CN107561360A - A kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit - Google Patents
A kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit Download PDFInfo
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Abstract
A kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit, comprises the following steps：1) according to the frequency and amplitude of measured signal, the sinusoidal signal of the identical amplitude of the identical frequency of FPGA and D/A modular converters generation two-way is utilized；2) sinusoidal signal of the identical amplitude of the identical frequency of two-way is subtracted each other by subtraction circuit, obtains sinusoidal signal all the way；3) sinusoidal signal all the way for subtracting each other to obtain is filtered, amplify and A/D sampling after be transferred in FPGA RAM；4) there will be the display control software that the Wave data in RAM is transmitted to host computer, and its peak-to-peak value is read；5) fit the linear relation between the phase difference between two-way sinusoidal signal and A/D sampling peak-to-peak values and be written to inside host computer procedure, so as to realize the detection of phase difference between two-way sinusoidal signal.The present invention carries hardware circuit simply and is not related to complicated algorithm, and can effectively improve the precision of measurement.
Description
Technical field
The present invention relates to phase difference measurement field, measurement side of especially a kind of two-way with phase difference between frequency sinusoidal signal
Method.
Background technology
Phase difference refers to the difference of phase between two-way homogenous frequency signal, is called and differs.Believe for two-way with the sine of frequency
Number, its phase difference is equal to the difference of the initial phase of this two-way sinusoidal signal, is a constant for not changing over time and changing.
In the last few years, two-way with the measurement of phase difference between frequency sinusoidal signal in signal analysis, industrial automation, intelligent control, electronics
And the field such as the communication technology, biomedicine, radar, sonar, sewage disposal suffers from being widely applied.Accurately measure by sensing
Phase difference between the two-way sinusoidal signal that device receives has great importance.For example, the sine number that frequency is 4KHz all the way
After the aqueous solution, the phase of the signal reflected can occur accordingly according to the size of dissolved oxygen concentration in the aqueous solution
Change, by measuring the phase difference between the signal reflected and reference signal, it can be dissolved with accurately detecting in water outlet
Oxygen concentration.
The measuring method of signal phase difference is segmented into software calculating method and hardware circuit method.Software calculating method can divide again
Into two major classes, a kind of is the processing method in time domain scale, that is to say, that all signal transactings are carried out in time domain scale
's；Another kind is the processing method in frequency domain, i.e., signal is transformed from the time domain to frequency domain, then according to signal in frequency domain model
Interior frequency characteristic is enclosed to handle signal.The biggest advantage of processing method in time domain scale is the processing side of signal
Method is fairly simple, directly perceived, and is easily achieved, but in detection process, and many factors being present, to cause measurement result to have very big
Uncertainty, cause measurement accuracy than relatively low.Processing method in frequency domain has certain antijamming capability to noise,
But this method needs to implement strictly integer-period sampled to sample, otherwise can cause spectral leakage and frequency spectrum fence effect, and
Ultimately result in larger measurement error.And conventional hardware circuit method is mainly cross zero detecting method, according to two paths of signals zero crossing
Time difference calculate phase difference, calculating speed is fast, but hardware cost is high, antijamming capability is weak, measurement accuracy is low.Therefore, it is existing
Some signal phase difference measuring method hardware circuits are complicated, and measurement error is larger, and measurement accuracy is low.
The content of the invention
In order to overcome the shortcomings of that the method measurement error of existing measurement sinusoidal signal phase difference is big, measurement accuracy is low, this hair
Bright to provide a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit, its hardware circuit is simple and is not related to
Complicated algorithm, and can effectively improve the precision of measurement.
The technical solution adopted for the present invention to solve the technical problems is：
A kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit, comprises the following steps：
1) according to the frequency and amplitude of measured signal, two-way same frequency is generated using FPGA and D/A modular converters
The sinusoidal signal of the identical amplitude of rate；
2) sinusoidal signal of the identical amplitude of the identical frequency of two-way is subtracted each other by subtraction circuit, obtains sinusoidal letter all the way
Number；
3) sinusoidal signal all the way for subtracting each other to obtain is filtered, amplify and A/D samplings after be transferred to FPGA RAM
In；
4) there will be the display control software that the Wave data in RAM is transmitted to host computer, and its peak-to-peak value is read；
5) linear relation between the phase difference between two-way sinusoidal signal and A/D sampling peak-to-peak values and write-in are fitted
To inside host computer procedure, so as to realize the detection of phase difference between two-way sinusoidal signal.
