CN101251390A - Apparatus for detecting weak signal based on time-frequency transformation - Google Patents

Apparatus for detecting weak signal based on time-frequency transformation Download PDF

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Publication number
CN101251390A
CN101251390A CNA2008100505848A CN200810050584A CN101251390A CN 101251390 A CN101251390 A CN 101251390A CN A2008100505848 A CNA2008100505848 A CN A2008100505848A CN 200810050584 A CN200810050584 A CN 200810050584A CN 101251390 A CN101251390 A CN 101251390A
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China
Prior art keywords
signal
frequency
time
detecting weak
signal based
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CNA2008100505848A
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Chinese (zh)
Inventor
叶新
杨东军
弓成虎
王玉鹏
方伟
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Changchun Institute of Optics Fine Mechanics and Physics of CAS
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Changchun Institute of Optics Fine Mechanics and Physics of CAS
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Priority to CNA2008100505848A priority Critical patent/CN101251390A/en
Publication of CN101251390A publication Critical patent/CN101251390A/en
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Abstract

The invention relates to a weak signal detection device based on time frequency conversion, which comprises a signal channel unit, an analog-digital conversion unit and a processor. A modulated signal to be tested is inputted into the signal channel unit for amplification and filtering by the signal channel unit; the analog-digital conversion unit outputs a quantized signal after sampling the analog signal outputted by the signal channel unit; the processor receives the quantized signal outputted by the analog-digital conversion unit and converts the quantized signal into a frequency domain signal for power spectral analysis, thereby obtaining the measuring results. The small signal detection device adopts the processor which converts the time domain signal into the frequency domain signal to detect the weak signal in the frequency domain and obtain the measuring results without a device producing a specific reference signal, thereby bringing about simple hardware structure and low cost.

Description

A kind of apparatus for detecting weak signal based on time-frequency conversion
Technical field:
The present invention relates to a kind of apparatus for detecting weak signal, particularly a kind of apparatus for detecting weak signal based on time-frequency conversion.
Background technology:
Detection of Weak Signals is the field, forward position in the measuring technique, generally does the electric weight conversion by sensor, makes detected object be converted to electric weight.When useful signal is covered by much noise, make to measure to be subjected to bigger restriction.The main means of Detection of Weak Signals are to improve the signal to noise ratio (S/N ratio) of signal.The method of Detection of Weak Signals technology is by phase-locked amplifying method at present, and phase-locked amplifying method is divided into digital phase-locked detection method and the phase-locked detection method of simulation again.Adopt the device of simulating phase-locked detection method detection feeble signal mainly by the signalling channel unit, reference unit, the phase sensitive detection unit, AD conversion unit, processor is formed.The course of work of this device is: the signal a to be detected that is modulated to fixed frequency through signalling channel unit amplification filtering after output signal b; Reference unit output and the signal d of signal b with the frequency homophase; Signal b and signal d send into the phase sensitive detection unit simultaneously, the phase sensitive detection unit filters 2 frequency-doubled signals of modulating frequency, the flip-flop that obtains the difference frequency phase obtains output signal e, obtain quantized output signal f by the AD conversion unit sampling again, processor obtains The ultimate results by reading the quantized output signal f of AD conversion unit.
The device that the phase-locked amplification detecting process of numeral detects feeble signal is mainly by the signalling channel unit, reference unit, and AD conversion unit and processor are formed, and have omitted the phase sensitive detection unit.The course of work of this device is: output signal h after the signal g process signalling channel to be detected unit amplification filtering; Reference signal is through reference unit phase shift output signal j, signal h and signal j together give AD conversion unit, AD conversion unit is given processor with signal h and the later output signal k of signal j digitizing, processor calculates the acquisition The ultimate results according to signal h and signal j, in fact is exactly the work that processor is finished phase sensitive detection.
Though the device that adopts digital phase-locked detection method and the phase-locked detection method of simulation to detect feeble signal can both be realized Detection of weak, but system hardware is comparatively complicated, no matter simulate phase locking technique, or digital phase locking technique, not only need the processing of signalling channel, also need to produce specific reference signal by certain methods.In addition, the simulation phase locking technique also needs phase-sensitive detector (PSD) (analog multiplier); The numeral phase locking technique needs the two-way analog to digital conversion, respectively reference signal and signal to be detected is sampled.
