CN112051445A - Sine wave frequency digital detection method and device based on phase estimation - Google Patents
Sine wave frequency digital detection method and device based on phase estimation Download PDFInfo
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- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
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Abstract
The invention belongs to the technical field of frequency measurement circuits, and particularly relates to a sine wave frequency digital detection method and device based on phase estimation. According to the method, four points are continuously sampled on the digital sine wave, the sampling period of the four sampling points is T, and the sine wave frequency is calculated according to the four continuous sampling points. According to the method, the frequency value can be calculated only by continuously sampling a plurality of points on the sine wave period, and a plurality of groups of sampling points can be obtained in one sine wave period so as to calculate a plurality of frequency values, so that the frequency detection real-time performance is high; the sine wave frequency digital detection method based on phase estimation does not need to convert sine waves into square waves for sine wave frequency measurement, and directly samples and measures the frequency of the sine waves, thereby reducing errors in the conversion process and improving the measurement precision.
Description
Technical Field
The invention belongs to the technical field of frequency measurement circuits, and particularly relates to a sine wave frequency digital detection method and device based on phase estimation.
Background
The frequency measuring circuit is widely applied to various sensors, actuators, various precision measuring instruments and the like, and has a very wide application range, so that the frequency measuring circuit with high precision and high real-time performance is pursued by researchers.
At present, the mainstream method for measuring the frequency of an analog sine wave is to convert the sine wave into a square wave with the same frequency in a digital circuit, and then to read out the frequency value by adopting a frequency digital converter based on a reset counter. However, the real-time performance of the frequency measurement method is limited, a frequency value can be read only by needing one period of time of a sine wave, the real-time performance of a low frequency domain is very poor, and the frequency measurement precision is influenced by the precision of conversion from the sine wave to a square wave. Therefore, the mainstream frequency measurement method cannot well meet the requirements in the occasions with high real-time performance and frequency accuracy and without high requirement.
Disclosure of Invention
The invention aims to provide a sine wave frequency digital detection method and a sine wave frequency digital detection device based on phase estimation.
The technical solution for realizing the purpose of the invention is as follows: a sine wave frequency digital detection method based on phase estimation is characterized in that four points are continuously sampled on a digital sine wave, the sampling period of four sampling points is T, and the sine wave frequency is calculated according to the four continuous sampling points.
Further, the calculating the sine wave frequency according to the four continuous sampling points specifically includes:
four sampling points sk、sk+1、sk+2、sk+3Respectively as follows:
sk＝Asin(2πft+θ) (1)
sk+1＝Asin(2πf(t+T)+θ) (2)
sk+2＝Asin(2πf(t+2T)+θ) (3)
sk+3＝Asin(2πf(t+3T)+θ) (4)
wherein A is the amplitude of the sine wave, f is the frequency of the sine wave signal to be detected, T is the sampling period, and T is the current time;
processing the formula to obtain:
the derivation of the equation (5) for the purpose of simplifying and facilitating the implementation on the hardware circuit is carried out, and finally the equation (5) becomes:
wherein S03Is s iskAnd sk3Sum of S12Is s isk1And sk2The sum is calculated as a sine wave frequency f by equation (6).
Furthermore, the number of the sampling points is 4n, wherein n is a natural number, and after the sine wave frequency f is calculated by each group of four sampling points, the average value of a plurality of groups is taken to obtain the final sine wave frequency.
The device for carrying out digital detection by using the digital detection method sequentially comprises the following steps:
the analog sine wave signal generation module: generating a sine wave for detection;
an analog-to-digital conversion module: sine wave sampling generated by the analog sine wave signal generation module is changed into discrete digital sine waves;
a delay sampling module: the sampling device is used for temporarily storing four continuous sampling points and then outputting the sampling points simultaneously;
an addition module: for addition operations;
a squaring module: for squaring operations;
an ACTAN module: and realizing mathematical actan trigonometric function transformation to obtain pi ft.
Furthermore, the delay sampling module adopts four stages of registers to output simultaneously.
Furthermore, when the addition module performs addition operation, the numerator in the formula (6) is regarded as sin (pi ft), and the denominator is regarded as cos (pi ft), that is, S is calculated12-S03To obtain sin2(π ft), calculate 3S12+S03To obtain cos2(πft)。
Further, the squaring module implements sin2(π ft) and cos2The transition from (π ft) to sin (π ft) and cos (π ft) may be implemented in an FPGA by calling the evolution ip core.
Compared with the prior art, the invention has the remarkable advantages that:
1) the invention adopts a sine wave frequency digital detection method based on phase estimation, frequency values can be calculated only by continuously sampling a plurality of points on a sine wave period, and a plurality of groups of sampling points can be obtained in one sine wave period so as to obtain a plurality of frequency values through calculation, so that the frequency detection real-time performance is high.
2) The sine wave frequency digital detection method based on phase estimation does not need to convert sine waves into square waves for sine wave frequency measurement, and directly samples and measures the frequency of the sine waves, thereby reducing errors in the conversion process and improving the measurement precision.
Drawings
Fig. 1 is a schematic diagram of a phase estimation frequency measurement circuit according to the present invention.
FIG. 2 is a block diagram of a delay sampling module 3 according to the present invention.
Detailed Description
The present invention is described in further detail below with reference to the attached drawing figures.
As shown in fig. 1, the frequency measurement principle of the phase estimation algorithm is to perform frequency detection by using four consecutive sampling points on a digital sine wave for calculation.
First, the module 1 is an analog sine wave signal generation module for generating a sine wave for detection. The module 2 through which the generated sine wave passes is an ADC module, i.e., an analog-to-digital conversion module, which converts the analog sine wave samples into discrete digital sine waves. After sampling, the entered module 3 is a delay sampling module, which can output four consecutive sampling data points temporarily and simultaneously to achieve the purpose of calculating four sampling points simultaneously, and the delay sampling module can be implemented in an fpga (field programmable Gate array) by adopting a mode of outputting four stages of registers simultaneously, as shown in fig. 2.
