CN116527055A - Low-harmonic excitation source based on band-pass sigma-delta modulation technology - Google Patents

Low-harmonic excitation source based on band-pass sigma-delta modulation technology Download PDF

Info

Publication number
CN116527055A
CN116527055A CN202310412439.4A CN202310412439A CN116527055A CN 116527055 A CN116527055 A CN 116527055A CN 202310412439 A CN202310412439 A CN 202310412439A CN 116527055 A CN116527055 A CN 116527055A
Authority
CN
China
Prior art keywords
signal
band
excitation source
noise
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202310412439.4A
Other languages
Chinese (zh)
Inventor
蔡天翼
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Maidi Microelectronics Hangzhou Co ltd
Original Assignee
Maidi Microelectronics Hangzhou Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Maidi Microelectronics Hangzhou Co ltd filed Critical Maidi Microelectronics Hangzhou Co ltd
Priority to CN202310412439.4A priority Critical patent/CN116527055A/en
Publication of CN116527055A publication Critical patent/CN116527055A/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M3/00—Conversion of analogue values to or from differential modulation
    • H03M3/30—Delta-sigma modulation
    • H03M3/322—Continuously compensating for, or preventing, undesired influence of physical parameters
    • H03M3/324—Continuously compensating for, or preventing, undesired influence of physical parameters characterised by means or methods for compensating or preventing more than one type of error at a time, e.g. by synchronisation or using a ratiometric arrangement
    • H03M3/344—Continuously compensating for, or preventing, undesired influence of physical parameters characterised by means or methods for compensating or preventing more than one type of error at a time, e.g. by synchronisation or using a ratiometric arrangement by filtering other than the noise-shaping inherent to delta-sigma modulators, e.g. anti-aliasing
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00—Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/02—Digital function generators
    • G06F1/03—Digital function generators working, at least partly, by table look-up
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a low-harmonic excitation source based on a band-pass sigma-delta modulation technology, which comprises a lookup table, a band-pass sigma-delta modulator, a direct current source and an analog multiplier. The invention modulates the discrete amplitude data of the signal to be excited by using the band-pass sigma-delta modulator, shifts the noise of the signal frequency and the integral frequency multiplication point thereof to other frequency bands, and finally outputs single-bit data stream consisting of 0 and 1, thereby achieving the purpose of reducing the noise at harmonic wave and frequency point, and simultaneously effectively avoiding the problems of matching and linearity. The LUT in the excitation source can store amplitude data of any signal according to the requirement of a user, including but not limited to sine waves, triangular waves and the like, wherein the order of the band-pass sigma-delta modulator can be adjusted according to the requirement of the user so as to realize different noise shaping effects.

Description

Low-harmonic excitation source based on band-pass sigma-delta modulation technology
Technical Field
The invention belongs to the technical field of CMOS bias circuits, and particularly relates to a low-harmonic excitation source based on a band-pass sigma-delta modulation technology.
Background
The excitation source is a device capable of providing electrical signals of various frequencies, waveforms and output levels, and is used as a signal source or excitation source for testing when measuring amplitude characteristics, frequency characteristics, transmission characteristics and other electrical parameters of various telecommunication systems or telecommunication devices and when measuring characteristics and parameters of components. The excitation source may be classified into a sinusoidal excitation source, a square wave excitation source, a triangular wave excitation source, etc. according to the type of the signal generated therefrom, and may be classified into a low frequency excitation source, a high frequency excitation source, a microwave excitation source, etc. according to the frequency range of the signal generated therefrom.
The excitation source has wide application value in the sensor field, for example, in the bioimpedance analysis field, the excitation source is required to output a current signal, and the corresponding voltage signal is read after passing through a bioimpedance sample, so that the impedance characteristic of the sample is analyzed; and the excitation source with high precision and low harmonic can output excitation current signals with higher quality, so that the precision of impedance analysis is improved.
The technologies used by conventional excitation sources widely used in the sensor field at present can be roughly divided into square wave excitation sources and excitation sources based on LUT (Look-Up-Table) +Σ - Δ modulation multi-bit output technology.
Teaching materials [ university of Qinghua electronics teaching and research group Tong Shibai, hua Chengying ] analog electronics technology foundation [ M ]. Higher education Press, 2015] describes a square wave excitation source which consists of an RC oscillator based on an operational amplifier, and as shown in FIG. 1 (a), square wave signals are directly output; according to Fourier transformation, the square wave signal has higher energy higher harmonic wave, the excitation signal precision is not high, and the square wave signal is easy to generate errors when being applied to the field of sensors such as bioimpedance analysis, and the subsequent analysis precision is influenced.
The literature [ Kim, kwantae, kim, sangyeob, yoo, hoi-jun. Design of Sub-10- μw Sub-0.1% THD Sinusoidal Current Generator IC for Bio-Impedance Sensing [ J ]. IEEE Journal of Solid-State Circuits,2022 (2): 57] proposes an excitation source based on lut+Σ - Δ modulation multibit output technique, which mainly consists of two parts, as shown in fig. 1 (b), which first stores the amplitude information of the signal to be excited in one LUT, and then inputs the data stored in the LUT into a sigma-delta modulator with a clock signal, which adopts a sigma-delta modulator, which is usually of a cascade noise Shaping (MASH) structure, and has a high-pass Shaping effect, and finally outputs a multibit excitation signal. However, the scheme also cannot avoid the generation of higher harmonic waves, so that an excitation signal generates errors and the subsequent analysis precision is affected; meanwhile, due to the characteristics of multi-bit output of the scheme, in the practical circuit implementation, the problems of complex matching and high difficulty exist, and the linearity is also poor.
Disclosure of Invention
In view of the above, the invention provides a low-harmonic excitation source based on a band-pass sigma-delta modulation technology, which generates a single-bit data stream by the band-pass sigma-delta modulation technology to achieve the purpose of reducing noise at harmonic waves and frequency points, effectively avoids the problems of matching and linearity, is suitable for excitation of signals such as sine waves, triangular waves and the like, and has the advantages of low harmonic waves and low noise.
An excitation source based on bandpass sigma-delta modulation technique, comprising:
the LUT (Look-Up Table) module is used for storing the amplitude information of the signal to be excited after sampling and quantization and outputting the discrete waveform of the signal to be excited at a specific clock frequency in operation;
the band-pass sigma-delta modulator is used for carrying out high-frequency modulation on the discrete waveform output by the LUT module, and realizing the suppression of output frequency harmonic waves and the shaping of quantization noise or interception noise through an oversampling band-pass loop filter in a negative feedback loop; the output of the bandpass sigma-delta modulator is a single bit data stream containing information of the signal to be excited and noise information shaped to high frequencies;
the direct current source is used for outputting a direct current voltage signal or a direct current signal;
and the analog multiplier is used for multiplying the direct-current voltage signal or the direct-current signal with the single-bit data stream and outputting a corresponding alternating voltage signal or alternating current signal.
Further, the bandpass sigma-delta modulator includes:
the oversampling band-pass loop filter performs related operations including delay, addition, subtraction and proportion adjustment based on discrete waveforms of signals to be excited, and realizes a specific signal transfer function and a noise transfer function through loop filtering, thereby realizing a noise shaping function;
and the quantizer is used for quantizing the output result of the oversampling band-pass loop filter, and finally generating a single-bit data stream consisting of 0 and 1 values.
Further, the oversampling band-pass loop filter includes two adders A1 to A2, a subtractor, two proportioners B1 to B2, and two retarders D1 to D2, wherein the input of the proportioner B1 is the output result of the quantizer, the subtractor subtracts the input of the quantizer from the output of the proportioner B1, the input of the retarder D1 is the calculation result of the subtractor, the input of the retarder D2 is the output of the retarder D1, the input of the proportioner B2 is the output of the retarder D1, the adder A2 adds the output of the retarder D2 to the output of the proportioner B2, and the adder A1 adds the input of the band-pass sigma-delta modulator to the calculation result of the adder A2 to serve as the input of the quantizer.
Further, the quantization process of the quantizer compares the input with a given threshold, and outputs 1 when the input is greater than the threshold; when the input is less than the threshold, 0 is output.
Further, the data source of the excitation source is from a lookup table, the data in the lookup table can be multi-bit, and different lookup tables can be manufactured according to the requirement of the signal to be excited.
Further, the band-pass sigma-delta modulator can suppress harmonic waves and noise near the frequency of the signal and the integral multiple of the frequency point of the signal, and move the harmonic waves and noise to other frequency bands.
Further, the band-pass sigma-delta modulator can shift noise of a signal frequency point generated by an excitation source to be near the signal frequency point, so that a signal with high signal-to-noise ratio is obtained near the signal frequency point, and meanwhile, harmonic waves and noise generated at an integral multiple frequency point by pulse density modulation can be effectively restrained.
Further, the quantizer in the band-pass sigma-delta modulator is single-bit, that is, the modulator finally outputs a single-bit data stream composed of 0 and 1 values, and the single-bit data stream output can avoid the matching problem and improve the linearity.
The invention modulates the discrete amplitude data of the signal to be excited by using the band-pass sigma-delta modulator, shifts the noise of the signal frequency and the integral frequency multiplication point thereof to other frequency bands, and finally outputs single-bit data stream consisting of 0 and 1, thereby achieving the purpose of reducing the noise at harmonic wave and frequency point, and simultaneously effectively avoiding the problems of matching and linearity. The LUT in the excitation source can store amplitude data of any signal according to the requirement of a user, including but not limited to sine waves, triangular waves and the like, wherein the order of the band-pass sigma-delta modulator can be adjusted according to the requirement of the user so as to realize different noise shaping effects.
Drawings
Fig. 1 (a) is a schematic structural diagram of a conventional square wave excitation source.
Fig. 1 (b) is a schematic diagram of an excitation source structure based on lut+Σ - Δ modulation multi-bit output technology.
FIG. 2 is a block diagram of an impedance detection system employing an excitation source according to the present invention.
FIG. 3 is a schematic diagram of the circuit principle of the impedance detection system using the excitation source of the present invention.
Fig. 4 is a schematic diagram of a lookup table storing the amplitude of a sinusoidal signal to be excited in an embodiment of the present invention.
Fig. 5 is a schematic diagram of a bandpass sigma-delta modulator implemented in the form of 2-order error feedback.
FIG. 6 is a graph showing the power density spectrum of an excitation signal and a square wave signal obtained from an excitation source according to the present invention.
Detailed Description
In order to more particularly describe the present invention, the following detailed description of the technical scheme of the present invention is provided with reference to the accompanying drawings and the specific embodiments.
The excitation source based on the band-pass sigma-delta modulation technology comprises: look-up table, bandpass sigma-delta modulator, direct current source, and analog multiplier, wherein:
the lookup table stores the digitized data of the amplitude of the sampled and quantized signal to be excited; the band-pass sigma-delta modulator carries out high-frequency modulation on the data output by the LUT, realizes the suppression of output frequency harmonic waves and the noise shaping of quantization noise or interception noise through an oversampling band-pass loop filter in a negative feedback loop, and outputs a single-bit data stream consisting of 0 and 1 and containing signals and noise information shaped to high frequency; the direct current source outputs direct voltage or direct current; the analog multiplier multiplies the direct-current voltage or current signal output by the direct-current source by the single-bit data stream output by the band-pass sigma-delta modulator, and outputs alternating voltage or current after multiplication.
The band-pass sigma-delta modulator comprises a band-pass loop filter and a quantizer, wherein the band-pass loop filter realizes a specific signal transfer function and a specific noise transfer function through loop filtering, thereby realizing a noise shaping function; the quantizer quantizes the output of the loop filter, and finally outputs a single-bit data stream, namely, if the input is greater than a threshold value, the output is 1; less than the threshold, 0 is output.
The data source of the excitation source is from a lookup table, the data in the lookup table can be multi-bit, and different lookup tables can be manufactured according to the requirements of signals to be excited.
The band-pass sigma-delta modulator can inhibit the harmonic wave and noise near the signal frequency and the integral multiple frequency point thereof, and move the harmonic wave and noise to other frequency bands; the band-pass sigma-delta modulator shifts noise of a signal frequency point generated by an excitation source out of the vicinity of the signal frequency point, so that a signal with high signal-to-noise ratio is obtained in the vicinity of the frequency point, and harmonic waves and noise generated by the traditional PDM at the integral multiple frequency point can be effectively restrained.
The quantizer at the output end of the band-pass sigma-delta modulator is single bit, namely the modulator finally outputs single bit data stream consisting of 0 and 1, and the single bit data stream output can avoid the matching problem and improve the linearity.
The lookup table in the excitation source can store the amplitude data of any signal according to the requirement of a user, including but not limited to sine waves, triangular waves and the like; the order of the band-pass sigma-delta modulator can be adjusted according to the needs of the user to realize different noise shaping effects.
Examples
The present embodiment is applied to an impedance detection system, and fig. 2 and 3 show an impedance detection system using the excitation source of the present invention, wherein fig. 2 is a system frame diagram, and fig. 3 is a circuit functional schematic diagram. The whole impedance detection system comprises a modulation part and a demodulation part, wherein the modulation part adopts the structure of the invention, the part is a current excitation source, and the output result of the LUT and the bandpass sigma-delta modulator is multiplied with direct current voltage or current through a multiplier to finally output a signal to be excited.
The LUT stores sampling amplitude information of the signal to be excited in advance, and outputs the amplitude information at a specific clock frequency in operation so as to achieve the purpose of outputting discrete waveforms of the signal to be excited to the band-pass sigma-delta modulator; the band-pass sigma-delta modulator receives the amplitude information of the signal to be excited output by the LUT, performs operations such as delay, accumulation and the like through the loop filter, outputs the operation result to the quantizer, judges according to the operation result received at the current sampling moment, and finally outputs a single-bit data stream consisting of '0' and '1' values; the voltage source (or current source) is controlled by the single bit data stream output by the modulator, and finally outputs corresponding direct current voltage or current.
Fig. 4 shows a sine look-up table used in this embodiment, which stores discrete amplitude data information obtained by sampling a sine signal with an amplitude of 2047 at equal intervals for 32 times in a period. When the user uses f lut When the lookup table is output by frequency traversal, the frequency of the lookup table is equivalent to outputting a frequency f lut A discrete sinusoidal signal of/32.
The mathematical model structure of the bandpass sigma-delta modulator used in this embodiment is shown in fig. 5, and this modulator example uses an Error-Feedback (EF) structure, and the order of the modulator is selected to be 2. A feature of this modulator structure is that the filter is present only in the feedback path and no operation is performed in the feed-forward path. The input to the feedback path is made up of the output of the quantizer minus the input of the quantizer, i.e. the only quantization error input to the feedback path is the quantization error input to the quantizer, which is filtered by the feedback path and added to the look-up table output, which is input to the feed-forward path of the modulator.
The transfer function of the band-pass sigma-delta modulator in this embodiment is derived as follows: set an input signalFor u, the output signal passing through the loop filter is y, quantization noise e is introduced by a single bit quantizer, the final output bit stream is v, and the transfer function of the loop filter is set to be H f The following expression is given:
e+y＝v (1)
(c 1 ·v-y)H f +u＝y (2)
H f ＝z -2i +a 1 z -i (3)
combining the expressions, and eliminating y to obtain the expression of the final output v about the input signal u and the quantization noise e:
in the present embodiment, let c 1 ＝1，a 1 = -2, there are:
v＝u+(1-z -i ) 2 e (5)
wherein: i is the number of delayed clock cycles, equation (5), i.e. the transfer function of the modulator, whereby the signal transfer function (Signal Transfer Function, STF) and the noise transfer function (Noise Transfer Function, NTF) of this system can also be derived as follows:
STF＝1 (6)
NTF＝(1-z -i ) z (7)
from the two sets of transfer functions, the system completely retains the original state of the signal, and shapes noise.
Eventually, the quantizer outputs a single bit data stream consisting of "0" and "1" values.
Using the look-up table of fig. 4, together with the modulator of fig. 5, the resulting spectrum of the signal can be obtained; the result of comparing the signal spectrum output by the conventional square wave excitation source with the excitation source based on the LUT plus sigma-delta modulation multi-bit output technology is shown in figure 6. It can be seen that the invention can carry out noise shaping on the sinusoidal signal and move the noise at the signal frequency and the integral multiple of the signal frequency to other frequency bands; compared with square waves, the invention improves the signal-to-noise ratio of the signals, and remarkably suppresses noise on harmonic waves and harmonic points, thereby remarkably improving the spurious-free dynamic range (Spurious Free Dynamic range, SFDR) of the signals.
The foregoing description of the embodiments is provided to facilitate the understanding and application of the present invention to those skilled in the art, and it will be apparent to those skilled in the art that various modifications may be made to the embodiments described above, such as using look-up tables of different signals, using band-pass sigma-delta modulators of different orders of different structures, etc., and that the general principles described herein may be applied to other embodiments without undue effort. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications within the scope of the present invention.

Claims (8)

1. An excitation source based on bandpass sigma-delta modulation technique, comprising:
the LUT module is used for storing the amplitude information of the signal to be excited after sampling and quantization and outputting discrete waveforms of the signal to be excited at a specific clock frequency in operation;
the band-pass sigma-delta modulator is used for carrying out high-frequency modulation on the discrete waveform output by the LUT module, and realizing the suppression of output frequency harmonic waves and the shaping of quantization noise or interception noise through an oversampling band-pass loop filter in a negative feedback loop; the output of the bandpass sigma-delta modulator is a single bit data stream containing information of the signal to be excited and noise information shaped to high frequencies;
the direct current source is used for outputting a direct current voltage signal or a direct current signal;
and the analog multiplier is used for multiplying the direct-current voltage signal or the direct-current signal with the single-bit data stream and outputting a corresponding alternating voltage signal or alternating current signal.
2. The excitation source of claim 1, wherein: the bandpass sigma-delta modulator includes:
the oversampling band-pass loop filter performs related operations including delay, addition, subtraction and proportion adjustment based on discrete waveforms of signals to be excited, and realizes a specific signal transfer function and a noise transfer function through loop filtering, thereby realizing a noise shaping function;
and the quantizer is used for quantizing the output result of the oversampling band-pass loop filter, and finally generating a single-bit data stream consisting of 0 and 1 values.
3. The excitation source of claim 2, wherein: the oversampling band-pass loop filter comprises two adders A1-A2, a subtracter, two proportional regulators B1-B2 and two retarders D1-D2, wherein the input of the proportional regulator B1 is the output result of the quantizer, the subtracter subtracts the input of the quantizer from the output of the proportional regulator B1, the input of the retarder D1 is the calculation result of the subtracter, the input of the retarder D2 is the output of the retarder D1, the input of the proportional regulator B2 is the output of the retarder D1, the adder A2 adds the output of the retarder D2 and the output of the proportional regulator B2, and the adder A1 adds the input of the band-pass sigma-delta modulator and the calculation result of the adder A2 to be used as the input of the quantizer.
4. The excitation source of claim 2, wherein: the quantization process of the quantizer compares the input with a given threshold, and outputs 1 when the input is greater than the threshold; when the input is less than the threshold, 0 is output.
5. The excitation source of claim 1, wherein: the data source of the excitation source is from a lookup table, the data in the lookup table can be multi-bit, and different lookup tables can be manufactured according to the requirement of the signal to be excited.
6. The excitation source of claim 1, wherein: the band-pass sigma-delta modulator can inhibit harmonic waves and noise near the frequency of a signal and the integral multiple frequency points of the signal, and can move the harmonic waves and the noise to other frequency bands.
7. The excitation source of claim 1, wherein: the band-pass sigma-delta modulator can shift noise of a signal frequency point generated by an excitation source out of the vicinity of the signal frequency point, so that a signal with high signal-to-noise ratio is obtained in the vicinity of the signal frequency point, and meanwhile, harmonic waves and noise generated at the integral multiple frequency point by pulse density modulation can be effectively restrained.
8. The excitation source of claim 2, wherein: the quantizer in the band-pass sigma-delta modulator is single bit, namely the modulator finally outputs a single bit data stream consisting of 0 and 1 values, and the single bit data stream output can avoid the matching problem and improve the linearity.
CN202310412439.4A 2023-04-18 2023-04-18 Low-harmonic excitation source based on band-pass sigma-delta modulation technology Pending CN116527055A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202310412439.4A CN116527055A (en) 2023-04-18 2023-04-18 Low-harmonic excitation source based on band-pass sigma-delta modulation technology

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202310412439.4A CN116527055A (en) 2023-04-18 2023-04-18 Low-harmonic excitation source based on band-pass sigma-delta modulation technology

Publications (1)

Publication Number Publication Date
CN116527055A true CN116527055A (en) 2023-08-01

Family

ID=87403995

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202310412439.4A Pending CN116527055A (en) 2023-04-18 2023-04-18 Low-harmonic excitation source based on band-pass sigma-delta modulation technology

Country Status (1)

Country Link
CN (1) CN116527055A (en)

Similar Documents

Publication Publication Date Title
US7746256B2 (en) Analog to digital conversion using irregular sampling
CN106899302B (en) Adaptive digital quantization noise elimination filter of MASH ADC
Ortmanns et al. A continuous-time/spl Sigma//spl Delta/Modulator with reduced sensitivity to clock jitter through SCR feedback
US8451156B2 (en) Asynchronous sigma delta analog to digital converter using a time to digital converter
JP3836328B2 (en) Integrated circuit having AD converter
US8633843B2 (en) System and method for chopping oversampled data converters
US6922161B2 (en) Delta-Sigma modulator for reducing quantization noise and oversampling ratio (OSR)
Fujisaka et al. Bit-stream signal processing and its application to communication systems
CN103329444B (en) Sigma-delta difference-of-squares LOG-RMS to DC converter with forward and feedback paths signal squaring
Przybysz et al. Josephson sigma-delta modulator for high dynamic range A/D conversion
US7453382B2 (en) Method and apparatus for A/D conversion
US9391634B1 (en) Systems and methods of low power decimation filter for sigma delta ADC
CN116527055A (en) Low-harmonic excitation source based on band-pass sigma-delta modulation technology
JP6316751B2 (en) converter
CN116192150A (en) Chopper modulation method for low-frequency metering and chopper Sigma-Delta modulator
US10951229B1 (en) Digital filter
KR101559456B1 (en) A low-power·low-area third order sigma-delta modulator with delayed feed-forward path
Colodro et al. Spectral analysis of pulsewidth-modulated sampled signals
Smedley Digital-PWM audio power amplifiers with noise and ripple shaping
JPH0563457A (en) Delta/sigma modulation amplifier
US11706062B1 (en) Digital filter
US11870453B2 (en) Circuits and methods for a noise shaping analog to digital converter
Fan et al. High-resolution adcs for biomedical imaging systems
Hernandez et al. Analog to digital conversion using a Pulse Width Modulator and an irregular sampling decoder
CN112953533B (en) Improved low-distortion Sigma-Delta modulator

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination