CN101562431A - Phase-locking amplifier - Google Patents
Phase-locking amplifier Download PDFInfo
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- CN101562431A CN101562431A CNA2009100515435A CN200910051543A CN101562431A CN 101562431 A CN101562431 A CN 101562431A CN A2009100515435 A CNA2009100515435 A CN A2009100515435A CN 200910051543 A CN200910051543 A CN 200910051543A CN 101562431 A CN101562431 A CN 101562431A
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Abstract
The invention provides a phase-locking amplifier, which comprises a signal conditioning unit, a phase demodulation unit and a digital-analog sampling unit, wherein the signal conditioning unit performs phase reversion, filtering and pressure partition on an input signal to be detected; the phase demodulation unit multiplies signals output by the signal conditioning unit and a reference signal phase-shifting unit; and the digital-analog sampling unit performs digital-analog conversion on the signal output by the phase demodulation unit to obtain a digital signal and feeds the digital signal back to the reference signal phase-shifting unit. The phase-locking amplifier also comprises the reference signal phase-shifting unit which is used for adjusting the phase of an input reference signal according to the digital signal fed back by the digital-analog sampling unit. Compared with the prior phase-locking amplifier, the phase-locking amplifier provided by the invention is provided with the reference signal phase-shifting unit to count the input reference signals simultaneously according to different phase clocks, thus the phase resolution is multiplied.
Description
Technical field
The present invention relates to a kind of Detection of Weak Signals instrument, specifically, relate to a kind of lock-in amplifier.
Background technology
When a faint measured signal is carried out detection limit, useless noise and the interference appearance that invariably accompanies, the accuracy and the sensitivity of measuring have been influenced, particularly when noise power surpasses measured signal power, just need recover or detect primary signal with the Detection of Weak Signals instrument and equipment.The invention of lock-in amplifier (Lock-in Amplifier is called for short LIA) makes the Detection of Weak Signals technology obtain significant breakthrough, has greatly promoted the development of basic science and engineering.
Lock-in amplifier is based on coherent detection technology, mainly comprises signalling channel, reference channel and correlator etc.Early stage lock-in amplifier is realized by analog circuit, along with the development of digital technology, lock-in amplifier and digital lock-in amplifier that simulation mixes with numeral have occurred.Digital lock-in amplifier has been realized the core phase-sensitive detector of lock-in amplifier or the Digital Signal Processing of demodulator, ratio simulation lock-in amplifier has many outstanding advantages (temperature as the simulation lock-in amplifier is floated problem) and gains great popularity, and becomes the focus of present Detection of Weak Signals research.
Lock-in amplifier must guarantee that the frequency of input signal and reference signal is identical, phase difference is zero (or fixing phase difference), and amplitude also should be changeless constant, and its output direct current signal just is directly proportional with the amplitude of measured signal.
Present simulation lock-in amplifier adopts the method for the resistance that changes the reference signal circuits for triggering to adjust the reference signal phase place mostly, not only inconvenience but also the bigger phase noise of existence; And the reference signal processing unit of most digital lock-in amplifiers adopts the digital reference phase shift to realize, though phase resolution can reach milli degree level, phase accuracy mostly is 0.01 degree.But phase noise is being required in the high measuring system, and such phase noise is not enough.
Summary of the invention
The technical problem to be solved in the present invention is: a kind of lock-in amplifier is provided, improves phase resolution.
For solving the problems of the technologies described above, a kind of lock-in amplifier provided by the invention comprises: signal condition unit, phase-demodulation unit, modulus sampling unit, wherein,
The input of described signal condition unit is connected with input signal, and output is connected with described phase-demodulation unit input, carries out anti-phase, filtering and dividing potential drop in order to the signal to input;
Two inputs of described phase-demodulation unit are connected with the output of described signal condition unit and reference signal phase-shifting unit respectively, output is connected with the input of described modulus sampling unit, multiplies each other in order to the output signal to described signal condition unit and reference signal phase-shifting unit;
Described reference signal phase-shifting unit contains three inputs, receive the feedback of the input of reference signal, the input of presetting phase place and modulus sampling unit respectively, output is connected with described phase-demodulation unit, carries out analog-to-digital conversion in order to the signal with phase-demodulation unit output and draws digital signal and feed back to the reference signal phase-shifting unit;
The input of described modulus sampling unit is connected with described phase-demodulation unit, and output is connected with described reference signal phase-shifting unit, in order to according to the digital signal of modulus sampling unit feedback the phase place of one reference signal of input is adjusted.
