说明：  用双线性变换法设计IIR数字滤波器 滤波就是将外界干扰的不需要的频率滤除掉，一面影响要测试数据的结果。比如如果是心电波的话，如果这是外界有很大的噪声干扰，滤波就是把不必要的信号给抑制掉，以便对心跳的正常测试。通过图比较，滤波后的明显比之前的要平滑，就是滤去干扰噪声的结果。采样间隔对实验有影响，取的过大会导致频率混叠。
(Bilinear transformation method using digital filter IIR filter design is to outside interference filter out unwanted frequencies, while the impact to test data results. For example, if it is so heart waves, if this is a great noise outside interference, filtering is unnecessary signal out to the curb in order to test the normal heartbeat. Through chart comparison, after filtering than before to smooth the noise interference is the result of least squares. Sampling interval of the experiment affect take-off frequency of the General Assembly leading to aliasing.)