Calibration in a spread spectrum communications system

An apparatus comprising:

• a code controller configured to assign first and second orthogonal spreading codes from a set of orthogonal spreading codes that are used for separating overlapping radio transmissions in a spread spectrum multiple access communication system, to respective antenna elements;
• a first combiner for combining a first input signal with the assigned first code to create, as output, a first spread input signal;
• a second combiner for combining a second input signal with the assigned second code to create, as output, a second spread input signal;
• a memory storing a predetermined sequence;
• a controller configured to control the code controller to assign a first available spreading code to a first antenna element and to control the code controller to assign a second available spreading code to a second antenna element and configured to provide the predetermined sequence simultaneously as the first input signal to the first combiner and as the second input signal to the second combiner and;
• a first transmitter configured to convert a spread predetermined sequence output by the first combiner to a first calibrating radio transmission of the first antenna element;
• a first detector configured to detect a first calibration signal corresponding to the first calibrating radio transmission;
• a second transmitter configured to convert a spread predetermined sequence output by the second combiner to a second calibrating radio transmission of the second antenna element;
• a second detector configured to detect a second calibration signal corresponding to the second calibrating radio transmission;
• a first filter configured to use a result of processing the first detected calibration signal to modify subsequent radio transmissions of the first antenna element;
• and
• a second filter configured to use a result of processing the second detected calibration signal to modify subsequent radio transmissions of the second antenna element.