Magnitude-only Bode plot of frequency response (2024)

FAQs

What is the magnitude of the Bode plot? ›

In a bode plot, the magnitude of the impedance and phase is plotted as a function of frequency on a log scale. The bode plot explicitly shows the frequency at which each data point was taken.

It is customary to plot the magnitude of the frequency response function on the log scale as |G(jω)|dB=20log10|G(jω)|. The magnitude of the loop gain is given in dB as: |KGH(jω)|dB=20logK+∑mi=120log|1+jωzi|−(20n0)logω−∑n1i=120log|1+jωpi|−∑n2i=120log|1−ω2ω2n,i+j2ζiωωn,i|.

bodemag(sys1,sys2,...,sysN) plots the frequency response of multiple dynamic systems on the same plot. All systems must have the same number of inputs and outputs. bodemag(sys1, LineSpec 1,...,sysN,LineSpecN) specifies a color, line style, and marker for each system in the plot.

the magnitude plot is a straight line with a slope of 20 d B per decade, passing through the abscissa axis at ω = 1 rad/s, and the phase plot is a constant equal to 90 ∘ (Fig. 5.9): Figure 5.9. Bode plots of the monomial term j ω .

For the magnitude plot, mark the starting point on the graph and draw a straight line with the starting slope until you reach the frequency of a pole or zero. At this point, zeros change the slope by 20 dB/dec and poles change the slope by −20 dB/dec.

In electrical engineering and control theory, a Bode plot /ˈboʊdi/ is a graph of the frequency response of a system. It is usually a combination of a Bode magnitude plot, expressing the magnitude (usually in decibels) of the frequency response, and a Bode phase plot, expressing the phase shift.

Simply divide the amplitude of the output by the amplitude of the input to get |H(f)| at that frequency. If you want the broadband frequency response, for example from 20 Hz to 20000 Hz, you have to provide an input signal that goes from 20 Hz to 20000 Hz, and record the output at each frequency.

Customize Bode Plot using Plot Handle

Change the units to Hz and suppress the phase plot. To do so, edit properties of the plot handle, h using setoptions . setoptions(h,'FreqUnits','Hz','PhaseVisible','off'); The Bode plot automatically updates when you call setoptions .

Frequency response plots provide insight into linear systems dynamics, such as frequency-dependent gains, resonances, and phase shifts. Frequency response plots also contain information about controller requirements and achievable bandwidths.

What should a frequency response graph look like? ›

The frequency response curve (so-called because a speaker's or headphone's frequency response will curve, or roll off, in the low bass and high treble) is pretty flat (“flat” is good, because it means the device is accurate), with no serious peaks, dips or other up-and-down variations.

Draw a pair of axes and label them with 'Frequency' on the vertical axis ( y y y-axis) and 'Measurement' on the horizontal axis ( x x x-axis). Use a ruler to draw each bar with the correct height. Draw the heights of the bars depending on its frequency.

Bode plots show the frequency response, that is, the changes in magnitude and phase as a function of frequency. This is done on two semi-log scale plots. The top plot is typically magnitude or “gain” in dB. The bottom plot is phase, most commonly in degrees.

Bode plots are a very useful way to represent the gain and phase of a system as a function of frequency. This is referred to as the frequency domain behavior of a system.

The magnitude of the transfer function is proportional to the product of the geometric distances on the s-plane from each zero to the point s divided by the product of the distances from each pole to the point.

Bode diagram in Figure 22a provides the relationship between the magnitude (in dB) and phase shift versus frequency (in rad/s) for the transfer function of the PI controller, = ().

The locations of every pole and every zero are called break points. At a zero breakpoint, the slope of the line increases by 20dB/Decade. At a pole, the slope of the line decreases by 20dB/Decade. At a zero breakpoint, the value of the actual graph differs from the value of the straight-line graph by 3dB.