Multiple-input multiple-output (MIMO) multi-band antennas with a conductive neutralization line for signal decoupling
View Patent ↗A MIMO antenna includes first and second radiating elements and a conductive neutralization line. Each of the first and second radiating elements includes a straight portion connected to a serpentine portion. The straight and serpentine portions are configured to resonate in at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a RF feed. The conductive neutralization line conducts resonant currents between the first and second radiating elements and has a conductive length that is configured to phase shift the conducted resonant currents to cause at least partial cancellation of currents in the first and second radiating elements which are generated by wireless RF signals received by the first and second radiating elements from each other.
1. A MIMO antenna comprising:
a first radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate in at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a first RF feed, and wherein the straight portion of the first radiating element separates the first RF feed from the serpentine portion thereof;
a second radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate in at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a second RF feed, and wherein the straight portion of the second radiating element separates the second RF feed from the serpentine portion thereof;
a conductive neutralization line that connects the first and second radiating elements to conduct resonant currents therebetween that at least partially cancel RF transmission coupling between the first and second radiating elements;
a third radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate within at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a third RF feed;
a fourth radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate within at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a fourth RF feed;
another conductive neutralization line that connects the third and fourth radiating elements; and
an interconnection conductive neutralization line that connects the conductive neutralization line to the other conductive neutralization line to at least partially cancel RF transmission coupling between the first, second, third, and fourth radiating elements,
wherein the straight portions of the first, second, third, and fourth radiating elements lie in a plane that is perpendicular to another plane in which the serpentine portions of the first, second, third, and fourth radiating elements lie.
2. The MIMO antenna of claim 1 , wherein:
the straight portions of the first and second radiating elements have an equal conductive path length; and
the serpentine portions of the first and second radiating elements have an equal conductive path length.
3. The MIMO antenna of claim 2 , wherein:
the straight and serpentine portions of the second radiating element are configured as a mirror image of the straight and serpentine portions of the first radiating element.
4. The MIMO antenna of claim 1 , wherein:
a conductive path length of the conductive neutralization line is configured to phase shift the conducted resonant currents to cause at least partial cancellation of RF signals wirelessly received by the first and second radiating elements from each other.
5. The MIMO antenna of claim 4 , wherein:
the location of connection of the conductive neutralization line to the first and second radiating elements and the conductive path length of the conductive neutralization line are configured to phase shift the resonant current conducted from the first radiating element to the second radiating element to cause its subtraction from a current induced by a wireless RF signal received by the second radiating element from the first radiating element, and configured to phase shift the resonant current conducted from the second radiating element to the first radiating element to cause its subtraction from a current induced by a wireless RF signal received by the first radiating element from the second radiating element.
6. The MIMO antenna of claim 1 , wherein:
the first and second radiating elements are spaced apart by less than the combined conductive lengths of the straight and serpentine portions of the first radiating element.
7. The MIMO antenna of claim 6 , wherein:
the first and second radiating elements are spaced apart by less than the conductive length of the straight portion of the first radiating element.
8. The MIMO antenna of claim 1 , wherein:
the first radiating element is configured to resonate within a lower RF frequency range defined by a combined conductive length of its straight and serpentine portions, and to resonate within a higher RF frequency range defined by a conductive length of its straight portion.
9. The MIMO antenna of claim 1 , wherein:
the first and second radiating elements are each configured to resonate within higher and lower RF frequency ranges, the higher frequency range including a frequency at least twice as great as frequencies within the lower RF frequency range.
10. The MIMO antenna of claim 9 , wherein the higher frequency range includes 5.2 GHz and the lower frequency range includes 2.4 GHz.
11. The MIMO antenna of claim 1 , wherein:
the conductive neutralization line includes at least two abrupt opposite direction changes along its conductive path to decrease distance between the first and second radiating elements.
12. The MIMO antenna of claim 1 , wherein:
a conductive length of the serpentine portion of each of the first and second radiating elements is at least four times greater than a respective conductive length of the straight portion of the first and second radiating elements.
13. The MIMO antenna of claim 1 , wherein:
the first and second radiating elements each include an inductive load element that is connected to a distal end of the serpentine portion from an end connected to the straight portion.
14. The MIMO antenna of claim 1 , further comprising:
a planar substrate comprising the straight portions of the first and second radiating elements, respectively, thereon;
a first parasitic radiating element that is on the planar substrate and is adjacent and parasitically coupled to the first radiating element to radiate responsive to the first radiating element resonating at a RF frequency;
a second parasitic radiating element that is physically isolated from the first parasitic radiating element on the planar substrate and is adjacent and parasitically coupled to the second radiating element to radiate responsive to the second radiating element resonating at a RF frequency,
wherein the first and second parasitic radiating elements are on a same side of the planar substrate as the straight portions of the first and second radiating elements, and
wherein the first and second parasitic radiating elements are configured to provide a third RF frequency range for the MIMO antenna.
15. The MIMO antenna of claim 1 , wherein:
the straight portions of the first and second radiating elements lie on a planar substrate surface is perpendicular to another planar substrate surface on which the serpentine portions of the first and second radiating elements lie.
16. The MIMO antenna of claim 1 , wherein:
the straight and serpentine portions of the first and second radiating elements are on a planar substrate.
17. A MIMO antenna comprising:
a first radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate in at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a first RF feed, and wherein the straight portion of the first radiating element separates the first RF feed from the serpentine portion thereof;
a second radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate in at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a second RF feed, and wherein the straight portion of the second radiating element separates the second RF feed from the serpentine portion thereof;
a conductive neutralization line that is configured to conduct resonant currents between the first and second radiating elements and has a conductive length that is configured to phase shift the conducted resonant currents to cause at least partial cancellation of currents in the first and second radiating elements which are generated by wireless RF signals received by the first and second radiating elements from each other, wherein first and second ends of the conductive neutralization line directly connect to the first and second radiating elements, respectively;
a first parasitic radiating element that is adjacent and parasitically coupled to the first radiating element to radiate responsive to the first radiating element resonating at a RF frequency; and
a second parasitic radiating element that is adjacent and parasitically coupled to the second radiating element to radiate responsive to the second radiating element resonating at a RF frequency;
a third radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate within at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a third RF feed;
a fourth radiating element that includes a straight portion connected to a serpentine portion, wherein the straight and serpentine portions are configured to resonate within at least two spaced apart RF frequency ranges in response to the straight portion being electrically excited through a fourth RF feed;
another conductive neutralization line that connects the third and fourth radiating elements; and
an interconnection conductive neutralization line that connects the conductive neutralization line to the other conductive neutralization line to at least partially cancel RF transmission coupling between the first, second, third, and fourth radiating elements,
wherein the straight portions of the first, second, third, and fourth radiating elements lie in a plane that is perpendicular to another plane in which the serpentine portions of the first, second, third, and fourth radiating elements lie.
18. The MIMO antenna of claim 17 , wherein the first and second ends of the conductive neutralization line directly connect to respective ones of the straight portions of the first and second radiating elements.
19. The MIMO antenna of claim 1 , wherein:
the straight portion of the first radiating element comprises a first width substantially wider than a second width of the serpentine portion of the first radiating element; and
the straight portion of the second radiating element comprises a third width substantially wider than a fourth width of the serpentine portion of the second radiating element.