Further, in the step 1), it is first determined the frequency and amplitude of measured signal, by calling in FPGA
Two DDS IP kernels, the numerical value of SIN function is taken out, and the identical amplitude of the identical frequency of two-way is generated respectively by D/A conversions
Sinusoidal signal, by setting the second tunnel to take the starting point of DDS IP kernel mileage values to make two-way sinusoidal signal that there is certain phase difference,
Two-way sinusoidal signal can be expressed as to following formula (1) and formula (2)：
x1(t)=Asin (2 π ft+ ψ1) (1)
x2(t)=Asin (2 π ft+ ψ2) (2)
Wherein, A be sinusoidal signal amplitude, f be sinusoidal signal frequency, ψ1, ψ2Respectively two-way sinusoidal signal is initial
Phase.
Further, in the step 2), two-way is subtracted each other with frequency with the sinusoidal signal of width by analog subtracter,
Formula (1) that will be above is subtracted each other with formula (2), shown in for example following formula of its result (3)：
Wherein, Δ ψ=ψ2-ψ1, the as phase difference of two-way sinusoidal signal；When doing approximation here, its phase difference ψ list
Position is represented with radian.
From formula (3) it can be seen that with subtracting each other obtain afterwards with the sinusoidal signal of width being frequently identical frequency all the way by two-way
Sinusoidal signal, its amplitude are the functions on phase difference, and the peak-to-peak value for subtracting each other the sinusoidal signal obtained afterwards by measurement measures
Phase difference between two-way sinusoidal signal.
Require that two-way sinusoidal signal frequency and amplitude must phases when surveying the phase difference between two-way sinusoidal signal using subtraction
Together, the amplitude of the two-way sinusoidal signal actually measured is possible to differ, therefore automatic gain is devised in hardware circuit
(Automatic Gain Control, AGC) circuit is controlled, measured two-way sinusoidal signal can be adjusted to identical width
Subtracted each other again after value, in order to not change original phase difference between them, measured two-way sinusoidal signal is passed through respectively
The agc circuit of identical topological structure, their amplitude is adjusted to the identical measurement for carrying out phase difference again afterwards.
Further, in the step 3), the sinusoidal signal all the way for subtracting each other to obtain is filtered, amplified and A/D is adopted
It is transferred to after sample in FPGA RAM, process is as follows：
(3.1) sinusoidal signal all the way that obtains afterwards will be subtracted each other to be filtered
Two-way sinusoidal signal, which subtracts each other the sinusoidal signal obtained afterwards, to be needed to filter out the letter of unwanted frequency by bandpass filter
Number, while retain the sinusoidal signal of specific frequency, in order to improve the quality of A/D sampled signals, fourth-order band-pass filter is devised here
Ripple device, its band connection frequency need to be set according to the frequency of measured signal.Because what we needed to measure is that frequency is 4KHz
Two-way sinusoidal signal between phase difference, so the band connection frequency of bandpass filter is arranged between 3KHz~5KHz.
(3.2) signal after after filtering is amplified
The sinusoidal signal that two paths of signals subtracts each other to obtain its amplitude depend on the two-way sinusoidal signal subtracted each other amplitude and he
Between phase difference, if during phase difference very little between two-way sinusoidal signal, subtracting each other the width of the sinusoidal signal obtained afterwards
Value also can very little, it is necessary to by amplification after could accurately be detected, three-stage operational is devised in hardware circuit and is put
Big device, and all it is connected with A/D sampling A/D chips afterwards per one-level operational amplifier, after host computer can amplify to every one-level
As a result individually read.
(3.3) signal after amplification is transferred in FPGA RAM by A/D sampling A/D chips
The sinusoidal signal obtained by bandpass filter is ambipolar, and A/D sampling A/D chips are powered using 5V unipolarities,
Must carry out the lifting of voltage before A/D samplings, the level ensured into A/D chips be all on the occasion of.Caused by triggers circuit
When trigger signal is high level, A/D chip operations are controlled, the analog signal after being amplified with 1.25MHz sample frequency collection,
The 12bit data signals collected are present in FPGA RAM, facilitate the reading of host computer.When trigger signal is low level, stop
Only gather.
Further, in the step 4), there will be the display control software that the Wave data in RAM is transmitted to host computer,
And its peak-to-peak value is read, step is as follows：
(4.1) maximum and minimum value of waveform are read
There will be the display control software that the Wave data in RAM is transmitted to host computer, host computer often reads a numerical value
All compared with current maximum and minimum value, while maximum and minimum value are updated, until reading a cycle
All data untill, finally obtain read waveform maximum and minimum value.
