CN104820145B - For the tester and its method of testing tested lock-in amplifier - Google Patents
For the tester and its method of testing tested lock-in amplifier Download PDFInfo
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- CN104820145B CN104820145B CN201510182065.7A CN201510182065A CN104820145B CN 104820145 B CN104820145 B CN 104820145B CN 201510182065 A CN201510182065 A CN 201510182065A CN 104820145 B CN104820145 B CN 104820145B
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Abstract
The invention discloses a kind of tester and method of testing for being tested lock-in amplifier.Including：Input interface, receive the adjustable signal parameter of user's input；Signal generator, according to first and second signals of the signal parameter generation with identical frequency, phase and pattern；White noise generator, white noise signal is generated according to signal parameter；Signal filter, the component corresponding with the frequency of the first signal is removed from white noise signal to obtain through filtering out noise signal；Signal synthesizer, by the first signal with synthesizing composite signal through filtering out noise signal；During test, inputted using composite signal as trial signal to be measured and using secondary signal as reference signal to lock-in amplifier.The test signal that sends of tester of the present invention is not simple signal to be superimposed with noise, but being superimposed for signal and the noise without measured signal frequency, is reduced the low measurement signal of the back of the body measured when echo signal is zero, be ensure that the accuracy of test result.
Description
Technical field
The present invention relates to electronic surveying and signal analysis technology field, is used to enter lock-in amplifier more particularly, to one kind
The tester and its method of testing of row test.
Background technology
With the arrival of information age, many scientific researches, the information of engineering technology need to be obtained with the means of detection.
When the signal of required measurement is very faint, it will usually be submerged in noise, to extract useful signal therefrom will
Become abnormal difficult.For this kind of signal, traditional detection method is no longer applicable, therefore, Detection of Weak Signals (Weak
Signal detection) just arise at the historic moment.It is extracted using modern electronics and signal processing method from noise it is useful
One emerging technology-oriented discipline of signal, it is complex art and leading-edge field in e measurement technology.
In Detection of Weak Signals field, lock-in amplifier (Lock-in Amplifier, LIA) plays very always
Important role.It shows excellent performance in terms of Detection of Weak Signals, it have CFS center frequency stabilization, passband it is narrow,
The advantages that quality factor are high, it is obtained for and is widely applied in many fields.Such as electronic spectrum measurement, single nanometer non-
Linear absorption spectrum analysis, laserfrequencystability analysis, the stability analysis of the bias voltage drift of electrooptic modulator, sensing
Device application, methane harmonic detecting, microwave imaging, measurement of mutual inductance, broadband electromagnetic measurement etc., greatly promoted earthquake, ocean,
The development of the industries such as astronomy, physical chemistry, biomedicine.
" millivoltmeter " is in general A.C. voltmeter, and " lock-in amplifier " is that a kind of special measurement tiny signal is (special
) A.C. voltmeter.The object that lock-in amplifier is detected, is the small-signal that can't detect using common method, example
Such as micro voltage, micro-current, micro- conductance, micrometeor, micro-vibration, micro-pressure-difference, tepor difference and dim light, weak magnetic and weak sound.But
Under normal circumstances, all it is that these faint amounts are converted into electric signal to measure by sensor.Small-signal refers to those
Useful signal is submerged in signal or useful signal amplitude absolute value very little itself among noise completely.
Lock-in amplifier instrument almost indispensable in the technical field related to faint ac signal measurement, its master
Want function be can be achieved noise it is very strong in the case of faint AC signal accurate measurement.On the test of lock-in amplifier,
Although having the method for testing general with other electronic instruments such as outward appearance test, electromagnetic compatibility test, stability test etc., but pin
The measurement precision such as wideband exchange Low SNR signal of the performance exclusive to lock-in amplifier still lacks in the world at present
Effective means of testing.
With the development of science and technology, these small-signals are extracted, detected and analyzed, be that exploration and discovery are new
The natural law, the development of association area is promoted to be significant.Therefore, lock-in amplifier in Detection of Weak Signals field
Effect just seems more and more important, and application field is more and more.Therefore, the lock-in amplifier meaning that design performance is good, cost is low
It is very great.Also, the shortage of lock-in amplifier tester also seriously governs the manufacturing, trade, biography of lock-in amplifier
Quality control in defeated and application overall process, can so as to have influence on all weak signal measurement results obtained from lock-in amplifier
By property.
