CN116015309A - A sigma-delta modulator based on double quantization - Google Patents

Abstract

The invention discloses a sigma-delta modulator based on double quantization, comprising: a loop filter module, a multi-bit quantizer module, a digital compensation filter module, a digital pulse width modulation module, a single-bit quantizer module and a digital filter Module, the external analog signal is filtered and input sequentially through the loop filter module, multi-bit quantizer module, digital compensation modulation module, 1-bit quantizer quantization, 1-bit quantizer quantization output to the digital filter, and further through the digital-analog The conversion is fed back to the input of the loop filter block. The modulator of the double quantization structure of the present invention reduces the quantization noise in the output, allows the oversampling rate to be reduced, thereby increasing the conversion rate. Furthermore, since the quantization noise injected into a multi-bit system is smaller than that injected into a single-bit system, the stability issues associated with quantizer overloading are also alleviated, allowing the construction of high-order stable unipolar modulators.

Description

A sigma-delta modulator based on double quantization

technical field

The invention belongs to the technical field of digital-to-analog electronics, in particular to a sigma-delta modulator circuit based on double quantization.

Background technique

There is an increasing number of high-precision micromechanical sensors with microgravity resolution for oil exploration, seismic monitoring, space microgravity measurements, and inertial navigation and guidance applications. The electromechanical sigma-delta modulator (EMSDM) closed-loop feedback architecture as a post-processing of the sensor signal has become popular because it not only improves the input dynamic range (IDR), linearity, and bandwidth of microelectromechanical system (MEMS) sensors, Simultaneously a digital output is provided in the form of a pulse density modulated signal.

In order to improve the signal-to-noise ratio performance, the traditional single-quantization sigma-delta modulator architecture adopts increasing the order of the loop or increasing the resolution of the internal quantizer. The loop above the third order will lead to system instability, and the internal quantizer is added. The resolution of the feedback DAC requires relatively high precision, and additional circuits to improve the linearity of the DAC are required, which increase the complexity of the circuit design and correspondingly increase the area and power consumption of the system. In addition, the compensator and 1bit quantizer in the traditional single-quantization sigma-delta modulator are implemented by analog circuits, which may cause low-frequency parameters to not match well with sensor parameters due to manufacturing tolerances and parasitic effects, thereby greatly reducing the system performance.

Contents of the invention

Aiming at the deficiency of the traditional single-quantization sigma-delta modulator architecture in the prior art, the present invention provides a double-quantization-based sigma-delta modulator circuit.

The present invention solves the above technical problems through the following technical solutions:

The invention provides a sigma-delta modulator circuit based on double quantization, comprising:

A loop filter module, which is used to perform noise shaping on the filtered external analog signal;

A multi-bit quantizer module, which is used to perform multi-bit quantization output on an analog signal;

The digital compensation filter module is used to receive the multi-bit digital signal output by the multi-bit quantizer module, provide an output signal that can meet the linearity requirements of the receiver, maintain loop stability, and further filter out noise components outside the signal bandwidth;

A digital pulse width modulation module, which is used to convert the signal output by the digital compensation modulation module into a pulse signal with higher linearity;

1bit quantizer module, which is used to receive the digital signal after compensation and modulation, generate feedback pulse, and output one signal to the digital filter module. At the same time, one signal is converted into an analog signal by DAC and input to the input terminal of the loop filter ;

The digital filter module is used to receive the mixed input of the compensator and the 1bit quantizer module.

Optionally, the loop filter module adopts a CIFF structure.

Optionally, the multi-bit quantizer module adopts 12-bit or above ADC.

Optionally, the digital compensation filtering module reduces one or more nonlinear distortion components in the sampled digital output signal to provide an output signal that meets the linearity requirement of the receiver.

Optionally, the digital pulse width modulation module converts the signal output by the digital compensation modulation module into a pulse signal with higher linearity.

Optionally, the digital filter module includes a digital filter D1 and a digital filter D2, the digital filter D1 receives the output of a 1-bit quantizer, and the digital filter D2 receives the mixed input of the compensator and the 1-bit quantization quantizer module, Therefore, the system output is more linearized, and the noise of the 1-bit quantization quantizer module is removed, and the influence of different noise sources can be checked.

Compared with the prior art, the present invention has the following beneficial effects:

1. The modulator of the double quantization structure provided by the present invention reduces the quantization noise in the output, allows the oversampling rate to be reduced, thereby increasing the conversion rate. Furthermore, since the quantization noise injected into a multi-bit system is smaller than that injected into a single-bit system, the stability issues associated with quantizer overloading are also alleviated, allowing the construction of high-order stable unipolar modulators.

2. The multi-bit quantizer and digital compensation modulation module provided by the present invention can further reduce noise components while compensating signal distortion, and make chirp and 1-bit quantizer can be realized in the digital domain, like this, the digital chirp Parameters can be flexibly adapted to changes in sensor parameters, precisely controlled, and perfectly matched to sensor parameters. At the same time, this enables more parts of the modulator to be implemented in the digital domain, and more digital algorithms can be used in the structure, which makes the inertial sensor system more versatile, flexible and intelligent.

Description of drawings

In order to illustrate the technical solution of the present invention more clearly, the accompanying drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only an embodiment of the present invention. Ordinary technicians can also obtain other drawings based on these drawings without paying creative work.

Fig. 1 is the structural representation of a kind of sigma-delta modulator based on double quantization according to the embodiment of the present invention;

FIG. 2 is a circuit diagram of a third-order loop filter according to an embodiment of the present invention.

Detailed ways

It should be noted that the present invention provides a sigma-delta modulator based on double quantization. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiment of the application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the application. Obviously, the described embodiment is only It is an embodiment of a part of the application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

In the description of the present invention, several means one or more, and multiple means more than two. Greater than, less than, exceeding, etc. are understood as not including the original number, and above, below, within, etc. are understood as including the original number. If the terms "first", "second", and "third" are described, they are only used for the purpose of describing and distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the indicated technical features The quantity or implicitly indicate the sequence relationship of the indicated technical features.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", "connection" and "setting" should be understood in a broad sense, for example, it can be a fixed connection, or It can be a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations. The embodiments of the present invention will be described below according to the overall structure of the present invention.

As shown in Figure 1, a sigma-delta modulator based on double quantization provided by the present invention includes: a loop filter module, a multi-bit quantizer module, a digital compensation filter module, and a digital pulse width modulation module (DPWM) , 1bit quantizer module, digital filter module.

The loop filter module is used to perform noise shaping on the filtered external analog signal.

The multi-bit quantizer module is used to perform multi-bit quantization output on the analog signal.

The digital compensation filter module is used to receive the input multi-bit digital signal, reduce one or more nonlinear distortion components in the sampled digital output signal, so as to provide an output signal that can meet the linearity requirements of the receiver, maintain loop stability, and Noise components outside the signal bandwidth are further filtered out.

The digital pulse width modulation module (DPWM) converts the signal output by the digital compensation modulation module into a pulse signal with high linearity.

The 1bit quantization quantizer module is used to receive the digital signal after compensation modulation and generate feedback pulses. One signal of the output signal is input to the digital filter D1, and one signal is converted into an analog signal by DAC and input to the input terminal of the loop filter. Among them, the DAC adopts 1bitDAC.

The digital filter module is used to receive the mixed input of the compensator and the 1bit quantization quantizer module, so that the system output is more linear, and the noise of the 1bit quantization quantizer module is removed, and the influence of different noise sources can be checked.

The above-mentioned sigma-delta modulator circuit based on double quantization greatly improves the signal-to-noise ratio performance of the modulator by performing double quantization on the input analog signal.

As an optional embodiment, when the sensor senses an external analog signal, the analog signal presented in the form of resistance, capacitance or other forms is converted into a voltage signal, output to the loop filter for noise shaping, and then output to the multi-bit quantizer , the multi-bit quantizer module is used to perform multi-bit quantization output on the analog signal, and the digital compensation modulation module performs digital compensation modulation on the signal to provide an output signal that can meet the linearity requirements of the receiver, maintain loop stability, and further The noise in the signal is filtered out, and the compensated and modulated digital signal is output to a 1bit quantizer. After receiving the compensated and modulated digital signal, the quantizer generates a feedback pulse, and the output signal is converted into an analog signal by DAC and input to the loop. One signal at the input end of the filter is input to the digital filter, and the digital filter performs digital filtering on the 1bit digital signal to make the system output more linear, and can not only remove the noise of the 1Bit quantizer, but also check the influence of different noise sources .

The system performance of the present invention is determined by four noise sources: electronic noise (E) caused by the sensor circuit of the present invention, mechanical noise forces (B) caused by Brownian motion of the massive mass, and quantization noise Q1 and Q2.