Summary of the invention:
The technical problem to be solved in the present invention provides the apparatus for detecting weak signal based on time-frequency conversion that a kind of hardware configuration is simple, cost is low.
Apparatus for detecting weak signal based on time-frequency conversion of the present invention comprises signalling channel unit, AD conversion unit, processor; Signal to be detected through ovennodulation is input to the signalling channel unit, is amplified and filtering by the signalling channel unit; Export quantized signal behind the analog signal sampling of AD conversion unit to the output of signalling channel unit; Processor receives the quantized signal of AD conversion unit output and is converted into frequency-region signal and carries out power spectrumanalysis, obtains measurement result.
Based on the Parseval theorem, signal equals the gross energy of its frequency domain at the gross energy of time domain, thereby in the input of time domain, can carry out on frequency domain.Signal to be detected is modulated onto fixed frequency, only need obtain the energy of this frequency in frequency domain, can obtain the result that will measure.The present invention detects and obtains measurement result to feeble signal owing to adopt processor that time-domain signal is transformed to frequency-region signal in frequency domain, do not need to produce the device of specific reference signals, thereby hardware configuration is simple, and cost is low.
Described processor application software comprises and is used for the AD conversion unit output signal is carried out power spectrumanalysis, obtains the fourier spectra analysis module of signal energy relative intensity to be detected.
Described signalling channel unit comprises amplifying circuit, gain control circuit, frequency overlapped-resistable filter; After the measured signal of ovennodulation amplifies through amplifying circuit, send into gain control circuit, by gain control circuit to the signal amplification that gains; The signal of gain control circuit output is sent into frequency overlapped-resistable filter, sends into AD conversion unit by the frequency overlapped-resistable filter filter away high frequency noise and after finishing the impedance matching of AD analog to digital converter.
Measured signal utilizes gain control circuit that amplifying signal is carried out gain control after amplifying output through amplifying circuit, and amplifying signal is adjusted to the optimizing level that AD conversion unit is sampled, and has improved the dynamic range that signal to noise ratio (S/N ratio) and feeble signal are measured; Adopt the frequency overlapped-resistable filter filter away high frequency noise, avoided the signal aliasing distortion of subsequent sampling, suppress high frequency noise simultaneously, further improved signal to noise ratio (S/N ratio).
Described amplifying circuit is made up of prime amplifier and two-stage amplifier; Measured signal amplifies back input two-stage amplifier through prime amplifier, further amplifies the back input-gain control circuit through two-stage amplifier.
Described prime amplifier is selected low noise amplifier for use; Select high input impedance for use, the low noise amplifier purpose of high cmrr is for still less introducing noise and finishes with genertor impedance and mate.Because signal is very faint, it is not enough only relying on preposition amplification, so adopt two-stage amplifier further to amplify.
Described gain control circuit is selected the programmable-gain controller for use.The programmable-gain controller can be adjusted the gain multiple by software programming, therefore can be according to the gain multiple of the intensity adjustments gain control circuit of measured signal, thereby can effectively the signal of amplifying circuit output be adjusted to the optimizing level of AD conversion unit sampling, improve the dynamic range that signal to noise ratio (S/N ratio) and feeble signal are measured.
Described frequency overlapped-resistable filter is selected active low-pass filter for use.
Described AD conversion unit adopts the bipolarity AD converter.
Can also comprise dc bias circuit in the described frequency overlapped-resistable filter; AD conversion unit adopts unipolarity ∑-Δ pattern number converter.
The effect of dc bias circuit is to increase a DC component in the gain control circuit output signal.By AD conversion unit the simulating signal of input is effectively sampled.Unipolarity ∑ in each sampling period-Δ pattern number converter monitors input signal, and exports the signal averaging in this sampling period, thereby reduces the influence of noise to system.Because the singularity of sinusoidal signal, unipolarity ∑-Δ pattern number converter sample frequency must be made as f s=(m+1) f c, wherein m is a positive integer, f cBe signal(-) carrier frequency.
