CN114966198A - Sinusoidal signal-to-noise ratio measuring method - Google Patents
Sinusoidal signal-to-noise ratio measuring method Download PDFInfo
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Abstract
The invention relates to a sinusoidal signal-to-noise ratio measuring method, which comprises the steps of respectively carrying out signal-to-noise ratio measurement aiming at a target sinusoidal digital signal and a target sinusoidal analog signal, obtaining the zero crossing points of a series of electric signals through a specific design method, calculating the frequency or the period of each zero crossing point calculated electric signal, and further calculating to obtain the sinusoidal signal-to-noise ratio; the design scheme is suitable for measuring the signal-to-noise ratio of the sinusoidal signal, the system detection is convenient, and the hardware overhead is low; the anti-interference capability of the system is strong; the method is simple and reasonable to realize, and the data is accurate and reliable.
Description
Technical Field
The invention relates to a method for measuring the signal-to-noise ratio of a sinusoidal signal, belonging to the technical field of signal-to-noise ratio measurement.
Background
In practical applications, a device receives a useful signal that needs to be processed by the device, as well as random noise that is not present in the useful signal. The ratio of the power of the desired signal to the power of the interference noise in the received signal is called the signal-to-noise ratio (SNR). The useful signal power and the noise power are respectively measured through effective values of all samples of a received signal sequence and a received noise sequence, the signal-to-noise ratio is an important parameter, can be measured in real time, can reflect the characteristics of a system in real time and is an important index for measuring the performance of a receiver; however, the prior art does not have a systematic complete and accurate process for measuring the signal-to-noise ratio of a sinusoidal signal.
Disclosure of Invention
The invention aims to solve the technical problem of providing a sinusoidal signal-to-noise ratio measuring method, adopting a brand-new design strategy, solving the defects of inaccurate signal-to-noise ratio measuring precision or overlarge calculation amount in the measuring process in the prior art, and improving the signal-to-noise ratio measuring efficiency.
The invention adopts the following technical scheme for solving the technical problems: the invention designs a sinusoidal signal-to-noise ratio measuring method, which is used for obtaining the signal-to-noise ratio of a target sinusoidal signal, wherein the target sinusoidal signal is a target sinusoidal digital signal, and the method comprises the following steps:
step A, sampling a target periodic signal to obtain a sampling signal, and then entering step B;
step B, acquiring a continuous zero-crossing time sequence T of at least two cycles passing through a negative peak value or passing through a positive peak value on a sampling signal by an analog or digital method z1 ，…，T zk ，…，T zK K denotes the number of zero crossing times in a time sequence of successive zero crossings, T zk Representing the kth zero-crossing time in the continuous zero-crossing time sequence, then initializing j ═ K +1, and entering step C;
step C. according to T z(j-1) ，…，T z(j-m) Calculating to obtain an average period T, and further calculating according to a preset parameter c in accordance with a value range of (0.5, 1) and according to T sj ＝T z(j-1) + T × c, calculating to obtain the jth zero-crossing time T zj Corresponding digital initial integration point time T sj Then entering step D, wherein m is more than 1 and less than j, T zj Represents the jth zero-crossing time;
d, selecting time T between each sampling point on the sampling signal and the digital initial integration point sj Sequentially forming a first sampling point to be analyzed and a second sampling point to be analyzed by two adjacent sampling points in front and back, combining the time corresponding to the sampling point to be analyzed and the sampling value corresponding to the sampling point to be analyzed to form the coordinate of the sampling point to be analyzed, and then entering the step E;
step E, according to the time T of the digital initial integration point sj Obtaining T between the first sampling point and the second sampling point by rectangular interpolation or trapezoidal interpolation sj Corresponding sampling value x sj Forming the starting point of the digital integralCoordinate (T) sj ，x sj ) Then initializing v to 2, sequentially defining each sampling point after a first sampling point to be analyzed and a second sampling point to be analyzed on the sampling signal as each sampling point to be analyzed, and entering the step F;
step F, executing digital integral operation from the coordinate position of the digital integral starting point to the coordinate position of the v-th sampling point to be analyzed on the sampling signal to form a digital integral result S v (ii) a And executing digital integration operation from the coordinate position of the digital integration starting point to the coordinate position of the v +1 th sampling point to be analyzed on the sampling signal to form a digital integration result S v+1 Then entering step G;
g, judging a digital integration result S v And the digital integration result S v+1 If the product of v is greater than 0, if yes, adding 1 for updating the value of v, and returning to the step F; otherwise, entering step H;
step H, obtaining the coordinate (T) of the digital integration end point between the v-th sampling point to be analyzed and the v + 1-th sampling point to be analyzed in a rectangular interpolation or trapezoidal interpolation mode according to the condition that the digital integration sum from the digital integration start point to the digital integration end point is zero ej ，x ej ) Then entering step I;
step I. press
Obtaining the jth zero-crossing time T zj (ii) a Further according to T tj ＝T ej -T sj Obtaining the jth zero-crossing time T zj Corresponding integration duration T tj Form the jth target zero-crossing time T zj Corresponding integration duration T tj (ii) a Then entering step J;
step J, according to the target zero crossing time T zj Press T p(j-1) ＝T zj -T z(j-1) Acquiring the period of the signal to be measured according to
Acquiring the frequency of a signal to be detected, and entering a step K;
step K, judging a signal zero crossing point time sequence { T z(K+1) ，...，T zj Whether the length of the step is smaller than a preset threshold value w +1 or not is judged, if yes, the step N is carried out; otherwise, the following operation is carried out: integration of time duration sequences by signals T t(K+1) ，...，T ti W newly generated integration time lengths are selected, and an average value T of the integration time lengths is calculated and obtained ta Converting the sampling period into a count value n corresponding to the sampling period multiple; from a sequence of signal periods T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the average value T of the obtained periods is calculated pa Converting the count value into a count value N corresponding to the sampling period multiple, and then entering a step L;
step L. based on the periodic sequence { T } of the signal p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the standard deviation sigma of the obtained periods is calculated T By passing
Obtaining a parameter σ R (ii) a Or from a signal frequency sequence F (K+1) ，...，F (j-1) Selecting w newly generated signal frequencies, and calculating the standard deviation sigma of the obtained frequencies F By passing
Obtaining a parameter σ R Then entering step M;
step M, according to the counting values N, N and the parameter sigma R Is combined with
Calculating and obtaining the signal-to-noise ratio SNR of the target sinusoidal signal, wherein A is the peak value of the sinusoidal signal, and sigma is the effective value of the noise signal, and then entering the step N;
and step N, adding 1 for updating the value of j, and returning to the step C.
