DDS signal generator in MEMS gyroscope

Abstract

The utility model discloses a DDS (Direct Digital Synthesizer) signal generator in an MEMS (Micro Electro Mechanical System) gyroscope, which comprises a control module which is formed by connecting more than three DDSs into a signal link in parallel and is used for connecting phase control words and frequency control words into the input ends of the DDSs one by one, each DDS has an initial phase and the frequency control words of the DDSs are kept consistent; each DDS points to and extracts storage data in a generator wave table, and the storage data are fitted into signal data with amplitude control words under the driving of a clock; the clock module is electrically connected with the control module; and a waveform generation module that generates a waveform based on the fitted signal data and outputs a signal through a digital-to-analog converter. By applying the DDS signal generator, the resolution of the DDS and the signal-to-noise ratio of the driving signal are improved, the problem of distortion of the driving signal of the gyroscope at a high sampling rate is solved, and the functions that any waveform is adjustable and the frequency and the phase can be independently configured can be realized.

Description

Technical Field

[0001] The utility model relates to a waveform generator, in particular to a DDS signal generator used for MEMS gyroscope algorithm verification. Background Art

[0002] In the verification of MEMS gyroscope algorithm, the DDS system is usually implemented using the existing IP core in FPGA. When designing and using, the user sets the appropriate IP core parameters according to the requirements and inputs excitation to the IP core. At this time, the IP outputs a sine wave or a cosine wave with the same frequency and phase. In the existing MEMS gyroscope algorithm, a single DDS IP core is usually used to directly output a waveform to drive MEMS or to demodulate the feedback signal of MEMS.

[0003] Since the current DDS system of the MEMS gyroscope algorithm is directly implemented using the IP core, its disadvantages are also obvious, that is, the performance indicators are not flexible enough. Its performance indicators can only be determined by the IP core, and the performance of the IP core is determined by the FPGA chip. In addition, key performance indicators such as waveform type, frequency resolution, phase resolution, minimum frequency, maximum frequency, and digital amplitude modulation often cannot meet the requirements of high-precision MEMS gyroscope algorithms.

[0004] In the current algorithm verification of high-precision MEMS gyroscopes, when the resonant frequency range is too narrow, it is easy to cause the lock problem due to the mechanical structure. In addition, at high sampling rates, signal integrity, signal-to-noise ratio of output signals, and adjustable flexibility are all key points that need to be paid attention to and urgently improved in verifying the drive signal. Summary of the invention

[0005] The utility model aims to provide a DDS signal generator in a MEMS gyroscope, so as to improve the output signal quality and degree of freedom of the high-precision MEMS gyroscope.

[0006] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a DDS signal generator in a MEMS gyroscope, comprising: a control module, in which more than three DDSs are connected to a signal link in parallel, and used to connect a phase control word and a frequency control word to the input end of each DDS one by one, each DDS has its own initial phase and their frequency control words are consistent, each DDS points to and extracts the stored data in the generator wave table, and is fitted into signal data with an amplitude control word under the drive of a clock; a clock module, electrically connected to the control module; a waveform generation module, which generates a waveform based on the fitted signal data and outputs the signal through a digital-to-analog converter.

[0007] Furthermore, four parallel DDSs are connected to the signal link of the control module, and the frequency control word is 8; the first DDS points to 0 and 8 in the wave table address list, corresponding to extracting data 0 and data 8 in the synthesized data, the second DDS points to 2 and 10 in the wave table address list, corresponding to extracting data 2 and 10 in the synthesized data, the third DDS points to 4 and 12 in the wave table address list, corresponding to extracting data 4 and 12 in the synthesized data, the fourth DDS points to 6 and 14 in the wave table address list, corresponding to extracting data 6 and 14 in the synthesized data, and so on.

[0008] Furthermore, in the signal chain of the control module, a signal-to-noise improvement module with a built-in decimal interpolation algorithm is provided at the storage data extraction end of each DDS.