Among them, the electronic noise generated by the sensor circuit is mainly thermal white noise. If the sensor circuit uses a high-frequency carrier signal and a high-pass filter, this noise can be effectively suppressed.

Among them, multi-bit quantizer noise Q1, when 12-bit ADC or higher resolution ADC is selected, ADC quantization noise is much lower than mechanical noise and electronic noise. Therefore, its impact on system resolution is negligible.

Wherein, 1 bit quantization quantizer module adopts 1 bit quantizer, the noise Q2 of 1 bit quantizer, this is the performance limiter of SD2, therefore, the key point of the present invention is to use digital filter D1 and D2 to remove it. Because the 1-bit quantizer works in the digital domain, the noise of the 1-bit quantizer can be effectively suppressed by controlling some parameters of the digital filter.

Through the above method, the invention can not only achieve higher dynamic range and better signal-to-noise ratio, but also, the added multi-bit quantizer and digital compensation modulation module can further reduce noise components while compensating signal distortion, and make linear The frequency modulation and 1-bit quantizer can be implemented in the digital domain, so that the parameters of the digital chirp can be flexibly adapted to changes in sensor parameters, precisely controlled, and perfectly matched to the sensor parameters.

FIG. 2 is a circuit diagram of a loop filter according to an embodiment of the present invention. As shown in Figure 2, the loop filter module adopts a CIFF structure (single-loop feedforward type includes feedforward summing integrator cascade type), in which three non-delayed integrators are connected, and the input signal is fed forward The form is connected to the input end of each level of integrator, and the integration results of each level of integrator are multiplied by different feedforward coefficients and output to the next level.

In summary, the modulator provided by the present invention adopts the sigma-delta modulator architecture of third-order double quantization digital compensation modulation, and the double quantization technique represents another method for designing ΣΔM (sigma-delta modulator), which Benefit from the error reduction of multi-bit quantizers, digitally compensated modulation, and the inherent linearity of single-bit quantizers in a single modulator. Compared with the third-order single-quantization architecture ΣΔM, the performance of the modulator can be significantly improved. In addition, the addition of multi-bit quantizers plus digital compensation modulation enables linear FM and 1-bit quantizer to be implemented in the digital domain. In this way, the digital linear FM Parameters can be flexibly adapted to changes in sensor parameters, precisely controlled, and perfectly matched to sensor parameters.

What is disclosed above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention.

Claims (6)

1. A sigma-delta modulator based on double quantization, characterized in that, comprising: A loop filter module, which is used to perform noise shaping on the filtered external analog signal; A multi-bit quantizer module, which is used to perform multi-bit quantization output on an analog signal; The digital compensation filter module is used to receive the multi-bit digital signal output by the multi-bit quantizer module, provide an output signal that can meet the linearity requirements of the receiver, maintain loop stability, and further filter out noise components outside the signal bandwidth; A digital pulse width modulation module, which is used to convert the signal output by the digital compensation modulation module into a pulse signal with higher linearity; 1bit quantizer module, which is used to receive the digital signal after compensation and modulation, generate feedback pulse, and output one signal to the digital filter module. At the same time, one signal is converted into an analog signal by DAC and input to the input terminal of the loop filter ; The digital filter module is used to receive the mixed input of the compensator and the 1bit quantizer module. 2. The sigma-delta modulator based on double quantization according to claim 1, wherein the loop filter module adopts a CIFF structure. 3. the sigma-delta modulator based on double quantization according to claim 1, is characterized in that, described multi-bit quantizer module adopts 12-bit and above ADC. 4. The sigma-delta modulator based on double quantization according to claim 1, characterized in that, the digital compensation filter module reduces one or more non-linear distortion components in the sampling digital output signal to provide the Output signal that meets receiver linearity requirements. 5. The sigma-delta modulator based on double quantization according to claim 1, wherein the digital pulse width modulation module converts the signal output by the digital compensation modulation module into a pulse signal with higher linearity. 6. the sigma-delta modulator based on double quantization according to claim 1, is characterized in that, described digital filter module comprises digital filter D1 and digital filter D2, and digital filter D1 receives 1 bit quantizer Output, the digital filter D2 receives the mixed input of the compensator and the 1bit quantization quantizer module, so that the system output is more linearized, and the noise of the 1bit quantization quantizer module is removed, and the influence of different noise sources can be checked.

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