As a preferred technical scheme of the invention: in said step C, according to T z(j-1) ，…，T z(j-m) Push-button
And calculating to obtain the average period T.
As a preferred technical scheme of the invention: in the step A, sampling is carried out on a target periodic signal by adopting an equal time interval sampling mode or an unequal time interval sampling mode to obtain a sampling signal; and carrying out whole-cycle sampling on the target periodic signal to obtain a sampling signal.
As a preferred technical scheme of the invention: the digital integration operation in step F is trapezoidal integration or rectangular integration.
As a preferred technical scheme of the invention: in the step M, according to the count values N and N and the parameter sigma R Is combined with
According to any one of the following four formulas:
and calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal.
Compared with the prior art, the sinusoidal signal-to-noise ratio measuring method adopting the technical scheme has the following technical effects:
the traditional zero crossing method adopts two continuous points with opposite signs to determine the zero crossing point, although the physical concept of the algorithm is clear, the method is easily interfered by harmonic waves, noise and the like, and the measurement precision is low; the invention relates to a method for measuring the signal-to-noise ratio of a designed sinusoidal signal, which aims at the characteristic that most target sinusoidal digital signals are symmetrical, carries out linear interpolation operation according to the integral starting time obtained by calculation, and selects a sampling point P S The method comprises the steps of taking the signal as an integration starting point, then carrying out digital integration, and obtaining an integration end point in an interpolation mode, so that the digital integration from the integration starting point to the integration end point is zero, calculating the zero point of an electric signal according to the sampling occurrence time of the integration starting point and the virtual occurrence time of the integration end point, after the zero crossing point of the signal is determined, calculating the frequency and the period of the electric signal, further calculating the signal-to-noise ratio of a sinusoidal signal, and greatly improving the accuracy of corresponding signal-to-noise ratio measurement.
Also, the present invention adopts the following technical solutions to solve the above technical problems: the invention designs a sinusoidal signal-to-noise ratio measuring method, which is used for obtaining the signal-to-noise ratio of a target sinusoidal signal, wherein the target sinusoidal signal is a target sinusoidal analog signal, and the method comprises the following steps:
step i, acquiring a continuous zero crossing point time sequence T of at least two cycles passing through a negative peak value or passing through a positive peak value on a sampling signal by an analog or digital method z1 ，…，T zk ，…，T zK K denotes the number of zero crossing times in a time sequence of successive zero crossings, T zk Representing the kth zero-crossing time in the sequence of consecutive zero-crossing times, then initializing j ═ K +1, and proceeding to step ii;
according to T z(j-1) ，…，T z(j-m) Calculating to obtain average weekAnd a period T, and further according to a preset parameter c meeting the value range of (0.5, 1) and according to T sj ＝T z(j-1) + T × c, calculating to obtain the jth zero-crossing time T zj Corresponding digital initial integration point time T sj Then go to step iii, where 1 < m < j, T zj Represents the jth zero-crossing time;
at time T sj The integrator is initialized before the voltage of the output voltage of the integrator returns to zero and is at the time T of the digital initial integration point sj Starting analog integration, ending integration when the output voltage of the integrator returns to zero again, and recording the time T of the integration ending point ej Then go to step iv;
step iv. press
Obtaining the jth zero-crossing time T zj (ii) a Further according to T tj ＝T ej -T sj Obtaining the jth zero-crossing time T zj Corresponding integration duration T tj Form the jth target zero-crossing time T zj Corresponding integration duration T tj (ii) a Then entering step v;
v. according to the target zero crossing time T zj Press T p(j-1) ＝T zj -T z(j-1) Obtaining the period of the signal under test, according to
Acquiring the frequency of a signal to be detected, and then entering the step vi;
step vi, judging a signal zero crossing point time sequence { T z(K+1) ，...，T zj Judging whether the length of the step is smaller than a preset threshold value w +1 or not, if so, entering a step ix; otherwise, the following operation is carried out: integration of time duration sequences by signals T t(K+1) ，...，T tj W integration durations generated latest are selected from the previous step, and an average value T of the integration durations is calculated and obtained ta Converting the counting value into a counting value n corresponding to the period multiple of the counter; from a sequence of signal periods T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the average value T of the obtained periods is calculated pa Converting the value into a count value N corresponding to the multiple of the counter period, and then entering step vii;
based on the periodic sequence of signals { T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the standard deviation sigma of the obtained periods is calculated T By passing
Obtaining a parameter σ R (ii) a Or from a signal frequency series F (K+1) ，...，F (j-1) Selecting w newly generated signal frequencies, and calculating the standard deviation sigma of the obtained frequencies F By passing
Obtaining a parameter σ R Then go to step viii;
step viii. according to the count values N, N, and the parameter σ R Is combined with
Calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal, wherein A is the sinusoidal signal peak value and sigma is the noise signal effective value, and then entering the step ix;
and step ix, updating by adding 1 for the value of j, and returning to the step iii.
