9.4 : ボード線図

Consider an electrocardiogram unit that utilizes a low-pass filter with a complex network function represented by its magnitude and phase angle.

The decibel logarithmic gain is calculated by multiplying the base ten logarithm of the network function's magnitude by 20.

Bode plots are semilogarithmic graphs that display the logarithmic gain in decibels and the phase angle in degrees across frequencies.

At lower frequencies, the logarithmic gain and the phase angle approaches zero.

This results in horizontal lines on the Bode plot, known as the low-frequency asymptotes.

At higher frequencies, the calculations for gain and phase angle reflect their dependence on frequency.

They are depicted as straight lines with negative slopes and are known as high-frequency asymptotes.

The low- and high-frequency asymptotes intersect at a corner, also known as the corner frequency.

At this frequency, the asymptotic magnitude deviates by nearly -3 decibels from the exact value, and the phase angle is approximately -45 degrees.

The asymptotic bode plots are good approximations to the actual bode plots.