(4.2) waveform peak-to-peak value is provided
The maximum of waveform in read complete cycle and minimum value are subtracted each other to the peak-to-peak value for just obtaining waveform,
In order to reduce error, the peak-to-peak value of 10 periodic waveforms can be read, final waveform peak peak is provided after then carrying out averagely
Value.
Further, in the step 5), communicated between FPGA and PC control software by serial ports.Host computer
Control software is with the second road DDS IP kernels in fixed step footpath (being usually the time difference corresponding to a 1 ° of phase difference) control FPGA
In access value starting point, make two-way sinusoidal signal caused by FPGA that there is different phase differences, PC control software reads one
The peak-to-peak value of waveform corresponding to series of phase difference.Sinusoidal signal peak-to-peak value data message according to corresponding to out of phase difference, intend
Close out the linear relation between them.Due to having done an approximation in formula (3), so when fit linear relationship formula
Must be that segmentation is fitted, usually carrying out linear fits at interval of 10 ° can be relatively good, i.e., respectively at 0 °~10 °, 10 °~
It is fitted respectively between 20 ° ... 80 °~90 °.Linear relation obtained by fitting is written to inside host computer procedure,
Can with realize two-way with frequency with phase difference between width sinusoidal signal measurement.Situation about being differed for measured signal amplitude
Under, it is the identical measurement for carrying out phase difference again afterwards that can first pass through agc circuit their range-adjusting.
The present invention technical concept be：With the development of electronic science and technology, accurately measure what is received by sensor
Phase difference technology between two row sinusoidal signals has been deep into many fields, in signal analysis, industrial automation, intelligence control
There is extremely universal application in the field such as system, electronics and the communication technology, biomedicine, radar, sonar, sewage monitoring.Therefore, it is right
Two-way realizes that accurate measurement has very important significance with the phase difference between the sinusoidal signal of frequency.
Two-way subtract each other with frequency with the sinusoidal signal of width obtain afterwards be identical frequency sinusoidal signal all the way, its amplitude is
On the sin functions of phase difference, when two-way sinusoidal signal phase difference is smaller, subtracting each other the amplitude of the sinusoidal signal obtained afterwards is
Linear function on phase difference.This feature after being subtracted each other using two-way with frequency with width sinusoidal signal, can design a mould
Intend subtraction circuit to be used for measuring with frequency with the phase difference between the two-way sinusoidal signal of width.
It is the frequency and amplitude according to measured signal first, goes to generate the identical amplitude of the identical frequency of two-way using FPGA
Sinusoidal signal, then subtracted each other, amplified and filtered, finally changed by A/D, Wave data is transmitted to by serial ports
Position machine control software, read the peak-to-peak value of its waveform.The sinusoidal letter of two-way is changed with certain step footpath by PC control software
Phase difference between number, waveform peak-to-peak value corresponding to reading, fit the phase difference and AD samplings peak between two-way sinusoidal signal
Linear relation between peak value, linear relation is written into host computer procedure to measure two-way with frequency with width to realize
Phase difference between sinusoidal signal.In the case of being differed for measured signal amplitude, agc circuit can be first passed through them
Range-adjusting for the measurement of phase difference is carried out after identical again.Compared with the method for other measurement sinusoidal signal phase differences,
Its hardware circuit is relatively easy, is not related to algorithm, and improves the precision of measurement.
Beneficial effects of the present invention are mainly manifested in：Hardware circuit is simple, is not related to algorithm, and measurement accuracy is higher.
Brief description of the drawings
Fig. 1 is a kind of flow chart of the sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit.
Embodiment
The present invention is described further with reference to flow chart.
A kind of reference picture 1, sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit, comprises the following steps：
1) according to the frequency and amplitude of measured signal, two-way same frequency is generated using FPGA and D/A modular converters
The sinusoidal signal of the identical amplitude of rate：
The frequency and amplitude of measured signal are determined first, by calling two DDS IP kernels in FPGA, by sine
The numerical value of function takes out, and generates the sinusoidal signal of the identical amplitude of the identical frequency of two-way respectively by D/A conversions, by setting the
Two tunnels take the starting point of DDS IP kernel mileage values two-way sinusoidal signal is had certain phase difference, can be by two-way sinusoidal signal point
(1) formula not being expressed as and (2) formula：
x1(t)=Asin (2 π ft+ ψ1) (1)
x2(t)=Asin (2 π ft+ ψ2) (2)
Wherein A be sinusoidal signal amplitude, f be sinusoidal signal frequency, ψ1, ψ2Respectively two-way sinusoidal signal is initial
Phase.