As a preferred technical scheme of the invention: said according to T z(j-1) ，…，T z(j-m) Push-button
And calculating to obtain the average period T.
As a preferred technical scheme of the invention: at the time T of respectively obtaining the initial integration points sj And an end point time T ej Then, according to the circuit delay parameter, divideAim at T sj 、T ej And carrying out correction updating.
As a preferred technical scheme of the invention: in the step viii, the counting value N, N, and the parameter σ are used R Is combined with
According to any one of the following four formulas:
and calculating to obtain the signal-to-noise ratio (SNR) of the target sinusoidal signal.
As a preferred technical scheme of the invention: the analog integration in step iii is implemented by using an operational amplifier or other devices with an integration function.
Compared with the prior art, the sinusoidal signal-to-noise ratio measuring method adopting the technical scheme has the following technical effects:
the traditional zero crossing method adopts two continuous points with opposite signs to determine the zero crossing point, although the physical concept of the algorithm is clear, the method is easily interfered by harmonic waves, noise and the like, and the measurement precision is low; the invention designs a method for measuring the signal-to-noise ratio of a sinusoidal signal, aiming at the characteristic that a target sinusoidal analog signal is symmetrical up and down, analog integration is carried out according to the integration starting time obtained by calculation, integration is stopped when the analog integration outputs zero, the zero point of the electrical signal is calculated according to the integration starting time and the integration ending time, the frequency and the period of the electrical signal can be calculated after the zero crossing point of the signal is determined, the signal-to-noise ratio of the sinusoidal signal can be further calculated, the accuracy of corresponding signal-to-noise ratio measurement is greatly improved, and the design method is very convenient and simple in calculation and is suitable for being used under an embedded system.
Drawings
FIG. 1 is a schematic diagram of obtaining a zero crossing point by calculating a virtual occurrence time of an integration end point by means of rectangular integration and rectangular interpolation after calculating the obtained integration start point;
FIG. 2 is a schematic diagram of obtaining a zero crossing point by calculating a virtual occurrence time of an integration end point by using trapezoidal integration and trapezoidal interpolation after calculating the obtained integration start point;
FIG. 3 is a schematic diagram of obtaining a zero crossing point by calculating a virtual occurrence time of an integration end point by using trapezoidal integration and rectangular interpolation after calculating the obtained integration start point;
FIG. 4 is a schematic diagram of obtaining a 3 rd zero crossing point by obtaining two zero crossing points after passing through a negative peak value by using a conventional zero crossing point comparison method, calculating to obtain an integration starting point, and then calculating to obtain a virtual occurrence time of an integration ending point by using trapezoidal integration and trapezoidal interpolation;
FIG. 5 is a schematic diagram of obtaining 10 th, 11 th and 12 th zero-crossing points by obtaining two zero-crossing points after passing through a negative peak value by using a conventional zero-crossing point comparison method, calculating to obtain an integration starting point, and then calculating to obtain virtual occurrence time of the integration ending point by using trapezoidal integration and trapezoidal interpolation;
FIG. 6 is a schematic diagram of integrating at a zero point of an electrical signal and calculating a zero crossing point;
FIG. 7 is a schematic diagram of a 3 rd zero crossing point obtained using the methods described herein after two zero crossing points have been obtained using a conventional zero crossing point comparison method;
FIG. 8 is a schematic diagram of analog integration performed after the measured electrical signal crosses the negative peak, i.e. one cycle integration and signal period calculation;
fig. 9 is a schematic diagram of analog integration, i.e. one cycle integration and signal period calculation, performed after the measured electric signal has passed through the positive peak.
Detailed Description
The following description will explain embodiments of the present invention in further detail with reference to the accompanying drawings.
The invention designs a method for measuring the signal-to-noise ratio of a sinusoidal signal, which designs a corresponding method for measuring the signal-to-noise ratio of a target sinusoidal digital signal and a target sinusoidal analog signal respectively.
And step A, carrying out whole cycle sampling on the target periodic signal according to an equal time interval sampling mode or an unequal time interval sampling mode to obtain a sampling signal, and then entering the step B.
Step B, acquiring a continuous zero-crossing time sequence T of at least two cycles passing through a negative peak value or passing through a positive peak value on a sampling signal by an analog or digital method z1 ，…，T zk ，…，T zK K denotes the number of zero crossing times in a time sequence of successive zero crossings, T zk Represents the kth zero-crossing time in the consecutive zero-crossing time sequence, then initializes j to K +1, and proceeds to step C.
Step C. according to T z(j-1) ，…，T z(j-m) Calculating to obtain an average period T, and further calculating according to a preset parameter c in accordance with a value range of (0.5, 1) and according to T sj ＝T z(j-1) + T × c, calculating to obtain the jth zero-crossing time T zj Corresponding digital initial integration point time T sj Then entering step D, wherein m is more than 1 and less than j, T zj Representing the jth zero-crossing time.
