Directional coupler is commonly used in the microwave system to measure the forward and backward power.Due to the limited directional isolation of the coupler
the crosstalk existing between the bi-directional coupling output signals will influence the accuracy of power measurement.The quadrature directional coupling method is developed to solve this problem.A pair of directional couplers with a phase difference of 90 are used to measure the coupling output power simultaneously
and the influence of crosstalk can be eliminated effectively by processing the measurement data.The relationship between forward and backward power and the outputs of quadrature couplers is derived
and the error due to the quadrature deviation is analyzed.In order to determine the quadrature situation
the method to measure the phase difference between two couplers is proposed.The experiment shows that the quadrature directional method can improve the accuracy of power and VSWR measurement effectively.