Further, described reference signal phase-shifting unit comprises: the feedback signal comparing unit, preset phase place holding unit, phase shift phase place self-adjusting unit, phase shift counting unit and phase shift output unit, wherein,
Described feedback signal comparing unit input is connected with the output of modulus sampling unit, and output is connected to phase shift phase place self-adjusting unit;
The described phase place holding unit input that presets receives the signal that presets phase place, and output is connected with the input of described phase shift phase place self-adjusting unit, in order to preserve presetting phase place and offering phase shift phase place self-adjusting unit of external processor;
The input of described phase shift phase place self-adjusting unit respectively with preset the output of phase place holding unit and be connected with the feedback signal comparing unit, output is connected with an input of described phase shift output unit, in order to according to presetting the signal that presets phase place and the output of feedback signal comparing unit that the phase place holding unit is preserved, adjust from the digital signal of modulus sampling unit output and offer the phase shift output unit;
The input of described phase shift counting unit receives the input of described reference signal, and output is connected with another input of described phase shift output unit, in order to the reference signal of input is counted;
Two inputs of described phase shift output unit are connected with the output of described phase shift counting unit with phase shift phase place self-adjusting unit respectively, output is connected with the input of described phase-demodulation unit, in order to the phase place according to the adjustment of phase shift phase place self-adjusting unit output needs the reference signal of phase shift counting unit output is carried out phase shift, the reference signal that draws after the phase shift is given described phase-demodulation unit.
Further, described feedback signal comparing unit comprises register and comparator, wherein,
Comparator compares in order to the digital signal with default default value and modulus sampling unit output feedback and draws optimum value, produces phase adjustment signal according to comparative result and exports to described phase shift phase place self-adjusting unit;
Register is in order to preserve the optimum value that comparator draws.
Further, described phase shift counting unit comprises clock phase-shifting unit and counting unit,
Described clock phase-shifting unit is in order to carry out phase shift to counting clock;
Counting unit is counted the reference signal of input simultaneously with the clock of out of phase.
Further, described phase-demodulation unit comprises band pass filter, synchronous demodulator and low pass filter.Wherein,
Synchronous demodulator multiplies each other in order to the homophase square wave of frequency that the signal of signal condition unit output and reference signal phase-shifting unit are exported, and the result is exported to described low pass filter;
The low pass filter signal is in order to the alternating current component of the signal of decay conditioning unit output.
Optionally, described phase-demodulation unit is the AD630KN cake core.
Optionally, described modulus sampling unit is the AD677 cake core.
Optionally, described signal condition unit is made up of signal instrumentation amplifier AD8221BR cake core, analog switch ADG451BRUZ cake core and operational amplifier A D8672ARZ cake core.
Compare with existing lock-in amplifier, lock-in amplifier provided by the invention is counted the reference signal of input with the clock of out of phase simultaneously by being provided with the reference signal phase-shifting unit, has improved phase resolution exponentially.
And in the time of the lock-in amplifier normal operating conditions, the digital signal result of phase shift output unit output feeds back to the feedback comparing unit, adjusts the phase shift phase place of reference signal in real time.
Description of drawings
Fig. 1 is the lock-in amplifier structural representation of the embodiment of the invention;
Fig. 2 is the reference signal phase-shifting unit structural representation of the embodiment of the invention.
Embodiment
Below in conjunction with the drawings and specific embodiments lock-in amplifier of the present invention is described.
Reference signal described in the present invention can be selected various signals, as square wave, and sine wave, triangular wave, oblique wave etc., in the present embodiment, selecting described reference signal is the square wave of 4KHZ.
See also Fig. 1, Fig. 1 is the lock-in amplifier structural representation of the embodiment of the invention, and this lock-in amplifier comprises: signal condition unit 1, phase-demodulation unit 2, modulus sampling unit 3 and reference signal phase-shifting unit 4, wherein,
The input of described signal condition unit 1 is connected with input signal, and output is connected with described phase-demodulation unit 2 inputs,, filtering anti-phase in order to input signal is carried out and dividing potential drop.Signal condition unit 1 can select for use signal instrumentation amplifier AD8221BR, analog switch ADG451BRUZ and operational amplifier A D8672ARZ to realize.