In the practical application of the step C, the step C is carried out according to T z(j-1) ，…，T z(j-m) Push-button
Calculating to obtain an average period T; regarding the value of the preset parameter c, c should not be too close to 1, and if c is close to 1, the calculation time will be shortened, and the measurement accuracy will be affected.
And D, step D.Based on each sampling point on the sampling signal, selecting the time T between the sampling point and the initial digital integration point sj And E, sequentially forming a first sampling point to be analyzed and a second sampling point to be analyzed by the front and rear adjacent sampling points, combining the time corresponding to the sampling point to be analyzed and the sampling value corresponding to the sampling point to be analyzed to form the coordinate of the sampling point to be analyzed, and then entering the step E.
Step E, according to the time T of the digital initial integration point sj Obtaining T between the first sampling point and the second sampling point by rectangular interpolation or trapezoidal interpolation sj Corresponding sampling value x sj Coordinates (T) forming the start point of the numerical integration sj ，x sj ) And then initializing v to be 2, sequentially defining each sampling point after the first sampling point to be analyzed and the second sampling point to be analyzed on the sampling signal as each sampling point to be analyzed, and entering the step F.
Step F, executing digital integral operation from the coordinate position of the digital integral starting point to the coordinate position of the v-th sampling point to be analyzed on the sampling signal to form a digital integral result S v (ii) a And executing digital integration operation from the coordinate position of the digital integration starting point to the coordinate position of the v +1 th sampling point to be analyzed on the sampling signal to form a digital integration result S v+1 Then entering step G; the digital integration here operates as trapezoidal integration or rectangular integration.
G, judging a digital integral result S v And the digital integration result S v+1 If the product of v is greater than 0, if yes, adding 1 for updating the value of v, and returning to the step F; otherwise, go to step H.
Step H, obtaining the coordinate (T) of the digital integration end point between the v-th sampling point to be analyzed and the v + 1-th sampling point to be analyzed in a rectangular interpolation or trapezoidal interpolation mode according to the condition that the digital integration sum from the digital integration start point to the digital integration end point is zero ej ，x ej ) Then step I is entered.
Step I. press
Obtaining the jth zero-crossing time T zj (ii) a Further according to T tj ＝T ej -T sj Obtaining the jth zero-crossing time T zj Corresponding integration duration T tj Form the jth target zero-crossing time T zj Corresponding integration duration T tj (ii) a Then proceed to step J.
Step J, according to the target zero crossing time T zj Press T p(j-1) ＝T zj -T z(j-1) Acquiring the period of the signal to be measured according to
And acquiring the frequency of the measured signal, and then entering the step K.
Step K, judging a signal zero crossing point time sequence { T z(K+1) ，...，T zj Whether the length of the step is smaller than a preset threshold value w +1 or not is judged, if yes, the step N is carried out; otherwise, the following operation is carried out: integration of time duration sequences by signals T t(K+1) ，...，T ti W integration durations generated latest are selected from the previous step, and an average value T of the integration durations is calculated and obtained ta Converting the sampling period into a count value n corresponding to the sampling period multiple; from a sequence of signal periods T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the average value T of the obtained periods is calculated pa And converting the value into a count value N corresponding to the sampling period multiple, and then entering the step L.
Step L. based on the periodic sequence { T } of the signal p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the standard deviation sigma of the obtained periods is calculated T By passing
Obtaining a parameter sigma R (ii) a Or from a signal frequency sequence F (K+1) ，...，F (j-1) Selecting w newly generated signal frequencies, and calculating the standard deviation sigma of the obtained frequencies F By passing
Obtaining a parameter σ R Then, step M is entered.
Step m, since N corresponds to the signal period (N is subject to noise and therefore varies), and the magnitude of N is controlled by c (N is subject to noise and is also subject to rounding, etc., during the operation), the formula N/N is equal to about 2 x (1-c), and thus there are variants of the formula, which are based on the count N, and the parameter σ R Is combined with
According to any one of the following four formulas:
and calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal, wherein A is the peak value of the sinusoidal signal, and sigma is the effective value of the noise signal, and then entering the step N. In practical applications, the expression is not limited to the above four formulas, and other formulas may be expressed.
And step N, adding 1 for updating the value of j, and returning to the step C.
