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在用PIN二极管做为接收元件的 邻近开关设计中,信号先进行放 大,然后必须滤掉任何的噪声再转送到邻近开关的几级信号调理级。一般来说,为了抑制来自50Hz电源、氖灯频率、100Hz谐波和其他预计的噪声源的任何噪声,使用增益为1的三阶Bessel滤波器是一个很好的选择,因为它能给出平坦的响应,不会使三分贝频率衰减(用Butterworth或Chebyshev滤波器做不到这一点)。 本文所示的滤波器在dc提供一零响应,而从三分贝频率f_(cp)到f_u都具有平坦的响应(图1)。f_u频率是A_(vc)增益穿过1处的频率(图2)。
In a proximity switch design using a PIN diode as a receiving element, the signal is first amplified and then any noise must be filtered out and sent to the next few stages of signal conditioning stages adjacent to the switch. In general, to suppress any noise from 50Hz power, neon frequency, 100Hz harmonics and other predicted noise sources, using a third-order Bessel filter with a gain of 1 is a good choice because it gives a flat The response does not attenuate the decibel frequency (this is not possible with Butterworth or Chebyshev filters). The filter shown here provides a zero response at dc and a flat response from the decibel frequency f_ (cp) to f_u (Figure 1). f_u frequency is the frequency at which A_ (vc) gain crosses 1 (Figure 2).