Application software can also comprise in the described processor:
Be used for DC component treatment module that the data of ∑-Δ pattern number converter sampling output are carried out DC processing; The signal of described fourier spectra analysis module after with DC processing carries out power spectrumanalysis, obtains signal energy relative intensity to be detected.
The key principle that the present invention is based on is the Parseval theorem, and promptly signal equals the gross energy of its frequency domain at the gross energy of time domain.Be expressed as:
Σ n = 0 N - 1 | x ( n ) | 2 = 1 N Σ k = 0 N - 1 | X ( k ) | 2 - - - ( 1 )
According to the Parseval theorem,, can on frequency, carry out in the input of time domain; Signal to be detected is modulated onto fixed frequency, only need obtain the energy of this frequency in frequency domain, promptly obtains the measurement result of wanting.
Utilize discrete-time signal Fourier transform (DFT) and Parseval theorem, can obtain the energy size of each Frequency point, and then draw the energy size on the signal modulating frequency, realize the relative measurement of feeble signal.
Described processor can also comprise the calibration correction module that is used for the signal energy relative intensity to be detected that power spectrumanalysis obtains is carried out scaled correction.
In order accurately to measure the absolute size of signal energy to be detected, need before test job, calibrate earlier.At first signal to be detected is made as known stronger accurate signal V H, the rated output spectrum is P H, and then signal to be detected is made as known more weak accurate signal V L, the rated output spectrum is P L, calculate system compensation coefficient s by strong power spectrum signal with than the weak signal power spectrum:
s = V H 2 - V L 2 P H - P L - - - ( 2 )
Can obtain the absolute size v of signal energy to be detected according to system compensation coefficient s:
v = s * u - - - ( 3 )
Wherein u is for carrying out the signal energy relative intensity to be detected that obtains behind the power spectrumanalysis by the fourier spectra analysis module.
Phase-sensitive detector (PSD) and reference signal that the present invention has reduced general Testing of Feeble Signals system to be needed produce passage, and hardware circuit is simple, and is reliable, reduced cost of manufacture; Strengthened the effect of digital signal processing method in Testing of Feeble Signals,, recorded signal to be detected from frequency domain by time-frequency conversion, measure highly sensitive, the wide dynamic range that feeble signal is measured.
The invention will be further described below in conjunction with the drawings and specific embodiments.
Description of drawings:
Fig. 1 is a structured flowchart of the present invention.1 signalling channel unit among the figure, 2 AD conversion unit, 3 processors.
Fig. 2 is signalling channel of the present invention unit 1 structured flowchart.11 amplifying circuits, 12 gain control circuits, 13 frequency overlapped-resistable filters, 111 prime amplifiers, 112 two-stage amplifiers.
Fig. 3 is processor 3 application software high-level schematic functional block diagram of the present invention.31 DC component treatment modules, 32 fourier spectra analysis modules, 33 calibration correction modules.
Embodiment:
The present invention comprises signalling channel unit 1 as shown in Figure 1, AD conversion unit 2, processor 3.Described signalling channel unit 1 comprises amplifying circuit 11, gain control circuit 12 and frequency overlapped-resistable filter 13; Wherein amplifying circuit 11 comprises prime amplifier 111 and two-stage amplifier 112.Prime amplifier 111 is a weak signal prime operational amplifier, adopts high precision, low noise instrument amplifier INA118; Two-stage amplifier 112 adopts OP07 type amplifier.Gain control circuit 12 adopts the programmable-gain controller, and its model is AD8321.Frequency overlapped-resistable filter 13 adopts operational amplifier (OP07) to realize active low-pass filter.AD conversion unit 2 adopts the bipolarity AD converter, and model is AD676.AD conversion unit 2 can also adopt unipolarity ∑-Δ pattern number converter, and its model is ADS1255.When AD conversion unit 2 adopts unipolarity ∑s-Δ pattern number converter, in frequency overlapped-resistable filter 13, dc bias circuit is set in mode well known in the art, making increases a DC component in the gain control circuit output signal.Processor 3 adopts digital signal processor 3, and its model is TMS320C5509.
