Multi-layered multi-band antenna
Embodiments provide multi-band, compound loop antennas (multi-band antennas). Embodiments of the multi-band antennas produce signals at two or more frequency bands, with the two or more frequency bands capable of being adjusted and tuned independently of each other. Embodiments of a multi-band antenna are comprised of at least one electric field radiator and at least one monopole formed out of the magnetic loop. At a particular frequency, the at least one electric field radiator in combination with various portions of the magnetic loop resonate and radiate an electric field at a first frequency band. At yet another particular frequency, the at least one monopole in combination with various portions of the magnetic loop resonate and radiate an electric field at a second frequency band. The shape of the magnetic loop can be tuned to increase the radiation efficiency at particular frequency bands and enable the multi-band operation of antenna embodiments.
1. A multi-layered planar multi-band antenna, comprising:
a magnetic loop located on a first plane and configured to generate a magnetic field, the magnetic loop including a first section and a second section, wherein the magnetic loop has a first inductive reactance adding to a total inductive reactance of the multi-band antenna;
a monopole formed by a substantially stair-shaped portion of the magnetic loop, the monopole configured to create a resonant mode of a first frequency band, and wherein one or more other portions of the magnetic loop resonate in phase with the monopole at the first frequency band; and
an electric field radiator located on the first plane and within the magnetic loop, the first electric field radiator coupled to the magnetic loop and configured to emit an electric field at a second frequency band, the electric field emitted orthogonal to the magnetic field, wherein the electric field radiator has a first capacitive reactance adding to a total capacitive reactance of the multi-band antenna, wherein a physical arrangement between the electric field radiator and the magnetic loop results in a second capacitive reactance adding to the total capacitive reactance, wherein one or more second sections of the magnetic loop resonate in phase with the electric field radiator at the second frequency band, and wherein the total inductive reactance substantially matches the total capacitive reactance.
2. The antenna as recited in claim 1 , further comprising a loading capacitor located on the second plane, the loading capacitor having a capacitance adding to the total capacitive reactance.
3. The antenna as recited in claim 1 , further comprising a second monopole positioned substantially opposite the monopole, the second monopole formed by a second substantially stair-shaped bend of the magnetic loop, wherein the monopole and the second monopole form a dipole and wherein the second monopole is a counterpoise to the monopole.
4. The antenna as recited in claim 1 , further comprising a second electric field radiator located on the plane and within the magnetic loop, the second electric field radiator coupled to the magnetic loop and configured to emit a third electric field at a third frequency band, the third electric field emitted orthogonal to the magnetic field, wherein the third electric field radiator has a third capacitive reactance adding to the total capacitive reactance, and wherein a physical arrangement between the second electric field radiator and the magnetic loop results in a fourth capacitive reactance adding to the total capacitive reactance.
5. The antenna as recited in claim 4 , wherein the first frequency band, the second frequency band, and the third frequency band are not harmonically related.
6. The antenna as recited in claim 1 , wherein the electric field radiator is substantially rectangular shaped, and wherein a corner of the electric field radiator is cut at an angle to reduce a capacitive coupling between the electric field radiator and the magnetic loop.
7. The antenna as recited in claim 1 , wherein the first frequency band and the second frequency band are not harmonically related.
8. The antenna as recited in claim 1 , wherein a downstream portion of the magnetic loop adjacent to the monopole is capacitively loaded to bring the monopole into resonance.
9. The antenna as recited in claim 1 , further comprising an electrical trace coupling the electric field radiator to the magnetic loop.
10. The antenna as recited in claim 9 , wherein the electrical trace couples the electric field radiator to the magnetic loop at an electrical degree location approximately 90 degrees or approximately 270 degrees from a drive point of the magnetic loop.
11. The antenna as recited in claim 9 , wherein the electrical trace couples the electric field radiator to the magnetic loop at a reflective minimum point where a current flowing through the magnetic loop is at a reflective minimum.
12. The antenna as recited in claim 9 , wherein the electrical trace is configured to electrically lengthen the electric field radiator.
13. The antenna as recited in claim 1 , wherein the electric field radiator is directly coupled to the magnetic loop at an electrical degree location approximately 90 degrees or approximately 270 degrees from a drive point of the magnetic loop.
14. The antenna as recited in claim 1 , wherein the electric field radiator is directly coupled to the magnetic loop at a reflective minimum point where a current flowing through the magnetic loop is at a reflective minimum.