Two inputs of described phase-demodulation unit 2 are connected with the output of described signal condition unit 1 and reference signal phase-shifting unit 4 respectively, output is connected with the input of described modulus sampling unit 3, multiply each other in order to the output signal to described signal condition unit 1 and reference signal phase-shifting unit 4, phase-demodulation unit 2 comprises band pass filter (not indicating), synchronous demodulator (not indicating) and three key links of low pass filter (not indicating).Band pass filter adopts third-order Butterworth filter (Butterworth Filter) to realize, in order to extract the measured signal V=Acos (2 π ft+ θ) that exports signal condition unit 1 and to reject interference signal, the frequency that synchronous demodulator is exported the measured signal V=Acos (2 π ft+ θ) and the reference signal phase-shifting unit 4 of 1 output of signal condition unit is that the homophase square-wave signal of f multiplies each other the output voltage behind the process low pass filter LPF:
The synchronous demodulator of phase-demodulation unit 2 uses AD630KN to realize.The low pass filter LPF of phase-demodulation unit 2 decays to the alternating current component of the signal of signal condition unit output, must guarantee certain bandwidth simultaneously, adopts three rank Bessel filters (Bessel Filter) to realize.The output voltage of phase-demodulation unit 2
Input as modulus sampling unit 3.
The input of described modulus sampling unit 3 is connected with described phase-demodulation unit 2, output is connected with described reference signal phase-shifting unit 4, carry out analog-to-digital conversion (A/D conversion) in order to signal and draw output signal 30 phase-demodulation unit 2 outputs, this output signal 30 is a digital signal, and the digital signal 30 that will export simultaneously feeds back to reference signal phase-shifting unit 4.Reference signal phase-shifting unit 4 is dynamically adjusted the phase place of reference signal in real time according to feedback signal, reduces phase noise to greatest extent.In the present embodiment, modulus sampling unit 3 adopts AD677 to realize.
See also Fig. 2, the reference signal phase-shifting unit structural representation of the embodiment of the invention.Reference signal phase-shifting unit 4 is adjusted according to the phase place of the reference signal of 30 pairs of inputs of digital signal of modulus sampling unit 3 outputs.Reference signal phase-shifting unit 4 has 3 input signals: the digital signal 30 of reference signal, preset signal and 3 outputs of modulus sampling unit, and by drawing an output signal after phase place is adjusted: through the reference signal of phase shift.The reference signal phase-shifting unit of present embodiment mainly contains phase shift counting unit 43, presets phase place holding unit 42, feedback signal comparing unit 41, phase shift phase place self-adjusting unit 44, phase shift output unit 45 etc. are partly formed, wherein:
Reference signal is the input signal of phase shift counting unit 43, and triggering phase shift counting unit 43 also begins reference signal is counted.Phase shift counting unit 43 comprises clock phase-shifting unit (not indicating) and counting unit (not indicating) two parts.Described counting unit is provided with counting clock, wherein, described clock phase-shifting unit is in order to carry out phase shift to counting clock, counting unit is counted the reference signal of input simultaneously with the clock of out of phase, because the counting unit in the present embodiment has adopted the scheme that phase shift is counted, in the present embodiment, phase resolution can reach the mired level, when counting clock is 100MHZ, its phase resolution can reach for 2 nanoseconds, can satisfy the requirement to the high measuring system of phase noise requirement.
The input of described phase shift counting unit 43 receives the input of described reference signal, output is connected with another input of described phase shift output unit 45, the reference signal of phase shift counting unit 43 outputs is as the input of phase shift output unit 45, phase shift output unit 45 is adjusted in order to the phase place that reference signal and 44 outputs of phase shift phase place self-adjusting unit with 43 outputs of phase shift counting unit need to adjust, and draws adjusted reference signal and gives described phase-demodulation unit 2.
Described phase place holding unit 42 inputs that preset receive the signal that presets phase place, preset phase place holding unit 42 and use a register to keep the phase place that presets of external processor, and it is output as the input of phase shift phase place self-adjusting unit 44.
Described feedback signal comparing unit 41 inputs are connected with the output of modulus sampling unit 3, and output is connected to phase shift phase place self-adjusting unit 44; Described feedback signal comparing unit 41 comprises register (not indicating) and comparator (not indicating), wherein, comparator compares in order to the digital signal with default default value and modulus sampling unit 3 output feedbacks and draws maximum, produce phase adjustment signal according to comparative result and export to described phase shift phase place self-adjusting unit 44, register is in order to preserve the maximum that comparator draws.Concrete comparison procedure is: when the numerical value in the register during greater than the value in the comparator, then the value of register is composed to comparator; When the value in the register during smaller or equal to the value in the comparator, the value of comparator remains unchanged.