The content of the invention
The purpose of the present invention aims to provide a kind of tester and its method of testing for being tested lock-in amplifier,
The test signal that the tester is sent is not simple signal is superimposed with noise, but signal with without measured signal frequency
The superposition of noise, so as to reduce the low measurement signal of back of the body when measurement echo signal is zero, it ensure that the accuracy of test result.
To achieve these goals, according to an aspect of the invention, there is provided a kind of be used to carry out lock-in amplifier
The tester of test, including：Input interface, for receiving the adjustable signal parameter of user's input；Signal generator, for root
Generating the first signal and secondary signal, the first signal and secondary signal according to signal parameter has identical frequency, phase and pattern；
White noise generator, for generating white noise signal according to signal parameter；Signal filter, for being removed from white noise signal
The component corresponding with the frequency of the first signal, to obtain through filtering out noise signal；Signal synthesizer, for by the first signal with
A composite signal is synthesized through filtering out noise signal；Wherein, when testing lock-in amplifier, using composite signal as treating
Test signal and inputted secondary signal as reference signal to lock-in amplifier.
Further, the first signal and secondary signal are the two-way separated from same signal.
Further, signal filter includes bandstop filter or trapper.
Further, signal filter includes：Phase measuring appliance is locked, for measuring the frequency in white noise signal with the first signal
The amplitude and phase of the corresponding component of rate；Trapper, white noise signal is fallen into for the amplitude according to component and phase
Ripple processing, to obtain through notched signal；Logic judgment unit, for judging whether be attenuated to through the component in notched signal
Predeterminated level；Wherein, in the case where the component in through notched signal has been attenuated to predeterminated level, through notched signal as warp
Filter out noise signal output；In the case where the component in through notched signal is not attenuated to predeterminated level, through notched signal quilt
Return to lock phase measuring appliance and trapper carries out the trap processing as white noise signal again.
Further, signal parameter includes the energy signal to noise ratio or amplitude signal to noise ratio of the first signal and white noise signal, the
Frequency, phase and the pattern of one signal, the pattern of white noise signal, the amplitude of composite signal.
According to another aspect of the present invention, a kind of method for being tested lock-in amplifier is additionally provided, including
Following steps：Receive the adjustable signal parameter of user's input；First signal and secondary signal, the first letter are generated according to signal parameter
Number and secondary signal there is identical frequency, phase and pattern；White noise signal is generated according to signal parameter；From white noise signal
It is middle to remove the component corresponding with the frequency of the first signal, to obtain through filtering out noise signal；By the first signal with being made an uproar through filtering out
Acoustical signal synthesizes a composite signal；Wherein, when testing lock-in amplifier, using composite signal as trial signal to be measured
And inputted secondary signal as reference signal to lock-in amplifier.
Further, the first signal and the secondary signal are the two-way separated from same signal.
Further, the component corresponding with the frequency of the first signal is removed from white noise signal, to obtain through filtering out
The step of noise signal, includes：Amplitude and phase to component corresponding with the frequency of the first signal in white noise signal are carried out
Measurement；Trap processing is carried out to white noise signal according to the amplitude of component and phase, to obtain through notched signal；With judgement through falling into
Whether the component in ripple signal has been attenuated to predeterminated level；Wherein, the component in through notched signal has been attenuated to predetermined
In the case of level, it is used as through notched signal through filtering out noise signal output；Component in through notched signal is not attenuated to
In the case of predeterminated level, progress trap processing again is sent back to through notched signal.
Further, signal parameter includes the energy signal to noise ratio or amplitude signal to noise ratio of the first signal and white noise signal, the
Frequency, phase and the pattern of one signal, the pattern of white noise signal, the amplitude of composite signal.
Apply the technical scheme of the present invention, tested using the lock-in amplifier tester, its innovation is to survey
Trial signal is not simple signal to be superimposed with noise, but being superimposed for signal and the noise without measured signal frequency, is reduced
The low measurement signal of back of the body when measurement echo signal is zero, so as to ensureing the accuracy of test result.The innovation of the present invention
The method of testing for the signal to noise ratio improving performance for devising lock-in amplifier is also resided in, this method energy control input is mutually put to tested lock
The signal to noise ratio of the test signal of big device, and the signal to noise ratio using the method measurement counted from lock-in amplifier output signal, so as to
Ensure the accuracy of signal to noise ratio improving performance test result.Compared with existing lock-in amplifier method of testing, the present invention is carried
The method of testing of confession can test signal amplitude, phase and noise of the lock-in amplifier under the conditions of different frequency, signal to noise ratio etc.