2) two-way is subtracted each other with frequency with the sinusoidal signal of width by analog subtracter, obtains sinusoidal signal all the way：
Two-way is subtracted each other with frequency with the sinusoidal signal of width by analog subtracter, (1) formula and (2) formula that will be above
Subtract each other, its result is as shown in following (3) formula：
Wherein Δ ψ=ψ2-ψ1, the as phase difference of two-way sinusoidal signal.When doing approximation here, its phase difference ψ unit
Represented with radian.
It can be seen that from (3) formula and two-way subtract each other to obtain afterwards is identical frequency all the way with frequency with the sinusoidal signal of width
Sinusoidal signal, its amplitude are the functions on phase difference, can subtract each other the peak-to-peak value of the sinusoidal signal obtained afterwards by measurement
Measure the phase difference between two-way sinusoidal signal.
Require that two-way sinusoidal signal frequency and amplitude must phases when surveying the phase difference between two-way sinusoidal signal using subtraction
Together, the amplitude of the two-way sinusoidal signal actually measured is possible to differ, therefore automatic gain is devised in hardware circuit
(Automatic Gain Control, AGC) circuit is controlled, measured two-way sinusoidal signal can be adjusted to identical width
Subtracted each other again after value, in order to not change original phase difference between them, measured two-way sinusoidal signal is passed through respectively
The agc circuit of identical topological structure, their amplitude is adjusted to the identical measurement for carrying out phase difference again afterwards.
3) sinusoidal signal all the way for subtracting each other to obtain is amplified, filter and A/D samplings after be transferred to FPGA RAM
In：
(3.1) sinusoidal signal all the way that obtains afterwards will be subtracted each other to be filtered
Two-way sinusoidal signal, which subtracts each other the sinusoidal signal obtained afterwards, to be needed to filter out the letter of unwanted frequency by bandpass filter
Number, while retain the sinusoidal signal of specific frequency, in order to improve the quality of A/D sampled signals, fourth-order band-pass filter is devised here
Ripple device, its band connection frequency need to be set according to the frequency of measured signal.Because what we needed to measure is that frequency is 4KHz
Two-way sinusoidal signal between phase difference, so the band connection frequency of bandpass filter is arranged between 3KHz~5KHz.
(3.2) signal after after filtering is amplified
The sinusoidal signal that two paths of signals subtracts each other to obtain its amplitude depend on the two-way sinusoidal signal subtracted each other amplitude and he
Between phase difference, if during phase difference very little between two-way sinusoidal signal, subtracting each other the width of the sinusoidal signal obtained afterwards
Value also can very little, it is necessary to by amplification after could accurately be detected, three-stage operational is devised in hardware circuit and is put
Big device, and all it is connected with A/D sampling A/D chips afterwards per one-level operational amplifier, after host computer can amplify to every one-level
As a result individually read.
(3.3) signal after amplification is transferred in FPGA RAM by A/D sampling A/D chips
The sinusoidal signal obtained by bandpass filter is ambipolar, and A/D sampling A/D chips are powered using 5V unipolarities,
Must carry out the lifting of voltage before A/D samplings, the level ensured into A/D chips be all on the occasion of.Caused by triggers circuit
When trigger signal is high level, A/D chip operations are controlled, the analog signal after being amplified with 1.25MHz sample frequency collection,
The 12bit data signals collected are present in FPGA RAM, facilitate the reading of host computer.When trigger signal is low level, stop
Only gather.
4) there will be the display control software that the Wave data in RAM is transmitted to host computer, and its peak-to-peak value is read, step is such as
Under：
(4.1) maximum and minimum value of waveform are read
There will be the display control software that the Wave data in RAM is transmitted to host computer, host computer often reads a numerical value
All compared with current maximum and minimum value, while maximum and minimum value are updated, until reading a cycle
All data untill, finally obtain read waveform maximum and minimum value.
(4.2) waveform peak-to-peak value is provided
The maximum of waveform in read complete cycle and minimum value are subtracted each other to the peak-to-peak value for just obtaining waveform,
In order to reduce error, the peak-to-peak value of 10 periodic waveforms can be read, final waveform peak peak is provided after then carrying out averagely
Value.