The output of presetting the output of phase place holding unit 42 and feedback signal comparing unit 41 is simultaneously as the input of phase shift phase place self-adjusting circuit 44.
The input of described phase shift phase place self-adjusting unit 44 respectively with preset the output of phase place holding unit 42 and be connected with feedback signal comparing unit 41, output is connected with an input of described phase shift output unit 45, in order to according to presetting the signal that presets phase place and 41 outputs of feedback signal comparing unit that phase place holding unit 42 is preserved, adjust from the digital signal of modulus sampling unit 3 outputs and offer phase shift output unit 45.
Two inputs of described phase shift output unit 45 are connected with the output of described phase shift counting unit 43 with phase shift phase place self-adjusting unit 44 respectively, and output is connected with the input of described phase-demodulation unit 2.
When phase shift output unit 45 counting phase places equaled the phase shift phase place of phase shift phase place self-adjusting unit 44 outputs, the reference signal after the output phase shift was exported to phase-demodulation unit 2.Whole reference signal phase-shifting unit 4 can adopt the EP2C35F484 chip to realize.
More than show and described basic principle of the present invention, principal character and advantage of the present invention.The technical staff of the industry should understand; the present invention is not restricted to the described embodiments; that describes in the foregoing description and the specification just illustrates principle of the present invention; the present invention also has various changes and modifications without departing from the spirit and scope of the present invention, and these changes and improvements all fall in the claimed scope of the invention.The claimed scope of the present invention is defined by appending claims and equivalent thereof.
Claims (8)
1. lock-in amplifier, described lock-in amplifier comprises: signal condition unit, phase-demodulation unit, modulus sampling unit is characterized in that: described lock-in amplifier also comprises the reference signal phase-shifting unit, wherein,
The input of described signal condition unit is connected with input signal, and output is connected with described phase-demodulation unit input, carries out anti-phase, filtering and dividing potential drop in order to the signal to input;
Two inputs of described phase-demodulation unit are connected with the output of described signal condition unit and reference signal phase-shifting unit respectively, output is connected with the input of described modulus sampling unit, multiplies each other in order to the output signal to described signal condition unit and reference signal phase-shifting unit;
Described reference signal phase-shifting unit contains three inputs, receive the feedback of the input of reference signal, the input of presetting phase place and modulus sampling unit respectively, output is connected with described phase-demodulation unit, carries out analog-to-digital conversion in order to the signal with phase-demodulation unit output and draws digital signal and feed back to the reference signal phase-shifting unit;
The input of described modulus sampling unit is connected with described phase-demodulation unit, and output is connected with described reference signal phase-shifting unit, in order to according to the digital signal of modulus sampling unit feedback the phase place of one reference signal of input is adjusted.
2. lock-in amplifier as claimed in claim 1 is characterized in that: described reference signal phase-shifting unit comprises: the feedback signal comparing unit, preset phase place holding unit, phase shift phase place self-adjusting unit, phase shift counting unit and phase shift output unit, wherein,
Described feedback signal comparing unit input is connected with the output of modulus sampling unit, and output is connected to phase shift phase place self-adjusting unit;
The described phase place holding unit input that presets receives the signal that presets phase place, and output is connected with the input of described phase shift phase place self-adjusting unit, in order to preserve presetting phase place and offering phase shift phase place self-adjusting unit of external processor;
The input of described phase shift phase place self-adjusting unit respectively with preset the output of phase place holding unit and be connected with the feedback signal comparing unit, output is connected with an input of described phase shift output unit, in order to according to presetting the signal that presets phase place and the output of feedback signal comparing unit that the phase place holding unit is preserved, adjust from the digital signal of modulus sampling unit output and offer the phase shift output unit;
The input of described phase shift counting unit receives the input of described reference signal, and output is connected with another input of described phase shift output unit, in order to the reference signal of input is counted;
Two inputs of described phase shift output unit are connected with the output of described phase shift counting unit with phase shift phase place self-adjusting unit respectively, output is connected with the input of described phase-demodulation unit, in order to the phase place according to the adjustment of phase shift phase place self-adjusting unit output needs the reference signal of phase shift counting unit output is carried out phase shift, the reference signal that draws after the phase shift is given described phase-demodulation unit.
