9.5 : 周波数応答

Consider the transfer function of a system expressed in standard form.

The transfer function has a constant gain, a zero and a pole at the origin, a simple zero, a simple pole, a quadratic pole, and a quadratic zero.

Bode plots for individual factors are plotted separately and combined graphically.

For the positive constant gain term, the magnitude gain is constant, and the phase angle is zero and frequency-independent.

For the negative constant gain term, the magnitude gain remains the same, and the phase angle is ±180°.

For a transfer function with a zero at the origin, the magnitude plot represents a straight line with a positive slope of 20dB/decade. The phase plot depicts a constant phase angle of 90°.

For a pole at the origin, the magnitude plot's slope is -20dB/decade, and the phase shift is -90°.

If there is more than one pole or zero at the origin, the slope of the magnitude plot and phase shift are multiplied by the number of poles or zeros present at the origin.