Embedded symmetric multiple axis antenna system with isolation among the multiple axes
The present disclosure pertains to a rotationally triply symmetric three axis magnetic antenna system having substantial isolation among the three axes, including a three axis skew orthogonal magnetic antenna system and device utilizing the antenna system. The antenna system comprising three substantially identical magnetic antenna elements disposed symmetrically about a reference point such that the magnetic axes from the three antenna elements are orthogonal to one another in direction and do not intersect one another. The three antenna elements are positioned in a substantial cross coupling null from one another to minimize cross coupling. The arrangement yields packaging efficiency for compact electronic devices. A 1, 1, diameter embodiment is disclosed. A location system utilizing the antenna system is disclosed. Methods for producing the antenna are disclosed. A moldable triple coil holder for the antenna system is described.
1. A three axis antenna system comprising:
three magnetic antennas comprising a first magnetic antenna, a second magnetic antenna and a third magnetic antenna, each magnetic antenna of the three magnetic antennas having a respective magnetic center, a respective magnetic moment vector direction and a respective diameter, each of the respective diameters being equal to one another to within plus or minus ten percent; the three magnetic antennas oriented according to a reference orthogonal coordinate system having x, y, and z axes meeting at a common origin, the three magnetic antennas being oriented such that the respective magnetic moment vectors thereof are skew orthogonal so that the respective magnetic moment vectors do not intersect and the respective magnetic moment vectors are orthogonal with respect to one another;
the first magnetic antenna of the three magnetic antennas placed with the respective magnetic center thereof at a first position: x=d 1 , y=d 2 , z=0 in the reference coordinate system; the first magnetic antenna oriented with the respective magnetic moment vector direction thereof parallel to, and spaced apart from, the y axis and nonintersecting with respect to the y axis;
the second magnetic antenna of the three magnetic antennas placed with the respective magnetic center thereof at a second position: y=d 1 , z=d 2 , x=0 in the reference coordinate system; the second magnetic antenna oriented with the respective magnetic moment vector direction parallel to, and spaced apart from, the z axis and nonintersecting with respect to the z axis;
the third magnetic antenna of the three magnetic antennas placed with the respective magnetic center thereof at a third position: z=d 1 , x=d 2 , y=0 in the reference coordinate system; the third magnetic antenna oriented with the respective magnetic moment vector direction parallel to, and spaced apart from, the x axis and nonintersecting with respect to the x axis;
wherein d 1 and d 2 are coordinate distances in the reference coordinate system that are selected to substantially minimize cross coupling among the three magnetic antennas by selecting d 1 and d 2 such that when the direction of each magnetic axis of the three antennas is expressed as a normalized direction vector in Cartesian coordinates, a scalar product between any two of the three magnetic antennas is less than 0.25;
wherein d 1 is at least one half of the respective diameter of the first magnetic antenna.
2. The three axis antenna system of claim 1 , wherein d 1 is substantially equal to d 2 within plus or minus ten percent.
3. The three axis antenna system of claim 2 , wherein d 1 and d 2 are substantially equal to the respective diameter of the first magnetic antenna within plus or minus ten percent.
4. The three axis antenna system of claim 1 , wherein d 2 is determined in accordance with achieving at least 15 dB isolation between at least the first magnetic antenna and the second magnetic antenna.
5. The three axis antenna system of claim 4 , wherein d 2 is determined by varying d 2 and evaluating cross coupling as a function of d 2 to find a local minimum cross coupling, then fixing d 2 at a value producing local minimum cross coupling.
6. The three axis antenna system of claim 5 , wherein d 2 is varied at a sequence of incremental values of d 2 , and determining minimal coupling value of d 2 to be the value of d 2 ; wherein the isolation values on either side of minimal coupling d 2 are higher than that of minimal coupling d 2 .
7. The three axis antenna system of claim 6 , wherein the incremental values of d 2 are incremented by less than ten percent of the respective diameter of the first magnetic antenna.
8. The three axis antenna system of claim 1 , wherein said reference orthogonal coordinate system is left handed.
9. The three axis antenna system of claim 1 , further including an antenna holder system supporting the three magnetic antennas wherein the antenna holder system comprises three substantially identical individual antenna holders configured to support the three magnetic antennas at a predetermined diagonal angle from a planar base plate.
10. The three axis antenna system of claim 9 , wherein the individual antenna holders further include mounting tabs configured to share a mounting screw with an adjacent antenna holder in a three mounting screw pattern that establishes a 120 degree rotation from one antenna holder to an adjacent antenna holder.
11. A method for producing a three axis antenna system comprising:
providing three substantially identical magnetic antennas comprising a first magnetic antenna, a second magnetic antenna, and a third magnetic antenna, each magnetic antenna of the three magnetic antennas having a respective center, a respective magnetic moment vector direction and a respective diameter, each of the respective diameters being substantially equal to one another to within plus or minus ten percent;
orienting the three magnetic antennas according to a reference orthogonal coordinate system having x, y, and z axes meeting at a common origin, the three magnetic antennas being oriented such that the respective magnetic moment vectors thereof are skew orthogonal so that the respective magnetic moment vectors do not intersect and the respective magnetic moment vectors are orthogonal with respect to one another;
placing the first magnetic antenna of said three magnetic antennas with the respective magnetic center thereof at a first position: x=d 1 , y=d 2 , z=0 in the reference coordinate system; orienting the first magnetic antenna with the respective magnetic moment vector direction thereof parallel to, and spaced apart from, the y axis and nonintersecting with respect to the y axis;
placing the second magnetic antenna of the three magnetic antennas with the respective magnetic center at a second position: y=d 1 , z=d 2 , x=0 in the reference coordinate system; orienting the second magnetic antenna with the respective magnetic moment vector direction-parallel to, and spaced apart from, the z axis and nonintersecting with respect to the z axis;
placing the third magnetic antenna of the three magnetic antennas with the respective magnetic center at a third position: z=d 1 , x=d 2 , y=0 in the reference coordinate system; orienting the third magnetic antenna with the respective magnetic moment vector direction parallel to, and spaced apart from, the x axis and nonintersecting with respect to the x axis;
where d 1 and d 2 are coordinate distances in the reference coordinate system that are selected to substantially minimize cross coupling among the three magnetic antennas by selecting d 1 and d 2 such that when the direction of each magnetic axis of the three antennas is expressed as a normalized direction vector in Cartesian coordinates, a scalar product between any two of the three magnetic antennas is less than 0.25;
wherein d 1 is at least one half of the respective diameter of the first magnetic antenna.
12. The method in accordance with claim 11 , wherein d 1 is substantially equal to d 2 within plus or minus ten percent.