Suppose four sample points sk、sk+1、sk+2、sk+3Respectively as follows:
sk＝Asin(2πft+θ) (1)
sk+1＝Asin(2πf(t+T)+θ) (2)
sk+2＝Asin(2πf(t+2T)+θ) (3)
sk+3＝Asin(2πf(t+3T)+θ) (4)
wherein A is the amplitude of the sine wave, f is the frequency of the sine wave signal to be detected, T is the sampling period, and T is the current time.
Processing the formula to obtain:
this establishes a relationship between the sine wave frequency and the sampled data.
The derivation final formula for the purpose of simplifying and facilitating the realization on hardware circuits becomes:
wherein S03Is s iskAnd sk3Sum of S12Is s isk1And sk2And (4) summing.
The module 4 is an addition module, realizes addition operation in the formula (6), and during calculation, the numerator in the formula (6) is regarded as sin (pi ft) and the denominator is regarded as cos (pi ft), namely S is calculated12-S03To obtain sin2(π ft), calculate 3S12+S03To obtain cos2(π ft). Module 5 is an evolution module, implementing sin2(π ft) and cos2The conversion from (pi ft) to sin (pi ft) and cos (pi ft) can be realized in FPGA by calling an opening ip (interactive property) core. The last module 6 is an ACTAN module, mathematical ACTAN trigonometric function transformation is realized to obtain pi ft, so that a sine wave frequency f value is obtained through simple calculation, the division and ACTAN realization of the last sin (pi ft) and cos (pi ft) can be realized by calling a CORDIC (coordinate Rotation Digital computer) ip core in an FPGA, the specific circuit realization only needs shifting and adding, and the circuit resources are saved.
The use is 4 continuous sampling points in this frequency measurement principle realization, but not only is limited to 4 continuous sampling points, can adopt more sampling points (the multiple of 4) to calculate in the reality, and four sampling points of earlier every group calculate according to the above-mentioned formula, get at last and average, and the sampling point can improve holistic frequency measurement precision more, but can lead to the real-time variation, and the sampling point number needs balance according to actual need.
Claims (7)
1. The sine wave frequency digital detection method based on phase estimation is characterized in that four points are continuously sampled on a digital sine wave, the sampling period of the four sampling points is T, and the sine wave frequency is calculated according to the four continuous sampling points.
2. The method according to claim 1, wherein said calculating the sine wave frequency from four consecutive sample points is specified as:
four sampling points sk、sk+1、sk+2、sk+3Respectively as follows:
sk＝Asin(2πft+θ) (1)
sk+1＝Asin(2πf(t+T)+θ) (2)
sk+2＝Asin(2πf(t+2T)+θ) (3)
sk+3＝Asin(2πf(t+3T)+θ) (4)
wherein A is the amplitude of the sine wave, f is the frequency of the sine wave signal to be detected, T is the sampling period, and T is the current time;
processing the formula to obtain:
the derivation of the equation (5) for the purpose of simplifying and facilitating the implementation on the hardware circuit is carried out, and finally the equation (5) becomes:
wherein S03Is s iskAnd sk3Sum of S12Is s isk1And sk2The sum is calculated as a sine wave frequency f by equation (6).
3. The method of claim 1, wherein the number of the sampling points is 4n, where n is a natural number, and after the sinusoidal frequency f is calculated for each set of four sampling points, the final sinusoidal frequency is obtained by averaging the sets.
4. An apparatus for digital detection using the digital detection method of any one of claims 1 to 3, comprising in sequence:
the analog sine wave signal generation module: generating a sine wave for detection;
an analog-to-digital conversion module: sine wave sampling generated by the analog sine wave signal generation module is changed into discrete digital sine waves;
a delay sampling module: the sampling device is used for temporarily storing four continuous sampling points and then outputting the sampling points simultaneously;
an addition module: for addition operations;
a squaring module: for squaring operations;
an ACTAN module: and realizing mathematical actan trigonometric function transformation to obtain pi ft.
5. The apparatus of claim 4, wherein the delayed sampling module employs four stages of registers for simultaneous output.
6. The apparatus of claim 4, wherein the adding module performs the addition operation by considering the numerator and the denominator in the formula (6) as sin (π ft) and cos (π ft), respectively, i.e. calculating S12-S03To obtain sin2(π ft), calculate 3S12+S03To obtain cos2(πft)。
7. The apparatus of claim 6, wherein the squaring module implements sin2(π ft) and cos2The transition from (π ft) to sin (π ft) and cos (π ft) may be implemented in an FPGA by calling the evolution ip core.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104330644A (en) * | 2014-10-29 | 2015-02-04 | 广东电网有限责任公司电力科学研究院 | Method and system for detecting amplitude value of sine wave signal in power system |
| CN110794208A (en) * | 2019-11-14 | 2020-02-14 | 中电科仪器仪表有限公司 | Broadband rapid modulation domain frequency measurement method based on digital phase calculation |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104330644A (en) * | 2014-10-29 | 2015-02-04 | 广东电网有限责任公司电力科学研究院 | Method and system for detecting amplitude value of sine wave signal in power system |
| CN110794208A (en) * | 2019-11-14 | 2020-02-14 | 中电科仪器仪表有限公司 | Broadband rapid modulation domain frequency measurement method based on digital phase calculation |
Non-Patent Citations (1)
| Title |
|---|
| 王伟旭: "《用相位推算法实现瞬时测频》", 《中国优秀硕士学位论文全文数据库 (工程科技Ⅱ辑)》 * |
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Application publication date: 20201208 |