Method for establishing correction lookup table, lookup table type digital filter chip and correction method

Abstract

The application provides a correction lookup table establishing method, a lookup table type digital filter chip and a correction method, wherein the correction lookup table establishing method comprises the following steps: obtaining a design value and an actual value of a sampling frequency; obtaining actual values of center frequencies based on the design value and the actual value of the sampling frequency and design values of the center frequencies of the lookup table type digital filter chip; obtaining first index values and second index values corresponding to the center frequencies respectively in a coefficient lookup table based on the design values and the actual values of the center frequencies, and obtaining index deviation values corresponding to the center frequencies based on the first index values and the second index values corresponding to the center frequencies; and establishing a correction lookup table based on the center frequencies and the index deviation values corresponding to the center frequencies. The application solves the problem that the prior art cannot improve the performance of a digital filter caused by sampling frequency deviation under the premise of low cost.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit design technology, and in particular relates to a method for establishing a correction lookup table, a lookup table-type digital filter chip, and a correction method. Background Technology

[0002] Digital filters receive discrete digital signals from sampled analog signals. The sampling frequency, a crucial parameter of digital filters, significantly impacts their performance. Analog signal sampling is typically achieved through an analog-to-digital converter (ADC). The sampling frequency of the ADC is usually a multiple of its input clock frequency (the exact ratio depends on the ADC's architecture, bit depth, etc.). The input clock is typically provided by a built-in oscillator. However, due to factors such as manufacturing variations, operating voltage, and ambient temperature, the built-in oscillator is prone to clock frequency shifts. These shifts directly lead to shifts in the sampling frequency, thus affecting the performance of the digital filter.

[0003] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for establishing a correction lookup table, a lookup table-type digital filter chip, and a correction method, so as to solve the problem that the prior art cannot improve the performance of digital filters caused by sampling frequency offset at a low cost.

[0005] To achieve the above and other related objectives, the present invention provides a method for establishing a correction lookup table, applicable to lookup table-type digital filter chips, characterized in that the establishment method includes:

[0006] Obtain the design value and actual value of the sampling frequency, wherein the sampling frequency is the sampling clock frequency when the lookup table type digital filter chip converts the analog input signal into a digital discrete signal;

[0007] Based on the design value and actual value of the sampling frequency and the design value of each center frequency of the lookup table type digital filter chip, the actual value of each center frequency is obtained;

[0008] Based on the design value and actual value of each center frequency, the first index value and the second index value corresponding to each center frequency are obtained from the coefficient lookup table of the lookup table type digital filter chip, and the index deviation value corresponding to each center frequency is obtained based on the first index value and the second index value corresponding to each center frequency.

[0009] A correction lookup table is established based on each center frequency and its corresponding index deviation value.

[0010] Optionally, the establishment method further includes: changing the actual value of the sampling frequency by changing the test environment to change the sampling frequency deviation value, and obtaining the index deviation value of each center frequency under different sampling frequency deviation values ​​under different test environments to improve the correction lookup table.

[0011] Optionally, the method for obtaining the design value and actual value of the sampling frequency includes: obtaining the design value of the sampling frequency based on the design value of the clock frequency of the built-in oscillator in the lookup table type digital filter chip, and obtaining the actual value of the clock frequency of the built-in oscillator and using it to obtain the actual value of the sampling frequency; wherein the design value of the sampling frequency satisfies the formula fs = fosc / m, and the actual value of the sampling frequency satisfies the formula fs' = fosc' / m, where fosc is the design value of the clock frequency of the built-in oscillator, m is the multiple of the design value, fs is the design value of the sampling frequency, fosc' is the actual value of the clock frequency of the built-in oscillator, and fs' is the actual value of the sampling frequency.

[0012] Optionally, the actual value of each center frequency satisfies the formula fi'=(fi*fs) / fs', where fi is the design value of the i-th center frequency, fs is the design value of the sampling frequency, fs' is the actual value of the sampling frequency, and fi' is the actual value of the i-th center frequency.

[0013] Optionally, the data width of the index deviation value is smaller than the data width of the index value in the coefficient lookup table.

[0014] The present invention also provides a method for correcting bias in a lookup table type digital filter chip, the method comprising:

[0015] A correction lookup table is established based on the method described above;

[0016] The target index deviation value corresponding to the target center frequency is obtained from the correction lookup table;

[0017] The target index value corresponding to the target center frequency is corrected based on the target index deviation value.

[0018] Optionally, when the correction lookup table includes index deviation values ​​of each center frequency under different sampling frequency deviation values, the method for obtaining the target index deviation value includes: obtaining the target sampling frequency deviation value based on the design value and actual value of the sampling frequency under the current test environment, and obtaining the target index deviation value of the target center frequency under the target sampling frequency deviation value in the correction lookup table.

[0019] Optionally, the correction method further includes: reading the tap coefficients based on the corrected target index value and completing the filter configuration.

[0020] The present invention also provides a lookup table type digital filter chip, the lookup table type digital filter chip comprising:

[0021] Built-in oscillator for providing input clock;

[0022] An analog-to-digital converter, connected to the built-in oscillator, is used to process the input clock to generate a sampling clock, and to convert the analog input signal into a digital discrete signal based on the sampling clock;

[0023] The lookup table module includes a correction lookup table and a coefficient lookup table. The correction lookup table is used to obtain the target index deviation value of the target center frequency under the target sampling frequency deviation value. The coefficient lookup table corrects the target index value corresponding to the target center frequency based on the target index deviation value, so as to read the tap coefficient based on the corrected target index value.

[0024] A digital filter, connected to the analog-to-digital converter and the lookup table module, completes filter configuration based on the read tap coefficients and performs digital filtering on the digital discrete signal.

[0025] Optionally, the correction lookup table and the coefficient lookup table are combined into a coefficient lookup table with correction function.

[0026] As described above, the correction lookup table establishment method, lookup table type digital filter chip, and correction method of the present invention, through the cooperation of the correction lookup table and the coefficient lookup table, can reduce or compensate for the impact of sampling frequency deviation on the performance of digital filters when sampling frequency deviation occurs, improve the adaptability of digital filters to process deviations, operating voltage, ambient temperature changes, etc., so that the performance of digital filters is not affected by sampling frequency deviation, and achieve the improvement of digital filter performance at a lower cost. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a typical digital filter chip.

[0028] Figure 2 The diagram shows a structural schematic of an existing lookup table type digital filter chip.

[0029] Figure 3 Displayed as Figure 2 The diagram shows an equivalent schematic of a lookup table in a lookup table-type digital filter chip.

[0030] Figure 4 The diagram shown is a flowchart of a method for establishing a correction lookup table in an embodiment of the present invention.

[0031] Figure 5 This is shown as another flowchart of the method for establishing a correction lookup table in an embodiment of the present invention.

[0032] Figure 6 The diagram shows a flowchart of a correction method for a lookup table type digital filter chip in an embodiment of the present invention.

[0033] Figure 7 This is shown as another flowchart of the correction method for a lookup table type digital filter chip in an embodiment of the present invention.

[0034] Figure 8 The diagram shown is a structural schematic of a lookup table type digital filter chip in an embodiment of the present invention.

[0035] Component designation explanation

[0036] 100 Lookup Table Type Digital Filter Chip

[0037] 110 Built-in oscillator

[0038] 120 Analog-to-Digital Converter

[0039] 130 Lookup Table Module

[0040] 131 Correction Lookup Table

[0041] 132 Coefficient Lookup Table

[0042] 140 digital filter Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] Please see Figures 1 to 8 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0045] Figure 1A digital filter chip is shown, including a built-in oscillator, an analog-to-digital converter (ADC), and a digital filter. The built-in oscillator provides an input clock to the ADC. The ADC generates a sampling clock based on the input clock and converts the analog input signal into a discrete digital signal based on the sampling clock, which is then output to the digital filter for digital filtering. The frequency of the sampling clock is determined by the frequency of the input clock, satisfying the formula fs = fosc / m, where fs is the frequency of the sampling clock, fosc is the frequency of the input clock, and m is a design multiplier value, which is usually determined by the structure and bit depth of the ADC. For example, in a 14-bit ADC, m equals 18.

[0046] In practical applications, digital filters are often designed as multi-frequency configurable circuit structures to cope with different application scenarios. For example, in ultrasonic radar ranging applications, different frequency bandpass filters need to be designed for ultrasonic transducers of different frequencies. Therefore, a lookup table is needed to store the tap coefficients of the digital filter at different center frequencies. The length of the lookup table is determined by the frequency range, frequency interval, etc. Figure 2 As shown. Taking 256 frequency points as an example (adjacent frequency points can be set at equal or unequal intervals), an 8-bit binary number is used to index and construct a lookup table. For different center frequencies f, the corresponding index f_index[7:0] is set, and the corresponding tap coefficients coef0~coefn of the output digital filter are addressed in this way, so that the digital filter can realize the corresponding digital filtering function, such as... Figure 3 As shown.

[0047] When using a lookup table to address the tap coefficients of a digital filter, accurate tap coefficients can be obtained if the sampling clock frequency is accurate, allowing the digital filter to perform its filtering function correctly. However, in practical applications, due to process variations, operating voltage changes, ambient temperature variations, etc., the frequency of the input clock provided by the built-in oscillator may deviate, resulting in a deviation in the sampling clock frequency. In this case, the actual center frequency, passband cutoff frequency, etc., of the digital filter will change. In this situation, accurate tap coefficients cannot be obtained using a lookup table, thus affecting the performance of the digital filter.

[0048] To ensure the accuracy of the sampling frequency, the precision of the input clock must be guaranteed. Currently, the following two technical solutions are mainly used to achieve this: Solution 1: Use a high-precision external clock generation circuit (e.g., a crystal oscillator) to provide the input clock. Solution 2: Use a built-in oscillator to provide the input clock, but a clock adjustment circuit is required to adjust the clock frequency of the built-in oscillator. The clock frequency of the built-in oscillator is calibrated before leaving the factory, and the adjustment value is stored in non-volatile memory. After the chip is powered on after leaving the factory, the clock adjustment circuit adjusts the clock frequency of the built-in oscillator to the preset value.

[0049] While the two aforementioned technical solutions can largely guarantee the accuracy of the input clock, they also have the following drawbacks: Solution 1: Requires an external crystal oscillator, increasing the overall system component cost; additionally, connecting the external crystal oscillator to the chip requires two additional I / O pins, increasing the chip's packaging cost. Solution 2: Requires adding clock tuning circuitry and non-volatile memory within the chip, increasing chip area and process complexity (indirectly increasing manufacturing costs). Furthermore, pre-shipment tuning consumes testing time, increasing testing costs. These combined factors undoubtedly significantly increase chip cost, reduce chip profit margin, and impact product competitiveness.

[0050] Based on this, this embodiment provides a method for establishing a correction lookup table, a lookup table-type digital filter chip, and a correction method. Without significantly increasing the chip cost, it solves the problem of sampling frequency deviation caused by the clock frequency deviation of the built-in oscillator, which ultimately leads to changes in the performance of the digital filter, thereby improving the performance of the digital filter.

[0051] like Figure 4 As shown, this embodiment provides a method for establishing a correction lookup table suitable for lookup table-type digital filter chips, including the following steps. In practical applications, the establishment method of this embodiment is usually performed before the lookup table-type digital filter chip leaves the factory, so as to solidify the correction lookup table in hardware form in the lookup table-type digital filter chip.

[0052] Step S11: Obtain the design value and actual value of the sampling frequency, wherein the sampling frequency is the sampling clock frequency when the lookup table type digital filter chip converts the analog input signal into a digital discrete signal.

[0053] In one implementation, the method for obtaining the design value of the sampling frequency includes: obtaining the design value of the sampling frequency based on the design value of the clock frequency of the built-in oscillator in the lookup table digital filter chip. Specifically, the design value of the sampling frequency satisfies the formula fs = fosc / m, where fs is the design value of the sampling frequency, fosc is the design value of the clock frequency of the built-in oscillator, and m is the design multiple. It should be noted that the design value of the clock frequency of the built-in oscillator is a known value, determined during chip design, while the design multiple is determined by the structure and bit depth of the analog-to-digital converter in the lookup table digital filter.

[0054] In one embodiment, the method for obtaining the actual value of the sampling frequency includes: obtaining the actual value of the clock frequency of the built-in oscillator, and obtaining the actual value of the sampling frequency based on the actual value of the clock frequency of the built-in oscillator. Specifically, the method for obtaining the actual value of the clock frequency of the built-in oscillator includes: obtaining the actual value of the clock frequency of the built-in oscillator based on wafer testing or finished product testing; furthermore, when obtaining the actual value of the sampling frequency based on the actual value of the clock frequency of the built-in oscillator, the actual value of the sampling frequency satisfies the formula fs' = fosc' / m, where fs' is the actual value of the sampling frequency, fosc' is the actual value of the clock frequency of the built-in oscillator, and m is the design multiple value. It should be noted that wafer testing or finished product testing are performed before the chip leaves the factory. Of course, other tests that can measure the actual value and are performed before the chip leaves the factory are also feasible and are not limited thereto.

[0055] Step S12: Based on the design value and actual value of the sampling frequency and the design value of each center frequency of the lookup table type digital filter chip, obtain the actual value of each center frequency.

[0056] In one implementation, the actual values ​​of each center frequency satisfy the formula fi'=(fi*fs) / fs', where fi is the design value of the i-th center frequency, fs is the design value of the sampling frequency, fs' is the actual value of the sampling frequency, and fi' is the actual value of the i-th center frequency.

[0057] The theoretical basis for obtaining the actual values ​​of each center frequency based on this step is as follows: For any center frequency, such as f0, due to the clock deviation of the built-in oscillator, the sampling frequency shifts from the design value fs to the actual value fs', and the center frequency also shifts from the design value f0 to f0'; at this time, a new index value is needed so that the lookup table type digital filter chip can still maintain the original center frequency after the sampling frequency shift. Assuming the new index value corresponds to a center frequency of fx in the coefficient lookup table, frequency normalization of the center frequency fx yields the formula Fx = 2fx / fs. Due to clock skew, the sampling frequency shifts from the design value fs to the actual value fs', and the center frequency also shifts from fx to fx'. At this point, the formula Fx = 2fx' / fs' holds, i.e., Fx = 2fx / fs = 2fx' / fs', thus deducing fx' = (fx * fs') / fs. Making fx' = f0, we have (fx * fs') / fs = f0, therefore fx = (f0 * fs) / fs'. It is evident that by treating fx as the actual value of f0, when clock skew occurs, the shifted center frequency is the target center frequency. This can compensate for the center frequency shift caused by the sampling frequency shift, achieving frequency correction.

[0058] It is important to note that the design value of the center frequency is a known value. For lookup table type digital filter chips, the design value and number of center frequencies are determined by the frequency range and frequency interval, which in turn are determined by specific application requirements. The frequency interval between any two adjacent center frequencies can be equal or unequal. In this embodiment, the frequency range is designed with a margin; for example, the target frequency range is 100kHz to 200kHz, and the actual frequency range is 96kHz to 204kHz, to ensure that all center frequencies within the target frequency range can be corrected.

[0059] Step S13: Based on the design value and actual value of each center frequency, obtain the first index value and the second index value corresponding to each center frequency from the coefficient lookup table of the lookup table-type digital filter chip, and obtain the index deviation value corresponding to each center frequency based on the first index value and the second index value corresponding to each center frequency; for any center frequency, for example, a center frequency with a design value of fi and an actual value of fi', obtain the first index value fia based on the design value fi from the coefficient lookup table, and obtain the second index value fib based on the actual value fi' from the coefficient lookup table. At this time, the index deviation value is fib-fia.

[0060] In practical applications, under mature chip manufacturing processes, the clock frequency offset of the built-in oscillator is generally not too large, meaning the index deviation value is not too large. Therefore, to effectively reduce chip overhead, the data width of the index deviation value can be appropriately reduced, making it smaller than the data width of the index value in the coefficient lookup table. For example, the data width of the index value in the coefficient lookup table is 8 bits, while the data width of the index deviation value is 4 bits. Step S14: Establish a correction lookup table based on each center frequency and its corresponding index deviation value. Its equivalent schematic diagram is similar to... Figure 3 It includes two items: center frequency and index deviation value.

[0061] In the above embodiment of the method for establishing the correction lookup table, the execution order of each step is only an illustration and is not limited to it. In fact, it is also feasible to make appropriate adjustments to the execution order of each step. For example, the part in step S13 that obtains the first index value and the second index value corresponding to each center frequency from the coefficient lookup table based on the design value of each center frequency can be executed before step S12 or during step S12.

[0062] Furthermore, in the above embodiment of the method for establishing the correction lookup table, the actual value of each center frequency is obtained in step S12 and the index deviation value corresponding to each center frequency is obtained in step S13. In fact, it is also feasible to first obtain the index deviation value corresponding to one center frequency based on steps S12 and S13, and then repeat steps S12 and S13 to obtain the index deviation value corresponding to another center frequency. By repeating this process until the index deviation value corresponding to each center frequency is obtained, which is essentially the same as the method described in the above embodiment.

[0063] It should be noted that the above embodiments only consider the impact of process deviations on the clock deviation of the built-in oscillator. It is assumed that the impact of factors such as changes in operating voltage and ambient temperature on the clock deviation of the built-in oscillator can be covered by the oscillator design margin, so they are not taken into account. Furthermore, since the clock frequency deviation of the built-in oscillator caused by process deviations can be regarded as constant, the establishment method of the above embodiments can be executed in any test environment, that is, there are no specific restrictions on operating voltage and ambient temperature.

[0064] like Figure 5 As shown, in order to further improve the correction lookup table, factors such as changes in operating voltage and ambient temperature can be taken into account. The test environment can be changed by changing at least one of the operating voltage and ambient temperature, thereby changing the actual value of the sampling frequency and thus changing the sampling frequency deviation value. Steps S11 to S13 are repeated continuously under different test environments to obtain the index deviation value of each center frequency under different sampling frequency deviation values, thereby improving the correction lookup table.

[0065] During this process, when obtaining the design and actual values ​​of the sampling frequency, the sampling frequency deviation value should also be obtained based on the design and actual values ​​of the sampling frequency. Finally, a more complete correction lookup table should be established based on the index deviation value of each center frequency under different sampling frequency deviation values. Among them, the sampling frequency deviation value satisfies the formula Δfs=fs'-fs=fosc' / m-fosc / m=(fosc'-fosc) / m, where Δfs is the sampling frequency deviation value, fs' is the actual value of the sampling frequency, fs is the design value of the sampling frequency, fosc' is the actual value of the clock frequency of the built-in oscillator, fosc is the design value of the clock frequency of the built-in oscillator, and m is the multiple of the design value.

[0066] like Figure 6 As shown, this embodiment also provides a correction method for a lookup table-type digital filter chip, including the following steps. In practical applications, the correction method of this embodiment is usually executed after the lookup table-type digital filter chip leaves the factory, in order to improve the performance of the digital filter.

[0067] Step S21: Establish a correction lookup table based on the establishment method described above. For details, please refer to the above text. It will not be repeated here.

[0068] Step S22: Obtain the target index deviation value corresponding to the target center frequency from the correction lookup table.

[0069] Step S23: Correct the target index value corresponding to the target center frequency based on the target index deviation value; specifically, obtain the target index value from the coefficient lookup table based on the target center frequency, and then correct the target index value based on the target index deviation value to obtain the corrected target index value.

[0070] Step S24: Read the tap coefficients based on the corrected target index value and complete the filter configuration to facilitate digital filtering.

[0071] In the above-described correction method, step S21 establishes an incomplete correction lookup table. If step S21 establishes a complete correction lookup table, then the correction lookup table includes the index deviation values ​​of each center frequency under different sampling frequency deviation values. In this case, step S22 needs to be changed to: obtaining the target sampling frequency deviation value based on the design value and actual value of the sampling frequency under the current test environment, and obtaining the target index deviation value of the target center frequency under the target sampling frequency deviation value in the complete correction lookup table, such as... Figure 7 As shown.

[0072] like Figure 8 As shown, this embodiment also provides a lookup table type digital filter chip 100, including a built-in oscillator 110, an analog-to-digital converter 120, a lookup table module 130, and a digital filter 140.

[0073] The built-in oscillator 110 is used to provide the input clock; in one embodiment, the built-in oscillator 110 is implemented using an RC oscillator circuit.

[0074] The analog-to-digital converter 120 is connected to a built-in oscillator 110 to process the input clock to generate a sampling clock, and to convert the analog input signal into a discrete digital signal based on the sampling clock. In one embodiment, the analog-to-digital converter is an integrating analog-to-digital converter, a Σ-Δ analog-to-digital converter, a pipelined analog-to-digital converter, or a successive approximation analog-to-digital converter.

[0075] The lookup table module 130 includes a correction lookup table 131 and a coefficient lookup table 132. The correction lookup table 131 is used to obtain the target index deviation value of the target center frequency under the target sampling frequency deviation value. The coefficient lookup table 132 corrects the target index value corresponding to the target center frequency based on the target index deviation value, and reads the tap coefficients based on the corrected target index value. It should be noted that for an incomplete correction lookup table, the target sampling frequency deviation value does not need to be considered; in this case, the correction lookup table 131 is used to obtain the target index deviation value corresponding to the target center frequency. In one embodiment, the correction lookup table 131 and the coefficient lookup table 132 can be combined into a coefficient lookup table with correction functionality. That is, the functions of the correction lookup table 131 and the coefficient lookup table 132 are integrated into one lookup table. In practical applications, the correction lookup table 131 can adopt any circuit structure capable of implementing its function, and the coefficient lookup table 132 can be built upon existing circuit structures by adding any circuit structure capable of implementing index value correction; there are no restrictions on this.

[0076] The digital filter 140 is connected to the analog-to-digital converter 120 and the lookup table module 130. It completes the filter configuration and performs digital filtering on the digital discrete signal based on the read tap coefficients.

[0077] The lookup table-type digital filter chip 100 in this embodiment, by adding a correction lookup table 131 and an improved coefficient lookup table 132, can reduce or compensate for the impact of sampling frequency deviation on the performance of the digital filter 140 when the clock frequency of the built-in oscillator 110 deviates. This improves the adaptability of the digital filter 140 to process deviations, operating voltage, and ambient temperature changes, ensuring that the performance of the digital filter 140 is unaffected by sampling frequency deviations. Compared with the existing solution one, the absence of an external crystal oscillator not only reduces device costs but also lowers chip packaging costs due to the reduced number of pins. Compared with the existing solution two, the addition of only the correction lookup table 131 greatly simplifies the internal chip design, reduces chip area and process complexity, and shortens chip testing time and reduces testing costs because precise adjustment of the built-in oscillator's clock frequency is not required.

[0078] In summary, the correction lookup table establishment method, lookup table-type digital filter chip, and correction method of the present invention, through the cooperation of the correction lookup table and the coefficient lookup table, can reduce or compensate for the impact of sampling frequency deviation on the performance of the digital filter when deviation occurs. This improves the adaptability of the digital filter to process variations, operating voltage changes, and environmental temperature variations, ensuring that the performance of the digital filter is unaffected by sampling frequency deviation, thus achieving performance improvement of the digital filter at a lower cost. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0079] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for establishing a correction lookup table, applicable to lookup table type digital filter chips, characterized in that, The establishment method includes: Obtain the design value and actual value of the sampling frequency, wherein the sampling frequency is the sampling clock frequency when the lookup table type digital filter chip converts the analog input signal into a digital discrete signal; Based on the design value and actual value of the sampling frequency and the design value of each center frequency of the lookup table type digital filter chip, the actual value of each center frequency is obtained; Based on the design value and actual value of each center frequency, the first index value and the second index value corresponding to each center frequency are obtained from the coefficient lookup table of the lookup table type digital filter chip, and the index deviation value corresponding to each center frequency is obtained based on the first index value and the second index value corresponding to each center frequency. A correction lookup table is established based on each center frequency and its corresponding index deviation value.

