A method of beamforming a beam using an active antenna (10; 80) having two antenna ports and predetermined aperture data, the antenna being a one-dimensional antenna having 1 x N dual polarized antenna subarrays (11; 81) within an aperture, each of the plural dual polarized antenna subarrays comprising a first antenna subarray (12; 82) having a first polarization and a second antenna subarray (13; 83) having a second polarization non-parallel with said first polarization, each antenna port being adapted to generate a separate beam using a combination of multiple antenna subarrays from said first antenna subarrays (12; 82) and/or said second antenna subarrays (13; 83), wherein said method comprises: b) in a control unit, selecting port properties, comprising target beamwidth (BW target) for each separate beam and desired polarization for each antenna port in relation to each other, and c) in the control unit, determining port partitioning based upon aperture data and selected port properties for each antenna port, to adjust an effective length of the aperture over which the beam is created by defining which first antenna subarray(s) (12; 82) and/or second antenna subarray(s) (13; 83) to use for each antenna port, wherein step c) further comprises: c1) determining a first port partitioning matrix, defining which first antenna subarray(s) (12; 82) and second antenna subarray(s) (13; 83) to use for a first antenna port by: c1a) determining a reference beamwidth (BW reference), obtained by feeding all subarrays in the active antenna with unit amplitude and zero phase, c1b) calculating a value "n" approximately given by dividing the reference beamwidth with the target beamwidth and multiplying with the total number of antenna subarrays N n = BW reference BW desired N, and c1c) determining the port partitioning based on the calculated value "n" and the total number of antenna subarrays N; and c2) generating port partitioning matrix defining which first antenna subarray(s) (12; 82) and second antenna subarray(s) (13; 83) to use for the second antenna port based upon said first port partitioning matrix. b) in a control unit, selecting port properties, comprising target beamwidth (BW target) for each separate beam and desired polarization for each antenna port in relation to each other, and c) in the control unit, determining port partitioning based upon aperture data and selected port properties for each antenna port, to adjust an effective length of the aperture over which the beam is created by defining which first antenna subarray(s) (12; 82) and/or second antenna subarray(s) (13; 83) to use for each antenna port, c1) determining a first port partitioning matrix, defining which first antenna subarray(s) (12; 82) and second antenna subarray(s) (13; 83) to use for a first antenna port by: c1a) determining a reference beamwidth (BW reference), obtained by feeding all subarrays in the active antenna with unit amplitude and zero phase, c1b) calculating a value "n" approximately given by dividing the reference beamwidth with the target beamwidth and multiplying with the total number of antenna subarrays N n = BW reference BW desired N, and c1c) determining the port partitioning based on the calculated value "n" and the total number of antenna subarrays N; and c1a) determining a reference beamwidth (BW reference), obtained by feeding all subarrays in the active antenna with unit amplitude and zero phase, c1b) calculating a value "n" approximately given by dividing the reference beamwidth with the target beamwidth and multiplying with the total number of antenna subarrays N n = BW reference BW desired N, and c1c) determining the port partitioning based on the calculated value "n" and the total number of antenna subarrays N; and c2) generating port partitioning matrix defining which first antenna subarray(s) (12; 82) and second antenna subarray(s) (13; 83) to use for the second antenna port based upon said first port partitioning matrix.