CN104702290A - Low-noise oversampling analog-digital converter - Google Patents
Low-noise oversampling analog-digital converter Download PDFInfo
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- CN104702290A CN104702290A CN201410857268.7A CN201410857268A CN104702290A CN 104702290 A CN104702290 A CN 104702290A CN 201410857268 A CN201410857268 A CN 201410857268A CN 104702290 A CN104702290 A CN 104702290A
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Abstract
The invention provides a low-noise oversampling analog-digital converter. The converter comprises a modulator, an oversampling analog-digital converter body and a demodulator. The modulator modulates low-frequency input signals and modulates the low-frequency input signals to high frequencies. The oversampling analog-digital converter body performs oversampling noise shaping on modulator output signals. The demodulator demodulates output signals of the oversampling analog-digital converter body and demodulates high-frequency signals in the output signals of the oversampling analog-digital converter body to low frequencies. By means of the converter, low-frequency noise of the converter can be restrained effectively, the system area is small, the power consumption is low, and the converter can be applied to lots of environments high in low-nose performance requirement.
Description
Technical field
The present invention relates to a kind of low noise oversampling analog-to-digital converter.
Background technology
In integrated circuit particularly hybrid digital-analog integrated circuit, over-sampling noise shaping circuit system is one of very important circuit system.In over-sampling noise shaping circuit, the main source of noise is quantizing noise, op-amp noise and capacitor noise etc.Especially high to the requirement of whole system noise in high accuracy, low-frequency application, such as, in the circuit such as electric energy metrical, audio frequency process, all need low-frequency noise enough little and the linearity is enough good.
There are some in prior art and be used for restraint speckle to improve the method for signal to noise ratio, because the noise of the first order transport and placing device in over-sampling noise shaping analog to digital converter plays Main Function, therefore, in prior art, general all imbalance at first order amplifier noise processes, and such as two sampling correlated noise is eliminated, capacitance stores lacks of proper care elimination, modulation-demodulation technique etc.; Or before the system of over-sampling, add the buffer of low noise.
But still there is a lot of problem in said method.The method of modulation /demodulation especially wherein, the effect of its reality is unsatisfactory.As shown in Figure 1, for adopting the structural representation of the low noise oversampling analog-to-digital converter of modulation and demodulation method in prior art, it was provided with modulator before the first order operational amplifier of oversampling analog-to-digital converter, had been provided with demodulator thereafter.As shown in Figure 2, (1) in Fig. 2 represents the frequency spectrum of low-frequency input signal to the technique effect of the program, and wherein fs is the centre frequency of input signal; (2) represent that signal enters the frequency spectrum after oversampling analog-to-digital converter after the modulation of ovennodulation device, wherein the centre frequency of low-frequency input signal has been modulated onto high frequency fc+fs, and centered by fn, the waveform of frequency is the noise introduced; (3) represent the frequency spectrum of signal after demodulator, wherein the centre frequency of low-frequency input signal is reduced to low frequency fs, and now the centre frequency of noise has been modulated to high frequency fc+fn by imbalance; (4) signal spectrum after oversampling analog-to-digital converter is represented, because over-sampling noise shaping system inherently includes modulation effect, therefore likely the noise signal being originally modulated to high frequency fc+fn is modulated to low frequency again, the noise signal of frequency centered by fc+fn-fsd as illustrated in the drawing, thus make can not, by noise filtering, cause noise reduction poor in whole noise shaping procedure.
In addition, this noise reduction schemes of the prior art, also needs to add low noise buffers usually before whole noise shaping system, and this needs larger area usually, thus increases the power consumption of whole system.
Therefore, the low-frequency noise how reducing over-sampling noise shaping analog to digital converter is problem to be solved by this invention.
Summary of the invention
For this reason, the invention provides a kind of low noise oversampling analog-to-digital converter, comprise the modulator, oversampling analog-to-digital converter and the demodulator that connect in turn, wherein, described modulator is modulated low-frequency input signal, and described low-frequency input signal is modulated to high frequency; Described oversampling analog-to-digital converter carries out over-sampling noise shaping to the output signal of described modulator; Described demodulator carries out demodulation to the output signal of described oversampling analog-to-digital converter, and the high-frequency signal solution in the output signal of described oversampling analog-to-digital converter is transferred to low frequency.Wherein, described low frequency refers to that frequency is less than the frequency range of 5KHz, and described high frequency refers to that frequency is greater than the frequency range of 10KHz.
Preferably, described modulator is modulation switch, and described demodulator is for separating tune switch.
Low noise oversampling analog-to-digital converter of the present invention, effectively can suppress the noise of the low frequency frequency range of oversampling analog-to-digital converter, and system area low power consumption is low, can be applied in a lot of environment higher to low-frequency noise performance requirement.
Accompanying drawing explanation
Fig. 1 is the structural representation of the low noise oversampling analog-to-digital converter adopting modulation and demodulation method in prior art;
Fig. 2 is the Spectrum Conversion schematic diagram of the oversampling analog-to-digital converter of low noise shown in Fig. 1;
Fig. 3 is the structural representation of low noise oversampling analog-to-digital converter of the present invention;
Fig. 4 is the structural representation of an execution mode of low noise oversampling analog-to-digital converter of the present invention;
Fig. 5 is the structural representation of the modulator in Fig. 4;
Fig. 6 is the structural representation of the demodulator in Fig. 4;
Fig. 7 is the Spectrum Conversion schematic diagram of low noise oversampling analog-to-digital converter of the present invention;
Fig. 8 is the comparison diagram of the low-frequency noise inhibition of scheme shown in low noise oversampling analog-to-digital converter of the present invention and Fig. 1.
