文档介绍：Analog Lowpass Filter Analog Lowpass Filter
Specifications Specifications
• Typical magnitude response H a ( j W ) of an
• In the passband, defined by 0 £ W £ W p , we
analog lowpass filter may be given as require
indicated below
1 ­δ p £ Ha( jW) £ 1+ δ p, W £ Wp
., H a ( j W ) approximates unity within an
error of ±δ p
• In the stopband, defined by W s £ W £ ¥ , we
require
Ha ( jW) £ δs , Ws £ W £ ¥
., H a ( j W ) approximates zero within an
1 2 error of δs
Copyright © 2001, S. K. Mitra Copyright © 2001, S. K. Mitra
Analog Lowpass Filter Analog Lowpass Filter
Specifications Specifications
• W p - passband edge frequency • Magnitude specifications may alternately be
• W s - stopband edge frequency given in a normalized form as indicated
below
•δ p - peak ripple value in the passband
•δ s - peak ripple value in the stopband
• Peak passband ripple
α p = ­20 log10 (1­δ p ) dB
• Minimum stopband attenuation
α s = ­ 20 log 10 ( δ s ) dB
3 4
Copyright © 2001, S. K. Mitra Copyright © 2001, S. K. Mitra
Analog Lowpass Filter
Analog Lowpass Filter Design
Specifications
• Two additional parameters are defined -
• Here, the maximum value of the magnitude
in the passband assumed to be unity W
(1) Transition ratio k = p
Ws
• 1 / 1 + ε 2 - Maximum passband deviation,
given by the minimum value of the For a lowpass f