FPGA Realization Of The Calibration Technology For Digital Beam Forming Antennas

In this paper, an array antenna calibration system based on FPGA was designed to overcome the channel mismatch in practical DBF systems. Two calibration algorithms based on the parallel orthogonal codes were selected. The downlink and uplink calibration systems were designed respectively. By using wireless signals, in these calibration systems, not only the variance between the branches but also the position errors and element errors can be calibrated. The digital processing parts run the calibration algorithms at the base band in the FPGA.The orthogonal codes are generated from an m sequence. Their orthogonality insures the accuracy of the calibration. Considering the real-time requirement of the calibration system, we used the parallel designing configurations. Every branch can be calibrated at the same time, and the operation time is almost independent of the element's number. In this paper, the whole system was programmed in VHDL. The functional simulation and the timing simulation were run on the simulator. The system was proved to be effective by simulation results. The estimation of the calibration time was obtained simultaneously. To obtain a group of the downlink calibration factors, it needs 2.577ms, and for uplink, 2.074ms. The type of the FPGA chips obtained from the synthesizer. The speed and effect of the calibration system shows that this system can satisfy the request of the real-time calibration of the digital beam forming.