# GainPhaseMargins

GainPhaseMargins[lsys]

gives the gain and phase margins of the linear time-invariant system lsys.

# Details and Options • The system lsys can be a TransferFunctionModel or a StateSpaceModel.
• GainPhaseMargins returns {{{ωp1,g1},{ωp2,g2},},{{ωg1,p1},{ωg2,p2},}}, where the ωpi are the phase crossover frequencies, the gi are the gain margins, the ωgi are the gain crossover frequencies, and the pi are the phase margins.
• The gain margins gi are absolute values and the phase margins pi are in radians.
• The gain margins are the reciprocals of the magnitude of lsys at the phase crossover frequencies.
• At the phase crossover frequencies, lsys has phase .
• The phase margins are phase lags needed to make the phase at the gain crossover frequencies.
• At the gain crossover frequencies, the gain of lsys is unity.
• The following options can be given:
•  FeedbackType "Negative" the feedback type Method Automatic method to use SamplingPeriod None the sampling period
• Explicit settings for the Method option include "Solve" and "NSolve". In each case the methods of Solve or NSolve can be specified as suboptions. The default setting of Automatic switches between these methods, depending on whether lsys is exact or inexact.
• GainPhaseMargins has the attribute Listable.

# Examples

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## Basic Examples(1)

The gain and phase margins of a system:

## Scope(3)

A system with multiple crossover frequencies:

The number of gain crossover frequencies:

A discrete-time system:

Margins of a time-delay system:

equals :

## Options(2)

### FeedbackType(2)

The system is assumed to be the loop transfer function of a negative-feedback system:

Specify the system as part of a positive-feedback system:

Specify the system as a closed-loop system:

A positive-feedback system:

## Properties & Relations(2)

The gain and phase margins can be visualized on all the frequency response plots:

The gain margins in decibels:

The phase margins in degrees:

If the crossover frequencies are in radians/second, they can be converted to hertz as follows:

The setting computes and draws the gain and phase margins: