ADC AC Measurement

R2026b

Measure AC performance metrics of ADC output

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  • ADC AC Measurement block

Libraries:
Mixed-Signal Blockset / ADC / Measurements & Testbenches

Description

The ADC AC Measurement block measures ADC AC performance metrics such as signal to noise ratio (SNR), signal to noise and distortion radio (SINAD), spurious free dynamic range (SFDR), effective number of bits (ENOB), noise floor, and conversion delay. You can use ADC AC Measurement block to validate the ADC architectural models provided in Mixed-Signal Blockset™, or you can use an ADC of your own implementation

Ports

Input

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Converted digital signal from an ADC, specified as a scalar.

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

Indicates whether the analog to digital conversion is complete, specified as a scalar.

Data Types: double

External conversion start clock, specified as a scalar. The analog to digital conversion process starts at the rising edge of the signal at the start port.

Data Types: double

Parameters

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Type of distortion the ADC AC Measurement block is set to measure, specified as Harmonic or Intermodulation.

Programmatic Use

Block parameter: DistortionMeasurement
Type: character vector
Values: Harmonic | Intermodulation
Default: Harmonic

Frequency of the analog input signal to an ADC block, specified as a positive real scalar or positive real valued vector in hertz. Analog stimulus frequency must match the input frequency to the ADC device under test.

  • When the ADC AC Measurement is set to measure the Harmonic distortion, the default value of Analog stimulus frequency is 10000.

  • When the ADC AC Measurement is set to measure the Intermodulation distortion, the default value of Analog stimulus frequency is [9000,11000].

Analog stimulus frequency must not share any common multiples other than 1 with the Start conversion frequency.

To satisfy this condition, use the equation fanalog=JMfstart,

where:

fanalog is the analog signal frequency,

fstart is the start conversion frequency,

J is the number of cycles of the stimulus per FFT window,

and M is the number of FFT points.

Note

J is selected as the largest prime number less than one tenth of the number of FFT points. The minimum value of M is allowed to be 16.

Programmatic Use

Block parameter: InputFrequency
Type: character vector
Values: positive real scalar | positive real valued vector
Default: 10000

Select the spectrum estimation method as one of the following:

  • Filter bank — Use an analysis filter bank to estimate the power spectrum. Compared to Welch's method, this method has a lower noise floor, better frequency resolution, lower spectral leakage, and requires fewer samples per update. For more information, see Spectrum Estimation — Filter Bank

  • Welch — Use Welch's method of averaged modified periodograms. For more information, see Spectrum Estimation — Welch's Method

Programmatic Use

Block parameter: Method
Type: character vector
Values: Filter bank | Welch
Default: Filter bank

Resolution bandwidth, specified as a positive real scalar in hertz. This parameter defines the smallest positive frequency that can be resolved. By default, this parameter is calculated automatically. You can deselect Set automatically to customize the value.

Programmatic Use

Block parameter: RBW
Type: character vector
Values: positive real scalar
Default: 976.5625

Frequency of the start conversion clock of the ADC, specified as a positive real scalar in hertz. Start conversion frequency must match the frequency of the start conversion clock of the ADC block.

Programmatic Use

Block parameter: Frequency
Type: character vector
Values: positive real scalar
Default: 1e6

Delays measurement analysis to avoid corruption by transients, specified as a nonnegative real scalar in seconds.

Programmatic Use

Block parameter: HoldOffTime
Type: character vector
Values: nonnegative real scalar
Default: 0

Minimum time the simulation must run to obtain meaningful results, specified as a positive real scalar in seconds.

For AC measurement, the simulation must run so that the ADC can generate 6 spectral updates of the ADC output. The time to generate one spectral output based on Welch's method is given by:

t=1.5·SamplingFrequencyRBW

where SamplingFrequency and RBW are the sampling frequency and resolution bandwidth of the spectrum estimator inside the ADC Testbench block.

This parameter is only reported by the testbench and is not editable.

Data Types: double

Click to automatically set the Recommended min. simulation stop time (s) as the stop time of the Simulink® model.

Store detailed test results in the base workspace for further processing at the end of simulation. By default, this option is not selected.

Name of the variable that stores detailed test results, specified as a character string.

Dependencies

This parameter is only available when Output result to base workspace is selected.

Programmatic Use

Block parameter: VariableName
Type: character vector
Values: character string
Default: adc_ac_out

Displays spectrum analyzer during simulation. By default, this option is not selected.

Programmatic Use: Add Block

To add the block programmatically, use the add_block function with one of these library block paths as the source.

"msbAdcMeasurements/ADC AC Measurement"

Example: add_block("msbAdcMeasurements/ADC AC Measurement","myModel/myBlock",MakeNameUnique="on")

For information about programmatic access to individual block parameters, see the Programmatic Use section of parameter descriptions on this page.

More About

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Version History

Introduced in R2019a

See Also

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