CN1758536A - Industry frequency automatic tracking filtering method and device - Google Patents
Industry frequency automatic tracking filtering method and device Download PDFInfo
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Abstract
This invention relates to a method for automatically tracking and filtering industrial frequency used in trap filter control in electronic devices, in which, said electronic device includes a trap with a digital control interface for suppressing interference of industrial frequencies, a microprocessor sets up a trapper parameter list with the central frequency as the index based on the performance requirement of the trapper and in the sphere of the industrial frequency to limit steps of the trapper under different central frequencies and corner frequency and controls the filter device to finish the sample, compute to the industrial frequency interference signal timely and look up at the parameter list to regulate the trapper to enable the central frequency to track the interference frequency automatically and keep rather small corner frequencies.
Description
Technical field the present invention relates to the low frequency filtering treatment technology of electronic instrument, equipment, relates in particular to the adaptive trap filter technology that anti-industrial frequency is disturbed.
Extensively existing power frequency in the background technology electronic device works process disturbs, it is the big and wide interference of a kind of amount, generally cause that by indoor heat light and power equipment interfering frequency is different with each national commercial frequency, is generally 50Hz or 60Hz.The low frequency signal treatment facility as audifier, ECG tester etc., disturbs especially responsive to power frequency.With the ECG tester is example, because interfering frequency just in time is in the frequency band range of electrocardiosignal, so the anti-power frequency interference capability of raising equipment is most important for the electrocardiosignal that obtains high-quality.
Power frequency is disturbed and can be coupled in the electrocardio circuit by number of ways: AC magnetic field causes interference by the line loop that leads, leakage current passes through bed to human body again by ceiling, wall and ground, lead through human body and electrode then, on human body-electrode contact resistance, form power frequency interference signals; Power line in the electrocardio circuit surrounding environment, no matter there is no current to pass through, always there is Electrostatic Coupling electric capacity in it with leading between line, will be by the caused displacement current of capacitive coupling by skin-electrode contact impedance to ground, the introducing interference; Electrocardiograph or electrocardiogram monitor often will be used simultaneously with other Medical Instruments, because every instrument all has the earth point of oneself, when they are in different earth points, on the earth lead between two contact points, produce to exchange pressure drop, and two " " potential difference between the point is exactly the common-mode voltage of electrocardio circuit; The stray field of electric devices such as instrument internal transformer and leakage current also can cause power frequency to disturb.Practice thinks, more than the power frequency that may introduce of various coupling paths disturb, can be inhibited by some measures of taking targetedly, but be difficult to be stopped fully.Therefore, most electrocardio measuring equipments also use the power frequency notch filter, to eliminate the influence that power frequency is disturbed.
The early stage analog circuits that adopt of power frequency notch filter constitute more.Along with the development of microprocessor and Digital Signal Processing, increasing electrocardio checkout equipment adopts digital trap to eliminate power frequency interference signals.The parameter of digital trap is mainly by following three factors decision: the one, and the trap centre frequency generally is fixed as 50Hz or 60Hz; The 2nd, corner frequency, on the theory, corner frequency is big more, more can the power frequency interference filtering is clean, but because the electrocardiosignal frequency range has contained 50Hz/60Hz, corner frequency is big more, the loss of the signal adjacent frequency components that causes is many more, so that distorted signals; The 3rd, filter order, exponent number are high more, the inhibition better effects if that trapper obtains, but required operand also increases greatly, the built-in filter of microprocessor is subjected to the restriction of processor calculating ability and real-time requirement, and exponent number all can not be very high, adopts second order filter more.In a word, under the condition that the exponent number and the corner frequency of trapper are determined, the filter effect of trapper depends on the industrial frequency that causes interference.Some scramble rates just equal the trap centre frequency, and then filter effect is more satisfactory; If the two has certain deviation, then filter effect can sharply descend.
And in fact, the electrical network industrial frequency is to have certain fluctuation.The nominal frequency of China's electric power system is 50Hz, regulation among the GB/T15945-1995 " quality of power supply unified power system frequency permissible variation ": electric power system normal frequency deviation allowable value is ± 0.2Hz, when power system capacity hour, deviate can be loosened to ± 0.5Hz, does not have the boundary of illustrative system amount of capacity in the standard.Stipulate the permissible variation of power supply administration's frequency of supply in " whole nation for electricity consumption rule ": net capacity is ± 0.2HZ 3,000,000 kilowatts and above person; Net capacity is person below 3,000,000 kilowatts, for ± 0.5HZ; When there is fault in electrical network, tolerance frequency fluctuation range 50 ± 1Hz.In vast grass roots, net capacity is little, and frequency fluctuation is big.
