Method for measuring Noise RMS of periodic signal and signal-to-noise ratio of sinusoidal signal
View Patent ↗The present application relates to a method for measuring a Noise RMS of a periodic signal and a signal-to-noise ratio of a sinusoidal signal. The technical points of the method comprise: respectively executing signal noise measurement on a target periodic digital signal and a target periodic analog signal; obtaining a series of zero-crossing points of electrical signals, performing analog-to-digital conversion once at a relative time determined by means of the series of zero-crossing points; and further calculating the noise of the periodic signals by means of a series of analog-to-digital conversion results. The method further comprises: respectively executing signal-to-noise ratio measurement on a target sinusoidal digital signal and a target sinusoidal analog signal; obtaining a series of zero-crossing points of electrical signals; according to each zero-crossing point, calculating the frequency or period of the electric signal; and then performing calculation to obtain a signal-to-noise ratio of a sinusoidal signal.
1 . A method for measuring a signal-to-noise ratio of a sinusoidal signal, applied in an embedded system, used to obtain a signal-to-noise ratio of a target sinusoidal signal, wherein the target sinusoidal signal is a target sine digital signal, and comprises following steps:
Step A′, sampling the target periodic signal by an analog-to-converter, to obtain a sampled signal, and then entering step B′;
Step B′, obtaining, through an analog means or a digital means, a continuous zero-crossing time series T z1 , . . . , T zk , . . . , T zK of at least two periods on the sampled signal after passing a negative peak value or a positive peak value, wherein K denotes a number of zero-crossing time instants in the continuous zero-crossing time series, and T zk denotes a k-th zero-crossing time instant in the continuous zero-crossing time series; and then initializing j=K+1 and entering Step C′;
Step C′, calculating and obtaining, according to T z(j-1) , . . . , T z(j-m) , an average period T, and further calculating and obtaining, according to a preset parameter c that satisfies a value range (0.5,1), a digital initial integration point time instant T sj corresponding to a j-th zero-crossing time instant T zj through T sj =T z(j-1) +T×c, and then entering Step D′, wherein, 1<m<j, and T zj denotes the j-th zero-crossing time instant;
Step D′, selecting, on a basis of each sampling point on the sampling signal, two sampling points that are adjacent front and back to the digital initial integration point time instant T sj , and sequentially forming a first sampling point to be analyzed, and a second sampling point to be analyzed, forming, by combining a time instant corresponding to the sampling point and a sampling value corresponding to the sampling point, a coordinate of the sampling point to be analyzed, and then entering Step E′;
Step E′, obtaining, according to the digital initial integration point time instant T sj , a sampling value x sj corresponding to T sj and at a position between a first sampling point and a second sampling point through a rectangular interpolation means or a trapezoidal interpolation means, to form a coordinate (T sj , x sj ) of a digital integration starting point, and then initializing v=2, sequentially defining each sampling point after the first sampling point and the second sampling point on the sampling signal as each sampling point to be analyzed, and entering Step F′;
Step F′, executing a digital integration operation on the sampling signal from a coordinate position of the digital integration starting point to a coordinate position of a v-th sampling point to be analyzed, to form a digital integration result S v ; and executing a digital integration operation on the sampling signal from a coordinate position of the digital integration starting point to a coordinate position of a v+1-th sampling point to be analyzed, to form a digital integration result S v+1 , and then entering Step G′;
Step G′, determining whether a product of the digital integration result S v , and the digital integration result S v+1 is greater than 0, updating, in a case of yes, a value for v by adding 1 and returning to Step F′; otherwise, entering Step H′;
