Name: reading frequency response on bode plots
Uploaded: 2024-07-08T13:20:02.000Z
Duration: 1 min 26 s
Channel: JoVE

Considérons un appareil d’électrocardiogramme qui utilise un filtre passe-bas avec une fonction de réseau complexe représentée par son amplitude et son angle de phase.
Le gain logarithmique en décibels est calculé en multipliant par 20 le logarithme en base dix de l'amplitude de la fonction de réseau.
Les diagrammes de Bode sont des graphiques semi-logarithmiques qui affichent le gain logarithmique en décibels et l’angle de phase en degrés à travers les fréquences.
Aux fréquences plus basses, le gain logarithmique et l’angle de phase sont proches de zéro.
Il en résulte des lignes horizontales sur le graphique de Bode, appelées asymptotes à basse fréquence.
À des fréquences plus élevées, les calculs de gain et d’angle de phase reflètent leur dépendance à la fréquence.
Elles sont représentées par des lignes droites avec des pentes négatives et sont connues sous le nom d’asymptotes à haute fréquence.
Les asymptotes de basse et de haute fréquence se coupent dans un coin, également connu sous le nom de fréquence d’angle.
À cette fréquence, la magnitude asymptotique s’écarte de près de -3 décibels de la valeur exacte, et l’angle de phase est d’environ -45 degrés.
Les diagrammes de présage asymptotiques sont de bonnes approximations des diagrammes de présage réels.

plots de bode

Les tracés de Bode sont des outils graphiques qui utilisent des échelles logarithmiques pour la fréquence sur l'axe des x et le gain en décibels sur l'axe des y. Cette méthode logarithmique permet d'afficher de manière compacte une large gamme de fréquences, permettant ainsi l'analyse des effets des composants sur le comportement du circuit sur un large spectre de fréquences.
Une fonction de réseau représente le rapport entre la sortie d'un système et son entrée, l'amplitude et l'angle de phase étant dérivés de la fonction de réseau complexe. Le gain logarithmique en décibels est déterminé en multipliant le logarithme en base dix de l'amplitude de la fonction réseau par 20. Le gain dans un tracé de Bode est exprimé de manière logarithmique. L'unité de gain logarithmique est le décibel, également appelé gain en dB. Les décibels (dB) quantifient le gain, où 1 dB équivaut à un dixième de bel, ce qui rend hommage à Alexander Graham Bell.
Les tracés de Bode, qui sont des graphiques semi-logarithmiques, montrent le gain logarithmique en décibels et l'angle de phase en degrés sur une plage de fréquences. Ces tracés facilitent la compréhension de la réponse en fréquence d'un système.

Aux basses fréquences, le gain logarithmique et l'angle de phase se rapprochent de zéro, formant des lignes horizontales sur le tracé de Bode connues sous le nom d'asymptotes basse fréquence. Ces lignes indiquent un impact minimal du filtre sur les signaux à ces fréquences. À mesure que la fréquence augmente, les calculs de gain et d’angle de phase reflètent leur dépendance en fréquence. Sur le tracé de Bode, ces dépendances apparaissent sous forme de lignes droites à pentes négatives, appelées asymptotes haute fréquence. Ces lignes montrent comment le filtre atténue les signaux à haute fréquence. Les asymptotes basse et haute fréquence se croisent à la fréquence angulaire. Ici, la magnitude asymptotique s'écarte d'environ -3 décibels par rapport à la valeur exacte, marquant un changement significatif dans la réponse du filtre. De plus, l'angle de phase à la fréquence angulaire est d'environ -45 degrés.

Les tracés de Bode asymptotiques fournissent des approximations raisonnables des tracés de Bode réels, permettant une analyse simplifiée tout en conservant une précision raisonnable.

Plots de Bode

Considérons un appareil d’électrocardiogramme qui utilise un filtre passe-bas avec une fonction de réseau complexe représentée par son amplitude et son angle de phase.
Le...

Education

Enseignement

JoVE Core

Electrical Engineering

Génie électrique

Unit 1

Unité 1

Frequency Response

Réponse en fréquence

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

Bode Plots

reading frequency response on bode plots

Bode plots show how a circuit or system responds across frequency. They use a logarithmic frequency scale on the x-axis and gain in decibels on the y-axis. This format makes it easier to display a wide range of frequencies and to see how circuit parts affect behavior over that range.

A network function gives the ratio of output to input for a system. Its complex form provides both magnitude and phase angle. The logarithmic gain on a Bode plot comes from the magnitude, calculated by multiplying the base-ten logarithm of that magnitude by 20. The gain is measured in decibels, or dB. A decibel is one-tenth of a bel, and the unit honors Alexander Graham Bell.

Because Bode plots are semilogarithmic graphs, they show gain in dB and phase angle in degrees over frequency. This makes the frequency response of a system easier to study. At low frequencies, both gain and phase angle approach zero. These flat regions are called low-frequency asymptotes, and they show that the filter has little effect on the signal there.

As frequency rises, the gain and phase angle change with frequency. On the plot, this appears as straight lines with negative slopes called high-frequency asymptotes. These lines show that the filter attenuates higher-frequency signals. The low- and high-frequency asymptotes meet at the corner frequency. At that point, the asymptotic magnitude is about -3 decibels from the exact value, and the phase angle is about -45 degrees. Asymptotic Bode plots give a reasonable approximation of the actual plot and make analysis simpler while keeping useful accuracy.

Reading Frequency Response on Bode Plots

analyzing-filter-response-with-bode-plots

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bode plots

Bode plots show how a circuit or system responds across frequency. They use a logarithmic frequency scale on the x-axis and gain in decibels on the y-axis. This format makes it easier to display a wide range of frequencies and to see how circuit parts affect behavior over that range. A network function gives the ratio of output to input for a system. Its complex form provides both magnitude and phase angle. The logarithmic gain on a Bode plot comes from the magnitude, calculated by multiplying...

transfer function and bode plots-i

Transfer Function Gain and Origin Effects

Transfer function gain and poles or zeros at the origin shape a system's Bode plot. The transfer function is often written in standard form after the polynomial coefficients are normalized. In that form, the constant gain, zeros, poles, and quadratic terms all appear clearly. The poles and zeros mark critical frequencies where the output magnitude and phase change noticeably. The constant gain K creates a fixed magnitude and phase term. Its magnitude is 20 log 10 K in decibels, and its phase...

transfer function and bode plots-ii

Bode Plot Slope and Phase Changes

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Reading Frequency Response with Bode Plots

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characteristics-of-series-resonant-circuit

Series Resonance and RLC Filter Behavior

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Op Amp Gain and Bode Plot Basics

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key terms and concepts

Learn how Bode plots use decibels, phase angle, and asymptotes to show frequency response, including corner frequency and filter behavior.

Reading Frequency Response on Bode Plots | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

electrical engineering

Reading Frequency Response on Bode Plots

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