At above-mentioned fluctuation, be example with 2 rank, 50 ± 2Hz Butterworth digital trap with amplitude frequency curve shown in Figure 1, this trapper to the decay of 50Hz greater than 35dB; In the time of as frequency change ± 0.05Hz and in the 50.05Hz-49.95Hz scope, the decay of trapper is about 27dB-38dB; As frequency change ± 0.2Hz and at 50.2Hz-49.8Hz, the decay of trapper is about 19dB-21dB, descend greater than 10dB; If frequency change ± 0.5Hz reaches in the 50.5Hz-49.5Hz scope, the decay of the trapper 11dB-12dB that only has an appointment, descending reaches 23dB.
In sum, existing electronic equipment, the weak point that comprises the power frequency notch filter processing of using in the electrocardio checkout equipment is, because the trap centre frequency is fixed, the trap rejection band is considered to widen the interference that the industrial frequency that causes filter effectively not suppress changing causes again to the influence of useful signal.In addition, existing notch filter generally can not be discerned the 50/60Hz industrial frequency automatically, needs manually to set its trap centre frequency according to the industrial frequency of territory of use, and is inconvenient in the use.
The summary of the invention the technical problem to be solved in the present invention provides a kind of method and apparatus of industrial frequency filtering, be used for electronic equipment, the fluctuation that can detect, follow the tracks of industrial frequency automatically changes, thereby trap centre frequency and narrow trap frequency band in real time are provided accurately, thus when suppressing power frequency and disturb to the minimum that influences of equipment useful signal.
For solving the problems of the technologies described above, of the present inventionly be contemplated that substantially: the notch filter separated into two parts, a part is the design and the parameter setting of trapper itself, adopt the digital trap of microprocessor internal, or adopt the trapper integrated circuit of microprocessor outside, according to its performance requirement its relevant parameter is set by microprocessor; Another part is the control section of trapper, be that microprocessor is finished sampling, the calculating to the industrial frequency interference signal, adjust trap parameter according to the frequency resultant of calculating, make its trap centre frequency from the motion tracking interfering frequency, thereby trapper can keep less corner frequency to reduce influence to useful signal.In the use of notch filter, can select and the corresponding sample mode of equipment according to the application characteristic of electronic equipment.
As the first kind of technical scheme that realizes the present invention's design be, the filtering method of a kind of industrial frequency from motion tracking is provided, be used for the notch filter control of electronic equipment, described electronic equipment comprises the trapper that at least one has digital control interface, disturb in order to suppress industrial frequency, described method comprises step
A. in the industrial frequency fluctuation range, generate at least one sequence with the Δ step interval with the frequency ordering, with this sequence is that benchmark is set up at least one trap parameter table in microprocessor, the contained parameter of each list cell of described parameter list, to limit the characteristic of described trapper, comprise that described trapper is with exponent number and corner frequency under this list cell respective frequencies prerequisite that is the trap centre frequency;
B. after described electronic equipment powered on, microprocessor carries out internal initialization and the trapper initial condition is set: the industrial frequency currency with a supposition was looked into described parameter list, obtains the parameter of the list cell of this frequency values correspondence, with this parameter trapper is set;
C. timing microprocessor is measured the industrial frequency currency: the power frequency interference signals that will introduce by sampling element is through amplification, relatively obtain and the corresponding count signal of this signal frequency, and being sent to rolling counters forward, timing microprocessor reads the result of described counter also with this counter O reset; According to described count results, microprocessor calculates the industrial frequency currency;
D. the microprocessor described industrial frequency currency and the trapper centre frequency currency that will at every turn measure compares judgement, if need to change the centre frequency of trapper, then look into described parameter list, upgrade that with the parameter of the corresponding list cell that obtains trapper being set with the frequency of the most approaching described industrial frequency currency in the sequence.
