CN104483548A - Cascade phase locking instrument and cascade phase locking method - Google Patents

Abstract

The invention discloses a cascade phase locking instrument, comprising a first stage of phase locking instrument and follow-up stages of phase locking instruments, wherein the first stage of phase locking instrument is used for receiving a tested signal, and simultaneously outputting a real part and a virtual part of the tested signal; the follow-up stages of phase locking instruments are connected to the previous stages of phase locking instruments of the follow-up stages of phase locking instruments through correlators, and are used for respectively carrying out real half-part phase locking processing on the real parts and the virtual parts output by the previous stages of phase locking instruments through the correlators, merging the real parts and the virtual parts processed by the correlators when one follow-up stage of phase locking instrument is the last stage of phase locking instrument of the cascade phase locking instrument, and then outputting the amplitude and the phase of the tested signal. The invention also discloses a cascade phase locking method.

Description

A kind of phase-locked instrument of cascade and cascade phase-lock technique

Technical field

The present invention relates to electronic surveying and signal analysis technology field, in particular, the present invention be more particularly directed to the phase-locked instrument of a kind of cascade and cascade phase-lock technique thereof.

Background technology

Weak absorption technology is in critical positions in electronic surveying and signal analysis technology, sensor technology, the basic guarantee that accurately measures in chemical analysis and physics and medical science testing process, wherein lock-in amplifier or phase-locked instrument are almost then the requisite instrumentation of faint ac signal measurement, even if it also can realize the Measurement accuracy of signal when noise is very strong.In order to improve signal to noise ratio (S/N ratio) more, being a kind of effective ways by multiple phase-locked instrument cascade, as publication number is: in the Chinese invention patent of CN 103712960A, disclosing by using the phase-locked instrument of cascade to improve Opto-thertnal detection sensitivity; In addition, name of document is: " Cascadinglock-in almplification:Application to wavelength modulation spectro6copy ", author is: the people such as M.J.Holcomb, and journal title is called: Review of Scientific Instruments (1992) the 63rd volume, the document of the 5570th page; And name of document is: " Tandem demodulation lock-inamplifier based on digital signal processor for dual-modulated spectroscopy ", journal title is called: Rev.Sci.Instrum.80,033112 (2009) the 80th volume, 033112nd page, author is: the people such as Jianhuan Qin, individually discloses one and carries out Detection of Weak Signals research method by the phase-locked instrument of cascade.

As shown in Figure 1A, publication number is: in the BrP of GB1128738A, disclose the ultimate principle figure of the phase-locked instrument of prior art cascade, as shown in Figure 1B, journal title is called: 2009 in Review ofScientific Instruments the 80th volume the 033112nd page for homepage, name of document is: " Tandemdemodulation lock-in amplifier based on digital signal processor fordual-modulated spectroscopy ", author is: the people such as Jianhuan Qin, current existing two-stage cascade phaselock technique is disclosed in the document, but, the phase-locked instrument of existing cascade and method are except only measuring-signal amplitude, outside the obvious deficiency can not measuring phase place because of have ignored phase information after the first stage, its amplitude measurements is also not accurate enough, be people such as Jianhuan Qin 2009 the 80th volume the 033112nd page in periodical Reviewof Scientific Instruments as can be seen from author be in the implementation method announced in the document " Tandemdemodulation lock-in amplifier based on digital signal processor fordual-modulated spectroscopy " of homepage, the range signal waveform that the phase-locked instrument of the first order exports is sine function absolute value (frequency is the twice of second level frequency of phase locking), range value after the phase-locked output in the second level will obviously depart from the amplitude of original signal, thus the measurement result that leads to errors.

Existing cascade phaselock technique exports modulated range signal in the first order, and phase-lockedly in the second level extract range signal, the main of this principle existence is miss phase information less than one, and two is that amplitude measurement is not accurate enough, thus brings and measures limitation or mistake.

Based on the problems referred to above, urgently develop the phase-locked instrument of a kind of novel cascade and phase-lock technique thereof.