5) fit the linear relation between the phase difference between two-way sinusoidal signal and A/D sampled values and be written to
Inside the machine program of position, so as to realize the detection of phase difference between two-way sinusoidal signal：
Communicated between FPGA and PC control software by serial ports.PC control software is with a fixed step
Footpath (being usually the time difference corresponding to 1 ° of phase difference) controls the starting point of access value in the second road DDS IP kernels in FPGA, produces FPGA
Raw two-way sinusoidal signal has different phase differences, and PC control software reads a series of peak of waveform corresponding to phase differences
Peak value.Sinusoidal signal peak-to-peak value data message according to corresponding to out of phase difference, fits the linear relation between them.
Due to having done an approximation in formula (3), so must be that segmentation is fitted when fit linear relationship formula, it be usually
Carrying out linear fit at interval of 10 ° can be relatively good, i.e., enters respectively between 0 °~10 °, 10 °~20 ° ... 80 °~90 ° respectively
Row fitting.Linear relation obtained by fitting is written to inside host computer procedure, can with realize two-way with frequency with width just
The measurement of phase difference between string signal.In the case of being differed for measured signal amplitude, agc circuit can be first passed through him
Range-adjusting for the measurement of phase difference is carried out after identical again.
Experimental result：In test data, we using FPGA and D/A change generation be amplitude into 1V, frequency is
4KHz sinusoidal signal, using step footpath as 1 ° of phase difference being configured between two-way sinusoidal signal, institute between testing 0 °~60 °
Corresponding AD sampled values, the linearity curve being fitted out according to the data sectional tested between phase difference and AD sampled values close
It is formula, its relational expression is as follows：
Δ θ=12.668U-0.0188 (0.0015 ＜ U≤0.9255) (4)
Δ θ=12.989U-0.3159 (0.9255 ＜ U≤1.5294) (5)
Δ θ=13.718U-1.4308 (1.5294 ＜ U≤2.3789) (6)
Δ θ=14.140U-2.4385 (2.3879 ＜ U≤3.2252) (7)
Δ θ=14.589U-3.8866 (3.2252 ＜ U≤3.6703) (9)
Δ θ=14.990U-5.3584 (3.6703 ＜ U≤4.3600) (10)
Wherein, Δ θ is the phase difference (unit is °) of two-way sinusoidal signal, and U is the peak-to-peak value for the sinusoidal signal that AD is collected
(unit V).
The R for 6 linear relations being fitted above2(i.e. degree of fitting) shows phase difference and A/ between 0.9997~1
There is good linear relationship between D sampled values, formula (4)~(10) above are write inside program, can be measured with realizing
Frequency is the phase difference between 4KHz two-way sinusoidal signal.
A/D collections are powered using ADS7883 chips, 12 bit resolutions, Serial output, the accurate voltages of 5V.Knot
Closing formula (the 4)~formula (10) in face can draw, the measurement accuracy of its phase difference can reach 0.018 °, actual measurement error
And within ± 0.02 °.Two-way sinusoidal signal after analog subtracter by simply having carried out one-level amplification, if carried out again
One-level or two-stage amplification, its measurement accuracy can be improved further, comparatively the scope simply measured can reduce.This
For the measuring method of phase difference compared to for other measuring methods, hardware circuit is simple, is not related to the algorithm of complexity, and precision has
Improved, certain application can be obtained.
Claims (8)
- A kind of 1. sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit, it is characterised in that：Methods described includes Following steps：1) according to the frequency and amplitude of measured signal, the identical frequency phase of two-way is generated using FPGA and D/A modular converters With the sinusoidal signal of amplitude；2) sinusoidal signal of the identical amplitude of the identical frequency of two-way is subtracted each other by subtraction circuit, obtains sinusoidal signal all the way；3) sinusoidal signal all the way for subtracting each other to obtain is filtered, amplify and A/D sampling after be transferred in FPGA RAM；4) there will be the display control software that the Wave data in RAM is transmitted to host computer, and its peak-to-peak value is read；5) fit the linear relation between the phase difference between two-way sinusoidal signal and A/D sampling peak-to-peak values and be written to Inside the machine program of position, so as to realize the detection of phase difference between two-way sinusoidal signal.