Embodiment
Below in conjunction with the drawings and specific embodiments, low noise oversampling analog-to-digital converter of the present invention is described in further detail, but not as a limitation of the invention.
As shown in Figure 3, low noise oversampling analog-to-digital converter of the present invention, comprise the modulator, oversampling analog-to-digital converter and the demodulator that connect in turn, wherein, modulator is modulated low-frequency input signal, and low-frequency input signal is modulated to high frequency; Oversampling analog-to-digital converter carries out over-sampling noise shaping to the output signal of modulator; Demodulator carries out demodulation to the output signal of oversampling analog-to-digital converter, and the high-frequency signal solution in the output signal of oversampling analog-to-digital converter is transferred to low frequency.
Low noise oversampling analog-to-digital converter of the present invention, a modulator is increased at the input of oversampling analog-to-digital converter, signal madulation to high frequency, after having carried out over-sampling noise shaping, carry out demodulation again, signals revivification to original frequency, and the noise modulated of over-sampling noise shaping system to high frequency, so just can obtain reasonable low frequency characteristic.
As the execution mode that Fig. 4-6 is low noise oversampling analog-to-digital converter of the present invention, wherein, modulator is modulation switch, and demodulator is for separating tune switch, and the alternate conduction all carrying out control switch by clock signal is seen, thus realizes the function of modulation and demodulation.
The technique effect of low noise oversampling analog-to-digital converter of the present invention is described below in conjunction with Fig. 7.(1) in Fig. 7 represents the frequency spectrum of low-frequency input signal, and its centre frequency is fs; (2) represent the frequency spectrum of the signal after modulator, low-frequency input signal is modulated to high frequency fc+fs by modulator, the noise that in figure, the waveform of frequency is introducing centered by fn; (3) represent through the over-sampling noise shaping of oversampling analog-to-digital converter and the signal waveform after demodulator demodulation, visible, after having carried out over-sampling noise shaping, demodulator carries out demodulation to the output signal of oversampling analog-to-digital converter, the signals revivification being positioned at high-frequency band fc+fs wherein to original Frequency fs, and the noise of over-sampling noise shaping system is modulated to high frequency fc+fn from original frequency f n.
Therefore, low noise oversampling analog-to-digital converter of the present invention, effectively can suppress the noise of the low frequency frequency range of oversampling analog-to-digital converter, obtain reasonable low frequency characteristic.With reference to the simulation comparison figure of Fig. 8, wherein, curve 100 is the performance curve of the noise suppressed of existing low noise oversampling analog-to-digital converter, curve 200 is the performance curve of the noise suppressed of low noise oversampling analog-to-digital converter of the present invention, can find out that low noise oversampling analog-to-digital converter of the present invention is compared to scheme of the prior art thus intuitively, in low-frequency noise suppression, have greatly improved.
Meanwhile, do not need to use large-area components and parts (such as, low noise buffers etc.), make system area low power consumption low, a lot of environment higher to low-frequency noise performance requirement can be applied in.
Low frequency described herein refers to that frequency is less than the frequency range of 5KHz, and high frequency refers to that frequency is greater than the frequency range of 10KHz.
Above embodiment is only illustrative embodiments of the present invention, can not be used for limiting the present invention, and protection scope of the present invention is defined by the claims.Those skilled in the art can in essence of the present invention and protection range, and make various amendment or equivalent replacement to the present invention, these are revised or be equal to replacement and also should be considered as dropping in protection scope of the present invention.
Claims (2)
1. a low noise oversampling analog-to-digital converter, is characterized in that, comprises the modulator, oversampling analog-to-digital converter and the demodulator that connect in turn, wherein,
Described modulator is modulated low-frequency input signal, and described low-frequency input signal is modulated to high frequency;
Described oversampling analog-to-digital converter carries out over-sampling noise shaping to the output signal of described modulator;
Described demodulator carries out demodulation to the output signal of described oversampling analog-to-digital converter, and the high-frequency signal solution in the output signal of described oversampling analog-to-digital converter is transferred to low frequency.
2. low noise oversampling analog-to-digital converter according to claim 1, is characterized in that, described modulator is modulation switch, and described demodulator is for separating tune switch.
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| CN201410857268.7A CN104702290A (en) | 2014-12-30 | 2014-12-30 | Low-noise oversampling analog-digital converter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104980159A (en) * | 2015-06-29 | 2015-10-14 | 清华大学深圳研究生院 | Charge pump and voltage controlled-oscillator-based oversampling analog-digital converter |
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| CN1524346A (en) * | 2000-08-11 | 2004-08-25 | �ʼҷ����ֵ�������˾ | Method and arrangement for synchronizing a sigma-delta-modulator |
| US20070035424A1 (en) * | 2003-04-16 | 2007-02-15 | Koninklijke Philips Electronics N.V. Groenewoudseweg 1 | Sigma-delta modulator |
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| CN101971502A (en) * | 2007-12-19 | 2011-02-09 | 意法爱立信有限公司 | A multi-bit sigma-delta modulator with reduced niumber of bits in feedback path |
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| CN104980159B (en) * | 2015-06-29 | 2017-11-28 | 清华大学深圳研究生院 | A kind of oversampling analog-to-digital converter based on charge pump and voltage controlled oscillator |
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Application publication date: 20150610 |