Auto calibrated distributed local loop configuration of array antenna for CDMA cellular base station

We have designed a new type of CDMA array antenna with distributed processing using a local loop data transmission system over its sub-array antenna components, and a new automatic real-time calibration system for this individual sub-array component is proposed. Our designed array antenna is covered by a conformal arrangement of sub-array elements on an 18th surface polygon structure. The transmitter and receiver components are located inside of the 18th polygon at the backside of each sub-array element. The automatic real-time calibration circuit is mounted on each transceiver component, and it operates using the transmit CDMA signal itself as its calibration reference. This reference signal is used for the LMS (least mean square) algorithm as phase and amplitude estimator. The calibration circuit has a high accuracy and a full-bandwidth tuning capability owing to additional auto- and cross-correlation circuits, and has a small interference by the reference signal because of the subtraction of the injected reference signal at the final stage of the receiver. We theoretically investigated the operations of the calibration circuit, and experimentally confirmed that the desired radiation patterns were formed by the prototype distributed local loop configuration of the array antenna