Bode Plots

Wednesday, 10 July 2019

5:35 PM

𝐴﷐𝑗𝜔﷯=﷐﷐𝐴﷮𝑜﷯﷐1+﷐𝑗𝜔﷮﷐ω﷮𝑧1﷯﷯﷯﷐1+﷐𝑗𝜔﷮﷐ω﷮𝑧2﷯﷯﷯…﷮﷐1+﷐𝑗𝜔﷮﷐ω﷮𝑝1﷯﷯﷯﷐1+﷐𝑗𝜔﷮﷐ω﷮𝑝2﷯﷯﷯… ﷯

Zeros at ﷐𝜔﷮𝑧1﷯, ﷐ω﷮𝑧2﷯, .… ﷐ω﷮𝑧𝑛﷯
Poles at ﷐𝜔﷮𝑝1﷯, ﷐ω﷮𝑝2﷯, .… ﷐ω﷮𝑝𝑛﷯

20﷐log﷮|𝐴﷐𝑗𝜔﷯|﷯


Drawing

Amplitude
Superimpose each zero and pole

Identify the poles and zero, then draw each contribution and add together

Zeroes cause an increase of 20dB / decade (Zero for frequencies less than the pole)
Poles cause a decrease of 20dB / decade (Zero for frequencies less than the pole)
Also add the constant (20𝑙𝑜𝑔(﷐𝐴﷮𝑜﷯))

For zeros/poles at the origin, locate 𝜔=1 and add/subtract 20dB / decade

Untitled picture.png Machine generated alternative text:



Phase

Sum the inverse tan of the zeros and subtract the sum of the inverse tan of the poles

﷐﷐tan﷮−1﷯﷮﷐𝜔﷮﷐ω﷮𝑧1﷯﷯﷯+﷐﷐tan﷮−1﷯﷮﷐𝜔﷮﷐ω﷮𝑧2﷯﷯﷯+…+﷐﷐tan﷮−1﷯﷮﷐ω﷮﷐ω﷮𝑧𝑛﷯﷯﷯−﷐﷐﷐tan﷮−1﷯﷮﷐ω﷮﷐𝜔﷮𝑝1﷯﷯﷯+﷐﷐tan﷮−1﷯﷮﷐ω﷮﷐ω﷮𝑝2﷯﷯﷯+…+﷐﷐tan﷮−1﷯﷮﷐ω﷮﷐ω﷮𝑝𝑛﷯﷯﷯﷯

𝜔<0.1﷐ω﷮𝑧𝑛﷯ 
0°
𝜔=﷐ω﷮𝑧𝑛﷯ 
45°
ω>10﷐𝜔﷮𝑧𝑛﷯ 
90°



Untitled picture.png Machine generated alternative text:

 

Created with Microsoft OneNote 2016.