Bode magnitude plot axes: A Bode magnitude plot is conventionally drawn between which two variables?

Introduction / Context:Bode plots provide a simplified way to visualize the frequency response of a system. The magnitude plot is especially useful for assessing gain margins and bandwidth.

Given Data / Assumptions:

• Magnitude in decibels (dB) is defined as 20 log10(|G(jω)|).
• Frequency is plotted on a logarithmic axis.

Concept / Approach:

The standard convention uses dB for the vertical axis and log-scaled frequency for the horizontal axis. This allows straight-line asymptotes for simple pole/zero factors, which makes hand-plotting and analysis easier.

Step-by-Step Solution:

Verification / Alternative check:

Classical control and signal processing textbooks define Bode plots exactly in this manner: magnitude in dB vs. log ω, and phase (in degrees) vs. log ω.

Why Other Options Are Wrong:

• (a) Magnitude vs. ω gives a frequency response plot, not Bode log form.
• (c) dB vs. ω is not logarithmic on x-axis, so asymptotes are not straight lines.
• (d) log magnitude vs. log ω is less common; Bode standard uses 20 log magnitude.

Common Pitfalls:

• Forgetting that both axes are logarithmic in nature: vertical log (dB) and horizontal log (frequency).

Final Answer:

dB magnitude and log ω.