[0009] Furthermore, the DDS module outputs frequency words in a multi-channel parallel manner, the frequency words of each DDS are the same, the initial phase difference is a fixed value, and the initial phase difference value of each DDS is the frequency word divided by the number of DDS channels.

[0010] Furthermore, the accumulated word width of the signal data fitted in the signal link is up to 51 bits.

[0011] Furthermore, the waveform types corresponding to the output signal include at least sine wave, cosine wave, triangle wave and square wave.

[0012] Compared with the prior art, the beneficial effects of the utility model are as follows: by connecting four DDS in parallel in the generator control module to address, extract and fit data respectively, and then combining the signal-to-noise improvement module of the decimal interpolation algorithm, the resolution of the DDS is greatly improved, so that it meets the frequency requirements of the driving signal in the high-precision gyroscope algorithm; the signal-to-noise ratio of the driving signal is improved, which is fully prepared for the signal demodulation after the high-precision gyroscope feedback, and solves the problem of gyroscope driving signal distortion at high sampling rates. In addition, the functions of arbitrary waveform adjustment and separate configuration of frequency and phase can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The utility model is a design principle diagram of a DDS signal generator of the utility model.

[0014] Figure 2 It is a schematic diagram of the error in extracting wave table data due to the influence of address truncation in the existing digital circuit. DETAILED DESCRIPTION

[0015] The specific implementation modes of the present invention will be further described below in conjunction with the accompanying drawings of the embodiments, so that the technical solution of the present invention is easier to understand and grasp, thereby making a clearer definition of the protection scope of the present invention.

[0016] The designer of the present invention aims at the fact that the existing DDS system in MEMS gyroscope is directly implemented using IP core, and the performance indicators are not flexible enough, especially the key performance indicators such as thin type, frequency resolution, phase resolution, minimum frequency, maximum frequency, digital amplitude modulation, etc. cannot meet the algorithm requirements of high-precision MEMS gyroscope. Therefore, a new type of DDS signal generator is proposed to improve and obtain a more ideal driving signal.

[0017] From the technical overview, the DDS signal generator in the MEMS gyroscope of the utility model mainly includes three parts: control module, clock module and waveform generation module, and of course also includes power modules and other auxiliary circuit elements for powering each component. In particular, the control module is connected to the signal link by more than three DDS in parallel, which is used to connect the phase control word and frequency control word to the input end of each DDS one by one. Each DDS has its own initial phase and their frequency control words are consistent. Each DDS points to and extracts the stored data in the generator wave table, and is fitted into signal data with amplitude control words under the drive of the clock; naturally, the clock module is electrically connected to the control module; the waveform generation module generates a waveform based on the fitted signal data and outputs the signal through a digital-to-analog converter.

[0018] From the perspective of further refinement of technical features, such as Figure 1 As shown, four DDSs are connected in parallel in the signal link of the control module, and the frequency control word is 8. This means that each DDS accumulates every 8 addresses, so the first DDS points to 0, 8, and 16 in the wave table address list, corresponding to extracting data 0, data 8, and data 16 in the synthesized data. The second DDS points to 2, 10, 18, etc. in the wave table address list, corresponding to extracting data 2, data 10, and data 18 in the synthesized data. The third DDS points to 4, 12, 20, etc. in the wave table address list, corresponding to extracting data 4, data 12, and data 20 in the synthesized data. The fourth DDS points to 6, 14, and 22 in the wave table address list, corresponding to extracting data 6, data 14, and data 22 in the synthesized data, and so on. Thus, the extracted data are fitted into a signal data string suitable for digital-to-analog conversion into the desired waveform according to the frequency control word and the phase control word, and the accumulated word width of the signal data is up to 51 bits. Here, an extended data type of the C51 compiler is used to define a bit scalar.