In practical applications as described above with respect to the target sinusoidal digital signal design method,the specific operation of calculating the zero-crossing point time can be seen in fig. 1, 2 and 3. The open triangles in the figure represent the integration start point and the integration end point. Fig. 1 is a schematic diagram of calculating a virtual occurrence time of an integration end point by means of rectangular integration and rectangular interpolation, and acquiring a zero crossing point. From t in FIG. 1 S Start of digital integration, t E Is the virtual occurrence time of the integration end point obtained by interpolation, from t in the figure S To t E The numerical integral of (a) is 0. T is z Is to calculate the zero crossings that are obtained. Fig. 2 is a schematic diagram of calculating the virtual occurrence time of the integration end point by adopting trapezoidal integration and trapezoidal interpolation, and acquiring a zero crossing point. From t in FIG. 2 s Start of digital integration, t E Is the virtual occurrence time of the integration end point obtained by interpolation, from t in the figure S To t E The integral of (c) is 0. T is z Is to calculate the zero crossings that are obtained. Fig. 3 is a schematic diagram of calculating the virtual occurrence time of the integration end point by adopting trapezoidal integration and rectangular interpolation, and acquiring a zero crossing point. From t in FIG. 3 S Start of digital integration, t E Is the virtual occurrence time of the integration end point obtained by interpolation, from t in the figure S To t E The numerical integral of (a) is 0. T is a unit of z Is to calculate the zero crossings that are obtained. If the trapezoidal interpolation method is used, the amount of calculation may be large when performing interpolation calculation. Fig. 3 adopts the trapezoidal integration method at the beginning of integration, but adopts the rectangular interpolation method at the time of interpolation operation, which aims to reduce the complexity of the operation. In order to obtain a more accurate measurement result, the height of the rectangle is set to be the average value of two adjacent sampling points in the calculation of the figure. T is sj (i.e., t in the figure) S ) Is the calculated integration start time, and the calculation formula is T Sj ＝T z(j-1) +(T z(j-1) -T z(j-2) ) X 0.89, i.e. c is 0.89 and T is (T) z(j-1) -T z(j-2) ) It is recommended to use T ═ T (T) z(j-1) -T z(j-3) )/2. The following may also be used: when calculating the integration starting time, judging the number of the zero-crossing points acquired before, if the number of the zero-crossing points acquired before is only two, adopting T ═ T (T) z(j-1) -T z(j-2) ) (ii) a If the previously obtained zero-crossing point is greater than two, T ═ may also be used (T ═ T) z(j-1) -T z(j-3) )/2. And after the electric signal passes through the positive peak value, the electric signal is integrated at a zero crossing point, and the zero crossing point is calculated.
Graphs in which the electric signal is sampled and calculated around each zero point and the frequency is measured are shown in fig. 4 and 5. FIG. 4 is a schematic diagram of obtaining a 3 rd zero crossing point by obtaining two zero crossing points after passing through a negative peak value by using a conventional zero crossing point comparison method, calculating to obtain an integration starting point, and then calculating to obtain a virtual occurrence time of an integration ending point by using trapezoidal integration and trapezoidal interpolation; fig. 5 is a schematic diagram of obtaining 10 th, 11 th and 12 th zero-crossing points by obtaining two zero-crossing points after passing through a negative peak value by using a conventional zero-crossing point comparison method, calculating and obtaining a virtual occurrence time of an integration end point by using trapezoidal integration and trapezoidal interpolation after calculating and obtaining the integration start point. FIG. 4 shows two zero-crossing points T obtained by conventional zero-crossing point comparison method Z1 、T Z2 From T Z1 、T Z2 Calculating to obtain T S3 Then at T S3 Start a digital integration at T E3 End integration, finally by T S3 、T E3 Calculating to obtain T Z3 . FIG. 5 is a schematic diagram of 10 th, 11 th and 12 th zero-crossing points obtained by calculation, the integration starting point and the integration ending point calculated on FIG. 5 are represented by open triangles, and T is Z10 、T Z11 And T Z12 Are the calculated 10 th, 11 th and 12 th zero crossings. The period of the signal can be denoted T p10 ＝T Z11 -T Z10 Or T p11 ＝T Z12 -T Z11 The frequency is the inverse of the period. Calculating to obtain a zero crossing point and calculating a graph outline of frequency by adopting a rectangular integral mode, a rectangular interpolation mode or a trapezoidal integral mode and a rectangular interpolation mode; a plot of zero crossings followed by two positive peaks and then frequency measurement is taken.
It can be seen from the figure that the zero point obtained by the trapezoidal integration and the trapezoidal interpolation method is closest to the zero point of the actual signal, the zero point obtained by the trapezoidal integration and the rectangular interpolation method has a certain error with the zero point of the actual signal, and the error between the zero point obtained by the rectangular integration and the rectangular interpolation method and the zero point of the actual signal is the largest. Of course, as the number of sampling points increases, the error will become smaller. In consideration of the characteristics of an embedded system, the preferred scheme is to calculate the zero crossing point of a signal by adopting trapezoidal integration and a rectangular interpolation method.
The traditional zero crossing method adopts two continuous points with opposite signs to determine the zero crossing point, although the physical concept of the algorithm is clear, the method is easily interfered by harmonic waves, noise and the like, and the measurement precision is low; the invention relates to a method for measuring the signal-to-noise ratio of a designed sinusoidal signal, which aims at the characteristic that most target sinusoidal digital signals are symmetrical, carries out linear interpolation operation according to the integral starting time obtained by calculation, and selects a sampling point P S As the start point of integration, carry on the digital integration later, obtain an integration end point by way of interpolation, make the digital integration from start point of integration to integration end point zero, sample the zero point of the electric signal of time calculation and virtual time of occurrence at the end point of integration from the start point of integration, after confirming the zero crossing point of the signal, can calculate the frequency and cycle of the electric signal, can further calculate the signal-to-noise ratio of the sinusoidal signal, the accuracy of the corresponding signal-to-noise ratio measurement is greatly improved too, and the design method is very convenient and simple while calculating, suitable for using under the embedded system.
In practical application, the following steps i to ix are designed and executed for a target sinusoidal analog signal.
Step i, acquiring a continuous zero crossing point time sequence T of at least two cycles passing through a negative peak value or passing through a positive peak value on a sampling signal by an analog or digital method z1 ，…，T zk ，…，T zK K denotes the number of zero crossing times in a time sequence of successive zero crossings, T zk Represents the kth zero-crossing time in the sequence of consecutive zero-crossing times, then initializes j to K +1, and proceeds to step ii.
