CN103326728B - A kind of noise suppressed strengthens sigma Delta modulator structure - Google Patents

Abstract

The invention discloses a kind of noise suppressed and strengthen sigma Delta modulator structure, quantizing noise is obtained by the input signal of quantizer Q and output signal being done difference, send into again in integrator after this quantizing noise is postponed one-period, therefore also single order noise shaping can be increased except normal noise suppressed can be realized, namely, when same integrators number, exponent number is suppressed to improve single order to quantizing noise single ring architecture modulator.Noise suppressed provided by the invention strengthens sigma Delta modulator structure on conventional modulated device basis, proposes a kind of noise suppressed enhancing technology, and the quantizing noise achieved by it suppresses exponent number, higher than the number of integrator in modulator; When realizing identical performance, reducing overall power, reducing chip area, substantially increase economic benefit.

Description

A kind of noise suppressed strengthens sigma Delta modulator structure

Technical field

The present invention relates to a kind of noise suppressed and strengthen sigma Delta modulator structure, belong to integrated circuit technique.

Background technology

Along with the develop rapidly of science and technology, the treatment technology of present digital signal is more and more ripe, and we can use powerful, flexible now and reliable digital signal processor (DSP) has come to operate the process of various information.But the signal in real world is all analog quantity, before being processed analog signal by digital form, first we need analog signal to be transformed to digital signal.Thus analog to digital converter (ADC) just becomes the important component part of numerical model analysis system, and its performance has very important effect to communication, Industry Control, measurement isoelectronic series system.Conventional ADC mainly contains successive approximation (SAR), pipeline-type (Pipeline) and Σ Δ type, and wherein Σ Δ type ADC is high with its precision, and speed is medium, receives publicity gradually, apply more and more wider in every field to features such as technique are insensitive.

Most quantization noise power is mainly moved HFS by over-sampling and noise shaping by Σ Δ type ADC, and recycling digital filter by quantizing noise filtering, thus realizes high accuracy.The precision of Σ Δ type ADC decides primarily of the exponent number of over-sampling multiple and noise shaping.Over-sampling multiple is higher, and the noise spectral density of quantizing noise is lower, and the exponent number of noise shaping is higher, and the noise in signal band is repressed more, thus improves the signal to noise ratio exported.

The performance improving Σ Δ type ADC can be realized by the exponent number improving over-sampling rate and raising noise shaping.Over-sampling rate is higher, higher to the bandwidth requirement of amplifier in integrator, thus causes larger power consumption and area.Traditionally, improving the exponent number of noise shaping can be realized by cascade system, will corresponding increase integrator but often increase one-level noise shaping exponent number, also just increases area and power consumption.So the increase that can realize shaping exponent number when not increasing integrator has a very big significance.

Summary of the invention

Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides a kind of noise suppressed and strengthen sigma Delta modulator structure, strengthen technology by noise suppressed, can, when same integrators number, suppress exponent number to improve single order to quantizing noise single ring architecture modulator.

Technical scheme: for achieving the above object, the technical solution used in the present invention is:

A kind of noise suppressed strengthens sigma Delta modulator structure, is included in integrator that z territory transfer function is H (z), quantizer Q, is the noise feedback loop of G (z) in z territory transfer function; Analog input signal X (z) subtracts each other the input signal of signal A (z) as integrator of acquisition with the output signal Y (z) of quantizer Q, and the output signal B (z) of integrator and the output signal C (z) in noise feedback loop subtract each other the input signal of signal D (z) as quantizer Q of acquisition; The input signal in noise feedback loop is signal F (z) that input signal D (z) of quantizer Q and quantizer Q feedback signal Y (z) subtract each other acquisition.

In said modulator structure, analog input signal X (z) is the input signal of modulator, and the output signal Y (z) of Q is the output signal of modulator.This modulator structure obtains quantizing noise by the input signal of quantizer Q and output signal being done difference, send into again in integrator after this quantizing noise being postponed a unit, therefore also single order noise shaping can be increased except normal noise suppressed can be realized, namely, when same integrators number, exponent number is suppressed to improve single order to quantizing noise single ring architecture modulator.

Concrete, described G (z)=z ^-1.

If this modulator is the modulator of single order single ring architecture, described in if this modulator is the modulator of the above single ring architecture of second order, H (z) has nothing in common with each other according to structure difference.

