Electromagnetic interference objective complexity evaluation method based on fast S-transformation time-frequency space model
An electromagnetic interference objective complexity evaluation method based on a fast S-transformation time-frequency space model comprises the following steps: (1) carrying out fast S-transformation on space electromagnetic signals acquired in real time to obtain a fast speed S-transformation two-dimensional time-frequency matrix of the signal; (2) calculating time domain occupancy rate T P , frequency occupancy rate F P , and energy occupancy rate E P of an evaluation object and interference signals in the fast speed S-transformation two-dimensional time-frequency matrix; (3) calculating electromagnetic interference objective complexity C=T P *F P *E P according to the time-frequency space model; and (4) finding a grading standard according to an objective complexity value so as to determine an electromagnetic interference objective complexity type. Compared with the prior art, the electromagnetic interference objective complexity evaluation method based on the fast S-transformation time-frequency space model has the characteristics that a fast S-transformation method is adopted, one-dimensional limitation of Fourier transformation is overcome, three evaluation parameters including the time domain occupancy rate, the frequency occupancy rate and the energy occupancy rate can be rapidly extracted simultaneously, and by adopting the time-frequency space model, the problem of synchronous and overall evaluation of multiple evaluation parameters can be effectively solved.
1. An electromagnetic interference objective complexity evaluation method based on a fast S-transformation time-frequency space model, comprising the following steps:
(1) carrying out, by a processor, fast S-transformation on space electromagnetic signals, comprising interference signals, acquired by sensors in real time to obtain a fast S-transformation two-dimensional time-frequency matrix of the space electromagnetic signals;
(2) calculating, by the processor, time domain occupancy rate T P , frequency occupancy rate F P and energy occupancy rate E P of the interference signals of an evaluation object in the fast S-transformation two-dimensional time-frequency matrix of the space electromagnetic signals according to the S-transformation two-dimensional time-frequency matrix;
(3) calculating, by the processor, electromagnetic interference objective complexity C=T P *F P *E P of the interference signals according to the time-frequency space model consisting of the time domain occupancy rate, the frequency occupancy rate and the energy occupancy rate; and
(4) determining, by the processor, a quality grade and a quantitative grade of the electromagnetic interference objective complexity of the interference signals according to the electromagnetic interference objective complexity of the interference signals.
2. The electromagnetic interference objective complexity evaluation method based on the fast S-transformation time-frequency space model according to claim 1 , wherein in step (1), the fast S-transformation is a short-time Fourier transformation fast speed algorithm which takes a Gaussian function as a window function, the expression of the algorithm is S(t,f)=∫ −∞ ∞ [G(f+f′)·W(f′,f)]·e i2πf′ t df′, in the expression, G(f+f′)=∫ −∞ +∞ x(t)·e −i2π·(f+f′)·t ·dt is Fourier transformation of the space electromagnetic interference signal x(t) acquired in real time,
W
(
f
′
,
f
)
=
∫
-
∞
+
∞
f
2
π
·
e
[
-
f
2
(
τ
-
t
)
2
2
]
·
e
-
i
2
π
f
′
t
·
dt
is Fourier transformation of a window function
ψ
(
t
)
=
1
2
π
e
-
t
2
2
,
t is time, f′ is sampling frequency, f is frequency, τ is a time shift factor, and i is an imaginary number.
3. The electromagnetic interference objective complexity evaluation method based on the fast S-transformation time-frequency space model according to claim 2 , wherein in step (2), the time domain occupancy rate T P is
T
P
=
∫
f
1
f
2
[
S
(
t
,
f
)
-
S
0
(
t
2
-
t
1
)
(
f
2
-
f
1
)
]
df
,
in the expression, t 1 and t 2 are effective starting time and effective ending time respectively, f 1 and f 2 are evaluated starting frequency and evaluated ending frequency respectively, S(t, f) is the fast S-transformation two-dimensional time-frequency matrix, and S 0 is a reference time-frequency matrix plane; the frequency occupancy rate F P is
F
P
=
∫
t
1
t
2
[
S
(
t
,
f
)
-
S
0
(
t
2
-
t
1
)
(
f
2
-
f
1
)
]
dt
;
and the energy occupancy rate E P is
E
P
=
S
(
t
,
f
)
-
S
0
max
[
S
(
t
,
f
)
]
-
S
0
,
and in the expression, max[S(t, f)] is a maximum value in all elements of the S-transformation time-frequency matrix.
4. The electromagnetic interference objective complexity evaluation method based on the fast S-transformation time-frequency space model according to claim 1 , wherein in step (4), the qualitative grade and the quantitative grade of the electromagnetic interference objective complexity is found by the processor through a lookup table stored in a storage device.