TWI650945B - Noise cancellation device - Google Patents

Abstract

A noise canceling device includes a sampling module, a first phase signal generation module, a first multiplication module connected to the sampling module and the first phase signal generation module, and a first multiplication operation module. A first accumulation operation module and a second accumulation operation module connected to the first accumulation operation module. The sampling module samples an input signal and generates a sampling signal. The first phase signal generating module generates a first phase signal. The first multiplication operation module multiplies the sampling signal and the first phase signal and generates a first signal. A composite signal, the first accumulation operation module performs accumulation operation on the first synthesis signal and generates a first accumulation signal, and the second accumulation operation module performs accumulation operation on the first accumulation signal and generates a first output signal.

Description

Noise Reduction Device

The present invention relates to a noise cancellation device, in particular to a noise cancellation device for eliminating touch noise.

Referring to FIG. 1, in a conventional mutual capacitance touch noise detection and elimination device, the touch signal RX is obtained by filtering and amplifying the analog front-end circuit 81, sampling by the analog digital converter 82, and demodulating by the demodulation circuit 83. Touch data to be detected VO. As the excitation signal generated by the touch is transmitted from each transmitting end to each receiving end, a different phase delay will occur, which will affect the accuracy of demodulation. Therefore, a sine / cosine wave generator 84 is usually added to perform quadrature demodulation to eliminate phase effects.

Generally speaking, the sine / cosine wave generator 84 is a digital circuit. If the initial phase is set to 0, it is a sine wave generator. If the phase is 90 degrees, it is a cosine wave generator. The initial phase is an arbitrary value. Initial phase sine generator. If the analog-to-digital converter 82 samples the sine wave received by the touch signal RX, the obtained sine wave sequence is x (n), and the demodulation sequence is sin (ωn) and cos (ωn), then the demodulation operation is expressed as follows : ((Σ x ( n ) sin (ω n )) ² + (Σ x ( n ) cos (ω n )) ² ) ^1/2

However, although the above-mentioned demodulation process can eliminate continuous noise interference that is not the same as the signal frequency, the demodulation operation will be performed for discontinuous discontinuous time domain mutations caused by external interference in the sampling sequence. The result of this method has a great impact. For example, if noise is superimposed on the sine signal sampled by the analog-to-digital converter 82, it will cause deviations in the demodulation results, further causing deviations in touch detection and even failure.

Therefore, an object of the present invention is to provide a noise cancellation device that can effectively solve the influence of discontinuous time-domain abrupt noise on demodulation.

Therefore, the noise cancellation device of the present invention includes a sampling module, a first phase signal generating module, a first multiplication operation module connected to the sampling module and the first phase signal generating module, and a first multiplication A first accumulation operation module of the operation module and a second accumulation operation module connected to the first accumulation operation module, wherein the sampling module samples an input signal and generates a sampling signal, and the first phase signal generation module The group generates a first phase signal. The first multiplication operation module multiplies the sampling signal and the first phase signal and generates a first composite signal. The first accumulation operation module performs an accumulation operation on the first composite signal and generates a The first accumulation signal and the second accumulation operation module accumulate the first accumulation signal and generate a first output signal.

In an embodiment, the noise cancellation device further includes a second phase signal generating module, a second multiplication operation module connected to the sampling module and the second phase signal generation module, and a second multiplication operation module. A third accumulation operation module and a fourth accumulation operation module connected to the third accumulation operation module, wherein the second phase signal generation module generates a second phase signal, and the second multiplication operation module performs sampling on the sampling signal and The second phase signal is multiplied to generate a second synthesized signal. The third accumulation operation module is used to accumulate the second synthesized signal and generate a second accumulation signal. The fourth accumulation operation module is used to accumulate the second accumulated signal. Calculate and generate a second output signal.

Further, the first phase signal is a sine wave signal, and the second phase signal is a cosine wave signal.

In one embodiment, the noise cancellation device further includes a first counting module connected to the first accumulation operation module, a second counting module connected to the second accumulation operation module, and a third accumulation operation module. A third counting module and a fourth counting module connected to the fourth accumulation operation module, wherein the first counting module is used to count the accumulation times of the first accumulation operation module, and the second counting module is used to count The accumulation number of the second accumulation operation module, the third counting module is used to count the accumulation times of the third accumulation operation module, and the fourth counting module is used to count the accumulation times of the fourth accumulation operation module.

