate connected at one end to said edge and extending over and down said upstanding plate.

5. A wide bandwidth low cut-off frequency meander line loaded antenna having a ground plane plate and a top plate to which one end of said meander line is connected, comprising;

a signal source coupled at one end to said ground plane plate; and

,

a capacitance feed between said signal source and said top plate.

6. The antenna of claim 5, wherein said capacitive feed includes an auxiliary plate having one end connected to said signal source and another end in spaced adjacency to said top plate.

7. The antenna of claim 6, and further including a capacitance increasing plate having one end connected to said top plate and extending over the gap between said top plate and said auxiliary plate and running down said auxiliary plate in spaced adjacency thereto.

8. The antenna of claim 6, wherein said auxiliary plate is perpendicular to said ground plane plate.

9. The antenna of claim 6 wherein said meander line has one end connected to that portion of said top plate adjacent to said auxiliary plate.

10. The antenna of claim 9, wherein the other end of said meander line is connected to said ground plane plate.

11. The antenna of claim 5, wherein said meander line is a slow meander line.

12. The antenna of claim 11, wherein said meander line has at least two sections, each of a different impedance.

14. The method of claim 13, wherein the antenna also accommodates the GPS band.

13. A method of lowering the cut-off frequency of a wideband meander line loaded antenna to be able to accommodate both the cellular band and the PCS band, 4 comprising the step of providing the antenna with a capacitive feed.