Summary of the invention

The object of the present invention is to provide the phase-locked instrument of a kind of cascade and cascade phase-lock technique thereof, with solve exist in prior art can only measuring-signal amplitude, and the inaccurate problem of the measurement result of amplitude.

For reaching above-mentioned purpose, the present invention proposes the phase-locked instrument of a kind of cascade, comprising:

The phase-locked instrument of the first order: for receiving measured signal, and the real part and the imaginary part that export measured signal simultaneously;

The phase-locked instrument of following stages: the phase-locked instrument of previous stage being connected to the phase-locked instrument of described following stages by correlator, carries out the phase-locked process of real half portion respectively for the described real part that exports the phase-locked instrument of described previous stage respectively by described correlator and imaginary part; When the phase-locked instrument of afterbody that the phase-locked instrument of described following stages is the phase-locked instrument of described cascade, after merging the described real part after described correlator process and imaginary part, export amplitude and the phase place of described measured signal.

The phase-locked instrument of above-mentioned cascade, the phase-locked instrument of described cascade, by isochronous controller, carries out time controling to the frequency of the phase-locked instrument of described cascade, to ensure accuracy and the Performance Match of phase measurement.

The phase-locked instrument of above-mentioned cascade, described isochronous controller control described measured signal enter the phase-locked instrument of described cascade after measuring process, to realize eachly the phase-locked instrument of described following stages can being made normally to work by the phase-locked result synchronously triggered.

The present invention also discloses a kind of cascade phase-lock technique, adopts instrument as phase-locked in above-mentioned cascade, and the phase-locked instrument of described cascade comprises the first phase-locked instrument and the phase-locked instrument of following stages, comprising:

The phase-locked step of the first order: for by the phase-locked instrument of the described first order, simultaneously export real part and the imaginary part of measured signal;

The phase-locked step of following stages: carry out the phase-locked process of real half portion respectively for the described real part that exports the phase-locked instrument of previous stage of the phase-locked instrument of described following stages respectively by correlator and imaginary part; When the phase-locked instrument of afterbody that the phase-locked instrument of described following stages is the phase-locked instrument of described cascade, after merging the described real part after described correlator process and imaginary part, export amplitude and the phase place of described measured signal.

Above-mentioned cascade phase-lock technique, the described measured signal that the phase-locked step of the described first order exports is S, and described S is expressed as by formula:

S=Asin (2 π f ₁+ Ψ)+n, wherein, described f ₁, Ψ, A and n represent the frequency of the phase-locked instrument of the described first order, the phase place of measured signal, measured signal amplitude and noise respectively.

Above-mentioned cascade phase-lock technique, the signal that the phase-locked step of described following stages exports is S _m, described S _mbe expressed as by formula:

S _m＝Mod(2πf _k)·Mod(2πf _k-1)·Mod(2πf _k-2)···[A·sin(2πf ₁+Ψ)+n]；

Wherein, f _k, f _k-1, Ψ, A and n represent the frequency of the phase-locked instrument of one-level arbitrarily after the frequency of the phase-locked instrument of described following stages, the phase-locked instrument of described following stages, the phase place of measured signal, measured signal amplitude and noise respectively.

Above-mentioned cascade phase-lock technique, the frequency f of the phase-locked instrument of described any one-level in the phase-locked step of described following stages _k-1for described following stages phase-locked instrument frequency f k be greater than 10 natural several times.

Above-mentioned cascade phase-lock technique, the real part of the measured signal that the phase-locked step of the described first order exports and imaginary part are expressed as S _{re (1)}and S _{im (1)}, described S _{re (1)}and S _{im (1)}be expressed as by formula:

$S_{\mathrm{Re}\left(1\right)}=\frac{2}{T_1}{\∫}_{t=0}^{T_1}[S_m\left(t\right)\×\sin \left(2\mathrm{\π}{f}_{1}t\right)]\mathrm{dt}$

$S_{\mathrm{Im}\left(1\right)}=\frac{2}{T_1}{\∫}_{t=0}^{T_1}[S_m\left(t\right)\×\cos \left(2\mathrm{\π}{f}_{1}t\right)]\mathrm{dt}$

Wherein, described T ₁for the natural several times in the described first order phase-locked instrument cycle.

