User Manual

3.10 FFT Analysis Modes
102
3.10.2 Analysis Mode Functions
Analysis Mode Internal analysis formula (linear, real, imag [imaginary], log [logarithm])
No Analysis
No analysis.
Storage Waveform
A waveform obtained by applying the window function to a time-domain waveform.
Linear Spectrum (LIN)
RMS Spectrum (RMS)
Power Spectrum (PSP)
Power Spectrum Density
(PSD)
Auto-correlation Func-
tion (ACR)
Histogram (HIS)
Counts amplitude data.
Transfer Function (TRF)
Cross Power Spectrum
(CSP)
Cross-correlation Func-
tion (CCR)
Impulse Response (IMP)
Coherence Function
(COH)
Phase Spectrum
(1ch / 2ch) (PHA)
Power Spectrum (LPC)
(Abbr.) Spectrum approximation from Linear Predictive Coding.
See "Linear Predictive Coding (LPC)" (⇒ p. 115)
⎩
⎨
⎧
===
∑
−
=
)
(/2
)
(/1
)()()()(
1
0
ACN
DCN
CkCXkFWnxkX
N
n
kn
{} {}
)
(log20log)(Im)(Re)( kFkFimagkFrealkF
l
inear ====
⎩
⎨
⎧
==
)
(2/1
)
(1
')(')('
AC
DC
CkFCkF
{} {}
)
('log20log)('Im)('Re)(' kFkFimagkFrealkF
l
inear ====
⎩
⎨
⎧
==
)
(2/1
)
(1
)()(
2
AC
DC
akFakP
)
(log10log)( kPkP
l
inear ==
f
kPkP
δ
/)()(' =
δ f: Frequency resolution
)
('log10log)(' kPkP
l
inear ==
∑
−
=
−
=
1
0
2
)(
1
)(
N
k
k
n
xx
WkX
N
nR
(recursive convolution)
)
(/)()( kXkYkH =
{} {}
)
(log20log)(Im)(Re)( kHkHimagkHrealkH
l
inear ====
)
()()(
*
kYkXk
S
yx
=
: Cross Spectrum
⎩
⎨
⎧
==
2
2
/2
/1
)()(
N
N
AkASkX
yxpower
{}
{}
)
(log10log)(Im
)(Re)(
kXkX
m
ag
kXrealkX
l
inear
powerpower
powerpower
==
==
(recursive convolution)
∑
−
=
−
=
1
0
)(
1
)(
N
k
k
n
yxyx
WkS
N
nR
∑
−
=
−
=
1
0
)(
)(1
)(
N
k
k
n
W
kX
kY
N
n
h
)
()(
)
()(
)(
*
kSkS
kSkS
k
c
oh
yyxx
yxyx
=
))
('Re(/))('(Im(tan/180)(
1
kFkFk
−
×= πθ
))
(Re(/))((Im(tan/180)(
1
kSkSk
yxyx
−
×= πθ