2. The method for establishing a correction lookup table according to claim 1, characterized in that, The establishment method further includes: changing the actual value of the sampling frequency by changing the test environment to change the sampling frequency deviation value, and obtaining the index deviation value of each center frequency under different sampling frequency deviation values ​​under different test environments to improve the correction lookup table.

3. The method for establishing a correction lookup table according to claim 1 or 2, characterized in that, Methods for obtaining the design and actual values ​​of the sampling frequency include: The design value of the sampling frequency is obtained based on the design value of the clock frequency of the built-in oscillator in the lookup table type digital filter chip, and the actual value of the clock frequency of the built-in oscillator is obtained and the actual value of the sampling frequency is obtained accordingly. Wherein, the design value of the sampling frequency satisfies the formula fs=fosc / m, and the actual value of the sampling frequency satisfies the formula fs'=fosc' / m, where fosc is the design value of the clock frequency of the built-in oscillator, m is the design multiple, fs is the design value of the sampling frequency, fosc' is the actual value of the clock frequency of the built-in oscillator, and fs' is the actual value of the sampling frequency.

4. The method for establishing a correction lookup table according to claim 1 or 2, characterized in that, The actual values ​​of each center frequency satisfy the formula fi'=(fi*fs) / fs', where fi is the design value of the i-th center frequency, fs is the design value of the sampling frequency, fs' is the actual value of the sampling frequency, and fi' is the actual value of the i-th center frequency.

5. The method for establishing a correction lookup table according to claim 1 or 2, characterized in that, The data width of the index deviation value is less than the data width of the index value in the coefficient lookup table.

6. A method for correcting bias in a lookup table type digital filter chip, characterized in that, The correction method includes: A correction lookup table is established based on the method described in any one of claims 1 to 5; The target index deviation value corresponding to the target center frequency is obtained from the correction lookup table; The target index value corresponding to the target center frequency is corrected based on the target index deviation value.

7. The correction method for a lookup table type digital filter chip according to claim 6, characterized in that, When the correction lookup table includes index deviation values ​​of each center frequency under different sampling frequency deviation values, the method for obtaining the target index deviation value includes: obtaining the target sampling frequency deviation value based on the design value and actual value of the sampling frequency under the current test environment, and obtaining the target index deviation value of the target center frequency under the target sampling frequency deviation value in the correction lookup table.

8. The correction method for a lookup table type digital filter chip according to claim 6 or 7, characterized in that, The correction method further includes: reading the tap coefficients based on the corrected target index value and completing the filter configuration.

9. A lookup table type digital filter chip, characterized in that, The lookup table type digital filter chip includes: Built-in oscillator for providing input clock; An analog-to-digital converter, connected to the built-in oscillator, is used to process the input clock to generate a sampling clock, and to convert the analog input signal into a digital discrete signal based on the sampling clock. The lookup table module includes a correction lookup table and a coefficient lookup table. The correction lookup table is used to obtain the target index deviation value of the target center frequency under the target sampling frequency deviation value. The coefficient lookup table corrects the target index value corresponding to the target center frequency based on the target index deviation value, so as to read the tap coefficient based on the corrected target index value. A digital filter, connected to the analog-to-digital converter and the lookup table module, completes filter configuration based on the read tap coefficients and performs digital filtering on the digital discrete signal.

10. The lookup table type digital filter chip according to claim 9, characterized in that, The correction lookup table and the coefficient lookup table are combined into a coefficient lookup table with correction function.

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