The course of work of the present invention is: input signal is the signal x to be detected that is modulated onto the 125Hz frequency 0Signal x to be detected 0Amplify back output signal x through prime amplifier 111 1, signal x 1Send into two-stage amplifier 112, further amplify through two-stage amplifier 112 and form signal x 2Be anti-stop signal x 2Amplitude surpass the input range that AD conversion unit 2 measures and improve precision and the dynamic range of measuring, the output signal x of two-stage amplifier 112 2Send into gain control circuit 12, signal x 2After programming gain controller gain control, form signal x 3, signal x 3Send into frequency overlapped-resistable filter 13.For eliminating the influence of aliased distortion as far as possible, adopt operational amplifier (OP07) to realize 4 rank active low-pass filters in frequency overlapped-resistable filter 13, its three dB bandwidth is made as 150Hz; In order to satisfy of the requirement of unipolarity ∑-Δ pattern number converter to sampled level, in this active low-pass filter, dc bias circuit is set in mode well known in the art, make signal x 3DC component of middle increase.Signal x 3Output signal x after frequency overlapped-resistable filter 13 filtering 4, signal x 4Send into AD conversion unit 2.Because sinusoidal sampling, the sample frequency of AD conversion unit 2 is made as 1000Hz here, promptly signal is carried out 8 times of over-samplings.For effectively input signal being carried out data sampling, AD conversion unit 2 adopts ∑-Δ pattern number converter.∑ in each sampling period-Δ pattern number converter is to input signal x 4Monitor, and export interior signal averaging x of this sampling period 5Thereby, reduce the influence of noise to system.Signal averaging x in each sampling period that sampling obtains 5Send into processor 3.In processor 3 at first by 31 couples of signal averaging x of DC component treatment module 5Go DC component treatment, form signal x 6, signal x 6Send into fourier spectra analysis module 32.
The longer the better for the frequency spectrum that accurately obtains signal just needs the sampling time, but the sampling time is long more, calculated amount, memory space also increase thereupon, and input need record measured signal in the short as far as possible time, so need carry out compromise at sampling precision with on the sampling time.According to actual needs, selected frequency resolution Δ f=0.1Hz, can determine the needed points N of Fourier transform:
N=f s/Δf=10000 (4)
F wherein sBe sample frequency.
Then this 10000 point data x (n) is directly carried out Fourier transform, obtain spectral density
And then get its amplitude square, and divided by N, just obtain the real power spectrum of sampled signal:
P ( w ) = 1 N | X N ( w ) | 2
Because sample frequency is f s, when sampling number was N, frequency resolution was f s/ N, establishing signal power is Es, at this moment, noise bandwidth is B N, the noise average power spectral density is G N, the signal to noise ratio (S/N ratio) of system is before the Fourier transform:
SNR in = 20 log ( S in N in ) = 20 log ( Es G N · B N ) - - - ( 5 )
SNR out = 20 log ( S out N out ) = 20 log ( Es G N · B N / N ) = 20 log ( Es · N G N · B N ) - - - ( 6 )
S InBe input signal power, S OutBe output signal power, N InBe input noise power, N OutBe output noise power.Can try to achieve the output input signal-to-noise ratio by (5), (6) is:
SNR out SNR in = 20 log ( N ) - - - ( 7 )
So working as sampling number N is 10000, the signal to noise ratio (S/N ratio) of system is improved as 80dB, has improved the ability of Testing of Feeble Signals greatly.
The data x that after 32 conversion of fourier spectra analysis module, exports 7Send into calibration correction module 33.
In order accurately to measure the absolute size of signal energy to be detected, need before test job, calibrate earlier.At first signal to be detected is made as known stronger accurate signal V H, the rated output spectrum is P H, and then signal to be detected is made as known more weak accurate signal V L, the rated output spectrum is P L, calculate system compensation coefficient s by strong power spectrum signal with than the weak signal power spectrum:
s = V H 2 - V L 2 P H - P L - - - ( 2 )
Can obtain the absolute size v of signal energy to be detected according to system compensation coefficient s:
v = s * u - - - ( 3 )
Wherein u is for carrying out the signal energy relative intensity to be detected that obtains behind the power spectrumanalysis by fourier spectra analysis module 32.