In one embodiment, the sampling frequency of the sampling module is an integer multiple of the frequency of the first phase signal and the frequency of the second phase signal.

In one embodiment, the accumulation number of the first accumulation operation module is N1, The accumulation number of the second accumulation operation module is N2, and N1 × N2 is the number of sampling points of the sampling module. Further, N1 is an integer multiple of a half period of the first phase signal, and N1 × N2 includes an integer number of periods of the first phase signal.

In one embodiment, the accumulation number of the third accumulation operation module is N3, the accumulation number of the fourth accumulation operation module is N4, and N3 × N4 is the number of sampling points of the sampling module. Further, N3 is an integer multiple of a half period of the second phase signal, and N3 × N4 includes an integer number of periods of the second phase signal.

In one embodiment, the noise cancellation device further includes a first detection unit, the first detection unit includes a first detection module connected to the first accumulation operation module and a fifth count connected to the first detection module. Module, the first detection module is used to detect the signal noise when the first accumulation operation module accumulates N1 sampling points, and the fifth counting module counts the number of times passed by the first detection module.

In an embodiment, the noise cancellation device further includes a second detection unit, the second detection unit includes a second detection module connected to the third accumulation operation module and a sixth count connected to the second detection module. Module, the second detection module is used to detect the signal noise when the third accumulation operation module accumulates N3 sampling points, and the sixth counting module counts the number of times passed by the second detection module.

The effect of the present invention is that it can effectively eliminate noise and solve the effect of discontinuous time domain abrupt noise on demodulation.

100‧‧‧Noise Cancellation Device

10‧‧‧ analog front-end module

20‧‧‧Sampling module

31‧‧‧The first multiplication module

32‧‧‧Second Multiplication Module

41‧‧‧First Phase Signal Generation Module

42‧‧‧Second Phase Signal Generation Module

51‧‧‧The first accumulation operation module

52‧‧‧Second accumulation module

53‧‧‧Third accumulation module

54‧‧‧Second accumulation module

61‧‧‧First counting module

62‧‧‧Second counting module

63‧‧‧Third counting module

64‧‧‧Fourth counting module

71‧‧‧first detection unit

711‧‧‧The first detection module

712‧‧‧Fifth counting module

72‧‧‧Second detection unit

721‧‧‧Second detection module

722‧‧‧Sixth counting module

RX‧‧‧touch signal

VA1‧‧‧The first cumulative signal

VA2‧‧‧Second cumulative signal

VD1‧‧‧First composite signal

VD2‧‧‧Second composite signal

VI‧‧‧Input signal

VO1‧‧‧First output signal

VO2‧‧‧Second output signal

VP1‧‧‧First Phase Signal

VP2‧‧‧Second Phase Signal

VS‧‧‧Sampling signal

S11 ~ S15‧‧‧step

S21 ~ S27‧‧‧ steps

Other features and effects of the present invention will be clearly presented in the embodiment with reference to the drawings, wherein: FIG. 1 is a circuit block diagram of a conventional noise canceling circuit; FIG. 2 is a first example of the noise canceling device of the present invention. A schematic circuit block diagram of the embodiment; FIG. 3 is a schematic circuit block diagram of the noise cancellation device of the present invention in a phase in which the phase shift of the sampling signal is stable and can be accurately measured; FIG. 4 is a first composite signal of the first embodiment 5 is a waveform diagram of the sampling signal of the first embodiment; FIG. 6 is a waveform diagram of the first composite signal of the first embodiment; and FIG. 7 is a waveform of the first accumulation signal of the first embodiment FIG. 8 is a waveform diagram of a first output signal of the first embodiment; FIG. 9 is a schematic circuit block diagram of a second embodiment of a noise canceling device of the present invention; and FIG. 10 is a first composite signal of the second embodiment Cumulative operation flowchart.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are represented by the same numbers.