Above-mentioned cascade phase-lock technique, the described real part that the phase-locked step of described following stages exports and imaginary part are expressed as S _{re (k)}and S _{im (k)}, described S _{re (k)}and S _{im (k)}be expressed as by formula::

$S_{\mathrm{Re}\left(k\right)}=\frac{2}{T_k}{\∫}_{t=0}^{T_k}[S_{\mathrm{Re}(k-1)}\left(t\right)\×\sin \left(2\mathrm{\π}{f}_{k}t\right)]\mathrm{dt}$

$S_{\mathrm{Im}\left(k\right)}=\frac{2}{T_k}{\∫}_{t=0}^{T_k}[S_{\mathrm{Im}(k-1)}\left(t\right)\×\sin \left(2\mathrm{\π}{f}_{k}t\right)]\mathrm{dt}$

Wherein, described T _kfor the integral multiple in kth level described follow-up phase-locked instrument cycle.

Above-mentioned cascade phase-lock technique, every moment, gather the measured signal needed for the phase-locked instrument of the described first order, and perform the phase-locked step of the described first order, described n is non-complex integers, described f ₁and f ₂be respectively the phase-locked instrument frequency in the second level after the described first order phase-locked instrument frequency and the phase-locked instrument of the described first order.

Above-mentioned cascade phase-lock technique, after the sampling number obtaining setting reaches N, performs the phase-locked step of described following stages, wherein, and described N=f ₁/ f ₂natural several times, described f ₁and f ₂be respectively the phase-locked instrument frequency in the second level after the described first order phase-locked instrument frequency and the phase-locked instrument of the described first order.

Compared to method of the prior art, the main beneficial effect of the present invention is, the present invention not only can measure the amplitude of measured signal more accurately, and can measure the phase information of measured signal.Use the present invention can carry out the synchro measure of phase and magnitude of low light level measurement, ultra-high frequency signal more accurately:

1, the present invention exports real part and the imaginary signals of measured signal simultaneously at the phase-locked instrument of the first order, respectively real half portion carried out respectively to real part and imaginary signals at the phase-locked instrument of following stages phase-locked, and in the end one-level merging real part and imaginary part export amplitude and the phase place of measured signal, ensure that and do not omit phase information, meanwhile, improve the accuracy of amplitude measurement;

2, the time controling using multistage phase-locked instrument frequency corresponding in cascade phase locking process is to ensure phase measurement accuracy;

3, the core component of phase-locked instrument at different levels adopts correlator, can improve the precision of measurement result more.

Accompanying drawing explanation

Figure 1A is the phase-locked instrument principle schematic of prior art cascade;

Figure 1B is the phase-locked instrument structural representation of prior art cascade;

Fig. 2 is the phase-locked instrument structural representation of cascade of the present invention;

Fig. 3 is the phase-locked instrument structural representation of specific embodiment of the invention three-stage cascade;

Fig. 4 is cascade phase-lock technique schematic flow sheet of the present invention;

Fig. 5 is embodiment of the present invention two-stage phase-lock technique schematic diagram;

Fig. 6 is cascade of the present invention phase-locked instrument application scenarios schematic diagram one;

Fig. 7 is cascade of the present invention phase-locked instrument application scenarios schematic diagram two.

Wherein, Reference numeral:

The phase-locked instrument of 1 first order phase-locked instrument 2 following stages

3 correlator 4 isochronous controllers

The phase-locked instrument of 5 first order phase-locked instrument 6 following stages

7 afterbody phase-locked instrument 8 correlator

9 isochronous controllers

S1 ~ S2, S3 ~ S4: specific embodiment of the invention step

Embodiment

Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.

The phase-locked instrument of a kind of cascade provided by the invention, its innovation is that the phase-locked instrument of the first order outputs signal real part and imaginary part to the phase-locked instrument of next stage simultaneously, it is phase-locked that the phase-locked instrument of following stages carries out real half portion respectively to real part and imaginary signals respectively, and in the end one-level merges amplitude and the phase place that real part and imaginary part export measured signal.Meanwhile, the present invention takes between multistage phase-locked instrument, to introduce specific time controling to ensure that the accuracy of phase measurement takes into account the Performance Match of phase-locked instrument at different levels simultaneously.