Beneficial effect: noise suppressed provided by the invention strengthens sigma Delta modulator structure, the sigma Delta modulator structure tool of comparing traditional has the following advantages: 1) modulator of the present invention does not need the number increasing integrator just can realize the increase of noise modulated exponent number, thus improve overall performance, greatly save area and the power consumption of higher order modulator; 2) stability problem can be produced when traditional modulator is more than three rank, and modulator of the present invention is not owing to needing the number increasing integrator in single ring architecture, therefore avoids the stability problem of high-order monocycle sigma Delta modulator; 3) the present invention does not need the number increasing integrator, and only need by sampling capacitance and suitable clock control, circuit structure is simple.

Accompanying drawing explanation

Fig. 1 is that noise suppressed of the present invention strengthens sigma Delta modulator structural representation;

Fig. 2 is the signal spectrum that conventional first order sigma Delta modulator exports;

Fig. 3 is the signal spectrum that noise suppressed of the present invention strengthens sigma Delta modulator output;

The input signal of Fig. 2, Fig. 3 is the sine wave of 93.75KHz, and sample frequency is counting of 64MHz, FFT is 4096.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.

Be illustrated in figure 1 a kind of noise suppressed and strengthen sigma Delta modulator structure, be included in integrator that z territory transfer function is H (z), quantizer Q, be the noise feedback loop of G (z) in z territory transfer function; Analog input signal X (z) subtracts each other the input signal of signal A (z) as integrator of acquisition with the output signal Y (z) of quantizer Q, and the output signal B (z) of integrator and the output signal C (z) in noise feedback loop subtract each other the input signal of signal D (z) as quantizer Q of acquisition; The input signal in noise feedback loop is signal F (z) that input signal D (z) of quantizer Q and quantizer Q feedback signal Y (z) subtract each other acquisition.Analog input signal X (z) is the input signal of modulator, and the output signal Y (z) of Q is the output signal of modulator.

Integrator, for the formation of integrating network, carries out noise modulated; Quantizer Q quantizes, and realizes the conversion of analog signal to digital signal; Noise feedback loop is used for realizing noise suppressed and strengthens

Below for a nd order modulator, carry out theory deduction (similar derivation is also applicable to the modulator of high-order).

The expression formula of G (z) in z territory can be expressed as: G (z)=z ^-1.Represent the quantizing noise introduced in quantizing process with E (z), below the noise transfer function (NoiseTransferFunction, NTF) of whole modulator and signal transfer function (SignalTransferFunction, STF) derived:

A(z)＝X(z)-Y(z)

B(z)＝A(z)*H(z)

D(z)＝B(z)-C(z)

C(z)＝F(z)*G(z)

Y(z)＝D(z)+E(z)

Y(z)-D(z)＝F(z)

Equation above comprehensive can obtain:

Noise transfer function: $\mathrm{NTF}\left(z\right)=\frac{E\left(z\right)}{Y\left(z\right)}=\frac{1-G\left(z\right)}{1+H\left(z\right)}$

Signal transfer function: $\mathrm{STF}\left(z\right)=\frac{H\left(z\right)}{1+H\left(z\right)}$

In a nd order modulator, can obtain: NTF (z)=[1-G (z)] ^*(1-z ^-1), make G (z)=z ^-1, then NTF (z)=(1-z ^-1) ², thus achieve 2 rank noise modulated.To 2 rank and 2 rank with modulator, its derivation is similar.

The signal spectrum that the single order sigma Delta modulator that Fig. 2, Fig. 3 are respectively traditional exports and the signal spectrum that single order Σ Δ of the present invention modulation exports.The input signal of Fig. 2, Fig. 3 is the sine wave of 93.75KHz, and sample frequency is counting of 64MHz, FFT is 4096.

As can be seen from Fig. 2, Fig. 3, the exponent number of modulator noise shaping of the present invention will apparently higher than the modulator of traditional structure, and advantage is obvious.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (3)

1. noise suppressed strengthens a sigma-delta-modulator structure, it is characterized in that: be included in integrator that z territory transfer function is H (z), quantizer Q, be the noise feedback loop of G (z) in z territory transfer function; Analog input signal X (z) and quantizer Q feedback signal Y (z) subtract each other the input signal of signal A (z) as integrator of acquisition, and the output signal B (z) of integrator and the output signal C (z) in noise feedback loop subtract each other the input signal of signal D (z) as quantizer Q of acquisition; The input signal in noise feedback loop is signal F (z) that input signal D (z) of quantizer Q and quantizer Q feedback signal Y (z) subtract each other acquisition.

2. noise suppressed according to claim 1 strengthens sigma-delta-modulator structure, it is characterized in that: described G (z)=z ^-1.

3. noise suppressed according to claim 1 strengthens sigma-delta-modulator structure, it is characterized in that: if this modulator is the modulator of single order single ring architecture, described in