Referring to FIG. 2, a first embodiment of a noise cancellation device 100 according to the present invention. The noise cancellation device 100 is applied to a touch display device to detect and eliminate touch. Noise generated from time to time. In this embodiment, the noise cancellation device 100 includes an analog front-end module 10, a sampling module 20 connected to the analog front-end module 10, a first multiplication module 31 connected to the sampling module 20, and a connection sampling A second multiplication module 32 of the module 20, a first phase signal generation module 41 connected to the first multiplication module 31, a second phase signal generation module 42 connected to the second multiplication module 32, A first accumulation operation module 51 connected to the first multiplication operation module 31, a second accumulation operation module 52 connected to the first accumulation operation module 51, and a third accumulation operation connected to the second multiplication operation module 32 Module 53, a second accumulation operation module 54 connected to the third accumulation operation module 53, a first count module 61 connected to the first accumulation operation module 51, and a first accumulation operation module 52 connected to the second accumulation operation module 52 Two counting modules 62, a third counting module 63 connected to the third accumulation operation module 53 and a fourth counting module 64 connected to the fourth accumulation operation module 54.

The analog front-end module 10 is an analog front-end (AFE) circuit, which receives a touch signal RX generated by a sensing electrode (not shown) in a touch display device, and performs filtering and filtering on the touch signal RX. The signal is amplified to generate an input signal VI. The sampling module 20 is an analog-to-digital converter (ADC) for sampling the input signal VI and generating a sampling signal VS.

The first phase signal generating module 41 is a sine wave / cosine wave signal generator, and is used for generating a first phase signal VP1. The first multiplication module 31 multiplies the sampling signal VS and the first phase signal VP1 and generates a first composite signal. No. VD1. The second phase signal generating module 42 is a sine wave / cosine wave signal generator for generating a second phase signal VP2. The second multiplication operation module 32 multiplies the sampling signal VS and the second phase signal VP2 and generates a second composite signal VD2.

In this embodiment, the first phase signal generating module 41 is a sine wave signal generator, that is, the first phase signal VP1 is a sine wave signal; the second phase signal generating module 42 is a cosine wave signal generator, that is, the second The phase signal VP2 is a cosine wave signal, and the phase of the first phase signal VP1 and the second phase signal VP2 are 90 degrees out of phase.

In particular, the phase signals generated by the first phase signal generating module 41 and the second phase signal generating module 42 are interchangeable, that is, the first phase signal generating module 41 is a cosine wave signal generator, and the second phase The signal generating module 42 is a sine wave signal generator, and is not limited to this embodiment.

In addition, the sampling frequency of the sampling module 20 is an integer multiple of the frequency of the first phase signal VP1 and the frequency of the second phase signal VP2, so that the first phase signal VP1 and the second phase signal VP2 each include an integer number of samples in each cycle. For example, if the sampling frequency of the sampling module 20 is 2MHz, and the frequency of the first phase signal VP1 (sine wave signal) and the second phase signal VP2 (cosine wave signal) is 100KHz, then the first of each cycle The phase signal VP1 and the second phase signal VP2 each include 20 sampling points.

The first accumulation operation module 51 and the second accumulation operation module 52 are respectively Accumulator, the first accumulation operation module 51 performs accumulation operation on the first composite signal VD1 and generates a first accumulation signal VA1, and the second accumulation operation module 52 performs accumulation operation on the first accumulation signal VA1, and A first output signal VO1 is generated. The first counting module 61 and the second counting module 62 are counters, respectively, for counting the times accumulated by the first accumulation operation module 51 and the second accumulation operation module 52, respectively. It should be noted that the number of accumulations preset by the first accumulation operation module 51 is N1, the number of accumulations preset by the second accumulation operation module 52 is N2, and N1 × N2 is the number of sampling points of the sampling module 20. Is the total number of accumulations.

In addition, the setting principle of N1 is an integer multiple of the half period of the first phase signal VP1. Taking the above example, for example, the first phase signal VP1 includes 20 sampling points in a single cycle, then N1 can be set to 10, 20, 30, 40 and so on. The setting principle of N2 is that N1 × N2 must include an integer number of periods of the first phase signal VP1. Taking the above example, N1 × N2 must be an integer multiple of 20, and the larger N2, the better the noise removal effect, but The relative time consumption is longer, so the settings of N1 and N2 will depend on different needs and performance.

