DAC AC Measurement
Libraries:
Mixed-Signal Blockset /
DAC /
Measurements & Testbenches
Description
The DAC AC Measurement block measures DAC 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), and noise floor. You can use DAC AC Measurement block to validate the DAC architecture models provided in Mixed-Signal Blockset™, or you can use a DAC of your own implementation
Examples
Ports
Input
digital — Digital input signal from DAC
scalar
Digital input signal from a DAC, specified as a scalar.
Data Types: fixed point
| single
| double
| int8
| int16
| int32
| uint8
| uint16
| uint32
analog — Converted analog signal from DAC
scalar
Converted analog signal from a DAC, specified as a scalar.
Data Types: double
start — External clock to start conversion
scalar
External clock to start conversion, specified as a scalar. This port determines when digital-to-analog conversion process starts.
Data Types: double
Parameters
Digital signal frequency (Hz) — Frequency of digital input signal to DAC
1e3
(default) | positive real scalar
Frequency of the digital input signal to the DAC block, specified as a positive real scalar in hertz. Digital signal frequency (Hz) must match the input frequency of the DAC device under test.
Digital input frequency (Hz) needs to satisfy two requirements:
All the output codes of the DAC must be activated.
The Digital signal frequency (Hz) must not share any common multiples other than 1 with the Conversion start frequency (Hz).
Programmatic Use
Block parameter:
InputFrequency |
Type: character vector |
Values: positive real scalar |
Default:
1e3 |
Data Types: double
Start conversion frequency (Hz) — Frequency of internal start conversion clock
1e6
(default) | positive real scalar
Frequency of the internal start conversion clock, specified as a real scalar in Hz. The Start conversion frequency parameter determines the conversion rate at the start of conversion.
Programmatic Use
Block parameter:
StartFreq |
Type: character vector |
Values: positive real scalar |
Default:
1e6 |
Data Types: double
Settling time tolerance (LSB) — Tolerance for calculating settling time
0.5
(default) | positive real scalar
The tolerance allowed for calculating settling time, specified as a positive real scalar in LSB. The output of the DAC must settle within the Settling time tolerance (LSB) by Settling time (s).
Programmatic Use
Block parameter:
SettlingTimeTolerance |
Type: character vector |
Values: positive real scalar |
Default:
0.5 |
Data Types: double
Hold off time (s) — Delay before measurement analysis to avoid corruption by transients
0
(default) | nonnegative real scalar
Delay before 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 |
Recommended simulation stop time (s) — Minimum time simulation must run for meaningful result
0.09
(default) | positive real scalar
Minimum time the simulation must run to obtain meaningful results, specified as a positive real scalar in seconds.
To measure AC performance, the simulation must run so that the DAC can generate six spectral updates of the DAC output. So, the Recommended simulation stop time (s) T is given by [1]:
,
where RBW is the resolution bandwidth of the spectrum estimator inside the DAC Testbench block and is given by the equation: .
This parameter is only reported by the block and is not editable.
Data Types: double
Output result to base workspace — Store detailed test results to base workspace
off (default) | on
Store detailed test results to a struct in the base workspace for further processing at the end of simulation. By default, this parameter is deselected.
Workspace variable name — Name of the variable that stores detailed test results
dac_ac_out
(default) | character string
Name of the variable that stores detailed test results, specified as a character string.
Dependencies
To enable this parameter, select Output result to base workspace parameter.
Programmatic Use
Block parameter:
VariableName |
Type: character vector |
Values: character string |
Default:
dac_ac_out |
Show spectrum analyzer during simulation — Displays Spectrum Analyzer during simulation
on (default) | off
Select this parameter to display the Spectrum Analyzer window during simulation. By default, this parameter is selected.
More About
SNR
Signal-to-noise ratio or SNR is the ratio of the RMS (root-mean-square) signal amplitude to the mean value of the root-sum-squares (RSS) of all other spectral components, excluding the DC and first five harmonics.
SINAD
Signal to noise and distortion ratio or SINAD is the ratio of the RMS signal amplitude to the mean value of the root-sum-squares of all other spectral components and harmonics, excluding DC.
SFDR
Spurious free dynamic range or SFDR is the ratio of the RMS signal amplitude to the RMS value of the peak spurious content, measured over the entire first Nyquist zone (DC to half of sampling frequency).
ENOB
Effective number of bits or ENOB represents the actual resolution of a DAC after considering internal noise and errors. It is given by .
Version History
Introduced in R2020a
See Also
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