According to T z(j-1) ，…，T z(j-m) Calculating to obtain an average period T, and further calculating according to a preset parameter c in accordance with a value range of (0.5, 1) and according to T sj ＝T z(j-1) + T × c, calculationObtaining the jth zero-crossing time T zj Corresponding digital initial integration point time T sj Then go to step iii, where 1 < m < j, T zj Representing the jth zero-crossing time.
In application, according to T z(j-1) ，…，T z(j-m) Push-button
Calculating to obtain an average period T; and in step ii, the jth zero-crossing time T is obtained zj Corresponding digital initial integration point time T sj Then, according to the circuit delay parameter, aiming at T sj Carrying out correction updating; and regarding the value of the preset parameter c, c should not be too close to 1, if c is close to 1, the integration time will be too short, the measurement precision of the measurement period will be affected, and the measurement precision of the signal-to-noise ratio will be further affected.
Step iii. at time T sj The integrator is initialized before the voltage of the output voltage of the integrator returns to zero and is at the time T of the digital initial integration point sj Starting analog integration, ending integration when the output voltage of the integrator returns to zero again, and recording the time T of the end point of integration ej Then to step iv; and T is obtained in step iii ej Then, according to the circuit delay parameter, aiming at T ej Carrying out correction updating; and the analog integration is realized by an operational amplifier or other devices with integration function.
Step iv. press
Obtaining the jth zero-crossing time T zj (ii) a Further according to T tj ＝T ej -T sj Obtaining the jth zero-crossing time T zj Corresponding integration duration T tj Form the jth target zero-crossing time T zj Corresponding integration duration T tj (ii) a Step v is then entered.
V. according to the target zero crossing time T zj Press T p(j-1) ＝T zj -T z(j-1) Acquiring the period of the signal to be measured according to
And acquiring the frequency of the measured signal, and then entering the step vi.
Step vi, judging a signal zero crossing point time sequence { T z(K+1 )，...，T zj Judging whether the length of the step is smaller than a preset threshold value w +1 or not, if so, entering a step ix; otherwise, the following operation is carried out: integration of a time series T from a signal t(K+1 )，...，T tj W integration durations generated latest are selected from the previous step, and an average value T of the integration durations is calculated and obtained ta Converting the counting value into a counting value n corresponding to the period multiple of the counter; from a sequence of signal periods T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the average value T of the obtained periods is calculated pa Then, the value is converted into a count value N corresponding to the multiple of the counter period, and then step vii is performed.
Based on the periodic sequence of signals { T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the standard deviation sigma of the obtained periods is calculated T By passing
Obtaining a parameter σ R (ii) a Or from a signal frequency sequence F (K+1) ，...，F (j-1) Selecting w newly generated signal frequencies, and calculating the standard deviation sigma of the obtained frequencies F By passing
Obtaining a parameter σ R Then proceed to step viii.
Step viii, since N corresponds to the signal period (N will be interfered by noise and will change), and the magnitude of N is controlled by c (N will be interfered by noise and will be rounded up when calculating), the method of the present invention is suitable for the signal period (N is not limited by noise and can be rounded up when calculating)The formula N/N is equal to about 2 x (1-c) and there are variants of the formula, so here based on the count N, and the parameter σ R Is combined with
According to any one of the following four formulas:
and calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal, wherein A is the peak value of the sinusoidal signal, and sigma is the effective value of the noise signal, and then entering the step ix. In practical application, the method is not limited to the four formulas, and other formulas can be expressed.
And step ix, updating by adding 1 for the value of j, and returning to the step iii.
In practical applications as described above with respect to the target sinusoidal analog signal design method,
the specific operation can be seen in fig. 6, where fig. 6 is divided into an upper part and a lower part, the upper part is a measured signal (abscissa T is time, and ordinate voltage is measured signal voltage), and the lower part is an integrated waveform of the measured signal. T in the figure si Is the integration start time, T ei Is the integration end time, T zi Is a calculated zero crossing. T is a unit of si Is the calculated integration start time, and the calculation formula is T si ＝T z(i-1) +(T z(i-1) -T z(i-2) ) X 0.89, i.e. c is 0.89 and T is (T) z(i-1) -T z(i-2) ) It is recommended to use T ═ T (T) z(i-1) -T z(i-3) )/2. The following may also be used: when calculating the integration starting time, judging the number of the zero-crossing points acquired before, if the number of the zero-crossing points acquired before is only two, adopting T ═ T (T) z(i-1) -T z(i-2) ) (ii) a If the previously obtained zero-crossing is greater than two, T ═ T (T) may also be used z(i-1) -T z(i-3) )/2. After the electric signal crosses a positive peak value, the electric signal is integrated at a zero crossing point, and a schematic diagram of the zero crossing point is calculated.
