Method for generating transfer function of filter

The invention provides a method for generating a transfer function of a filter, namely a method for reducing the maximal Q value of poles of the transfer function of the filter and capable of reducing the sensitivity of amplitude-frequency response of the filter to circuit parameter change of the filter. The method comprises the following steps: firstly, normalizing indexes of the filter into indexes of a corresponding normalized low-pass filter prototype, calculating the minimal order N of the transfer function required for achieving the indexes by a classical method, increasing the order by n, wherein n is greater than or equal to 1, and generating the transfer function of the (N+n)-order low-pass filter by the classical method; secondly, reducing the maximal Q value of the poles of the transfer function by changing the Q value and an absolute value of the poles of the transfer function, and calculating a new pole value according to the adjusted Q value and absolute value; thirdly, recalculating the transfer function of the filter according to the new pole value, checking whether the transfer function meets the design index, selecting a proper transfer function from the transfer functions meeting the indexes as the prototype, carrying out frequency transformation, and generating the required transfer function of the filter.