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Справка Scilab >> CACSD > Linear Analysis > Frequency Domain > bode


Bode plot


bode(sl, [fmin, fmax] [,step] [,comments] )
bode(sl, [fmin, fmax] [,step] [,comments] [,"rad"] )
bode(sl, frq [,comments] )
bode(sl, frq [,comments] [,"rad"] )
bode(frq, db, phi [,comments] )
bode(frq, repf [,comments] [,"rad"] )



syslin list (SISO or SIMO linear system) in continuous or discrete time.


real (frequency bounds (in Hz))


real (logarithmic step.)


vector of character strings (captions).


row vector or matrix (frequencies (in Hz) ) (one row for each SISO subsystem).


row vector or matrix ( magnitudes (in Db)). (one row for each SISO subsystem).


row vector or matrix ( phases (in degree)) (one row for each SISO subsystem).


row vector or matrix of complex numbers (complex frequency response).


converts the frequency from Hz into rad/s (multiplies by 2π),


Bode plot, i.e magnitude and phase of the frequency response of sl.

sl can be a continuous-time or discrete-time SIMO system (see syslin). In case of multi-output the outputs are plotted with different symbols.

The frequencies are given by the bounds fmin,fmax (in Hz) or by a row-vector (or a matrix for multi-output) frq.

step is the ( logarithmic ) discretization step. (see calfrq for the choice of default value).

comments is a vector of character strings (captions).

db,phi are the matrices of modulus (in Db) and phases (in degrees). (One row for each response).

repf matrix of complex numbers. One row for each response.

Default values for fmin and fmax are 1.d-3, 1.d+3 if sl is continuous-time or 1.d-3, 0.5/sl.dt (nyquist frequency) if sl is discrete-time. Automatic discretization of frequencies is made by calfrq.

The datatips tool may be used to display data along the phase and modulus curves.


s = poly(0, 's');
h = syslin('c', (s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01));

clf(); bode(h, 0.01, 100);

s = poly(0, 's');
h1 = syslin('c', (s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01));
num = 22801+4406.18*s+382.37*s^2+21.02*s^3+s^4;
den = 22952.25+4117.77*s+490.63*s^2+33.06*s^3+s^4;
h2 = syslin('c', num/den);

clf(); bode([h1; h2], 0.01, 100, ['h1'; 'h2']);

s = %s;
G = (10*(s+3))/(s*(s+2)*(s^2+s+2)); // A rational matrix
sys = syslin('c', G); // A continuous-time linear system in transfer matrix representation.
f_min = .0001; f_max = 16; // Frequencies in Hz

clf(); bode(sys, f_min, f_max, "rad"); // Converts Hz to rad/s

See also

  • bode_asymp — Bode plot asymptote
  • black — Black-Nichols diagram of a linear dynamical system
  • nyquist — nyquist plot
  • gainplot — magnitude plot
  • repfreq — frequency response
  • g_margin — gain margin and associated crossover frequency
  • p_margin — phase margin and associated crossover frequency
  • calfrq — frequency response discretization
  • phasemag — phase and magnitude computation
  • datatips — Tool for placing and editing tips along the plotted curves.
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Last updated:
Tue Feb 14 15:13:23 CET 2017