And see fig. 7, 8, 9. Fig. 7, 8 and 9 are divided into an upper part and a lower part, wherein the upper part is a measured signal, and the lower part is an integral waveform of the measured signal. FIG. 7 shows two zero-crossing points T obtained by conventional zero-crossing point comparison method Z1 、T Z2 From T Z1 、T Z2 Calculating to obtain T S3 Then at T S3 Start integration once at T E3 End integration, finally by T S3 、T E3 Calculating to obtain T Z3 . The schematic illustration of integrating after the electrical signal crosses the positive peak and obtaining the 3 rd zero crossing point is omitted. FIG. 8 is a schematic diagram of analog integration after the measured electric signal has passed through the negative peak, i.e. one cycle integration and signal period calculation. T in FIG. 8 S10 And T S11 Is the calculated integration start time, T E10 And T E11 Is the corresponding integration end time, T Z10 And T Z11 Are the calculated 10 th and 11 th zero-crossings. Fig. 9 is a schematic diagram of analog integration, i.e. one cycle integration and signal period calculation, performed after the measured electrical signal crosses the positive peak. T in FIG. 9 S10 And T S11 Is the calculated integration start time, T E10 And T E11 Is the corresponding integration end time, T Z10 And T Z11 Are the calculated 10 th and 11 th zero crossings.
The traditional zero crossing method adopts two continuous points with opposite signs to determine the zero crossing point, although the physical concept of the algorithm is clear, the method is easily interfered by harmonic waves, noise and the like, and the measurement precision is low; the invention designs a method for measuring the signal-to-noise ratio of a sinusoidal signal, aiming at the characteristic that a target sinusoidal analog signal is symmetrical up and down, analog integration is carried out according to the integration starting time obtained by calculation, integration is stopped when the analog integration outputs zero, the zero point of the electrical signal is calculated according to the integration starting time and the integration ending time, the frequency and the period of the electrical signal can be calculated after the zero crossing point of the signal is determined, the signal-to-noise ratio of the sinusoidal signal can be further calculated, the accuracy of corresponding signal-to-noise ratio measurement is greatly improved, and the design method is very convenient and simple in calculation and is suitable for being used under an embedded system.
The embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present invention.
Claims (10)
1. A sinusoidal signal-to-noise ratio measuring method is used for obtaining the signal-to-noise ratio of a target sinusoidal signal, and is characterized in that the target sinusoidal signal is a target sinusoidal digital signal, and the method comprises the following steps:
step A, sampling a target periodic signal to obtain a sampling signal, and then entering step B;
step B, acquiring a continuous zero-crossing time sequence T of at least two cycles passing through a negative peak value or passing through a positive peak value on a sampling signal by an analog or digital method z1 ，…，T zk ，…，T zK Where K denotes the number of zero crossing times in a time series of consecutive zero crossing times, T zk Representing the kth zero-crossing time in the continuous zero-crossing time sequence, then initializing j ═ K +1, and entering step C; step C. according to T z(j-1) ，…，T z(j-m) Calculating to obtain an average period T, and further calculating according to a preset parameter c in accordance with a value range of (0.5, 1) and according to T sj ＝T z(j-1) + T × c, calculating to obtain the jth zero-crossing time T zj Corresponding digital initial integration point time T sj Then entering step D, wherein m is more than 1 and less than j, T zj Represents the jth zero-crossing time;
d, selecting time T between each sampling point on the sampling signal and the digital initial integration point sj Sequentially forming a first sampling point to be analyzed and a second sampling point to be analyzed by two adjacent sampling points in front and back, combining the time corresponding to the sampling point to be analyzed and the sampling value corresponding to the sampling point to be analyzed to form the coordinate of the sampling point to be analyzed, and then entering the step E;
step E, according to the time T of the digital initial integration point sj Obtaining T between the first sampling point and the second sampling point by rectangular interpolation or trapezoidal interpolation sj Corresponding sampling value x sj Coordinates (T) forming the start point of the numerical integration sj ，x sj ) Then initializing v to 2, sequentially defining each sampling point after a first sampling point to be analyzed and a second sampling point to be analyzed on the sampling signal as each sampling point to be analyzed, and entering the step F;
step F, executing digital integral operation from the coordinate position of the digital integral starting point to the coordinate position of the v-th sampling point to be analyzed on the sampling signal to form a digital integral result S v (ii) a And executing digital integration operation from the coordinate position of the digital integration starting point to the coordinate position of the v +1 th sampling point to be analyzed on the sampling signal to form a digital integration result S v+1 Then entering step G;
g, judging a digital integration result S v And the digital integration result S v+1 If the product of v is greater than 0, if yes, adding 1 for updating the value of v, and returning to the step F; otherwise, entering step H;
step H, obtaining the coordinate (T) of the digital integration end point between the v-th sampling point to be analyzed and the v + 1-th sampling point to be analyzed in a rectangular interpolation or trapezoidal interpolation mode according to the condition that the digital integration sum from the digital integration start point to the digital integration end point is zero ej ，x ej ) Then entering step I;
step I. press
Obtaining the jth zero-crossing pointTime T zj (ii) a Further according to T tj ＝T ej -T sj Obtaining the jth zero-crossing time T zj Corresponding integration duration T tj Form the jth target zero-crossing time T zj Corresponding integration duration T tj (ii) a Then entering step J;
step J, according to the target zero crossing time T zj Press T p(i-1) ＝T zj -T z(i-1) Acquiring the period of the signal to be measured according to
Acquiring the frequency of a signal to be detected, and entering a step K;
step K, judging a signal zero crossing point time sequence { T z(K+1) ，...，T zj Whether the length of the step is smaller than a preset threshold value w +1 or not is judged, if yes, the step N is carried out; otherwise, the following operation is carried out: integration of a time series T from a signal t(K+1) ，...，T tj W integration durations generated latest are selected from the previous step, and an average value T of the integration durations is calculated and obtained ta Converting the sampling period into a count value n corresponding to the sampling period multiple; from a sequence of signal periods T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the average value T of the obtained periods is calculated pa Converting the count value into a count value N corresponding to the sampling period multiple, and then entering the step L;
step L. based on the periodic sequence { T } of the signal p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the standard deviation sigma of the obtained periods is calculated T By passing
Obtaining a parameter σ R (ii) a Or from a signal frequency sequence F (K+1) ，...，F (j-1) Selecting w newly generated signal frequencies, and calculating the standard deviation sigma of the obtained frequencies F By passing
Obtaining a parameter σ R Then entering step M;
step M, according to the counting values N, N and the parameter sigma R Is combined with
Calculating and obtaining the signal-to-noise ratio SNR of the target sinusoidal signal, wherein A is the peak value of the sinusoidal signal, and sigma is the effective value of the noise signal, and then entering the step N;
and step N, adding 1 for updating the value of j, and returning to the step C.