The third accumulation operation module 53 and the fourth accumulation operation module 54 are respectively an accumulator. The third accumulation operation module 53 performs accumulation operation on the second composite signal VD2, and generates a second accumulation signal VA2, and the fourth accumulation operation. The operation module 54 then performs an accumulation operation on the second accumulation signal VA2 and generates a second output signal VO2. The third counting module 63 and the fourth counting module 64 are respectively a counter for counting the third tiredness. The number of times accumulated by the addition module 53 and the fourth accumulation module 54. Similar to the first accumulation operation module 51 and the second accumulation operation module 52, the preset accumulation number of the third accumulation operation module 53 is N3, and the preset accumulation number of the fourth accumulation operation module 54 is N4, N3. × N4 is the number of sampling points (total accumulation times) of the sampling module 20, and the setting principles of N3 and N4 are the same as N1 and N2, respectively, so it will not be repeated.

In addition, the sampling signal VS output by the sampling module 20 is multiplied and accumulated with the first phase signal VP1 (sine wave signal) and the second phase signal VP2 (cosine wave signal) to orthogonalize the sampling signal VS. Demodulation to eliminate demodulation deviation caused by the phase uncertainty of the sampled signal VS. If the phase shift of the sampling signal VS is stable and can be accurately measured, demodulation can be performed using only a single sine wave signal or a cosine wave signal. The internal circuit of the noise cancellation device 100 can be shown in FIG. 3, At this time, the initial phase of the sine wave signal needs to be adjusted to match the phase offset of the sampling signal VS.

In addition, the first counting module 61, the second counting module 62, the third counting module 63, and the fourth counting module 64 may be single independent counters, or integrated into the same counter or computing device. Or they are respectively built in the first accumulation operation module 51, the second accumulation operation module 52, the third accumulation operation module 53 and the fourth accumulation operation module 54, which are not limited to this embodiment.

Referring to FIG. 2 and FIG. 4, FIG. 4 is an accumulation operation flow of the first composite signal VD1. Due to the accumulation operation flow of the second composite signal VD2 in this embodiment and the first composite signal The accumulation operation process of the signal VD1 is the same, so only the first composite signal VD1 is used for explanation.

After the analog front-end module 10 receives the touch signal RX and filters and amplifies the signal, the sampling module 20 samples the output of the analog front-end module 10 to generate a sampling signal VS, and its waveform is shown in FIG. 5 . Next, the first multiplication module 31 multiplies the sampling signal VS and the first phase signal VP1 to generate a first composite signal VD1. The waveform of the first composite signal VD1 is shown in FIG.

In step S11, the accumulation times and results of the first accumulation operation module 51 and the second accumulation operation module 52 are reset to zero, and the count times of the first count module 61 and the second count module 62 are reset to zero.

In step S12, the first accumulation operation module 51 receives the sampling points of the sampling module 20, and the number of counts of the first counting module 61 is increased by one.

In step S13, it is determined whether the number of times counted by the first counting module 61 is N1 (the number of accumulations preset by the first accumulation operation module 51). If yes, the process proceeds to step S14;

In step S14, the first accumulation operation module 51 transmits the first accumulation signal VA1 generated after the accumulation operation to the second accumulation operation module 52, and the count number of the second counting module 62 is increased by one, and the first accumulation operation is performed. The accumulation times and results of the module 51 and the count times of the first counting module 61 are reset to zero.

Step S15, determining whether the number of times counted by the second counting module 62 is N2 (the number of accumulations preset by the second accumulation operation module 52). If yes, the accumulation ends and the first output signal VO1 is output; if not, the process returns to step S12.

For example, if the number of sampling points of the sampling module 20 is 60, and the sequence is defined as a1, a2, a3 ... a60, and N1 is 10, N2 is 6, the first accumulation operation module 51 will accumulate 10 each time Sampling points (ie, a1 ~ a10, a11 ~ a20, and so on), and then segmented into the second accumulation operation module 52 for accumulation.

