Antenna with a magnetic interface
View Patent ↗An antenna includes a magnetic interface generator that generates a magnetic interface at a center frequency f 0 . The magnetic interface generator is a passive array of spirals that are deposited on one layer of a multi-layer substrate. The magnetic interface is generated in a plane at a distance Z above the surface of the substrate layer that it is printed on, where the antenna in printed on a second layer of the multi-layer substrate. The distance Z where the magnetic interface is created is determined by the cell size of the spiral array, where the cell size is based on the spiral arm length and the spacing S between the spirals. The center frequency of the magnetic interface is determined by the average track length D AV of the spirals in the spiral array. The spacing S of the spiral array is chosen to project the magnetic interface to the second layer in the multi-layer substrate so as to improve performance of the antenna that printed on the second layer. The magnetic interface can be used to increase the gain, matching, and bandwidth of a microstrip patch antenna, or other type of antenna.
1. An antenna assembly, comprising:
a first substrate layer having a first surface and a second surface, wherein said first surface is coupled to a ground node;
a spiral layer having a planar array of spirals with a spacing S between the spirals, printed on said second surface of said first substrate layer, that generates a magnetic interface above said second surface at a center frequency f 0 , wherein said center frequency f 0 for the magnetic interface is determined by an average track length D AV for said spirals;
a second substrate layer having a first surface coupled to said planar array of spirals and a second surface; and
an antenna printed on said second surface of said second substrate layer, wherein said spiral layer is configured to generate said magnetic interface approximately in a plane of said antenna.
2. The antenna assembly of claim 1 , wherein f 0 is determined according to the following equation:
f
0
=
c
2
D
av
1
+
ɛ
r
2
;
wherein c represents a speed of light, and wherein ε r represents a relative dielectric constant of said first substrate layer and said second substrate layer.
3. The antenna assembly of claim 1 , wherein a first terminal and a second terminal of each spiral in said planar array of spirals is open circuited.
4. The antenna assembly of claim 1 , wherein said magnetic interface is generated at a distance Z above said second surface of said first substrate layer, wherein said distance Z is determined based on a cell size of a spiral in said planar array of spirals.
5. The antenna assembly of claim 1 , wherein a cell size of said spirals is adapted so that said magnetic interface is generated approximately in said plane of said antenna, said cell size is determined by a length L of a spiral arm and a spacing S between said spirals.
6. The antenna assembly of claim 1 , wherein said antenna printed on said second substrate layer is a patch antenna.
7. The antenna assembly of claim 1 , wherein said antenna printed on said second layer of said second substrate is a microstrip patch antenna.
8. An antenna assembly, comprising:
a ground layer;
a first substrate layer having a first surface and a second surface, said first surface coupled to said ground layer;
a spiral layer having a planar array of spirals with a spacing S between the spiral that are printed on said second surface of said first substrate layer;
a second substrate layer having a first surface and a second surface, said first surface of said second substrate layer coupled to said spiral layer; and
an antenna printed on said second surface of said second substrate layer;
wherein said spiral layer generates a magnetic interface centered at a frequency f 0 in a plane of said antenna printed on said second surface of said second substrate layer, wherein said center frequency f 0 is determined by an average track length D AV of said spirals.
9. The antenna assembly of claim 8 , wherein said average track length D AV is determined according to the following equation:
D
av
=
c
2
f
0
1
+
ɛ
r
2
wherein c represents a speed of light; and
wherein ε r is a relative dielectric constant of said first substrate layer and said second substrate layer.
10. The antenna assembly of claim 8 , wherein a cell size of said planar array of spirals is based on a thickness of said second substrate layer, wherein said cell size includes a length L of a spiral arm and a spacing S between adjacent spirals.
11. The antenna assembly of claim 8 , wherein said terminals of said spirals are open circuited.
12. The antenna assembly of claim 8 , wherein said antenna printed on said second surface of said second substrate layer is a patch antenna.
13. The antenna assembly of claim 8 , wherein said antenna printed on said second surface of said second substrate layer is a microstrip patch antenna.
14. An antenna assembly, comprising:
a ground layer;
a first substrate layer having a first surface and a second surface, said first surface coupled to said ground layer;
a spiral layer having an array of spirals with a spacing S between the spirals that are printed on said second surface of said first substrate layer;
a second substrate layer having a first surface and a second surface, said first surface of said second substrate layer coupled to said spiral layer; and
an antenna printed on said second surface of said second substrate layer;
wherein said spiral layer generates a magnetic interface centered at a frequency f 0 in a plane of said antenna printed on said second surface of said second substrate layer, and wherein said center frequency f 0 is determined by an average track length D AV of said spirals;
wherein said array of spirals includes a cell size determined by a length L of a spiral arm and a spacing S between said spirals, said cell size controlling placement of said magnetic interface in a plane of said antenna.