Than measurement performances such as liftings.The present invention can be used for the quality control during the manufacture, transmission or use of lock-in amplifier.
According to the accompanying drawings will be brighter to the detailed description of the specific embodiment of the invention, those skilled in the art
Above-mentioned and other purposes, the advantages and features of the present invention.
Brief description of the drawings
Some specific embodiments of the present invention are described in detail by way of example, and not by way of limitation with reference to the accompanying drawings hereinafter.
Identical reference denotes same or similar part or part in accompanying drawing.It should be appreciated by those skilled in the art that these
What accompanying drawing was not necessarily drawn to scale.In accompanying drawing：
Fig. 1 is for the FB(flow block) for the tester tested lock-in amplifier in one embodiment of the present of invention；
Fig. 2 is the FB(flow block) for being used to test lock-in amplifier in one embodiment of the present of invention；
Fig. 3 is the structural representation according to signal filter in one embodiment of the invention；
Fig. 4 is according to multistage lock phase trap principle schematic in one embodiment of the invention；
Schematic diagrames of the Fig. 5 for the trap exponent number according to an exemplary embodiments of the invention to trap influential effect；
Fig. 6 is to be compareed according to the Time Domain Spectrum of the noise component(s) signal of test signal before and after trap in one embodiment of the invention
Figure；
Fig. 7 is to be compareed according to the frequency spectrum of the noise component(s) signal of test signal before and after trap in one embodiment of the invention
Figure；
Fig. 8 is to change survey of the measurement frequency under typical case Parameter Conditions to certain commercial lock-in amplifier in 1 embodiment 1
Discharge amplitude and phase measurement accuracy test result；And
Fig. 9 is to change measurement of the signal to noise ratio under typical case Parameter Conditions to certain commercial lock-in amplifier in embodiment 2
Amplitude measurement accuracy and signal to noise ratio improving performance test result.
Embodiment
As shown in figure 1, in the exemplary embodiments of the present invention, for the survey tested lock-in amplifier 106
Examination instrument includes input interface 101, signal generator 102, white noise generator 103 and signal synthesizer 105.Wherein, input connects
Mouth 101 is used for the adjustable signal parameters for receiving user's input.Specifically, signal parameter includes the first signal and white noise signal
Energy signal to noise ratio or amplitude signal to noise ratio, the frequency of the first signal, phase and pattern waveform in other words, the pattern of white noise signal
The amplitude of waveform, composite signal in other words.
On the one hand signal generator 102 generates the first signal and second after signal parameter is received according to signal parameter
Signal, while parameter signal is delivered to white noise generator 103 simultaneously, white noise generator 103 generates according to signal parameter
White noise signal.In one embodiment of the invention, the first signal and secondary signal can separate from same signal
Two-way.Preferably, the first signal and secondary signal have identical frequency, phase and pattern.
The white noise signal generated from white noise generator 103 is transported to signal filter 104, such signal filtering
Device 104 removes the component corresponding with the frequency of the first signal contained in white noise signal, so as to obtain through filtering out noise
Signal.First signal in signal synthesizer 105 through filtering out noise signal with synthesizing a composite signal.So, to locking phase
When amplifier 106 is tested, using composite signal as trial signal to be measured and using secondary signal as reference signal input to
Lock-in amplifier 106.
Fig. 2 is the FB(flow block) tested lock-in amplifier.Lock is mutually amplified with reference to the structure shown in Fig. 1
The step of device is tested is described in detail：The adjustable signal parameter of user's input, the letter are received by input interface 101
Number parameter include the energy signal to noise ratio or amplitude signal to noise ratio of the first signal and white noise signal, the frequency of the first signal, phase and
Pattern waveform in other words, the amplitude of the pattern of white noise signal waveform, composite signal in other words.As described in Figure 2, specifically include：
Step S201, input default signal to noise ratio snr, frequency f, pattern, amplitude A0With phase ф0；The bar that mutually works is locked in step S202, setting
Part；Step S203, lock-in amplifier 106 is tested, then reads amplitude A1With phase ф1, and then calculate signal to noise ratio and carry
Rise；Step S204, judgement test whether to finish, if be completed, output amplitude with impose a condition dependence, output
Signal to noise ratio is lifted with the relation and phase to impose a condition with the dependence to impose a condition；If test does not finish, return
Step S205, reset test condition.So it is used to that to the instrument of lock-in amplifier test user's setting can be received again
Signal parameter, signal generator 102 produce the first signal and secondary signal after receiving signal parameter.White noise generator 103
White noise signal is produced after receiving signal parameter, and is fallen into the trapper 108 being transported in signal filter 104
Ripple processing, i.e., remove the component corresponding with the frequency of the first signal from white noise signal, to obtain through filtering out noise signal.