Fig. 2 is the structural representation of the phase-locked instrument of cascade of the present invention, and as shown in Figure 2, the phase-locked instrument of a kind of cascade provided by the invention, comprising:

The phase-locked instrument 1 of the first order: for receiving measured signal, and export real part and the imaginary part of measured signal simultaneously;

The phase-locked instrument of following stages 2: the phase-locked instrument of previous stage being connected to the phase-locked instrument of following stages 2 by correlator 3, carries out the phase-locked process of real half portion respectively for the real part that exports respectively by the correlator 3 pairs of phase-locked instrument of previous stage and imaginary part; When the phase-locked instrument of afterbody that the phase-locked instrument of following stages is the phase-locked instrument of cascade, after merging the real part after correlator 3 process and imaginary part, export amplitude and the phase place of measured signal.

Further, the phase-locked instrument of cascade, by isochronous controller 4, carries out time controling to the frequency of the phase-locked instrument of cascade, to ensure accuracy and the Performance Match of phase measurement; Isochronous controller 4 control measured signal enter the phase-locked instrument of cascade after measuring process, to realize eachly the phase-locked instrument 2 of following stages can being made normally to work by the phase-locked result synchronously triggered.

The specific embodiment that the present invention adopts the phase-locked instrument of three-stage cascade is below described in detail in detail, Fig. 3 is the phase-locked instrument structural representation of three-stage cascade of the present invention, as shown in Figure 3, the phase-locked instrument of cascade of the present invention, the phase-locked instrument 5 of the first order outputs signal real part and imaginary part, carry out real half portion respectively at the real part of the phase-locked instrument of following stages 6 pairs of original signals and imaginary part phase-locked, and in the end one-level 7 merges amplitude and the phase place that real part and imaginary part export measured signal.

Introduce between this multistage phase-locked instrument with the time controling of the frequency dependence of multistage phase-locked instrument to ensure that the accuracy of phase measurement takes into account the Performance Match of phase-locked instrument at different levels simultaneously.

Wherein, the core of the phase-locked instrument of cascade is correlator 8, instead of traditional multiplier and low-pass filter.Further, the frequency of isochronous controller 9 pairs of phase-locked instrument of cascade is adopted to carry out time controling, to ensure accuracy and the Performance Match of phase measurement.

The present invention also provides a kind of cascade phase-lock technique, adopts the phase-locked instrument of cascade described above, and the phase-locked instrument of this cascade comprises the first phase-locked instrument and the phase-locked instrument of following stages, and Fig. 4 is cascade phase-lock technique schematic flow sheet of the present invention, and as shown in Figure 4, the method comprises:

The phase-locked step S1 of the first order: for by the phase-locked instrument 1 of the first order, simultaneously export real part and the imaginary part of measured signal;

The phase-locked step S2 of following stages: carry out the phase-locked process of real half portion respectively for the real part that exports respectively by the phase-locked instrument of previous stage of correlator 3 pairs of phase-locked instrument of following stages 2 and imaginary part; When the phase-locked instrument of afterbody that the phase-locked instrument 2 of following stages is the phase-locked instrument of cascade, after merging the real part after correlator 3 process and imaginary part, export amplitude and the phase place of measured signal.

Specifically, cascade phase-lock technique of the present invention, the ultimate principle of the phase-locked instrument of cascade used is: direct current signal S=Asin (2 π f1+ the Ψ)+n establishing the original AC signal of measured signal or modulated by the first phase-locked instrument in rank, wherein f1, Ψ, A and n represent the frequency of the phase-locked instrument of the first order, the phase place of measured signal, measured signal amplitude and noise respectively, and after the phase-locked instrument modulation in follow-up k rank, signal becomes Sm=Mod (2 π fk) Mod (2 π fk-1) Mod (2 π fk-2) [Asin (2 π f1+ Ψ)+n].Wherein phase-locked instrument frequency at different levels meet any one-level phase-locked instrument frequency f k-1 be its rear stage phase-locked instrument frequency f k be greater than 10 natural several times, why being greater than 10 is because adjacent phase-locked instrument frequency is too close to the accuracy that obviously can affect measurement result.By isochronous controller control survey process after the signal input first order phase-locked instrument, meet and eachly can just in time normally to be worked for the phase-locked instrument of subsequent stages by the phase-locked result synchronously triggered.The real part of each time point output two paths of signals and measured signal and imaginary part are respectively as shown in formula (1) Yu (2).