Step H′, obtaining, according to a condition that a sum of a digital integration from the digital integration starting point to an digital integration ending point is zero to overcome interference from harmonics or noises, a coordinate (T ej , x ej ) of an digital integration ending point located between the v-th sampling point to be analyzed and the v+1-th sampling point to be analyzed through the rectangular interpolation means or the trapezoidal interpolation means, and then entering Step I′;
Step I′, obtaining, according to
T
zj
=
T
sj
+
T
ej
2
,
the j-th zero-crossing time instant T zj , further, obtaining, according to T tj =T ej −T sj , an integration time duration T tj corresponding to the j-th zero-crossing time instant T zj , and forming an integration time duration T tj corresponding to a j-th target zero-crossing time instant T zj , and then entering Step J′;
Step J′, obtaining, according to the target zero-crossing time instant T zj , a measured signal period through T p(j-1) =T zj −T z(j-1) , obtaining, through
F
(
j
-
1
)
=
1
T
p
(
j
-
1
)
=
1
T
zj
-
T
z
(
j
-
1
)
,
a tested signal frequency, and then entering Step K′;
Step K′, determining whether a length of a signal zero-crossing time series {T z(K+1) , . . . , T zj } is less than a preset threshold w+1, entering, in case of yes, Step N′;
otherwise, performing a following calculation: selecting w latest generated integration time durations from the signal integration time duration series {T t(K+1) , . . . , T tj }, calculating and acquiring an average integration time duration T ta , and converting the average integration time duration T ta into a count value n corresponding to a sampling period multiple; selecting w latest generated signal periods from a signal period series {T p(K+1) , . . . , T p(j-1) }, calculating and acquiring an average period value T pa , converting the average period value T pa into a count value N corresponding to the sampling period multiple, and then entering Step L′;
Step L′, calculating and obtaining, according to the w latest generated signal periods selected from the signal period series {T p(K+1) , . . . , T p(j-1) }, a period standard deviation σ T , and obtaining, through
σ
R
=
σ
T
T
pa
,
a parameter σ R ; or, calculating and obtaining, according to w latest generated signal frequencies selected from a signal frequency series {F (K+1) , . . . , F (j-1) }, a frequency standard deviation σ F , obtaining, through
σ
R
=
σ
F
1
/
T
pa
,
a parameter σ R , and then entering step M′; and
Step M′, calculating and obtaining, according to count values n and N, as well as the parameter σ R , a signal-to-noise ratio SNR of the target sinusoidal signal through
SNR
=
A
2
2
σ
2
,
wherein A denotes a peak value for the sinusoidal signal and a denotes a Noise RMS for the signal, and then entering Step N′;
Step N′, updating, by adding 1, a value for j, and returning to Step C′.
2 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 1 , wherein in Step C′, according to T z(j-1) , . . . , T z(j-m) , the average period T is calculated and obtained through
T
=
T
z
(
j
-
1
)
-
T
z
(
j
-
m
)
m
-
1
.
3 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 1 , wherein in Step A′, the target periodic signal is sampled by adopting an equal time interval sampling means or an unequal time interval sampling means to obtain the sampled signal; and a whole period sampling is executed on the target periodic signal to obtain the sampled signal.
4 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 1 , wherein in Step F′, the digital integration operation is either a trapezoidal integration or a rectangular integration.
5 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 1 , wherein in Step M′, the step of calculating and obtaining, according to count values n and N, as well as the parameter σ R , a signal-to-noise ratio SNR of the target sinusoidal signal through
SNR
=
A
2
2
σ
2
follows an arbitrary of following four formulas:
SNR
=
A
2
2
σ
2
=
n
{
2
×
σ
R
×
N
×
sin
[
n
N
×
π
]
}
2
SNR
=
A
2
2
σ
2
=
N
×
2
×
(
1
-
c
)
{
2
×
σ
R
×
N
×
sin
[
n
N
×
π
]
}
2
SNR
=
A
2
2
σ
2
=
n
{
2
×
σ
R
×
N
×
sin
[
2
×
(
1
-
c
)
×
π
]
}
2
SNR
=
A
2
2
σ
2
=
N
×
2
×
(
1
-
c
)
{
2
×
σ
R
×
N
×
sin
[
2
×
(
1
-
c
)
×
π
]
}
2
.