Through trap handle to obtain through filter out noise signal with signal generator 102 caused by the first signal in signal synthesizer 105
A composite signal is synthesized, and is inputted using the composite signal as trial signal to be measured and using secondary signal as reference signal to lock
Phase amplifier.And inputted as test signal and continue to test into tested lock-in amplifier.Preferably, the first signal and the second letter
Number can be the two-way that is separated from same signal, and the first signal and secondary signal can have identical frequency, phase
With pattern waveform in other words.
One feature of the composite signal of the present invention is noise signal and non-generic white noise, but passes through multistage trap
The white noise of processing.Why trap processing is carried out, be because itself including a certain amount of measured signal frequency in white noise
Component of signal, this on faint signal-noise ratio signal measurement for influence can not ignore, in order to ensure the accuracy of test result, make an uproar
Frequency-portions energy demand is tested in sound to be cut down.In the present invention, signal filter 104 can include bandstop filter or
Trapper 108, therefore bandstop filter or trapper 108 can be used to cut down tested frequency-portions energy.
Fig. 3 is the structural representation of signal filter 104, it can be seen that signal filter 104 includes lock phase measuring appliance
107th, trapper 108 and logic judgment unit 109.Fig. 4 shows for multistage lock phase trap principle in one embodiment of the invention
It is intended to.The operation principle of signal filter 104 is illustrated with reference to Fig. 4.Original input signal such as white noise signal quilt
To lock phase measuring appliance 107, the lock phase measuring appliance 107 measures point corresponding with the frequency of the first signal in white noise signal for input
The amplitude and phase of amount.The amplitude and phase of component after processing are transported in trapper 108, and trapper 108 is according to component
Amplitude and phase to white noise signal carry out trap processing, with obtain through notched signal.Logic judgment unit 109 is used to judge
Whether reach setting trap exponent number through the component in notched signal, i.e., whether be attenuated to predeterminated level.Set if reached
Determine trap exponent number, then output is through filtering out noise signal；If being not reaching to setting trap exponent number, it is sent back to through notched signal
Lock phase measuring appliance 107 and trapper 108 enter horizontal lock measurement and trap processing again as white noise signal.
That is, original input signal as white noise signal first pass around lock mutually measurement obtain treat rejection frequency signal
Amplitude and phase, then carry out reducing obtaining trap result in original signal according to the amplitude of measurement and phase, by more than 5 times
The processing of repeatedly multistage trap, the signal amplitude of target frequency can decay more than 100dB, as shown in Figure 5.Handled by trap
White noise signal although there is no notable difference on time domain waveform and virtual value, as shown in fig. 6, but visible by falling on frequency domain
Almost without the energy component of measured signal frequency in signal after ripple processing, as shown in fig. 7, thus by tested periodic signal and
The test signal of signal synthesis after trap is handled has more high accuracy in the case of small-signal is measured.
In test process, the running parameter of lock-in amplifier 106 is pre-arranged, lock-in amplifier to be tested
After 106 normal works, the amplitude and phase value of tested composite signal are read as needed, and according to multiple under the same terms
Measuring amplitude analyzes its measuring accuracy with phase value, and calculates signal to noise ratio improving performance, eventually passes through more wheel change noises
Than the test result that the conditions of work such as, frequency and pattern obtain complete signal amplitude, phase and signal to noise ratio improving performance.
The present invention is using the composite signal of strict difinition signal to noise ratio as trial signal to be measured, and test signal is by not Noise
Echo signal forms with noise two parts without signal frequency, and according to formula 1 synthesize setting energy signal to noise ratio, frequency,
And signal and the test signal under noise pattern.