$S_{\mathrm{Re}\left(1\right)}=\frac{2}{T_1}{\∫}_{t=0}^{T_1}[S_m\left(t\right)\×\sin \left(2\mathrm{\π}{f}_{1}t\right)]\mathrm{dt}---\left(1\right)$

$S_{\mathrm{Im}\left(1\right)}=\frac{2}{T_1}{\∫}_{t=0}^{T_1}[S_m\left(t\right)\×\cos \left(2\mathrm{\π}{f}_{1}t\right)]\mathrm{dt}---\left(2\right)$

Wherein T ₁for the natural several times in the first order phase-locked instrument cycle.The correlator that follow-up phase-locked instrument carries out calculates slightly different, and mainly the input signal of pairwise correlation device is all relevant to the sinusoidal signal of this grade of phaselocked loop, as shown in formula (3) Yu (4).

$S_{\mathrm{Re}\left(k\right)}=\frac{2}{T_k}{\∫}_{t=0}^{T_k}[S_{\mathrm{Re}(k-1)}\left(t\right)\×\sin \left(2\mathrm{\π}{f}_{k}t\right)]\mathrm{dt}---\left(3\right)$

$S_{\mathrm{Im}\left(k\right)}=\frac{2}{T_k}{\∫}_{t=0}^{T_k}[S_{\mathrm{Im}(k-1)}\left(t\right)\×\sin \left(2\mathrm{\π}{f}_{k}t\right)]\mathrm{dt}---\left(4\right)$

Wherein Tk is the natural several times in kth level phase-locked instrument cycle.In the end the phase-locked instrument of one-level exports two-way direct current signal, represents real part and the imaginary part of measured signal respectively, through well known to a person skilled in the art that real part and imaginary part obtain the phase and magnitude of original measured signal to phase and magnitude angular transformation method.

In order to further illustrate above-mentioned principle, Fig. 5 is embodiment of the present invention two-stage phase-lock technique schematic flow sheet, and as shown in Figure 5, what show a phase-locked instrument of two-stage realizes flow chart, concrete implementation step:

Step S3: tested AC signal is first modulated according to second level frequency of phase locking, under the control of isochronous controller, every moment gather digital signal needed for the first order phase-locked instrument, and calculated the real part in this moment and imaginary part that export measured signal by correlator, wherein n is non-complex integers;

Step S4: get smaller value as far as possible according in the working time situation meeting the phase-locked instrument of the first order, the secondary sampling number N of setting to be obtained (is natural several times) after to start to carry out the second level of the real part of the phase-locked output of the first order and imaginary signals phase-locked, to the first order phase-locked signal carried out with the sine of phaselocked loop and cosine signal respectively relevant unlike, the phase-locked two-way input signal in the second level all carries out to the sinusoidal signal of this grade of phaselocked loop relevant and exports real part and the imaginary part of original measured signal respectively, through well known to a person skilled in the art that real part and imaginary part obtain the phase and magnitude of original measured signal to phase and magnitude angular transformation method.

Application scenarios one of the present invention: use the phase-locked instrument of cascade to measure low light signals

As shown in Figure 6, measuring system is primarily of measured light, modulation and detection module, and light source module drives the secondary souce of direct illuminating source or the light after reflection-absorption or refraction or the generation of the principle such as frequency doubling non-linear's light or fluorescence by driving circuit; Modulation module is divided into the low frequency modulations realized by chopper in directly series connection high frequency modulated in the driving circuit and light path; First detection module realizes photoelectric signal transformation by photo-detector, the phase-locked instrument 11 of cascade that the present invention describes is inputted after being converted to digital signal by analog to digital conversion, detailed process is as shown in Figure 5 illustrated in summary of the invention, exports the intensity of low light signals after the phase-locked instrument of cascade passes through to do demodulation respectively to High-frequency and low-frequency modulation signal with higher precision.

