Distributed antenna system robust to human body loading effects
A wireless handheld device comprises an internal antenna system that operates in first and second non-overlapping frequency bands with respective bandwidths. The antenna system includes: a ground plane; first and second antenna elements connected to a common input/output port, wherein a bandwidth of each of the antenna elements is less than at least one of the first and second operating frequency bandwidths and less than a frequency bandwidth for the antenna system; a combining structure to couple first and second signal transmission paths from the antenna elements to the common input/output port; and a phase shifting element on the first signal transmission path that imparts a phase delay to signals on the first signal transmission path. The phase delay minimizes a sum of reflection coefficients of the antenna elements to cause the frequency bandwidth for the antenna system to include at least the first and second operating frequency bands.
1. A wireless device comprising:
an antenna system included within the wireless device and configured to operate in at least one operating frequency region having a first required operating frequency bandwidth, the antenna system comprising:
a ground plane layer contained in a printed circuit board having a shorter edge; and
at least two antenna elements connected to a common input/output port, each of the at least two antenna elements comprising one driven point, and having a resonant frequency measured at the driven point above a highest frequency of the at least one operating frequency region, wherein the at least two antenna elements are not arranged as a directive antenna array that provides a directive radiation pattern,
wherein:
one or more of the at least two antenna elements comprises a surface mount device (SMD) element;
at least one antenna element comprises a conductive trace upon one or more of the surfaces of a dielectric substrate featuring a relative dielectric permittivity greater than 2;
the ground plane layer is cut out to leave a clearance for placing the at least two antenna elements; and
at least one of the at least two antenna elements is placed near the shorter edge of the printed circuit board.
2. The wireless device according to claim 1 , wherein the antenna system operates in at least one operating frequency region comprised in a frequency range between 400 MHz and 6 GHz.
3. The wireless device according to claim 1 , wherein a first operating frequency band comprises a 824-960 MHz frequency range, and a second operating frequency band comprises a 1710-2500 MHz frequency range.
4. The wireless device according to claim 1 , wherein the at least two antenna elements feature a footprint on the printed circuit board of the wireless device smaller than 50% of the footprint of a single-element antenna system containing a rectangular PIFA antenna element operating at the same lowest frequency band.
5. The wireless device according to claim 4 , wherein the footprint of the at least two antenna elements on the printed circuit board of the wireless device is smaller than 30% of the footprint of a single-element antenna system containing a rectangular PIFA antenna element operating at the same lowest frequency band.
6. The wireless device according to claim 4 , wherein the footprint of the at least two antenna elements on the printed circuit board of the wireless device is smaller than 15% of the footprint of a single-element antenna system containing a rectangular PIFA antenna element operating at the same lowest frequency band.
7. The wireless device according to claim 1 , wherein the frequency bandwidth of each of a first antenna element and a second antenna element at respective driven points is smaller than a first required operating frequency bandwidth for the antenna system.
8. The wireless device according to claim 1 , wherein at least one of the at least two antenna elements comprises a grid dimension curve with a grid dimension D greater than 1.1.
9. The wireless device according to claim 1 , wherein at least one of the at least two antenna elements features a partial footprint on the ground plane layer.
10. The wireless device according to claim 1 , wherein at least one of the at least two antenna elements is placed entirely over the ground plane layer.
11. The wireless device according to claim 1 , wherein at least one of the at least two antenna elements is placed entirely over the ground plane clearance.
12. The wireless device according to claim 1 , wherein a first resonant frequency of a first antenna element is at least 5% higher than a second resonant frequency of a second antenna element, the resonant frequencies being measured at respective driven points.
13. The wireless device according to claim 1 , wherein a first resonant frequency of a first antenna element is less than 1% higher than a second resonant frequency of a second antenna element, the resonant frequencies being measured at respective driven points.
14. The wireless device according to claim 1 , wherein a first resonant frequency of a first antenna element is more than 1% but less than 5% higher than a second resonant frequency of a second antenna element, the resonant frequencies being measured at respective driven points.
15. A wireless device comprising:
an antenna system included within the wireless device and configured to operate in at least one operating frequency region having a first required operating frequency bandwidth, the antenna system comprising:
a ground plane layer contained in a printed circuit board having a shorter edge; and
at least two antenna elements connected to a common input/output port, each of the at least two antenna elements comprising one driven point, and having a resonant frequency measured at the driven point above a highest frequency of the at least one operating frequency region, wherein the at least two antenna elements are not arranged as a directive antenna array that provides a directive radiation pattern,
wherein:
one or more of the at least two antenna elements comprises a surface mount device (SMD) element;
at least one antenna element comprises a conductive trace upon one or more of the surfaces of a dielectric substrate featuring a relative dielectric permittivity higher than 2;
the ground plane layer is cut out to leave a clearance for placing the antenna elements, which feature a footprint of a selected percentage over the ground plane;
at least one of the at least two antenna elements is placed near the shorter edge of the printed circuit board;
the at least two antenna elements feature a footprint on the printed circuit board of the wireless device smaller than 50% of the footprint of a single-element antenna system containing a rectangular PIFA antenna element operating at the same lowest frequency band; and
the frequency bandwidth of each of a first and a second antenna elements at respective driven points is smaller than a first required operating frequency bandwidth for the antenna system.
16. The wireless device according to claim 15 , wherein at least one of the at least two antenna elements is placed entirely over the ground plane layer.
17. The wireless device according to claim 15 , wherein at least one of the at least two antenna elements is placed entirely over the ground plane clearance.
18. The wireless device according to claim 15 , wherein the antenna system operates in at least one operating frequency region comprised in a frequency range between 400 MHz and 6 GHz.
19. The wireless device according to claim 15 , wherein at least one antenna element comprises a grid dimension curve with a grid dimension D greater than 1.1.