- 2. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as claimed in claim 1, its feature It is：In the step 1), it is first determined the frequency and amplitude of measured signal, by calling two DDS IP in FPGA Core, the numerical value of SIN function is taken out, generates the sinusoidal signal of the identical amplitude of the identical frequency of two-way respectively by D/A conversions, It is by setting the second tunnel to take the starting point of DDS IP kernel mileage values to make two-way sinusoidal signal that there is certain phase difference, two-way is sinusoidal Signal is expressed as following formula (1) and formula (2)：x1(t)=Asin (2 π ft+ ψ1) (1)x2(t)=Asin (2 π ft+ ψ2) (2)Wherein, A be sinusoidal signal amplitude, f be sinusoidal signal frequency, ψ1, ψ2The respectively initial phase of two-way sinusoidal signal Position.
- 3. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as claimed in claim 2, its feature It is：In the step 2), two-way is subtracted each other with frequency with the sinusoidal signal of width by analog subtracter, formula that will be above (1) subtract each other with formula (2), shown in for example following formula of its result (3)：Wherein, Δ ψ=ψ2-ψ1, the as phase difference of two-way sinusoidal signal.When doing approximation here, its phase difference ψ unit is used Radian represents.From (3) formula can be seen that by two-way with frequency subtract each other with the sinusoidal signal of width obtain afterwards be identical frequency all the way sine Signal, its amplitude are the functions on phase difference, and the peak-to-peak value for subtracting each other the sinusoidal signal obtained afterwards by measurement measures two-way Phase difference between sinusoidal signal.
- 4. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as claimed in claim 3, its feature It is：Automatic gain control circuit is devised in hardware circuit, measured two-way sinusoidal signal can be adjusted to identical Amplitude after subtracted each other again；Measured two-way sinusoidal signal passes through the agc circuit of identical topological structure respectively, them Amplitude be adjusted to it is identical after carry out the measurement of phase difference again.
- 5. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as described in one of Claims 1 to 4, It is characterized in that：In the step 3), the sinusoidal signal all the way for subtracting each other to obtain is filtered, amplify and A/D sampling after It is transferred in FPGA RAM, process is as follows：(3.1) sinusoidal signal all the way that obtains afterwards will be subtracted each other to be filteredFourth-order band-pass wave filter is devised, the band connection frequency of bandpass filter is arranged between 3KHz~5KHz；(3.2) signal after after filtering is amplifiedThree-stage operational amplifier is devised, and A/D sampling A/D chips are all connected with afterwards per one-level operational amplifier, host computer can Individually read with the result after amplifying to every one-level；(3.3) signal after amplification is transferred in FPGA RAM by A/D sampling A/D chipsWhen trigger signal caused by triggers circuit is high level, A/D chip operations are controlled, are adopted with 1.25MHz sample frequency Analog signal after collection amplification, the 12bit data signals collected are present in FPGA RAM, facilitate the reading of host computer； When trigger signal is low level, stop collection.
- 6. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as described in one of Claims 1 to 4, It is characterized in that：In the step 4), there will be the display control software that the Wave data in RAM is transmitted to host computer, and read Its peak-to-peak value, step are as follows：(4.1) maximum and minimum value of waveform are readThere will be the display control software that the Wave data in RAM is transmitted to host computer, host computer often read a numerical value all with Current maximum and minimum value is compared, while updates maximum and minimum value, the institute until reading a cycle Untill there are data, the maximum and minimum value for reading waveform are finally obtained；(4.2) waveform peak-to-peak value is providedThe maximum of waveform in read complete cycle and minimum value are subtracted each other to the peak-to-peak value for just obtaining waveform, read The peak-to-peak value of quantity periodic waveform is set, final waveform peak-to-peak value is provided after then carrying out averagely.
- 7. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as described in one of Claims 1 to 4, It is characterized in that：In the step 5), communicated between FPGA and PC control software by serial ports, PC control is soft Part makes two-way caused by FPGA sinusoidal with the starting point of access value in the second road DDS IP kernels in a fixed step footpath control FPGA Signal has different phase differences, and PC control software reads a series of peak-to-peak value of waveform corresponding to phase differences, according to not Sinusoidal signal peak-to-peak value data message corresponding to same-phase difference, fits the linear relation between them.
- 8. a kind of sinusoidal signal method for measuring phase difference based on FPGA and subtraction circuit as claimed in claim 7, its feature It is：At interval of 10 ° of progress linear fits, i.e., intended respectively between 0 °~10 °, 10 °~20 ° ... 80 °~90 ° respectively Conjunction, the linear relation obtained by being fitted is written to inside host computer procedure, can be believed frequently with width sine with realizing that two-way is same The measurement of phase difference between number.
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