As the second kind of technical scheme that realizes the present invention's design be, the filter of a kind of industrial frequency from motion tracking is provided, comprise trapper, the power frequency interference signals that is used for electronic equipment filtering useful signal, especially, also comprise microprocessor 4 and AC coupled amplifying circuit 1, low pass filter 2 and comparator 3; Interference signal is sent to described comparator 3 behind described AC coupled amplifying circuit 1 and low pass filter 2, output is sent to counter with the corresponding count signal of power frequency interfering frequency; Described microprocessor 4 described counter of control and described trappers, can regularly calculate current work frequency according to the count results of described counter, and judge described trapper is carried out relative set, make described trapper centre frequency from motion tracking current industrial frequency change.
As the third technical scheme that realizes the present invention's design be, a kind of electrocardio checkout equipment is provided, comprise the electrocardio detecting electrode that contacts with human body, trapper, especially, also comprise microprocessor 4, AC coupled amplifying circuit 1, low pass filter 2 and comparator 3, and the interference signal sampling electrode that connects AC coupled amplifying circuit 1 input; Interference signal is sent to described comparator 3 behind described AC coupled amplifying circuit 1 and low pass filter 2, export the count signal relevant with the power frequency interfering frequency and be sent to counter; Described microprocessor 4 described counter of control and described trappers, can regularly calculate current work frequency according to the count results of described counter, and judge described trapper is carried out relative set, make described trapper centre frequency from motion tracking current industrial frequency change.
Described AC coupled amplifying circuit 1 and low pass filter 2 or front and back are connected into one the tunnel, or series and parallel and constitute AC coupled low pass amplifying circuit.
Adopt technique scheme, the notch filter of electronic equipment is changed from the fluctuation of motion tracking industrial frequency, thus when effectively suppressing power frequency and disturb to the minimum that influences of equipment useful signal.It is simple also to have the notch filter apparatus structure in addition, the advantage that volume is little.
Description of drawings Fig. 1 is the amplitude-versus-frequency curve figure of second order 50 ± 2Hz Butterworth trapper
Fig. 2 is a trapper control circuit theory of constitution block diagram of the present invention
Fig. 3 is the concrete line map of trapper control circuit of the present invention
Fig. 4 is the inventive method program flow diagram
Below the embodiment, the most preferred embodiment shown in is described in further detail the present invention in conjunction with the accompanying drawings.
In electronic equipment, especially handle audifier, the electrocardio testing equipment of low frequency signal, and in the image processing display device, trapper can be used for the power frequency interference signals in the filtering useful signal.Described trapper can be the digital notch unit of microprocessor 4 inside among Fig. 2, also can be microprocessor 4 outsides, and is controlled by the trapper integrated circuit (not being shown among the figure) of microprocessor 4; It can adopt the Butterworth trapper with characteristic shown in Figure 1, also can adopt Chebyshev's trapper, or other form.As shown in Figure 2 trapper control device just can have automatic tracking filter characteristic of the present invention as long as described trapper adds, reach jamproof simultaneously to the minimum that influences of useful signal.
As shown in Figure 2, this control device comprises microprocessor 4 and the AC coupled amplifying circuit 1 of connecting one by one, low pass filter 2 and comparator 3, after interference signal was imported described AC coupled amplifying circuit 1, described comparator 3 outputs were sent to counter with the count signal that is used to count of power frequency interfering frequency corresponding (such as unanimity); Described microprocessor 4 described counter of control and described trappers, can regularly calculate current work frequency according to the count results of described counter, and judge described trapper is carried out relative set, make described trapper centre frequency from motion tracking current industrial frequency change.Described counter is not shown among the figure, and it can be the internal counter of microprocessor 4; Also can be in microprocessor 4 outsides, and be controlled by the integrated circuit of counter of microprocessor 4.
Described AC coupled amplifying circuit 1 also can be connected not according to the series system among Fig. 2 with low pass filter 2, but constitutes AC coupled low pass amplifying circuit by the series and parallel mode.With the electrocardio checkout equipment is example, comprise the electrocardio detecting electrode that contacts with human body, trapper, the control section that also comprises the above, concrete circuit connects as shown in Figure 3, the electrode of the right leg of electrocardio circuit contacts is set to the electrode of sampling, and its signal main component that is sent to AC coupled amplifying circuit 1 is that power frequency is disturbed, and also is attended by the noise of other type.Carry out frequency measurement in order to extract power frequency interference signals, described AC coupled amplifying circuit 1 comprises one-level computing amplification circuit U1 at least, and Resistor-Capacitor Unit R1, the C1 of series connection connects sampling electrode and described computing amplification circuit U1 input; Described low pass filter 2 comprises the parallel branch that resistance R 2 and capacitor C 2 constitute, these parallel branch two ends connect output and the reverse input end of described computing amplification circuit U1 respectively, thereby constituting with computing amplification circuit U1 is the AC coupled low pass amplifying circuit of core, its high pass cut off frequency is designed to 40Hz, influence that can effectively filtering low-frequency noise; The low-pass filtering cut-off frequency is designed to 80Hz, can effectively amplify power frequency interference signals.
