Calibration circuits for beam-forming antennas and related base station antennas
A base station antenna includes a backplane and a plurality of radiating elements that extend forwardly from the backplane. The antenna further includes a plurality of feed boards, and each of the feed boards has a respective group of one or more of the radiating elements mounted thereon. The antenna also includes a calibration port and a calibration circuit that has a calibration combiner that has an output that is coupled to the calibration port and a plurality of directional couplers that are coupled to the calibration combiner. At least a first portion of a first of the first directional couplers is implemented on a first of the feed boards.
1. A base station antenna, comprising:
a backplane;
a plurality of radiating elements that are arranged in a plurality of rows and columns, the plurality of radiating elements including at least a first radiating element and a second radiating element, each of the radiating elements extending forwardly from the backplane;
a plurality of separate feed boards including a first feed board, wherein each of the feed boards has a respective group of one or more of the radiating elements mounted thereon, and wherein multiple feed boards are included in each column and at least some of the rows, and wherein the first feed board extends across multiple of the columns;
a calibration port; and
a calibration circuit that comprises:
a calibration combiner that has an output that is coupled to the calibration port; and
a plurality of directional couplers that are coupled to the calibration combiner,
wherein the calibration combiner and at least a first portion of each directional coupler are implemented on the first feed board, and
wherein the calibration circuit is only coupled to a subset of the radiating elements.
2. The base station antenna of claim 1 , wherein at least one radiating element from each of the plurality of columns is mounted on the first feed board.
3. The base station antenna of claim 1 , wherein the first feed board is larger than at least some of the other feed boards.
4. The base station antenna of claim 1 , wherein the first feed board is larger than all of the other feed boards.
5. A base station antenna, comprising:
a backplane;
a first plurality of radiating elements that are arranged to define a first column of radiating elements;
a second plurality of radiating elements that are arranged to define a second column of radiating elements;
a plurality of separate feed boards including, wherein each of the feed boards has a respective group of one or more of the radiating elements mounted thereon, and wherein multiple feed boards are included in each of the first and second columns and the feed boards do not span the first and second columns;
a first radio frequency (“RF”) port;
a second RF port;
a first electromechanical phase shifter that includes a first phase shifter printed circuit board that is electrically coupled between the first RF port and the first column of radiating elements;
a second electromechanical phase shifter that includes a second phase shifter printed circuit board that is electrically coupled between the second RF port and the second column of radiating elements; and
a calibration circuit that includes:
a first directional coupler that is coupled along a first RF transmission path that extends between an input of the first electromechanical phase shifter and a first of the radiating elements in the first column of radiating elements, the first directional coupler implemented on the first phase shifter printed circuit board; and
a second directional coupler that is coupled along a second RF transmission path that extends between an input of the second electromechanical phase shifter and a first of the radiating elements in the second column of radiating elements, the second directional coupler implemented on the second phase shifter printed circuit board.
6. The base station antenna of claim 5 , wherein the calibration circuit further includes a combiner that is configured to combine RF energy present on a tap port of the first directional coupler with RF energy present on a tap port of the second directional coupler, where an output of the combiner is coupled to a calibration port of the base station antenna.
7. The base station antenna of claim 6 , wherein the first of the radiating elements and the second of the radiating elements are each dual-polarized radiating element that include a first radiator that is coupled to the first RF transmission path and that radiates at a first polarization and a second radiator that is coupled to a third RF transmission path and that radiates at a second polarization that is different than the first polarization, the base station antenna further comprising a third directional coupler that is coupled along the third RF transmission path.