Application scenarios two of the present invention: use multistage phase-locked instrument to measure while the amplitude-phase of ultra-high frequency signal

As shown in Figure 7, in order to measure ultrahigh frequency AC signal, the basis of ultra-high frequency signal is introduced twice modulation, i.e. intermediate frequency Modulation and low frequency modulations, being translated into after digital signal through ultra-high frequency signal collecting device uses the phase-locked instrument 12 of cascade provided by the invention to carry out demodulation of phase locking, realizes accurately measuring of ultra-high frequency signal amplitude and phase place.The principle of the phase-locked instrument of three cascades that this example uses is as FB(flow block) 5, as shown in Figure 7, relative to the twin-stage interlocking phase instrument FB(flow block) shown in Fig. 2, the real part that the second level exports by the phase-locked instrument of three cascades on the basis of twin-stage interlocking phase instrument and imaginary signals input into the third level phase-locked, and in the phase-locked instrument of the third level to this two paths of signals carry out respectively as in the phase-locked instrument in the second level according to the real half portion correlation computations of principle shown in formula 3 and formula 4, the real part of the tested ultra-high frequency signal of final output and imaginary part, again through well known to a person skilled in the art that real part and imaginary part obtain the phase and magnitude of the tested ultra-high frequency signal compared with high accurancy and precision to phase and magnitude angular transformation method.

In sum, the phase-locked instrument of cascade that the present invention proposes and phase-lock technique thereof, export real part and the imaginary signals of measured signal at the phase-locked instrument of the first order simultaneously, respectively real half portion carried out respectively to real part and imaginary signals at the phase-locked instrument of following stages phase-locked, and in the end one-level merging real part and imaginary part export amplitude and the phase place of measured signal, the time controling using multistage phase-locked instrument frequency corresponding in cascade phase locking process is to ensure phase measurement accuracy.In addition, the core component of phase-locked instrument at different levels adopts correlator, can also improve the precision of measurement result more.

Certainly; the present invention also can have other various embodiments; when not deviating from the present invention's spirit and essence thereof; those of ordinary skill in the art are when making various corresponding change and distortion according to the present invention, but these change accordingly and are out of shape the protection domain that all should belong to the claim appended by the present invention.

Claims (11)

1. the phase-locked instrument of cascade, is characterized in that, comprising:

The phase-locked instrument of the first order: for receiving measured signal, and the real part and the imaginary part that export measured signal simultaneously;

The phase-locked instrument of following stages: the phase-locked instrument of previous stage being connected to the phase-locked instrument of described following stages by correlator, carries out the phase-locked process of real half portion respectively for the described real part that exports the phase-locked instrument of described previous stage respectively by described correlator and imaginary part; When the phase-locked instrument of afterbody that the phase-locked instrument of described following stages is the phase-locked instrument of described cascade, after merging the described real part after described correlator process and imaginary part, export amplitude and the phase place of described measured signal.

2. the phase-locked instrument of cascade according to claim 1, is characterized in that, the phase-locked instrument of described cascade, by isochronous controller, carries out time controling to the frequency of the phase-locked instrument of described cascade, to ensure accuracy and the Performance Match of phase measurement.

3. the phase-locked instrument of cascade according to claim 2, it is characterized in that, described isochronous controller control described measured signal enter the phase-locked instrument of described cascade after measuring process, to realize eachly the phase-locked instrument of described following stages can being made normally to work by the phase-locked result synchronously triggered.

4. a cascade phase-lock technique, adopt the phase-locked instrument of cascade according to any one of claim 1-3, the phase-locked instrument of described cascade comprises the first phase-locked instrument and the phase-locked instrument of following stages, it is characterized in that, comprising:

The phase-locked step of the first order: for by the phase-locked instrument of the described first order, simultaneously export real part and the imaginary part of measured signal;

The phase-locked step of following stages: carry out the phase-locked process of real half portion respectively for the described real part that exports the phase-locked instrument of previous stage of the phase-locked instrument of described following stages respectively by correlator and imaginary part; When the phase-locked instrument of afterbody that the phase-locked instrument of described following stages is the phase-locked instrument of described cascade, after merging the described real part after described correlator process and imaginary part, export amplitude and the phase place of described measured signal.