The invention is not restricted to above-mentioned embodiment, processor 3 can also adopt other to have the device of signal analysis and processing ability as programmable logic device (PLD) (FPGA), ARM, single-chip microcomputer or PC etc.Carry out power spectrumanalysis so long as adopt device that faint time-domain signal to be measured is converted to frequency-region signal, obtain measurement result, do not break away from thought of the present invention, all within the scope that the invention is intended to protect with signal analysis and processing ability.

Claims (10)

1, a kind of apparatus for detecting weak signal based on time-frequency conversion comprises signalling channel unit (1), AD conversion unit (2), processor (3); Signal to be detected through ovennodulation is input to signalling channel unit (1), is amplified and filtering by signalling channel unit (1); It is characterized in that exporting quantized signal behind the analog signal sampling of AD conversion unit (2) to signalling channel unit (1) output; Processor (3) receives the quantized signal of AD conversion unit (2) output and is converted into frequency-region signal and carries out power spectrumanalysis, obtains measurement result.
2, the apparatus for detecting weak signal based on time-frequency conversion according to claim 1, it is characterized in that described processor (3) application software comprises is used for AD conversion unit (2) output signal is carried out power spectrumanalysis, obtains the fourier spectra analysis module (32) of signal energy relative intensity to be detected.
3, the apparatus for detecting weak signal based on time-frequency conversion according to claim 1 is characterized in that described signalling channel unit (1) comprises amplifying circuit (11), gain control circuit (12), frequency overlapped-resistable filter (13); After the measured signal of ovennodulation amplifies through amplifying circuit (11), send into gain control circuit (12), by gain control circuit (12) to the signal amplification that gains; The signal of gain control circuit (12) output is sent into frequency overlapped-resistable filter (13), sends into AD conversion unit (2) by frequency overlapped-resistable filter (13) filter away high frequency noise and after finishing the impedance matching of AD analog to digital converter.
4, the apparatus for detecting weak signal based on time-frequency conversion according to claim 3 is characterized in that described amplifying circuit (11) is made up of prime amplifier (111) and two-stage amplifier (112); Measured signal amplifies back input two-stage amplifier (112) through prime amplifier (111), further amplifies back input-gain control circuit (12) through two-stage amplifier (112).
5, the apparatus for detecting weak signal based on time-frequency conversion according to claim 4 is characterized in that described prime amplifier (111) selects low noise amplifier for use.
6, the apparatus for detecting weak signal based on time-frequency conversion according to claim 3 is characterized in that described gain control circuit (12) selects the programmable-gain controller for use.
7, the apparatus for detecting weak signal based on time-frequency conversion according to claim 3 is characterized in that described frequency overlapped-resistable filter (13) selects active low-pass filter for use.
8, the apparatus for detecting weak signal based on time-frequency conversion according to claim 7 is characterized in that comprising dc bias circuit in the described frequency overlapped-resistable filter (13); Described AD conversion unit (2) adopts unipolarity ∑-Δ pattern number converter.
9, the apparatus for detecting weak signal based on time-frequency conversion according to claim 8 is characterized in that described processor (3) application software also comprises and is used for DC component treatment module (31) that the data of unipolarity AD converter sampling output are carried out DC processing; Described fourier spectra analysis module (32) carries out power spectrumanalysis with the signal after the DC processing, obtains signal energy relative intensity to be detected.
10,, it is characterized in that described processor (3) also comprises the calibration correction module (33) that is used for the signal energy relative intensity to be detected that power spectrumanalysis obtains is carried out scaled correction according to claim 2 or the described apparatus for detecting weak signal of 9 each claims based on time-frequency conversion.
