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滤波器选择与设计：系统性能的网关
通常，设计师要花那么多的时间专注于其复杂的规范和选择成本较高的设备，如处理器、FPGA与ADC，他们没有充分考虑到的主要性能的影响，以及成本和功耗问题，这是由选择和整合的所谓“低端“部件如过滤器。
事实上，滤波器电路的规格和设计常常是决定整个系统成功的最重要因素。例如，如果在相对低带宽应用中的滤波设计不能消除信号链前端的高带宽噪声，则系统必须烧毁额外的能量，以将不必要的噪声传播到信号链上。或者，在处理某些带宽的信号时，例如在基于信道的无线电接收机中，不适当的滤波设计会导致从相邻信道的信号进行不必要的处理。这就导致了电源的浪费和目标信号的潜在退化。
Proper filter design also prevents the signal path from contribuTIng noise to other parts of the system， such as keeping high-frequency signals from coupling back into the power circuit and causing instability or fluctuaTIons. In essence， bypass capacitors are actually the simplest category of analog filters and are widely used in all types of designs.
Below is a brief overview of the role of filters， the types of filters， and differences between digital and analog approaches as well as between passive and acTIve filtering designs. Then there are some specific design TIps for simulating and selecting analog filters for an example application to drive high-performance analog-digital converters （ADCs）。
