An amplitude-phase measurement method for beam forming network with non-orthogonal codes

The application of an amplitude and phase measurement system based on the spreading codes is limited by the requirements of code orthogonality. An amplitude-phase measurement method for digital beam forming network based on non-orthogonal codes was proposed to overcome the limitation. The main source of errors in the measurement system with non-orthogonal codes was multiple access interference (MAI). Therefore, de-correlating algorithm was proposed to suppress the MAI at the cost of increasing the noise slightly. Theoretical analysis provided the theory lower bound of the amplitude and phase measurement and the effect of the system error and mutual coupling on the measurement accuracy. Simulation results demonstrate that the accuracy of the measurement system without de-correlating algorithm is unacceptable. However, the proposed method can satisfy the accuracy requirements of ±0.1 dB and ±1 degree under the conditions that the in-band signal-to-noise ratio (SNR) is higher than 10 dB. Moreover, the simulation results are in good agreement with those of theoretical analysis.