6 . A method for measuring a signal-to-noise ratio of a sinusoidal signal, applied in an embedded system, used to obtain a signal-to-noise ratio of a target sinusoidal signal, wherein the target sinusoidal signal is a target sinusoidal analog signal, and comprises following steps:
Step i′, obtaining, through an analog means or a digital means, a continuous zero-crossing time series T z1 , . . . , T zk , . . . , T zK of at least two periods on the sampled signal after passing a negative peak value or a positive peak value, wherein K denotes a number of zero-crossing time instants in the continuous zero-crossing time series, and T zk denotes a k-th zero-crossing time instant in the continuous zero-crossing time series; and then initializing j=K+1 and entering Step ii′;
Step ii′, calculating and obtaining, according to T z(j-1) , . . . , T z(j-m) , an average period T, and further calculating and obtaining, according to a preset parameter c that satisfies a value range (0.5,1), a digital initial integration point time instant T sj corresponding to a j-th zero-crossing time instant T zk through T sj =T z(j-1) +T×c, and then entering Step iii′, wherein 1<m<j, T zk denotes the j-th zero-crossing time instant;
Step iii′, initializing, before the time instant T sj , an integrator, to return an integrator output voltage to zero, and starting an analog integration at a digital integration starting point time instant T sj , terminating, in a case where the integrator output voltage returns to zero again, the integration, and recording an integration ending point time instant T ej , to overcome interference from harmonics or noises, and then entering Step iv′;
Step iv′, obtaining, according to
T
zj
=
T
sj
+
T
ej
2
,
the j-th zero-crossing time instant T zj , and further obtaining, according to T tj =T ej −T sj , an integration time duration T tj corresponding to the j-th zero-crossing time instant T zj , and forming an integration time duration T tj corresponding to a j-th target zero-crossing time instant T zj , and then entering Step v′;
Step v′, obtaining, according to the target zero-crossing time instant T zj , a measured signal period through T p(j-1) =T zj −T z(j-1) , obtaining, through
F
(
j
-
1
)
=
1
T
p
(
j
-
1
)
=
1
T
zj
-
T
z
(
j
-
1
)
,
a tested signal frequency, and then entering Step vi′;
Step vi′, determining whether a length of a signal zero-crossing time series {T z(K+1) , . . . , T zj } is less than a preset threshold w+1, entering, in case of yes, Step ix′; otherwise, performing a following calculation: selecting w latest generated integration time durations from the signal integration time duration series {T t(K+1) , . . . , T tj }, calculating and acquiring an average integration time duration T ta , and converting the average integration time duration T ta into a count value n corresponding to a counter period multiple; selecting w latest generated signal periods from a signal period series {T p(K+1) , . . . , T p(j-1) }, calculating and acquiring an average period value T pa , converting the average period value T pa into a count value N corresponding to the counter period multiple, and then entering Step vii′;
Step vii′, calculating and obtaining, according to the w latest generated signal periods selected from the signal period series {T p(K+1) , . . . , T p(j-1) }, a period standard deviation σ T , and obtaining, through
σ
R
=
σ
T
T
pa
,
a parameter σ R ; or, calculating and obtaining, according to w latest generated signal frequencies selected from a signal frequency series {F (K+1) , . . . , F (j-1) }, a frequency standard deviation, obtaining, through
σ
R
=
σ
F
1
/
T
pa
,
a parameter σ R , and then entering Step viii′; and
Step viii′, calculating and obtaining, according to count values n and N, as well as the parameter σ R , a signal-to-noise ratio SNR of the target sinusoidal signal through
SNR
=
A
2
2
σ
2
,
wherein A denotes a peak value for the sinusoidal signal and σ denotes a Noise RMS for the signal, and then entering Step ix′; and
Step ix′, updating, by adding 1, a value for j, and returning to Step ii′.
7 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 6 , wherein, according to T z(j-1) , . . . , T z(j-m) , the average period T is calculated and obtained through
T
=
T
z
(
j
-
1
)
-
T
z
(
j
-
m
)
m
-
1
.
8 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 6 , wherein after respectively obtaining the digital integration starting point time instant T sj and the digital integration ending point time instant T ej , T sj and T ej are respectively calibrated and updated according to circuit delay parameters.
9 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 6 , wherein in Step viii′, the step of calculating and obtaining, according to count values n and N, as well as the parameter σ R , a signal-to-noise ratio SNR of the target sinusoidal signal through
SNR
=
A
2
2
σ
2
follows an arbitrary of following four formulas:
SNR
=
A
2
2
σ
2
=
n
{
2
×
σ
R
×
N
×
sin
[
n
N
×
π
]
}
2
SNR
=
A
2
2
σ
2
=
N
×
2
×
(
1
-
c
)
{
2
×
σ
R
×
N
×
sin
[
n
N
×
π
]
}
2
SNR
=
A
2
2
σ
2
=
n
{
2
×
σ
R
×
N
×
sin
[
2
×
(
1
-
c
)
×
π
]
}
2
SNR
=
A
2
2
σ
2
=
N
×
2
×
(
1
-
c
)
{
2
×
σ
R
×
N
×
sin
[
2
×
(
1
-
c
)
×
π
]
}
2
.
10 . The method for measuring the signal-to-noise ratio of the sinusoidal signal according to claim 6 , wherein in Step iii′, the analog integration is implemented by utilizing an operational amplifier or other devices with integration functions.