A low complexity measurement method for beam-forming network based on DS-CDMA

High performance spatial signal processing relies on accurate beam-forming. In a practical antenna system, due to inevitable aging and heat distortion of the components, there exists an inconsistency between the designed Beam-forming Network (BFN) Weighted Matrix (WM) and the actual value of it. However, the complexity of BFN WM measurement is in direct ratio to the channel numbers of BFN. For large-scale phased array antennas, the measurement of the BFN WM requires burdensome work. To solve the problem, this paper proposes a novel efficient WM measurement method for BFN based on Direct Sequence-Code Division Multiple Access (DS-CDMA), which significantly reduces the complexity of the test by multi-port testing and parallel signal processing. Moreover, benefiting from the correlation characteristics of Direct Sequence Spread Spectrum (DSSS) signals, the measurement precision of the proposed method achieves 0.038 in amplitude and 0.511 in phase. This paper also discusses selections of DSSS codes. By borrowing the concept of Multi-User Detection (MUD), we proposed a special de-correlation algorithm to solve the problem of using non-orthogonal codes. Hardware implementation and practical tests have strongly demonstrated the feasibility and accuracy of the proposed method.