A modified pole-zero matched discretization method is peresented for overcoming performance degradation of the notch filter discreted by currently popular methods when the notch frequency approaching the Nyquist frequency.The frequency characteristic of the discreted notch filter is kept up with that of notch filter in continuous domain by modifying damping ratio of transfer function in continuous domain to a constrained expectation. The numerical solution is obtained by solving a specified

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... traint equation and the difficulty of solving complex transcendental equation is avoided.The performance of digital notch filter is tested in digital simulation with conditions that the notch frequency with limited uncertainties.The simulation results show that the modified pole-zero matched discretization method presented in this paper is valid to overcome the drawback of currently popular discretization methods when the notch frequency approaching the Nyquist frequency.