For the better interference that suppresses high-frequency noise, low pass filter 2 can also comprise switching capacity filter circuit shown in Figure 3, have gain with the very steep characteristic of frequency change decay, U2 constitutes by integrated circuit, and it can constitute the very steep low pass filter of attenuation curve.Five rank low pass oblong switches capacitive filter MAX7426 with MAXIM company are example, and at 1.25 times more than the cut-off frequency, decay can be filtered the passband external noise quite clean up to 40dB.The low-pass cut-off frequencies of described switching capacity filter is determined by the frequency of the clock signal that microprocessor 4 is sent here, in order to take into account two kinds of industrial frequencies of 50Hz and 60Hz, it can be made as 70Hz.
Counter is the counting unit of microprocessor 4 inside among the figure, so microprocessor 4 directly is sent in the output of U3.
The electrode of the right leg of present embodiment electrocardio circuit contacts human body is set to the electrode of sampling, from the electrocardiosignal that this electrode picks up, extract the industrial frequency signal, rather than directly measure electric supply system, even electronic equipment utilizes powered battery like this, also can calculate industrial frequency by meter.Adopt other electronic equipment of the above-mentioned microwave trap of the present invention, as long as according to operating position, select the suitable sampling induction pole or the contact utmost point, system is able to select out power frequency component from outer signals, described electronic equipment just can also conveniently be applicable to different mains frequencies area to the minimum that influences of useful signal when suppressing the power frequency interference.Its concrete processing method is described below in conjunction with Fig. 4 program flow diagram: when described electronic equipment comprised at least one trapper that digital control interface is arranged, the described filtering method that is used for the industrial frequency of notch filter control from motion tracking comprised step,
A. in the industrial frequency fluctuation range, generate at least one sequence with the Δ step interval with the frequency ordering, with this sequence is that benchmark is set up at least one trap parameter table in microprocessor, the contained parameter of each list cell of described parameter list, to limit the characteristic of described trapper, comprise that described trapper is with exponent number and corner frequency under this list cell respective frequencies prerequisite that is the trap centre frequency;
B. after described electronic equipment powered on, microprocessor carries out internal initialization and the trapper initial condition is set: the industrial frequency currency with a supposition was looked into described parameter list, obtains the parameter of the list cell of this frequency values correspondence, with this parameter trapper is set;
C. timing microprocessor is measured the industrial frequency currency: the power frequency interference signals that will introduce by sampling element is through amplification, relatively obtain and the corresponding count signal of this signal frequency, and being sent to rolling counters forward, timing microprocessor reads the result of described counter also with this counter O reset; According to described count results, microprocessor calculates the industrial frequency currency;
D. the microprocessor described industrial frequency currency and the trapper centre frequency currency that will at every turn measure compares judgement, if need to change the centre frequency of trapper, then look into described parameter list, upgrade that with the parameter of the corresponding list cell that obtains trapper being set with the frequency of the most approaching described industrial frequency currency in the sequence.
Among the described step a, microprocessor can be a frequency interval with Δ=0.01Hz-0.1Hz, defines frequency sequence in 50Hz or 60Hz mains frequency fluctuation range, sets up corresponding trap parameter table; Perhaps setting up with 50Hz and 60Hz is two corresponding described parameter lists in two center vibration frequency scopes, just can satisfy the notch filter Automatic Frequency conversion requirement of described electronic equipment in different electrical networks area.Under the situation that the trapper type is fixed, the frequency interval of each list cell is more little, and trapper is more little from the centre frequency and the actual work frequency deviation of motion tracking, and the power frequency attenuating that obtains is good more.With China is example, the industrial frequency fluctuation range is 50Hz ± 1Hz, if with Δ=0.1Hz is frequency interval, setting up one is the parameter list of index with the work frequency value, just can guarantee that trapper is no more than ± 0.05Hz from the centre frequency and the actual work frequency deviation of motion tracking; The parameter of each list cell is the Butterworth trapper as if the trapper that limits, and has second order shown in Figure 1 ± 2Hz corner frequency, just can guarantee the decay of industrial frequency is kept greater than 27dB in its fluctuation range.