Wherein, SNRdBPWith SNRVRespectively energy signal to noise ratio and amplitude signal to noise ratio, ESWith ENRespectively signal and noise
Root-mean-square value or virtual value are (as the sinusoidal virtual value with white noise is respectivelyWith), A is the amplitude of output signal,
UWFMS(MS,fS, ψ) and UWFMN(MN,fN) it is respectively that the peak value of signal and noise is 1 unit waveform, wherein ψ, f, MS、MNPoint
Wei not setting signal phase, test frequency, signal mode and noise pattern.WFMouputFor final test signal (i.e. composite signal)
Waveform.
Evaluation in the test process of the present invention to signal amplitude and phase measurement precision is based on being tested under similarity condition
The multiple measurement statistic analysis result of the amplitude output valve of lock-in amplifier, i.e. amplitude average value and signal waveform in formula 1
Difference of coefficients assesses the difference assessment phase accuracy that ψ is set in amplitude accuracy, phase average and company 1, the side of the two
Difference is respectively used to assess respective accuracy.In addition, the average value AS and variances sigma S of signal amplitude and the energy signal to noise ratio of setting
The signal to noise ratio improving performance of lock-in amplifier is calculated according to formula (2).
The application of lock-in amplifier tester is further illustrated with reference to embodiment.
Embodiment 1
The response of lock-in amplifier frequency is assessed using the lock-in amplifier tester of the present invention
The SR830 that Signal Revovery companies are assessed using lock-in amplifier tester provided by the present invention locks phase
The frequency response results of amplifier, it is specific as shown in Figure 8.As can be seen that SR830 can below 100KHz 1s time constant
Accurately recover the sinusoidal signal of 0dB energy signal to noise ratio under 8 measuring conditions, the relative uncertainty degree of amplitude is about ± 1.2%, phase
Position uncertainty is ± 1 °.
Embodiment 2
Lock-in amplifier noise robustness is assessed using the lock-in amplifier tester of the present invention.
The SR830 that Signal Revovery companies are assessed using lock-in amplifier tester provided by the present invention locks phase
The antinoise response results of amplifier, as shown in Figure 9, it can be seen that SR830 can be accurately extensive in 1s 8 measurements of time constant
Reactivation amount signal to noise ratio is more than -40dB sinusoidal signal, when input signal-to-noise ratio is between -40dB and 40dB to its signal noise
Ratio is promoted to 41 ± 4dB.
So far, although those skilled in the art will appreciate that detailed herein have shown and described multiple showing for the present invention
Example property embodiment, still, still can be direct according to present disclosure without departing from the spirit and scope of the present invention
It is determined that or derive many other variations or modifications for meeting the principle of the invention.Therefore, the scope of the present invention is understood that and recognized
It is set to and covers other all these variations or modifications.
Claims (7)
1. a kind of tester for being tested lock-in amplifier, including：
Input interface (101), for receiving the adjustable signal parameter of user's input；
Signal generator (102), for generating the first signal and secondary signal according to the signal parameter, first signal and
Secondary signal has identical frequency, phase and pattern；
White noise generator (103), for generating white noise signal according to the signal parameter；
Signal filter (104), for removing the frequency identical component with first signal from the white noise signal,
To obtain through filtering out noise signal；
Signal synthesizer (105), for first signal to be synthesized into a composite signal through filtering out noise signal with described；
Wherein, the signal parameter includes the energy signal to noise ratio or amplitude noise of first signal and the white noise signal
Than frequency, phase and the pattern of, first signal, the pattern of the white noise signal, the amplitude of the composite signal；
When testing the lock-in amplifier (106), using the composite signal as trial signal to be measured and by described in
Secondary signal is inputted to the lock-in amplifier (106) as reference signal.
2. tester according to claim 1, it is characterised in that first signal and the secondary signal are from same
The two-way separated in signal.
3. tester according to claim 1 or 2, it is characterised in that the signal filter (104) includes bandreject filtering
Device or trapper (108).
4. tester according to claim 1 or 2, it is characterised in that the signal filter (104) includes：
Phase measuring appliance (107) is locked, for measuring in the white noise signal with dividing described in the frequency identical of first signal
The amplitude and phase of amount；
Trapper (108), trap processing is carried out to the white noise signal for the amplitude according to the component and phase, to obtain
Must be through notched signal；With
Logic judgment unit (109), for judging whether the component through in notched signal has been attenuated to predetermined water
It is flat；
Wherein, it is described through falling into the case where the component through in notched signal has been attenuated to the predeterminated level
Ripple signal is as described through filtering out noise signal output；It is not attenuated in the component through in notched signal described pre-
It is described to be sent back to described lock phase measuring appliance (107) and the trapper (108) conduct through notched signal in the case of fixed level
The white noise signal carries out the trap processing again.
