巴特沃兹Pi LC低通滤波器计算

巴特沃思型滤波器最早是由英国工程师斯蒂芬·巴特沃思（Stephen Butterworth）描述的。 PI滤波器是一种具有串联元件和两个并联元件的滤波器，其连接形状为希腊字母PI。 巴特沃斯滤波器的特征是电路中频带范围内的增益恒定（响应平坦），电路中每个极点每十倍频的滚降率为20 dB。 巴特沃斯滤波器被称为最大平坦幅度响应滤波器，针对通带内的增益平坦度进行了优化。在截止频率处衰减为-3db。在截止频率以上，衰减为-20db。 巴特沃斯滤波器是唯一一种在较高阶时保持相同形状的滤波器，而其他类型的滤波器（贝塞尔、切比雪夫、椭圆）在较高阶时具有不同的形状。 低通滤波器是一种通过低频信号但衰减频率高于截止频率的信号的滤波器。 The Butterworth type filter was first described by the British engineer Stephen Butterworth. 
A PI filter is a filter that has a series element and two parallel elements connected in the shape of the Greek letter PI.
Butterworth filter are characterized by a constant gain (flat response) across the midband of the circuit and a 20 dB per decade roll-off rate for each pole contained in the circuit.
Butterworth filters are termed maximally flat magnitude response filters, optimized for gain flatness in the pass band. The attenuation is -3db at cutoff frequency. Above the cutoff frequency the attenuation is -20 db.
The Butterworth is the only filter that maintains same shape for higher orders whereas other varieties of filters (Bessel, Chebyshev, elliptic) have different shapes at higher orders. 
A Low pass filter is a filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency.