High-precision Delta Sigma analog-to-digital converter
By introducing a dual-channel sampling module and a calibration digital filter into the Delta Sigma analog-to-digital converter, the problems of high modulator power consumption and path mismatch were solved, achieving high-precision signal-to-noise ratio and resolution, reducing modulator power consumption and improving the accuracy of digital signals.
Patent Information
- Application Number
- CN202511064397.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2025-11-18
AI Technical Summary
Existing Delta Sigma analog-to-digital converters amplify out-of-band quantization noise during high-order noise shaping, leading to loop instability and high power consumption. Path mismatch in the dual-sampling structure causes a decrease in signal-to-noise ratio, and existing technologies cannot effectively solve these problems.
A dual-channel sampling module and a calibration digital filter are used. The analog input signal is quantized by a quantizer, and the complementary functions of the dual-channel sampling module are used for signal sampling and feedback. The calibration coefficient is used for filtering to eliminate path mismatch and reduce modulator power supply voltage and noise.
It achieves reduced modulator power consumption, reduced thermal noise, improved signal-to-noise ratio and resolution, and enhanced digital signal accuracy without reducing the amplitude of the input signal.
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Figure CN120979457A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of analog-to-digital conversion, and particularly relates to a high-precision Delta Sigma analog-to-digital converter. BACKGROUND
[0002] The Delta Sigma analog-to-digital converter is a circuit for converting an analog signal into a digital signal, and generally comprises an integrator, an adder, a quantizer, a digital-to-analog converter and the like, and through oversampling, noise shaping and digital filtering, quantization noise is pushed to a high-frequency region, so that an extremely high signal-to-noise ratio and resolution are achieved in a target frequency band.
[0003] At present, the Delta Sigma analog-to-digital converter comprises a single-stage loop and a multi-stage loop structure. The single-stage loop structure will amplify the out-of-band quantization noise when high-order noise shaping is performed, so that the loop is unstable and saturated. Meanwhile, the single-stage loop and the multi-stage loop structure also have the following problems: (1) The power supply voltage of the entire modulator needs to be greater than or equal to the input signal amplitude, thereby increasing the power consumption of the modulator.
[0004] (2) The integrator has two working periods of a hold period and an integration period, and has the problem of wasting power consumption.
[0005] The double sampling technology can solve the problem of wasting current in the hold period of the integrator, double the oversampling rate of the Delta Sigma modulator under the premise of not significantly increasing the power consumption, and achieve higher signal-to-noise ratio and resolution. There are two schemes at present: (1) Double sampling structure with separated sampling path and feedback path: the limitation is that the separated sampling path and feedback path will introduce thermal noise into the two paths at the same time, so that the noise energy is doubled and the signal-to-noise ratio is reduced.
[0006] (2) Double sampling structure with combined sampling path and feedback path: the limitation is that the input signal and the feedback signal are in different phases and are used by different paths, and the coefficient mismatch of different paths will cause the signal-to-noise ratio of the Delta Sigma analog-to-digital converter to decrease.
[0007] In summary, the existing technology cannot meet the current needs, and based on the current situation, it is urgent to improve the existing Delta Sigma analog-to-digital converter technology. SUMMARY
[0008] In view of the above problems in the prior art, the purpose of the present application is to provide a high-precision Delta Sigma analog-to-digital converter, which reduces the power supply voltage of the modulation loop without reducing the input signal amplitude, reduces the power consumption of the modulator, and solves the mismatch problem between different channels in the double sampling technology through calibration.
[0009] A high-precision delta sigma analog-to-digital converter comprises an input quantizer, a double-channel sampling module, a modulator and a calibration digital filter. An analog input signal is quantized by the input quantizer and then enters the double-channel sampling module, and then enters the modulator to be noise-shaped to obtain a digital output signal. The digital output signal is fed back to the input of the double-channel sampling module on one hand, and is filtered by the calibration digital filter after being multiplied by a corresponding calibration coefficient according to different stages of a control signal on the other hand. The filtered signal, after removing an input offset voltage, is the calibrated digital output signal.
[0010] Preferably, the double-channel sampling module comprises a channel one and a channel two, which are controlled by the control signal to sample or feedback signals. When the high-precision delta sigma analog-to-digital converter is in digital-to-analog conversion, the functions of the channel one and the channel two of the double-channel sampling module are complementary, one of which is used for signal sampling and the other is used for signal feedback.
[0011] Preferably, the channel one is used for signal sampling when the control signal is in a first stage, and the channel two is used for signal feedback when the control signal is in the first stage. Then, the channel one is used for signal feedback when the control signal is in a second stage, and the channel two is used for signal sampling when the control signal is in the second stage. Or the channel two is used for signal sampling when the control signal is in the first stage, and the channel one is used for signal feedback when the control signal is in the first stage. Then, the channel two is used for signal feedback when the control signal is in the second stage, and the channel one is used for signal sampling when the control signal is in the second stage.
[0012] Preferably, the modulator adopts a multi-stage modulation structure, which comprises a plurality of single-stage modulation loops connected in series from the input end, and the first modulation loop is connected with the double-channel sampling module.
[0013] Preferably, the single-stage modulation loop comprises a cascade integrator, an adder, a modulation quantizer, a modulation digital filter, a feedforward path and a feedback path. The input signal is connected to the cascade integrator and the feedforward path. The output signals of the feedforward path and the cascade integrator are connected to the adder. The output signal of the adder is connected to the modulation quantizer. The output signal of the modulation quantizer is filtered by the modulation digital filter to output a digital signal. The output signal of the modulation quantizer is connected to the cascade integrator through the feedback path to realize signal feedback. The difference between the output signal of the adder and the output signal of the modulation quantizer is the input signal of the next-stage modulation loop.
[0014] Preferably, the output signal of the input quantizer is outputted after the input digital filter, and the digital signal outputted by the modulating digital filter is added to the digital signal outputted by the input digital filter to obtain the final digital output signal.
[0015] Preferably, the process of calibrating the high-precision delta sigma analog-digital converter is as follows: setting the direct current input signal less than the saturation voltage of the modulator, inputting the direct current input signal to the double-channel sampling module, and keeping the direct current input signal alternately sampled by the channel one and the channel two of the double-channel sampling module, and then fed back by the fixed channel, wherein the selection of the sampling channel is determined by the stage of the control signal, and the selection of the feedback channel is determined by the calibration channel selection signal.
[0016] Preferably, there is an input offset voltage between the double-channel sampling module and the modulator, and the process of calibrating the input offset voltage is as follows: setting the direct current input signal to zero, inputting the direct current input signal to the double-channel sampling module, and keeping the direct current input signal zero, wherein the calibration channel selection signal selects the channel one as the feedback channel, and the analog-digital conversion is continuously performed N times, and the average value of the digital output results of the N times is . Preferably, there is a gain error between the double-channel sampling module and the modulator, and the process of calibrating the gain error is as follows: setting the value of the direct current input signal to , inputting the direct current input signal to the double-channel sampling module, and keeping the direct current input signal .
[0017] Preferably, there is a gain error between the double-channel sampling module and the modulator, and the process of calibrating the gain error is as follows: setting the value of the direct current input signal to , inputting the direct current input signal to the double-channel sampling module, and keeping the direct current input signal . zero, wherein the calibration channel selection signal selects the channel one as the feedback channel, and the analog-digital conversion is continuously performed N times, and the average value of the digital output results of the N times is . Preferably, there is a gain error between the double-channel sampling module and the modulator, and the process of calibrating the gain error is as follows: setting the value of the direct current input signal Gain mismatch error after calibration , the calculation formula is as follows: .
[0018] The beneficial effects of the present application are: the high-precision Delta Sigma analog-to-digital converter, by setting an input quantizer at the input end of the dual-channel sampling module to quantize the analog input signal, and removing the quantized value of the analog input signal, only the quantization noise is transmitted to the modulator loop, which greatly reduces the power supply voltage of the modulator loop, so that the power supply voltage of the modulator loop is lower than the input signal amplitude, thereby greatly reducing the power consumption of the modulator.
[0019] In addition, by calibrating the mismatch between the two paths of the dual-channel sampling module, the negative effects of the mismatch on the performance of the modulator are eliminated, and the thermal noise is greatly reduced compared to the existing feedback path and sampling path separation structure. BRIEF DESCRIPTION OF DRAWINGS
[0020] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, together with the embodiments of the present application, to explain the present application, and do not constitute a limitation on the present application. In the drawings: Figure 1 is a system block diagram of the present application; Figure 2 is a system block diagram of the modulator of the present application; Figure 3 is a circuit diagram of the dual-channel sampling module and the modulator of the present application; Figure 4 is a flow chart of the system calibration of the present application. DETAILED DESCRIPTION
[0021] Embodiment one As shown in Figure 1 , a high-precision Delta Sigma analog-to-digital converter includes an input quantizer, a dual-channel sampling module, a modulator, and a digital filter. The analog input signal is first quantized by the input quantizer and then enters the dual-channel sampling module, and then enters the modulator for noise shaping to obtain a digital output signal. The digital output signal is fed back to the input end of the dual-channel sampling module on one hand, and is filtered by the digital filter after being multiplied by the corresponding calibration coefficient according to the different stages of the control signal on the other hand. The calibrated digital output signal is obtained after removing the input offset voltage from the filtered signal. When the control signal is low, the calibration coefficient is , when the control signal is high, the calibration coefficient is , and the offset voltage is , is the gain mismatch error.
[0022] Unlike the prior art, the analog input signal is not directly input into the modulation loop, but is first subjected to signal quantization by the input quantizer, and then the quantized value of the analog input signal is removed by the capacitive digital-to-analog converter in the dual-channel sampling module, so that the signal transmitted to the modulator is only quantization noise, thus the signal amplitude in the modulation loop is greatly reduced, so that the supply voltage can be correspondingly reduced, thereby saving a large amount of power consumption.
[0023] The dual-channel sampling module includes channel one and channel two, which can be used for signal sampling or signal feedback, and the functions of channel one and channel two are selected by the control signal, and the functions are complementary when the control signal is in different stages, and are respectively used for signal sampling and signal feedback.
[0024] It should be noted that one of channel one and channel two is a sampling channel, and the other is a feedback channel. The dual-channel sampling structure only introduces thermal noise in one channel in a stage, so the thermal noise in the entire modulation system is greatly reduced.
[0025] Specifically, channel one is used for signal sampling when the control signal is in the first stage, and channel two is used for signal feedback when the control signal is in the first stage, and channel one is used for signal feedback when the control signal is in the second stage, and channel two is used for signal sampling when the control signal is in the second stage.
[0026] Or channel two is used for signal sampling when the control signal is in the first stage, and channel one is used for signal feedback when the control signal is in the first stage, and channel two is used for signal feedback when the control signal is in the second stage, and channel one is used for signal sampling when the control signal is in the second stage.
[0027] As shown in Figure 2 The modulator adopts a multi-stage modulation structure, and the multi-stage modulation structure includes a plurality of single-stage modulation loops, which are sequentially divided into a first modulation loop, a second modulation loop,..., and an Nth modulation loop from the input end, wherein the first modulation loop is connected with the dual-channel sampling module.
[0028] Among them, since the first modulation loop is connected with the dual-channel sampling module, the structure of the first modulation loop is slightly different from that of the other modulation loops, and except for the first modulation loop, the structures of the other modulation loops are the same, and here the structure of the second modulation loop is taken as an example for description.
[0029] As shown in Figure 2As shown, the second modulation loop includes a cascaded integrator, an adder, a modulation quantizer, a modulation digital filter, a feedforward path, and a feedback path. Specifically, the output signal of the previous modulation loop is fed into the cascaded integrator and the feedforward path, respectively. The output signals of the feedforward path and the cascaded integrator are both fed into the adder. The output signal of the adder is fed into the modulation quantizer. The output signal of the modulation quantizer is then passed through the modulation digital filter to output a digital signal. Furthermore, the output signal of the modulation quantizer is also fed into the cascaded integrator through the feedback path, affecting the output signal of the cascaded integrator. Finally, the difference between the adder output signal and the modulation quantizer output signal is sent to the next modulation loop for re-modulation.
[0030] Finally, the digital signal output from the input quantizer is added to the digital signals output from all modulation loops after passing through the input digital filter to obtain the final digital output signal, which is the modulator output signal.
[0031] It should be noted that the first modulation loop also includes a cascaded integrator, an adder, a modulation quantizer, a modulation digital filter, a feedforward path, and a feedback path. The first modulation loop is connected to the dual-channel sampling module. Specifically, the output of the dual-channel sampling module is connected to the input of the cascaded integrator, and the input of the dual-channel sampling module is connected to the input of the feedforward path. The output signals of the cascaded integrator and the feedforward path are both fed into the adder. The output signal of the adder is fed into the modulation quantizer. The output signal of the modulation quantizer is output as a digital signal after passing through the modulation digital filter. The output signal of the modulation quantizer is fed into the input of the dual-channel sampling module through the feedback path.
[0032] The specific circuit diagram of the dual-channel sampling module and modulator is as follows: Figure 3 As shown, by setting multiple switching elements to control the conduction or closure of the path, a corresponding digital-to-analog conversion circuit is formed to achieve high-precision digital-to-analog conversion operation.
[0033] However, due to the coefficient mismatch between the two paths in the dual-channel sampling module, the signal-to-noise ratio of the modulation system will decrease, so calibration is required.
[0034] Set DC input signal The DC input signal is less than the modulation loop saturation voltage. DC input signal is input to the dual-channel sampling module. The sampling is performed alternately by path one and path two in the dual-channel sampling module, and then feedback is provided through a fixed path. The selection of the sampling path is determined by the stage of the control signal, and the selection of the feedback path is determined by the calibration path selection signal.
[0035] Specifically, such as Figure 4As shown, there is an input offset voltage between the dual-channel sampling module and the modulator in the whole modulation system , gain error . The input offset voltage represents the difference between the actual input signal and the output signal of the modulator, and the gain error represents the system noise.
[0036] The process of calibrating the gain error is as follows: After setting the DC input signal to 0 and inputting it into the dual-channel sampling module, when the modulation system is performing digital-to-analog conversion, the output signal only includes quantization noise, thermal noise and noise caused by channel mismatch, among which the noise caused by channel mismatch is dominant, i.e., the gain error is dominant.
[0037] At this time, the calibration channel selection signal selects channel 0 shown in Figure 4 as the feedback channel, and the digital-to-analog conversion is continuously performed N times, and the average value of the N digital output results is . Keep the DC input signal to 0, at this time, the calibration channel selection signal selects channel 1 shown in Figure 4 as the feedback channel, and the digital-to-analog conversion is continuously performed N times, and the average value of the N digital output results is . The calibrated input offset voltage is obtained, and the calculation formula is:
[0038] After setting the value of the DC input signal to and inputting it into the dual-channel sampling module, at this time, the calibration channel selection signal selects channel 0 shown in Figure 4 as the feedback channel, and the digital-to-analog conversion is continuously performed N times, and the average value of the N digital output results is . Keep the DC input signal , at this time, the calibration channel selection signal selects channel 1 shown in Figure 4 as the feedback channel, and the digital-to-analog conversion is continuously performed N times, and the average value of the N digital output results is . The calibrated gain offset error is obtained, and the calculation formula is as follows:
[0039] By alternately using the two channels to sample the DC input signal , the gain error between the two channels can be modulated to nearby, wherein is the sampling frequency, and the gain error at this time can be filtered out by a digital filter, which can guarantee the accuracy of the sampled signal and not be affected by the channel gain error .
[0040] By calibrating the input offset voltage and the gain error, the noise caused by the channel mismatch is reduced to below the quantization noise and the thermal noise, so that it does not affect the performance of the modulator, and the precision of the digital signal output by the high-precision Delta Sigma analog-to-digital converter can be effectively improved.
[0041] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A high precision delta sigma analog-to-digital converter, characterized by, The system includes an input quantizer, a dual-channel sampling module, a modulator, and a calibration digital filter. The analog input signal is first quantized by the input quantizer and then enters the dual-channel sampling module. It then enters the modulator for noise shaping to obtain a digital output signal. The digital output signal is connected to the input of the dual-channel sampling module for signal feedback. On the other hand, it is multiplied by the corresponding calibration coefficient according to different stages of the control signal and then filtered by the calibration digital filter. After removing the input offset voltage from the filtered signal, the calibrated digital output signal is obtained.
2. The high precision delta sigma analog-to-digital converter of claim 1, wherein, The dual-channel sampling module includes a first channel and a second channel, which are controlled by a control signal to perform signal sampling or signal feedback. When the high-precision Delta Sigma analog-to-digital converter performs digital-to-analog conversion, the functions of the first and second channels of the dual-channel sampling module are complementary, with one channel used for signal sampling and the other channel used for signal feedback.
3. The high precision delta sigma analog-to-digital converter of claim 2, wherein, If path one is used for signal sampling when the control signal is in the first stage, and path two is used for signal feedback when the control signal is in the first stage, then path one is used for signal feedback when the control signal is in the second stage, and path two is used for signal sampling when the control signal is in the second stage. Alternatively, if path two is used for signal sampling when the control signal is in the first stage, and path one is used for signal feedback when the control signal is in the first stage, then path two is used for signal feedback when the control signal is in the second stage, and path one is used for signal sampling when the control signal is in the second stage.
4. The high-precision Delta Sigma analog-to-digital converter according to claim 1, characterized in that, The modulator adopts a multi-level modulation structure, which includes multiple single-level modulation loops, which are sequentially divided into a first modulation loop, a second modulation loop, ..., an Nth modulation loop from the input end. The first modulation loop is connected to the dual-channel sampling module.
5. The high-precision Delta Sigma analog-to-digital converter according to claim 4, characterized in that, The single-stage modulation loop includes a cascaded integrator, an adder, a modulation quantizer, a modulation digital filter, a feedforward path, and a feedback path. The cascaded integrator and the feedforward path are connected to the input signal. The output signals of the feedforward path and the cascaded integrator are both connected to the adder. The output signal of the adder is connected to the modulation quantizer. The output signal of the modulation quantizer is output as a digital signal after passing through the modulation digital filter. The output signal of the modulation quantizer is also connected to the cascaded integrator through the feedback path to achieve signal feedback. The difference between the output signal of the adder and the output signal of the modulation quantizer is used as the input signal of the next stage modulation loop.
6. The high-precision Delta Sigma analog-to-digital converter according to claim 5, characterized in that, The output signal of the input quantizer is passed through the input digital filter to output a digital signal. The digital signals output by the modulation digital filters in multiple single-stage modulation loops are added to the digital signals output by the input digital filters to obtain the final digital output signal.
7. The high-precision Delta Sigma analog-to-digital converter according to claim 1, characterized in that, The calibration process for a high-precision DeltaSigma analog-to-digital converter is as follows: Set the DC input signal The DC input signal is less than the modulator saturation voltage. DC input signal is input to the dual-channel sampling module. The signal is sampled alternately by path one and path two in the dual-channel sampling module, and then fed back through a fixed path. The selection of the sampling path is determined by the stage of the control signal, and the selection of the feedback path is determined by the calibration path selection signal.
8. The high-precision Delta Sigma analog-to-digital converter according to claim 7, characterized in that, There is an input offset voltage between the dual-channel sampling module and the modulator. The process of calibrating the input offset voltage is as follows: DC input signal set to 0 Input is sent to the dual-channel sampling module; The calibration path selects path one as the feedback path, performs N consecutive analog-to-digital conversions, and takes the average of the N digital output results as the value. ; Maintain DC input signal When the value is 0, the calibration path selection signal selects path two as the feedback path, continuously performing N analog-to-analog conversions, and taking the average of the N digital output results as the value. ; Obtain the calibrated input offset voltage The calculation formula is: 。 9. The high-precision Delta Sigma analog-to-digital converter according to claim 8, characterized in that, There is a gain error between the dual-channel sampling module and the modulator. The process of calibrating the gain error is as follows: DC input signal The value is set to The data is then input into the dual-channel sampling module; The calibration path selects path one as the feedback path, performs N consecutive analog-to-digital conversions, and takes the average of the N digital output results as the value. ; Maintain DC input signal for At this point, the calibration path selection signal selects path two as the feedback path, continuously performing N analog-to-digital conversions, and taking the average of the N digital output results as the value. ; Gain offset error after calibration The calculation formula is as follows: 。