CNA2008100505848A 2008-04-10 2008-04-10 Apparatus for detecting weak signal based on time-frequency transformation Pending CN101251390A (en)

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CN102012458A (en) * 2009-03-13 2011-04-13 特克特朗尼克公司 Occupancy measurement and triggering in frequency domain bitmaps
CN102109553A (en) * 2009-12-25 2011-06-29 北京普源精电科技有限公司 Digital spectrum analyzer and method for fast positioning of measuring signals
WO2012000283A1 (en) * 2010-06-29 2012-01-05 中兴通讯股份有限公司 Method for quick frequency scan and mobile terminal thereof
CN103411902A (en) * 2013-07-22 2013-11-27 山东大学 Wide-range micro-water measuring system based on programmable amplifier
CN103472493A (en) * 2013-09-06 2013-12-25 北京航天控制仪器研究所 Weak signal detecting circuit used for gravity gradient measurement
CN104601174A (en) * 2013-10-31 2015-05-06 珠海格力电器股份有限公司 Processing and integrating method and device for sine-wave signal
CN104655929A (en) * 2015-01-04 2015-05-27 中国科学院物理研究所 Measuring method for digital time frequency of time domain signal and corresponding target identification method
CN107505401A (en) * 2017-08-09 2017-12-22 武汉理工大学 Frequency domain detection system based on Fourier transform
CN107656139A (en) * 2017-09-19 2018-02-02 南京南瑞继保电气有限公司 A kind of signal determines method, apparatus, equipment and computer-readable recording medium
CN107942799A (en) * 2017-11-30 2018-04-20 天津百利机械装备集团有限公司中央研究院 A kind of operating condition of mechanical equipment network data acquisition circuit
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Cited By (18)

* Cited by examiner, † Cited by third party
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CN102012458A (en) * 2009-03-13 2011-04-13 特克特朗尼克公司 Occupancy measurement and triggering in frequency domain bitmaps
US10459008B2 (en) 2009-03-13 2019-10-29 Tektronix, Inc. Occupancy measurement and triggering in frequency domain bitmaps
CN105092924A (en) * 2009-03-13 2015-11-25 特克特朗尼克公司 Occupancy measurement and triggering in frequency domain bitmaps
CN102012458B (en) * 2009-03-13 2015-11-25 特克特朗尼克公司 Occupying of frequency domain bitmap is measured and is triggered
CN102109553A (en) * 2009-12-25 2011-06-29 北京普源精电科技有限公司 Digital spectrum analyzer and method for fast positioning of measuring signals
CN102109553B (en) * 2009-12-25 2015-05-20 北京普源精电科技有限公司 Digital spectrum analyzer and method for fast positioning of measuring signals
WO2012000283A1 (en) * 2010-06-29 2012-01-05 中兴通讯股份有限公司 Method for quick frequency scan and mobile terminal thereof
CN103411902A (en) * 2013-07-22 2013-11-27 山东大学 Wide-range micro-water measuring system based on programmable amplifier
CN103472493B (en) * 2013-09-06 2015-11-25 北京航天控制仪器研究所 A kind of Weak Signal Detecting Circuit for gradiometry
CN103472493A (en) * 2013-09-06 2013-12-25 北京航天控制仪器研究所 Weak signal detecting circuit used for gravity gradient measurement
CN104601174A (en) * 2013-10-31 2015-05-06 珠海格力电器股份有限公司 Processing and integrating method and device for sine-wave signal
CN104655929A (en) * 2015-01-04 2015-05-27 中国科学院物理研究所 Measuring method for digital time frequency of time domain signal and corresponding target identification method
CN107505401A (en) * 2017-08-09 2017-12-22 武汉理工大学 Frequency domain detection system based on Fourier transform
CN107656139A (en) * 2017-09-19 2018-02-02 南京南瑞继保电气有限公司 A kind of signal determines method, apparatus, equipment and computer-readable recording medium
CN107942799A (en) * 2017-11-30 2018-04-20 天津百利机械装备集团有限公司中央研究院 A kind of operating condition of mechanical equipment network data acquisition circuit
CN108957120A (en) * 2018-05-17 2018-12-07 北华航天工业学院 A kind of weak signal extraction and system
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