[0019] The waveform types corresponding to the output signal include at least sine wave, cosine wave, triangle wave and square wave. For example, if the output is a sine wave, the sine wave data of one cycle is stored in the wave table, and the frequency word and phase word are set according to the frequency and phase of the final output sine wave. The frequency word calculation formula is as follows: Figure 1As shown in , Fout represents the final waveform output frequency, M is the frequency word, N is 51 (DDS accumulation word width 51bit), and fc is the sampling rate (DDS actual working clock). DDS will address and extract data from the wave table according to the step of the frequency word. Four DDSs extract in parallel, and finally fit the four wave table data by converting parallel to serial, and fit the four data into one data output.

[0020] like Figure 2 As shown in the figure, due to the influence of digital circuit address truncation, the wave table data taken out is not the data in the ideal state. The black dots are the data taken out from the wave table, and the green dots are the ideal data. Due to the address truncation (the wave table data is not 2N), the actual output data has an error with the ideal state. For this reason, in the signal link of the control module, each DDS storage data extraction end is equipped with a signal-to-noise improvement module with a built-in decimal interpolation algorithm. The decimal interpolation algorithm restores the data result of the theoretical point through the error of the decimal address between the two points, thereby reducing the noise problem of the original signal.

[0021] From the above introduction to the scheme of the DDS signal generator in the new MEMS gyroscope and the detailed description of the implementation example, it can be seen that this scheme has substantial characteristics and progress: by connecting four DDSs in parallel in the generator control module to address, extract and fit data respectively, and then combining the signal-to-noise improvement module of the decimal interpolation algorithm, the resolution of the DDS is greatly improved, so that it meets the frequency requirements of the driving signal in the high-precision gyroscope algorithm; the signal-to-noise ratio of the driving signal is improved, which is fully prepared for the signal demodulation after the high-precision gyroscope feedback, and at the same time solves the problem of gyroscope driving signal distortion at high sampling rates. In addition, without increasing logic resources, the functions of arbitrary waveform adjustment and separate configuration of frequency and phase can be realized.

[0022] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the scope of protection required by the present invention.

Claims

1. A DDS signal generator in a MEMS gyroscope, characterized in that: include: The control module is composed of more than three DDS connected to the signal link in parallel, and is used to connect the phase control word and the frequency control word to the input end of each DDS one by one. Each DDS has its own initial phase and their frequency control words are consistent. Each DDS points to and extracts the stored data in the generator wave table, and is fitted into signal data with amplitude control words under the drive of the clock; A clock module, electrically connected to the control module; The waveform generation module generates a waveform based on the fitted signal data and outputs the signal through a digital-to-analog converter.

2. The DDS signal generator in the MEMS gyroscope according to claim 1, characterized in that: Four parallel DDSs are connected to the signal link of the control module, and the frequency control word is 8; the first DDS points to 0 and 8 in the wave table address list, corresponding to extracting data 0 and data 8 in the synthesized data, the second DDS points to 2 and 10 in the wave table address list, corresponding to extracting data 2 and 10 in the synthesized data, the third DDS points to 4 and 12 in the wave table address list, corresponding to extracting data 4 and 12 in the synthesized data, the fourth DDS points to 6 and 14 in the wave table address list, corresponding to extracting data 6 and 14 in the synthesized data, and so on.

3. The DDS signal generator in the MEMS gyroscope according to claim 1, characterized in that: In the signal chain of the control module, each DDS storage data extraction terminal is provided with a signal-to-noise improvement module with a built-in decimal interpolation algorithm.

4. The DDS signal generator in the MEMS gyroscope according to claim 1, characterized in that: The DDS module outputs frequency words in a multi-channel parallel manner. The frequency words of each DDS are the same, and the initial phase difference is a fixed value. The value of the initial phase difference of each DDS is the frequency word divided by the number of DDS channels.

5. The DDS signal generator in the MEMS gyroscope according to claim 1, characterized in that: The accumulated word width of the signal data fitted in the signal link is up to 51 bits.

6. The DDS signal generator in the MEMS gyroscope according to claim 1, characterized in that: The waveform corresponding to the output signal is a sine wave, a cosine wave, a triangle wave, a square wave or an arbitrary wave that meets the depth of the wave table.

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