The initialization state of the trapper among the described step b can be that centre frequency is set with 50Hz or 60Hz or optional frequency.Using switching capacity filter better to suppress under the disturbed condition of high-frequency noise, microprocessor 4 also is provided with clock signal of output and gives described switching capacity filter, determines its cut-off frequency.Described clock signal can be produced by the counter of microprocessor 4 inside.The internal initialization of microprocessor also comprises the initial condition setting to the counter of recipient's ripple signal.
Timing measuring process among the described step c can utilize the timing of microprocessor 4 to interrupt realizing, every 50-100 can be set produce once second and to interrupt.Automatically to the pulse number accumulated counts from comparator output, its gate time length will determine the precision of this device frequency detecting to described counter.In order to guarantee certain frequency measurement accuracy, microprocessor 4 can be provided with per 100 seconds and produce once and interrupt, read the count value of described counter after interrupt taking place and with counter O reset, at last with the numerical value that reads divided by promptly obtaining actual industrial frequency value in 100 seconds.If this frequency is F, then 100 seconds inside counting values are 100F ± 1, obtain F ± 0.01Hz after 100.Therefore, with 100 seconds be unit calculated rate value, can obtain the precision of 0.01Hz, it is enough that such precision is used to adjust the trapper centre frequency.
In the described steps d relatively deterministic process also can in above-mentioned interruption, handle, be benchmark whether with the two frequency departure relatively greater than (0.5* Δ) Hz.When Δ=0.1Hz, if described deviation＞0.05Hz, then need to change the centre frequency of trapper, be that described parameter list looked in index to differ 0.05Hz with frequency values in the frequency sequence with interior centre frequency, and described trapper be set with the parameter update of finding.
The trapper type that the filter apparatus of employing this method is not limited to mention in the literary composition.Trapper is determined by parameter list is unique: as if needing to change the trapper type, only need to regenerate the alternative original parameter list of a trap parameter table according to new trapper type in advance and get final product.Because of its numerical computations is existing known technology, not at this detailed description.Described FILTER TO CONTROL part can also make integrating electronic device further combined with trapper.
In sum, it is simple in structure that notch filter device of the present invention has testing circuit, tracking frequency precision height, the effectively advantage of filtering noise, many kinds of mains frequencies of recognition and tracking 50H/60Hz automatically.
The selected main components and parts of the embodiment of the invention are: U1 selects the general amplifier TL062 of TI company for use; U2 selects the MAX7426 of MAXIM company for use; U3 selects the LM393 of TI company for use; Microprocessor can have multiple choices, as MCS51 series etc.
Claims (12)
1. an industrial frequency is used for the notch filter control of electronic equipment from the filtering method of motion tracking, and described electronic equipment comprises the trapper that at least one has digital control interface, disturbs in order to suppress industrial frequency, and described method comprises step,
A. in the industrial frequency fluctuation range, generate at least one sequence with the Δ step interval with the frequency ordering, with this sequence is that benchmark is set up at least one trap parameter table in microprocessor, the contained parameter of each list cell of described parameter list, to limit the characteristic of described trapper, comprise that described trapper is with exponent number and corner frequency under this list cell respective frequencies prerequisite that is the trap centre frequency;
B. after described electronic equipment powered on, microprocessor carries out internal initialization and the trapper initial condition is set: the industrial frequency currency with a supposition was looked into described parameter list, obtains the parameter of the list cell of this frequency values correspondence, with this parameter trapper is set;
C. timing microprocessor is measured the industrial frequency currency: the power frequency interference signals that will introduce by sampling element is through amplification, relatively obtain and the corresponding count signal of this signal frequency, and being sent to rolling counters forward, timing microprocessor reads the result of described counter also with this counter O reset; According to described count results, microprocessor calculates the industrial frequency currency;
D. the microprocessor described industrial frequency currency and the trapper centre frequency currency that will at every turn measure compares judgement, if need to change the centre frequency of trapper, then look into described parameter list, upgrade that with the parameter of the corresponding list cell that obtains trapper being set with the frequency of the most approaching described industrial frequency currency in the sequence.