5. a kind of method for being tested lock-in amplifier, comprise the following steps：
Receive the adjustable signal parameter of user's input；
First signal and secondary signal are generated according to the signal parameter, first signal and secondary signal have identical frequency
Rate, phase and pattern；
White noise signal is generated according to the signal parameter；
The frequency identical component with first signal is removed from the white noise signal, to obtain through filtering out noise letter
Number；
First signal is synthesized into a composite signal with described through filtering out noise signal；
Wherein, the signal parameter includes the energy signal to noise ratio or amplitude noise of first signal and the white noise signal
Than frequency, phase and the pattern of, first signal, the pattern of the white noise signal, the amplitude of the composite signal；
When testing the lock-in amplifier (106), using the composite signal as trial signal to be measured and by described in
Secondary signal is inputted to the lock-in amplifier (106) as reference signal.
6. according to the method for claim 5, it is characterised in that first signal and the secondary signal are from same letter
The two-way separated in number.
7. the method according to claim 5 or 6, it is characterised in that removed and described first from the white noise signal
The frequency identical component of signal, to include the step of acquisition through filtering out noise signal：
Amplitude and phase in the white noise signal with component described in the frequency identical of first signal is measured；
Trap processing is carried out to the white noise signal according to the amplitude of the component and phase, to obtain through notched signal；With
Judge whether the component through in notched signal has been attenuated to predeterminated level；
Wherein, it is described through falling into the case where the component through in notched signal has been attenuated to the predeterminated level
Ripple signal is as described through filtering out noise signal output；It is not attenuated in the component through in notched signal described pre-
In the case of fixed level, described be sent back to through notched signal carries out the trap processing again.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106199389A (en) * | 2016-08-17 | 2016-12-07 | 中国电子科技集团公司第四十研究所 | A kind of efficiently lock-in amplifier performance testing device and method |
| CN106483402A (en) * | 2016-09-28 | 2017-03-08 | 深圳市太赫兹科技创新研究院 | Lock-in amplifier test structure and method |
| CN110161470A (en) * | 2018-03-28 | 2019-08-23 | 中国人民解放军陆军工程大学军械士官学校 | A kind of realization scope display fast debugging platform |
| CN113583832B (en) * | 2020-04-30 | 2023-04-21 | 中国科学院过程工程研究所 | Nucleic acid detecting apparatus |
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| US3586993A (en) * | 1968-08-14 | 1971-06-22 | Marconi Instruments Ltd | Testing instruments for telecommunication systems |
| CN102455239A (en) * | 2010-10-29 | 2012-05-16 | 中国科学院沈阳自动化研究所 | Method utilizing phase-locking amplifier to detect weak signals of dynamic balancer and device for method |
| CN103427930A (en) * | 2013-07-24 | 2013-12-04 | 四川九洲电器集团有限责任公司 | Blocking type interference signal generation device and method based on digital noise |
| CN103916899A (en) * | 2013-01-04 | 2014-07-09 | 中国移动通信集团公司 | Interference signal generating device and method, and test signal generating system and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53129941A (en) * | 1977-04-20 | 1978-11-13 | Hitachi Ltd | Test method for electronic device and test signal generator circuit |
| JP4578741B2 (en) * | 2001-09-21 | 2010-11-10 | 三菱電機株式会社 | Signal generation apparatus, signal generation method, and signal generation program |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3586993A (en) * | 1968-08-14 | 1971-06-22 | Marconi Instruments Ltd | Testing instruments for telecommunication systems |
| CN102455239A (en) * | 2010-10-29 | 2012-05-16 | 中国科学院沈阳自动化研究所 | Method utilizing phase-locking amplifier to detect weak signals of dynamic balancer and device for method |
| CN103916899A (en) * | 2013-01-04 | 2014-07-09 | 中国移动通信集团公司 | Interference signal generating device and method, and test signal generating system and method |
| CN103427930A (en) * | 2013-07-24 | 2013-12-04 | 四川九洲电器集团有限责任公司 | Blocking type interference signal generation device and method based on digital noise |
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