ADC AC Measurement

Measure AC performance metrics of ADC output

  • Library:
  • 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 signal at the start port indicates when the analog to digital conversion process starts.

Data Types: double

Parameters

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Number of physical bits in ADC, specified as a unitless positive real integer. Number of bits must match the resolution specified in the ADC block.

Programmatic Use

  • Use get_param(gcb,'NBits') to view the current Number of bits.

  • Use set_param(gcb,'NBits',value) to set Number of bits to a specific value.

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

Analog signal frequency needs to satisfy two requirements:

  • All the output codes of the ADC must be activated.

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

To satisfy both the conditions, use the equation fanalog=JMfstart [2],

where:

fanalog is the analog signal frequency,

fstart is the start conversion frequency,

M>2Nbits·π, where Nbits is the number of bits of the ADC,

and J is an integer with no common factors with M.

Programmatic Use

  • Use get_param(gcb,'InputFrequency') to view the current value of Input signal frequency.

  • Use set_param(gcb,'InputFrequency',value) to set Input signal frequency to a specific value.

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

  • Use get_param(gcb,'Frequency') to view the current value of Start conversion frequency.

  • Use set_param(gcb,'Frequency',value) to set Start conversion frequency to a specific value.

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

Programmatic Use

  • Use get_param(gcb,'HoldOffTime') to view the current value of Hold off time.

  • Use set_param(gcb,'HoldOffTime',value) to set Hold off time to a specific value.

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 [1] 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

  • Use get_param(gcb,'VariableName') to view the current value of Workspace variable name.

  • Use set_param(gcb,'VariableName',value) to set Workspace variable name to a specific value.

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

More About

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References

[1] Spectrum Analyzer, DSP System Toolbox, MathWorks Documentation.

[2] IEEE Std 1241-2010. "IEEE Standard for Terminology and Test Methods for Analog-to-Digital Converters," pp. 29-30, 14 January 2011.

Introduced in R2019a