Therefore, through the double accumulation of the first accumulation operation module 51 and the second accumulation operation module 52, and using the average value as the demodulation output, the noise generated during touch can be effectively eliminated, and the first accumulation operation mode The waveform of the output (first accumulation signal VA1) of the group 51 and the waveform of the output (first output signal VO1) of the second accumulation operation module 52 are shown in Figs. 7 and 8, respectively. As is clear from FIG. 7 and FIG. 8, after two accumulation operations, the first output signal VO1 is an ideal straight line whose slope is related to the phase of the sampling module 20.

Referring to FIG. 9, a second embodiment of a noise cancellation device 100 according to the present invention is substantially the same as the first embodiment. The difference is that the noise cancellation device 100 further includes a first connection module 51 connected to the first accumulation operation module 51. The detection unit 71 and a second detection unit 72 connected to the third accumulation operation module 53.

The first detection unit 71 includes a first detection module 711 connected to the first accumulation operation module 51 and a fifth counting module 712 connected to the first detection module 711. The first detection module 711 is used to detect the first Accumulation module 51 accumulates N1 sampling points The fifth signal module 712 counts the number of times detected by the first detection module 711.

The second detection unit 72 includes a second detection module 721 connected to the third accumulation operation module 53 and a sixth counting module 722 connected to the second detection module 721. The second detection module 721 is used to detect the third The accumulation operation module 53 accumulates signal noise every N3 sampling points, and the sixth counting module 722 counts the number of times detected by the second detection module 721. It is specifically noted that the operations and functions of the other modules in the noise cancellation device 100 are the same as those of the first embodiment, and therefore will not be described further.

With reference to FIG. 10, FIG. 10 is an accumulation operation flow of the first composite signal VD1 of the second embodiment. Similarly, since the accumulation operation flow of the second composite signal VD2 in this embodiment is the same as the accumulation operation flow of the first composite signal VD1, only the first composite signal VD1 will be described.

After the analog front-end module 10 receives the touch signal RX and filters and amplifies the signal, the sampling module 20 samples the output of the analog front-end module 10 to generate a sampling signal VS. Then, the first multiplication mode The group 31 performs a multiplication operation on the sampling signal VS and the first phase signal VP1 to generate a first composite signal VD1, and then enters the accumulation operation flow.

In step S21, the accumulation times and results of the first accumulation operation module 51 and the second accumulation operation module 52 are reset to zero, and the values of the first counting module 61, the second counting module 62, and the fifth counting module 712 are reset to zero. The count is reset to zero.

In step S22, the sampling points of the sampling module 20 are received, and the number of counts of the first counting module 61 is increased by one.

In step S23, it is determined whether the number of times counted by the first counting module 61 is N1 (the number of accumulations preset by the first accumulation operation module 51). If yes, the process proceeds to step S24; if not, the process returns to step S22.

In step S24, the first detection module 711 detects whether the signal noise at the N1 sampling points in the first accumulation operation module 51 is too large (for example, exceeds a predetermined range). If yes, go to step S26; if not, then Go to step S25.

In step S25, the first accumulation operation module 51 transmits the first accumulation signal VA1 generated after the accumulation operation to the second accumulation operation module 52, and the number of counts of the fifth counting module 712 is incremented by one.

In step S26, the accumulation times and results of the first accumulation operation module 51 and the count times of the first counting module 61 are reset to zero, and the count times of the second counting module 62 are incremented by one.

In step S27, it is determined whether the number of times counted by the second counting module 62 is N2 (the number of accumulations preset by the second accumulation operation module 52). If yes, the accumulation ends and the first output signal VO1 is output; if not, it returns Go to step S22.

Taking the same example as above, if the number of sampling points of the sampling module 20 is 60, and the sequence is defined as a1, a2, a3 ... a60, and N1 is 10, N2 is 6, the first accumulation operation module 51 Will accumulate 10 sampling points (i.e. a1 ~ a10, a11 ~ a20 And so on), and then stepwise enter the second accumulation operation module 52 for accumulation. Among them, if the first detection module 711 detects that the noise such as a1 to a10 is too large, the accumulated results of a1 to a10 are discarded, that is, the accumulated results of the first accumulation operation module 51 are not entered in step S25. Sent to the second accumulation operation module 52, so the counting result of the fifth counting module 712 will be less than or equal to the counting result of the second counting module 62 (ie, N2), so that the local data with excessive noise can be excluded from the first The two accumulation operation modules 52 are used to remove abrupt noise in the time domain.