2. The method of claim 1, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises: in said step C, according to T z(j-1) ，…，T z(j-m) Push-button
And calculating to obtain the average period T.
3. The method of claim 1, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises: in the step A, sampling is carried out on a target periodic signal by adopting an equal time interval sampling mode or an unequal time interval sampling mode to obtain a sampling signal; and carrying out whole-cycle sampling on the target periodic signal to obtain a sampling signal.
4. The method according to claim 1, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises the steps of: the digital integration operation in step F is trapezoidal integration or rectangular integration.
5. The method according to claim 1, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises the steps of: in the step M, according to the count values N and N and the parameter sigma R Is combined with
According to any one of the following four formulas:
and calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal.
6. A sinusoidal signal-to-noise ratio measuring method is used for obtaining the signal-to-noise ratio of a target sinusoidal signal, and is characterized in that the target sinusoidal signal is a target sinusoidal analog signal, and the method comprises the following steps:
step i, acquiring a continuous zero crossing point time sequence T of at least two cycles passing through a negative peak value or passing through a positive peak value on a sampling signal by an analog or digital method z1 ，…，T zk ，…，T zK K denotes the number of zero crossing times in a time sequence of successive zero crossings, T zk Representing the kth zero-crossing time in the continuous zero-crossing time sequence, then initializing j ═ K +1, and entering step ii;
according to T z(j-1) ，…，T z(j-m) Calculating to obtain an average period T, and further calculating according to a preset parameter c in accordance with a value range of (0.5, 1) and according to T sj ＝T z(j-1) + T × c, calculating to obtain the jth zero-crossing time T zj Corresponding digital initial integration point time T sj Then proceed to step iii, where 1 <m＜j，T zj Represents the jth zero-crossing time;
step iii. at time T sj Initializing the integrator to make the output voltage of the integrator return to zero and starting at the digital start integration point time T sj Starting analog integration, ending integration when the output voltage of the integrator returns to zero again, and recording the time T of the integration ending point ej Then go to step iv;
step iv. press
Obtaining the jth zero-crossing time T zj (ii) a Further according to T tj ＝T ej -T sj To obtain the jth zero-crossing time T zj Corresponding integration duration T tj Form the jth target zero-crossing time T zj Corresponding integration duration T tj (ii) a Then entering step v;
v. according to the target zero crossing time T zj Press T p(j-1) ＝T zj -T z(j-1) Acquiring the period of the signal to be measured according to
Acquiring the frequency of a signal to be detected, and then entering the step vi;
step vi, judging a signal zero crossing point time sequence { T z(K+1) ，...，T zj Whether the length of the device is smaller than a preset threshold value w +1 or not is judged, if yes, the device enters
Step ix; otherwise, the following operation is carried out: integration of time duration sequences by signals T t(K+1) ，...，T tj W integration durations generated latest are selected from the previous step, and an average value T of the integration durations is calculated and obtained ta Converting the counting value into a counting value n corresponding to the period multiple of the counter; from a sequence of signal periods T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the average value T of the obtained periods is calculated pa Converting the value into a count value N corresponding to the multiple of the counter period, and enteringStep vii;
based on the periodic sequence of signals { T p(K+1) ，...，T p(j-1) W newly generated signal periods are selected, and the standard deviation sigma of the obtained periods is calculated T By passing
Obtaining a parameter σ R (ii) a Or from a signal frequency sequence F (K+1) ，...，F (j-1) Selecting w newly generated signal frequencies, and calculating the standard deviation sigma of the obtained frequencies F By passing
Obtaining a parameter σ R Then go to step viii;
step viii. according to the count values N, N, and the parameter σ R Is combined with
Calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal, wherein A is the sinusoidal signal peak value and sigma is the noise signal effective value, and then entering the step ix;
and step ix, updating by adding 1 for the value of j, and returning to the step iii.
7. The method of claim 6, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises: said according to T z(j-1) ，…，T z(j-m) Push-button
And calculating to obtain the average period T.
8. The method of claim 6, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises: at the time of respectively obtaining the initial integration points T sj And end point time T ej Then, according to the circuit delay parameters, respectively aiming at T sj 、T ej And carrying out correction updating.
9. The method of claim 6, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises: in the step viii, the counting value N, N, and the parameter σ are used R Is combined with
According to any one of the following four formulas:
and calculating to obtain the signal-to-noise ratio SNR of the target sinusoidal signal.
10. The method of claim 6, wherein the step of measuring the signal-to-noise ratio of the sinusoidal signal comprises: the analog integration in step iii is implemented by using an operational amplifier or other devices with an integration function.
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