Beam alignment in an apparatus

1 . An apparatus comprising:

at least one antenna array comprising a plurality of array elements having cross-polarized coupled branches;

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform:

measuring, while transmitting a combined uplink signal via the plurality of the array elements as individual signals forming the combined uplink signal, per an array element, a first signal on an unused branch of the array element, the first signal being a coupled individual signal of the transmitted combined uplink signal;

performing, per an array element, at least following:

determining a delta value based on a phase value of the first signal and reference information comprising a plurality of reference values, wherein determining the delta value comprises at least retrieving, from the reference information, a reference value of the plurality of reference values for the antenna element based on the order of the antenna element in the antenna array; and

adjusting, in response to the delta value not being within a tolerance, phase at least in the branch used for transmitting correspondingly.

2 . The apparatus of claim 1 , wherein (i) the memory further comprises a factor value for relative phase difference between adjacent antenna elements, (ii) the reference information comprises boresight cross-polarized coupled values, and (iii) determining the delta value further comprises:

extrapolating the reference value using the factor value to an estimated reference value for a beam steering direction in use; and

using the estimated reference value to determine the delta value.

3 . The apparatus of claim 1 , wherein (i) the reference information comprises reference values for different beam steering directions, (ii) retrieving from the reference information the reference value for the antenna element is further based on a beam steering direction in use, and (iii) determining the delta value further comprises:

using the reference value to determine the delta value.

4 . The apparatus of claim 3 , wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus further to perform, per an array element:

retrieving from the reference information a further reference value for the antenna element based on the order of the antenna element in the antenna array and the beam steering direction in use;

determining a further delta value between an amplitude value of the first signal and the further reference value; and

adjusting, in response to the further delta not being within a further tolerance, power at least in the branch used for transmitting correspondingly.

5 . The apparatus of claim 1 , wherein one antenna element of the antenna array is a reference antenna element and the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to use with the reference antenna element absolute values of the first signal of the reference antenna element and with other antenna elements first signals that are relative to the first signal of the reference antenna element.

6 . The apparatus of claim 5 , wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to use with the other antenna elements first signals that are further normalized to the first signal of the reference antenna element.

7 . The apparatus of claim 1 , wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to further perform measuring first signals in response to the apparatus sending as the combined uplink signal an uplink signal comprising user data.

8 . The apparatus of claim 1 , wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to further perform measuring first signals in response to the apparatus sending as the combined uplink signal an uplink signal comprising control data.

9 . The apparatus of claim 1 , wherein the reference information comprises values obtained during over the air calibration of another apparatus.

10 . The apparatus of claim 1 , wherein the apparatus comprises at least per a reception branch a coupler coupled to an antenna element of the antenna array.

11 . The apparatus of claim 1 , wherein the apparatus comprises at least per a reception branch an adjustable attenuator coupled to an antenna element of the antenna array.

12 . A method comprising:

measuring, by an apparatus, while transmitting a combined uplink signal via a plurality of array elements having cross-polarized coupled branches as individual signals forming the combined uplink signal, per an array element, a first signal on an unused branch of the array element, the first signal being a coupled individual signal of the transmitted combined uplink signal;

determining, by the apparatus, per an array element, a delta value based on a phase value of the first signal and the reference information comprising a plurality of reference values, wherein determining the delta value comprises at least retrieving, from the reference information, a reference value of the plurality of reference values for the antenna element based on the order of the antenna element in the antenna array; and

adjusting, by the apparatus, in response to the delta value not being within a tolerance, phase at least in the branch of the array element used for transmitting correspondingly.

13 . The method of claim 12 , wherein (i) the method further comprises a factor value for relative phase difference between adjacent antenna elements, (ii) the reference information comprises boresight cross-polarized coupled values, and (iii) determining the delta value further comprises:

extrapolating the reference value using the factor value to an estimated reference value for a beam steering direction in use; and

using the estimated reference value to determine the delta value.

14 . The method of claim 12 , wherein (i) the reference information comprises reference values for different beam steering directions, (ii) retrieving from the reference information the reference value for the antenna element is further based on a beam steering direction in use, and (iii) determining the delta value further comprises:

using the reference value to determine the delta value.

15 . The method as claimed in claim 14 , wherein the method further comprises:

retrieving from reference information, which comprises reference values for different beam steering directions, reference values for phase and for amplitude for the antenna element based on the order of the antenna element in the antenna array and a beam steering direction in use;

using the reference value for phase to determine the delta value;

determining a further delta value between an amplitude value of the first signal and the reference value for amplitude; and

adjusting, in response to the further delta not being within a further tolerance, power at least in the branch used for transmitting correspondingly.

16 . The method of claim 12 , wherein one antenna element of an antenna array is a reference antenna element and the method further comprises using with the reference antenna element absolute values of the first signal of the reference antenna element and with other antenna elements first signals that are relative to the first signal of the reference antenna element.

17 . The method of claim 16 , wherein the method further comprises using with the other antenna elements first signals that are further normalized to the first signal of the reference antenna element.

18 . The method of claim 12 , wherein the method further comprises performing measuring first signals in response to the apparatus sending as the combined uplink signal an uplink signal comprising user data.

19 . The method of claim 12 , wherein the method further comprises performing measuring first signals in response to the apparatus sending as the combined uplink signal an uplink signal comprising control data.

20 . A non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to perform at least the following:

measuring, while transmitting a combined uplink signal via a plurality of array elements having cross-polarized coupled branches as individual signals forming the combined uplink signal, per an array element, a first signal on an unused branch of the array element, the first signal being a coupled individual signal of the transmitted combined uplink signal;

determining, per an array element, a delta value based on a phase value of the first signal and the reference information comprising a plurality of reference values, wherein determining the delta value comprises at least retrieving, from the reference information, a reference value of the plurality of reference values for the antenna element based on the order of the antenna element in the antenna array; and

adjusting, in response to the delta value not being within a tolerance, phase at least in the branch of the array element used for transmitting correspondingly.