2. the method for the automatic tracking filter of industrial frequency according to claim 1 is characterized in that:
The initial center frequency of trapper can be set at the optional frequency value among the described step b.
3. the method for the automatic tracking filter of industrial frequency according to claim 1 is characterized in that:
Among the described step a, be to be frequency interval, in 50Hz or 60Hz mains frequency fluctuation range, define frequency sequence, set up corresponding trap parameter table with Δ=0.01Hz-0.1Hz; Perhaps setting up with 50Hz and 60Hz is two corresponding described parameter lists in two center vibration frequency scopes.
4. according to the method for claim 1, the automatic tracking filter of 3 described industrial frequencies, it is characterized in that:
Timing measurement among described step c and the d has utilized the timing of microprocessor to interrupt handling, and every 50-100 can be set produce once second and to interrupt; Needing the condition of the centre frequency of change trapper is the two frequency departure＞(0.5* Δ) Hz.
5. an industrial frequency comprises trapper from the filter of motion tracking, is used for the power frequency interference signals of electronic equipment filtering useful signal, it is characterized in that:
Also comprise microprocessor (4) and AC coupled amplifying circuit (1), low pass filter (2) and comparator (3); Interference signal is sent to described comparator (3) behind described AC coupled amplifying circuit (1) and low pass filter (2), output is sent to counter with the corresponding count signal of power frequency interfering frequency; Described microprocessor (4) described counter of control and described trapper, can regularly calculate current work frequency according to the count results of described counter, and judge described trapper is carried out relative set, make described trapper centre frequency from motion tracking current industrial frequency change.
6. industrial frequency according to claim 5 is characterized in that from the filter of motion tracking:
Described AC coupled amplifying circuit (1) and low pass filter (2) or front and back are connected into one the tunnel, or series and parallel and constitute AC coupled low pass amplifying circuit.
7. industrial frequency according to claim 5 is characterized in that from the filter of motion tracking:
Described AC coupled amplifying circuit (1) comprises one-level computing amplification circuit U1 at least, and described interference signal is coupled to the input of described computing amplification circuit U1 through capacitor C 1.
8. according to claim 5,7 described industrial frequencies filter, it is characterized in that from motion tracking:
Described low pass filter (2) comprises the parallel branch that resistance R 2 and capacitor C 2 constitute, and these parallel branch two ends connect output and the reverse input end of described computing amplification circuit U1 respectively, thereby constitutes AC coupled low pass amplifying circuit.
9. industrial frequency according to claim 5 is characterized in that from the filter of motion tracking:
Described low pass filter (2) comprises the switching capacity filter circuit, has gain with the very steep characteristic of frequency change decay; Described microprocessor 4 provide clock signal to described switching capacity filter to limit its low-pass cut-off frequencies.
10. industrial frequency according to claim 5 is characterized in that from the filter of motion tracking:
Described trapper is second order ± 2Hz Butterworth trapper, perhaps is positioned at the inside of described microprocessor (4), perhaps is positioned at the outside of described microprocessor (4).
11. an electrocardio checkout equipment comprises the electrocardio detecting electrode that contacts with human body, trapper is characterized in that:
Also comprise microprocessor (4) and AC coupled amplifying circuit (1), low pass filter (2) and comparator (3), and the interference signal sampling electrode that connects AC coupled amplifying circuit (1) input; Interference signal is sent to described comparator (3) behind described AC coupled amplifying circuit (1) and low pass filter (2), output is sent to counter with the corresponding count signal of power frequency interfering frequency; Described microprocessor (4) described counter of control and described trapper, can regularly calculate current work frequency according to the count results of described counter, and judge described trapper is carried out relative set, make described trapper centre frequency from motion tracking current industrial frequency change; Described AC coupled amplifying circuit (1) and low pass filter (2) or front and back are connected into one the tunnel, or series and parallel and constitute AC coupled low pass amplifying circuit.
12. electrocardio checkout equipment according to claim 11 is characterized in that:
Described interference signal sampling electrode is one of electrocardio detecting electrode that contacts with human body.
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| WO2018227952A1 (en) * | 2017-06-14 | 2018-12-20 | 京东方科技集团股份有限公司 | Method and device for use in adjusting passband bandwidth of filter |
| US10622971B2 (en) | 2017-06-14 | 2020-04-14 | Beijing Boe Optoelectronics Technology Co., Ltd. | Method and device for adjusting passband width of filter |
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