5. cascade phase-lock technique according to claim 4, is characterized in that, the described measured signal that the phase-locked step of the described first order exports is S, and described S is expressed as by formula:

S=Asin (2 π f ₁+ Ψ)+n, wherein, described f ₁, Ψ, A and n represent the frequency of the phase-locked instrument of the described first order, the phase place of measured signal, measured signal amplitude and noise respectively.

6. cascade phase-lock technique according to claim 4, is characterized in that, the signal that the phase-locked step of described following stages exports is S _m, described S _mbe expressed as by formula:

S _m＝Mod(2πf _k)·Mod(2πf _k-1)·Mod(2πf _k-2)···[A·sin(2πf ₁+Ψ)+n]；

Wherein, f _k, f _k-1, Ψ, A and n represent the frequency of the phase-locked instrument of one-level arbitrarily after the frequency of the phase-locked instrument of described following stages, the phase-locked instrument of described following stages, the phase place of measured signal, measured signal amplitude and noise respectively.

7. cascade phase-lock technique according to claim 6, is characterized in that, the frequency f of the phase-locked instrument of described any one-level in the phase-locked step of described following stages _k-1for described following stages phase-locked instrument frequency f k be greater than 10 natural several times.

8. cascade phase-lock technique according to claim 5, is characterized in that, the real part of the measured signal that the phase-locked step of the described first order exports and imaginary part are expressed as S _{re (1)}and S _{im (1)}, described S _{re (1)}and S _{im (1)}be expressed as by formula:

$S_{\mathrm{Re}\left(1\right)}=\frac{2}{T_1}{\∫}_{t=0}^{T_1}[S_m\left(t\right)\×\sin \left({2\mathrm{\πf}}_{1}t\right)]\mathrm{dt}$

$S_{\mathrm{Im}\left(1\right)}=\frac{2}{T_1}{\∫}_{t=0}^{T_1}[S_m\left(t\right)\×\cos \left({2\mathrm{\πf}}_{1}t\right)]\mathrm{dt}$

Wherein, described T ₁for the natural several times in the described first order phase-locked instrument cycle.

9. cascade phase-lock technique according to claim 4, is characterized in that, the described real part that the phase-locked step of described following stages exports and imaginary part are expressed as S _{re (k)}and S _{im (k)}, described S _{re (k)}and S _{im (k)}be expressed as by formula::

$S_{\mathrm{Re}\left(k\right)}=\frac{2}{T_k}{\∫}_{t=0}^{T_k}[S_{\mathrm{Re}(k-1)}\left(t\right)\×\sin \left({2\mathrm{\πf}}_{k}t\right)]\mathrm{dt}$

$S_{\mathrm{Im}\left(k\right)}=\frac{2}{T_k}{\∫}_{t=0}^{T_k}[S_{\mathrm{Im}(k-1)}\left(t\right)\×\sin \left({2\mathrm{\πf}}_{k}t\right)]\mathrm{dt}$

Wherein, described T _kfor the integral multiple in kth level described follow-up phase-locked instrument cycle.

10. cascade phase-lock technique according to claim 4, is characterized in that, every moment, gather the measured signal needed for the phase-locked instrument of the described first order, and perform the phase-locked step of the described first order, described n is non-complex integers, described f ₁and f ₂be respectively the phase-locked instrument frequency in the second level after the described first order phase-locked instrument frequency and the phase-locked instrument of the described first order.

11. cascade phase-lock techniques according to claim 4, is characterized in that, obtaining after the sampling number arranged reaches N, perform the phase-locked step of described following stages, wherein, and described N=f ₁/ f ₂natural several times, described f ₁and f ₂be respectively the phase-locked instrument frequency in the second level after the described first order phase-locked instrument frequency and the phase-locked instrument of the described first order.