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Delta Sigma Modulator

Model a discrete delta sigma modulator based ADC

Since R2021b

  • Delta-Sigma Modulator

Libraries:
Mixed-Signal Blockset / ADC / Building Blocks

Description

Use the Delta Sigma Modulator block to model a discrete delta sigma modulator based ADC using a set of different architectures. The block supports these architectures:

  • Cascade of feedback resonators.

  • Cascade of feedback integrators.

  • Cascade of feed-forward resonators.

  • Cascade of feed-forward integrators.

You can model an ADC of orders from two to six. You can also model circuit based noise.

Ports

Input

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Analog input signal, specified as a scalar.

Data Types: double

Reset signal for Delta Sigma Modulator block, specified as a scalar.

Data Types: double

Output

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Digital output signal, returned as a scalar.

Data Types: fixed point | single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Parameters

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Architecture of the delta sigma modulator, specified as:

  • CIFB — cascade of feedback integrators.

  • CRFB — cascade of feedback resonators.

  • CIFF — cascade of feed-forward integrators.

  • CRFF — cascade of feed-forward resonators.

Programmatic Use

Block parameter: dsmArchitecture
Type: character vector
Values: CIFB | CRFB | CIFF | CRFF
Default: CIFB

Order of delta sigma modulator. You can choose between orders two to six.

Programmatic Use

Block parameter: dsmOrder
Type: character vector
Values: 2nd order | 3rd order | 4th order | 5th order | 6th order
Default: 2nd order

Input Parameters

Bandwidth of the delta sigma modulator system, specified as a nonnegative real scalar.

Programmatic Use

Block parameter: BandWidth
Type: character vector
Values: nonnegative real scalar
Default: 1000

Ratio of the delta sigma modulator sampling rate to the Nyquist rate, defined as a nonnegative real scalar. A high oversampling ratio results in a relaxed anti-aliasing filter and reduced in-band quantization noise.

Programmatic Use

Block parameter: OSR
Type: character vector
Values: nonnegative real scalar
Default: 64

Sampling frequency of the delta sigma modulator. This read-only parameter is calculated from the System bandwidth and OSR.

Programmatic Use

Block parameter: SamplingFrequency
Type: character vector
Values: positive real scalar
Default: 128e3

Number of quantizer levels in delta sigma modulator, specified as a positive real scalar.

Programmatic Use

Block parameter: NumberLevels
Type: character vector
Values: positive real scalar
Default: 2

Range of the quantizer output in the delta sigma modulator architecture, returned as a vector with real elements. this parameter is read-only.

Programmatic Use

Block parameter: QuantizerOutput
Type: character vector
Values: real valued vector
Default: [-1;1]

Enable dynamic range scaling of coefficients. This prevents premature saturation of internal states.

Dependencies

When this parameter is enabled, Use custom coefficient values option is deselected.

Use custom values for coefficients 'a', 'g', 'b', and 'c'.

Dependencies

When this parameter is enabled, Enable dynamic range scaling option is deselected.

Feedback coefficients from the quantizer or feed-forward coefficients to the quantizer, specified as a vector with real elements.

Dependencies

To enable this parameter, select the Use custom coefficient values option.

Programmatic Use

Block parameter: a
Type: character vector
Values: real valued vector
Default: [0.1601 0.6515]

Resonator coefficients, specified as a vector with real elements.

Dependencies

To enable this parameter, select the Use custom coefficient values option.

Programmatic Use

Block parameter: g
Type: character vector
Values: real valued vector
Default: [0.0000]

Feed-in coefficients from the modulator input to each integrator, specified as a vector with real elements.

Dependencies

To enable this parameter, select the Use custom coefficient values option.

Programmatic Use

Block parameter: b
Type: character vector
Values: real valued vector
Default: [0.1601 0.6515 1.0000]

Integrator inter-stage coefficients, specified as a vector with real elements.

Dependencies

To enable this parameter, select the Use custom coefficient values option.

Programmatic Use

Block parameter: c
Type: character vector
Values: real valued vector
Default: [1.0000 1.0000]

Impairment

Enable noise calculations in the delta sigma modulator ADC.

Thermal noise density value, specified in units of Vrms or dB/Hz.

When thermal noise is specified in units of Vrms, it must be a nonnegative real scalar.

Programmatic Use

Block parameter: thermalNoiseValue
Type: character vector
Values: real scalar
Default: 0.125

Reference noise used for power calculations, specified as a positive real scalar in ohms.

Programmatic Use

Block parameter: refResistance
Type: character vector
Values: positive real scalar
Default: 50

Corner frequency for flicker (1/f) noise, specified as a positive real scalar in Hz. At this frequency, the 1/f noise approximately equals to the thermal noise.

Programmatic Use

Block parameter: fcorner
Type: character vector
Values: positive real scalar
Default: 1000

Advanced

Type of passband of the delta sigma modulator.

Programmatic Use

Block parameter: passbandType
Type: character vector
Values: Lowpass | Bandpass
Default: Lowpass

Center frequency of the modulator, specified as a scalar in the range [0 0.5]. For a lowpass filter, the center frequency is zero.

Dependencies

To enable this parameter, set the Modulator passband option to Bandpass.

Programmatic Use

Block parameter: centerFrequency
Type: character vector
Values: scalar in the range [0 0.5]
Default: 0

Select to use custom values of H_inf. By default, this option is deselected.

Maximum out-of-band gain of the noise transfer function (NTF).

Lee’s rule states that H_inf < 2 should yield a stable modulator with a binary quantizer. Reducing H_inf increases the likelihood of success, but reduces the magnitude of the attenuation provided by the NTF and thus the theoretical resolution of the modulator.

Dependencies

To enable this parameter, select the Use custom value of H_inf option.

Programmatic Use

Block parameter: Hinf
Type: character vector
Values: positive real scalar
Default: 1.4

Note

You need license to Control System Toolbox™ to use the parameters in the Advanced tab.

Version History

Introduced in R2021b

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