def Fit(self):
"""
Fits a two-port RLGC model for the specified s-parameter file
"""
sp = SParameterFile(self.spfile, self.Z0)
stepResponse = sp.FrequencyResponse(2, 1).ImpulseResponse().Integral()
threshold = (stepResponse[len(stepResponse) - 1] +
stepResponse[0]) / 2.0
for k in range(len(stepResponse)):
if stepResponse[k] > threshold: break
dly = stepResponse.Times()[k]
rho = sp.FrequencyResponse(
1, 1).ImpulseResponse().Integral(scale=False).Measure(dly)
Z0 = sp.m_Z0 * (1. + rho) / (1. - rho)
L = dly * Z0
C = dly / Z0
guess = [0., L, 0., C, 0., 0.]
fitter = RLGCFitter(sp, guess)
(R, L, G, C, Rse, df) = [r[0] for r in fitter.Solve().Results()]
# print "series resistance: "+ToSI(R,'ohm')
# print "series inductance: "+ToSI(L,'H')
# print "shunt conductance: "+ToSI(G,'S')
# print "shunt capacitance: "+ToSI(C,'F')
# print "skin-effect resistance: "+ToSI(Rse,'ohm/sqrt(Hz)')
# print "dissipation factor: "+ToSI(df,'')
s = self.scale
self.RLGC = TLineTwoPortRLGCAnalytic(self.m_f,
R * s,
Rse * s,
L * s,
G * s,
C * s,
df,
Z0=50.)
return self.RLGC
def SParameterRegressionChecker(self,sp,spfilename):
from SignalIntegrity.Lib.SParameters.SParameterFile import SParameterFile
currentDirectory=os.getcwd()
os.chdir(self.path)
if not os.path.exists(spfilename):
sp.WriteToFile(spfilename)
if not self.relearn:
self.assertTrue(False, spfilename + ' not found')
regression=SParameterFile(spfilename)
SpAreEqual=self.SParametersAreEqual(sp, regression,self.SPCompareResolution)
if not SpAreEqual:
if SignalIntegrityAppTestHelper.plotErrors:
import matplotlib.pyplot as plt
plt.clf()
plt.title(spfilename)
plt.xlabel('frequency (Hz)')
plt.ylabel('amplitude')
for r in range(regression.m_P):
for c in range(regression.m_P):
plt.semilogy(regression.f(),[abs(sp[n][r][c]-regression[n][r][c]) for n in range(len(regression))],label='S'+str(r+1)+str(c+1))
plt.legend(loc='upper right')
plt.grid(True)
plt.show()
for r in range(regression.m_P):
for c in range(regression.m_P):
plt.clf()
plt.title('S'+str(r+1)+str(c+1)+' Magnitude')
plt.plot(sp.FrequencyResponse(r+1,c+1).Frequencies(),sp.FrequencyResponse(r+1,c+1).Values('dB'),label='calculated')
plt.plot(regression.FrequencyResponse(r+1,c+1).Frequencies(),regression.FrequencyResponse(r+1,c+1).Values('dB'),label='regression')
plt.xlabel('frequency (Hz)')
plt.ylabel('amplitude (dB)')
plt.legend(loc='upper right')
plt.grid(True)
plt.show()
plt.clf()
plt.title('S'+str(r+1)+str(c+1)+' Phase')
plt.plot(sp.FrequencyResponse(r+1,c+1).Frequencies(),sp.FrequencyResponse(r+1,c+1).Values('deg'),label='calculated')
plt.plot(regression.FrequencyResponse(r+1,c+1).Frequencies(),regression.FrequencyResponse(r+1,c+1).Values('deg'),label='regression')
plt.xlabel('frequency (Hz)')
plt.ylabel('amplitude (dB)')
plt.legend(loc='upper right')
plt.grid(True)
plt.show()
self.assertTrue(SpAreEqual,spfilename + ' incorrect')
os.chdir(currentDirectory)