It is added that, in a special case, if the counting result of the fifth counting module 712 is 0, it means that the noise interference of the touch signal RX is extremely strong, and effective touch data cannot be obtained. The signal cancellation device 100 may send an interrupt or status flag to the microprocessor (MCU, not shown) of the system, indicating that the interference is very strong at this time, and the microprocessor will further process it.

In summary, the noise cancellation device 100 of the present invention can effectively eliminate noise and solve the impact of discontinuous time-domain sudden noise on demodulation by demodulating sine / cosine wave signals and double accumulation operation. It can really achieve the purpose of the invention.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited in this way, any simple equivalent changes and modifications made in accordance with the scope of the patent application and the content of the patent specification of the present invention are still Within the scope of the invention patent.

Claims (11)

A noise canceling device includes: a sampling module for sampling an input signal and generating a sampling signal; a first phase signal generating module for generating a first phase signal; a first multiplication module, Directly connected to the sampling module and the first phase signal generating module, the first multiplication operation module multiplies the sampling signal and the first phase signal, and generates a first composite signal; a first accumulation operation A module that is directly connected to the first multiplication module, the first accumulation operation module that accumulates the first composite signal and generates a first accumulation signal; and a second accumulation operation module that is directly connected to the A first accumulation operation module, which performs an accumulation operation on the first accumulation signal and generates a first output signal. The noise cancellation device according to claim 1, further comprising a second phase signal generation module to generate a second phase signal; a second multiplication module connected to the sampling module and the second phase signal generation Module, the second multiplication operation module multiplies the sampling signal and the second phase signal to generate a second composite signal; a third accumulation operation module connected to the second multiplication operation module, the The third accumulation operation module performs accumulation operation on the second composite signal and generates a second accumulation signal; and a fourth accumulation operation module connected to the third accumulation operation module, and the fourth accumulation operation module pairs The second accumulation signal is accumulated and generates a second output signal. The noise cancellation device according to claim 2, wherein the first phase signal is a sine wave signal and the second phase signal is a cosine wave signal. The noise cancellation device according to claim 1, further comprising a first counting module connected to the first accumulation operation module for counting the accumulation times of the first accumulation operation module; a second counting module Connected to the second accumulation operation module to count the accumulation times of the second accumulation operation module; a third counting module connected to the third accumulation operation module to count the third accumulation operation module And a fourth counting module connected to the fourth accumulation operation module for counting the accumulation times of the fourth accumulation operation module. The noise cancellation device according to claim 2, wherein the number of accumulations of the third accumulation operation module is N3, the number of accumulations of the fourth accumulation operation module is N4, and N3 × N4 is the number of accumulations of the sampling module. Number of sampling points. The noise cancellation device according to claim 5, wherein N3 is an integer multiple of a half period of the second phase signal, and N3 × N4 includes an integer number of periods of the second phase signal. The noise cancellation device according to claim 1, 2, or 5, wherein the number of accumulations of the first accumulation operation module is N1, the number of accumulations of the second accumulation operation module is N2, and N1 × N2 is the Number of sampling points of the sampling module. The noise cancellation device according to claim 7, wherein N1 is an integer multiple of a half period of the first phase signal, and N1 × N2 includes an integer number of periods of the first phase signal. The noise cancellation device according to claim 2, wherein the sampling frequency of the sampling module is an integer multiple of the frequency of the first phase signal and the frequency of the second phase signal. The noise cancellation device according to claim 7, further comprising a first detection unit. The first detection unit includes a first detection module connected to the first accumulation operation module and a first detection module connected to the first detection module. The fifth counting module, the first detecting module is configured to detect signal noise when the first accumulation operation module accumulates N1 sampling points, and the fifth counting module counts through the first detecting module Times. The noise cancellation device according to claim 5, further comprising a second detection unit. The second detection unit includes a second detection module connected to the third accumulation operation module and a second detection module connected to the second detection module. The sixth counting module, the second detection module is used to detect the signal noise when the third accumulation operation module accumulates N3 sampling points, and the sixth counting module counts through the second detection module to detect Times.