随着通信技术的不断发展,人们对滤波器提出了越来越高的要求。无源 LC 滤波器是各种滤波器中使用最为普遍的一种,如何按照实际要求来设计 LC 滤波器是提高滤波器质量,改善特性,降低成本的重要一环。用影象参数法设计滤波器的优点是计算简单。将已研究成熟的滤波器基本节按一定规律连接起来,就可得到所要求的滤波器网络。但是,这种设计方法的最大缺点是在整个通带范围内终端阻抗不能得到良好的匹配,特别是在理论截止频率附近,阻抗失配现象更严重,会产生所谓“圆角”,导致工作衰减增大。因此用影象参数法设计的滤波器的理论通带不能全部利用,过渡带也不可能做得十分陡峭。此外,由于在阻带中工作衰减有可能比固有衰减小6dB,因此,在用影象参数法设计滤波器时,必须人为地将阻带衰减要求提高6dB,这就在一定程度上增加了滤波器的复杂性。用 With the continuous development of communication technology, people put forward higher and higher requirements on the filter. Passive LC filter is the most commonly used in a variety of filters, how to design the LC filter according to the actual requirements is to improve the quality of the filter to improve the characteristics of an important part of reducing costs. The advantage of designing the filter with the image parameter method is that the calculation is simple. Will have studied the basic section of the filter connected by a certain law, you can get the required filter network. However, the biggest disadvantage of this design method is that the termination impedance can not be well matched over the entire passband. Especially in the vicinity of the theoretical cutoff frequency, the impedance mismatch phenomenon is more serious, resulting in the so-called “fillet” Increase. Therefore, with the image parameter design of the theoretical pass filter can not be fully utilized, the transition band can not be done very steep. In addition, since the attenuation in the stopband is likely to be 6dB less than the inherent attenuation, it is necessary to artificially increase the stop-band attenuation requirement by 6dB when using the image parameter method to filter, which adds filtering to a certain extent Complexity of the device. use