Method and apparatus for limiting VSWR spikes in a compact broadband meander line loaded antenna assembly
View Patent ↗A method of operating a higher conductivity broadband loaded meander line antenna ( 10 ) is provided wherein the meander line is positioned on a sheet of a lower conductivity material ( 22 ) having a conductivity of from about 0.01 siemens/m to about 0.10 siemens/m; and allowing a first electrical current to flow in a first current path in the meander line. An electrical field is formed in the vicinity of the lower conductivity material and a second current flows in a second current path in the lower conductivity material, whereby anti-resonance in the meander line loaded antenna is diminished so that a broadband response can be achieved over bandwidths of 5:1 or more. An assembly for carrying out this method is also disclosed.
1. A method for minimizing VSWR spikes in a meander line loaded antenna having a number of electrically interconnected meander line conductive sections including at least one low impedance meander line section located above a conductive plate comprising interposing a poor conductor between the low impedance section and the conductive plate.
2. The method of claim 1 , wherein the resistivity of the poor conductor is 0.01 siemens/meter to 0.2 siemens/meter.
3. The method of claim 1 , wherein the meander line has a number of segments, each segment having a low impedance section, the poor conductor extending between the conductive plate and the low impedance sections of the segment.
4. The method of claim 1 , wherein the antenna is a double monopole meander line loaded antenna.
5. The method of claim 4 , wherein the double monopole meander line loaded antenna includes a bifurcated hemispherical surface, each comprised of semi-hemispherical surfaces.
6. A method of minimizing VSWR spikes in a meander line antenna coupler having at least one low impedance meander line section located above a conductive plate, comprising interposing a poor conductor between the low impedance section and the conductive plate.
7. The method of claim 6 , wherein the resistivity of the poor conductor is 0.01 siemens/meter to 0.2 siemens/meter.
8. A meander line loaded antenna comprising:
a meander line having at least one low impedance section;
a conductive plate; and,
a layer of a poor conductor interposed between said low impedance section and said plate, whereby a distributed resistance is positioned at said meander line to limit VSWR spikes without affecting the bandwidth of said antenna.
9. The antenna of claim 8 , wherein said poor conductor has a resistivity of 0.01 siemens/meter to 0.2 siemens/meter.
10. The antenna of claim 8 , wherein said poor conductor is in the form of a layer.
11. The antenna of claim 8 . wherein said layer is a sheet.
12. The antenna of claim 8 , wherein one end of said meander line is electrically connected to said conductive plate and wherein the other end of said meander line is the feed point for said antenna.
13. The antenna of claim 8 , wherein said poor conductor includes a vinyl resistive plastic film.
14. A method for minimizing VSWR spikes in a meander line loaded antenna having at least one low impedance meander line section located above a conductive plate comprising interposing a lossy dielectric material between the low impedance section and the conductive plate, the meander line having a number of segments, each segment having a low impedance section, the lossy dielectric material extending between the conductive plate and the low impedance sections of the segment.
15. The method of claim 14 , wherein the antenna is a double monopole meander line loaded antenna.
16. The method of claim 15 , wherein the double monopole meander line loaded antenna includes a bifurcated hemispherical surface, each comprised of semi-hemispherical surfaces.
17. A meander line loaded antenna comprising:
a meander line having at least one low impedance section;
a conductive plate; and,
a layer of lossy dielectric material interposed between said low impedance section and said plate, whereby a distributed resistance is positioned at said meander line to limit VSWR spikes without affecting the bandwidth of said antenna, one end of said meander line being electrically connected to said conductive plate and the other end of said meander line being the feed point for said antenna.