3. lock-in amplifier as claimed in claim 2 is characterized in that: described feedback signal comparing unit comprises register and comparator, wherein,
Comparator compares in order to the digital signal with default default value and the output of modulus sampling unit and draws maximum, produces phase adjustment signal according to comparative result and exports to described phase shift phase place self-adjusting unit;
Register is in order to preserve the optimum value that comparator draws.
4. lock-in amplifier as claimed in claim 2 is characterized in that: described phase shift counting unit comprises clock phase-shifting unit and counting unit, and described counting unit is provided with counting clock,
Described clock phase-shifting unit is in order to carry out phase shift to counting clock;
Counting unit is counted the reference signal of input simultaneously with the clock of out of phase.
5. lock-in amplifier as claimed in claim 1 is characterized in that: described phase-demodulation unit comprises band pass filter, synchronous demodulator and low pass filter, wherein,
Band pass filter is in order to the signal that extracts the output of signal condition unit and reject interference signal;
Synchronous demodulator multiplies each other in order to the homophase square wave that the signal and the reference signal phase-shifting unit of the output of signal condition unit are exported, and the result is exported to described low pass filter;
Low pass filter is in order to the alternating current component of the signal of deamplification conditioning unit output.
6. as claim 1 or 5 described lock-in amplifiers, it is characterized in that: described phase-demodulation unit is the AD630KN cake core.
7. lock-in amplifier as claimed in claim 1 is characterized in that: described modulus sampling unit is the AD677 cake core.
8. lock-in amplifier as claimed in claim 1 is characterized in that: described signal condition unit is made up of signal instrumentation amplifier AD8221BR cake core, analog switch ADG451BRUZ cake core and operational amplifier A D8672ARZ cake core.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101964633A (en) * | 2010-10-22 | 2011-02-02 | 天津大学 | Lock-in amplifier circuit for detecting terahertz pulse signals |
| CN103095249A (en) * | 2011-10-28 | 2013-05-08 | 上海微电子装备有限公司 | Median filtering circuit and method thereof |
| CN103107788A (en) * | 2012-11-06 | 2013-05-15 | 苏州聚阳环保科技有限公司 | Double-phase-lock amplifier used in water quality monitoring equipment |
| CN103344610A (en) * | 2013-07-03 | 2013-10-09 | 邱宁 | CDMA (code division multiple access) forward scatter visibility detector and detection method |
| CN106685633A (en) * | 2016-12-30 | 2017-05-17 | 重庆邮电大学 | Full-digital phase shift weak signal phase lock detection method and equipment |
| CN108227541A (en) * | 2016-12-14 | 2018-06-29 | 中国航空工业集团公司西安航空计算技术研究所 | A kind of discontinuous analog difference signal frequency and phase acquisition method |
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2009
- 2009-05-19 CN CN2009100515435A patent/CN101562431B/en active Active
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101964633A (en) * | 2010-10-22 | 2011-02-02 | 天津大学 | Lock-in amplifier circuit for detecting terahertz pulse signals |
| CN101964633B (en) * | 2010-10-22 | 2013-09-11 | 天津大学 | Lock-in amplifier circuit for detecting terahertz pulse signals |
| CN103095249A (en) * | 2011-10-28 | 2013-05-08 | 上海微电子装备有限公司 | Median filtering circuit and method thereof |
| CN103095249B (en) * | 2011-10-28 | 2016-03-30 | 上海微电子装备有限公司 | A kind of Median Filter Circuit and method |
| CN103107788A (en) * | 2012-11-06 | 2013-05-15 | 苏州聚阳环保科技有限公司 | Double-phase-lock amplifier used in water quality monitoring equipment |
| CN103107788B (en) * | 2012-11-06 | 2016-05-18 | 苏州聚阳环保科技股份有限公司 | A kind of two lock-in amplifiers for water quality monitoring equipment and signal processing method and water quality monitoring equipment |
| CN103344610A (en) * | 2013-07-03 | 2013-10-09 | 邱宁 | CDMA (code division multiple access) forward scatter visibility detector and detection method |
| CN108227541A (en) * | 2016-12-14 | 2018-06-29 | 中国航空工业集团公司西安航空计算技术研究所 | A kind of discontinuous analog difference signal frequency and phase acquisition method |
| CN106685633A (en) * | 2016-12-30 | 2017-05-17 | 重庆邮电大学 | Full-digital phase shift weak signal phase lock detection method and equipment |
| CN106685633B (en) * | 2016-12-30 | 2021-02-09 | 重庆邮电大学 | Full digital phase-shift micro signal phase-lock detection method and equipment |
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