Hello, These measurements are fairly standard and common to any EVM. I always use Audio Precision(AP)   to send the digital input and clocks and  do the measurement.  

I put the general description and procedure for AP here, if you are not using AP ,  you can use it as a guide to do your own  measurements:

For THD you need 3 things:

1-Digital generator to create pulses 

2-Analog analyzer to measure the analog signal generated at the output of DAC or LP filter 

3- sweep window to do the sweep.

THD vs Power

THD vs Power

In Sweep window Data1  and data2 are the values that will be plotted on Y-axis on left and right vs parameters that is being swept by Source 1 (on X-axis), which in this case it is the Digital Generator Amplitude. Note that in order to avoid OCP event, we start the sweep from -18DBFS  to -100dBFS .

Also note “X-Y Data2 on X”  is being selected which means it will plot data1 on Y axis and Data 2 on X axis . It is similar to the traditional plot from any simulation.

When it sweeps the power, for a given power on the x-axis, it adjust the amplitude according to boundary that is given in Source 1 to get the target power, then in measures THD+N for the obtained  power. Then moves to the next power, adjust the power by changing the amplitude within the given range, then calculates THD+N for this power and keeps going on until the last point on power axis.

While the sweep is going on,  you can monitor the amplitude in Dig Gen. and you see it is sweeping according to the range you put in Siurce1 .

THD vs freq,

If we want to plot THD vs Freq, simply select X-Y  and for Data 2 select “None” . For Source1  select DGen  freq  and set start and stop freq. The plot will be TDH vs freq. for the given amplitude that you have in Digital generator.

Dynamic Range using FFT

Dynamic Range is an expression of the ratio of the largest signal a device can pass to the device’s noise floor. “Largest signal” usually refers to a signal at a specified degree of distortion, often 1%.

Signal-to-Noise Ratio and Dynamic Range are essentially the same measurement, except that the signal in SNR is arbitrary and should be stated in the results, and the signal in Dynamic Range is at the maximum.

How do you define what the loudest signal is that a device can reproduce? Then, when you measure the noise level, over what bandwidth do you measure and do you apply any weighting filters?
The AES17 standard specifies the maximum output amplitude of a device as its highest undistorted output and defines an undistorted output as one with less than 1% THD+N.

For noise level, the  AES17 standard specifies that the device be measured with a sinusoidal signal at 997Hz with amplitude 60dB below the maximum signal amplitude. This is in order to ensure that the channel is not muted and the noise is measured in the presence of a signal. The tone itself is removed by using a band reject filter. This is what we usually refer to 60dB method in data sheets.

To do this test, we regulate the THD to 1% as shown in the set up here. Note the amplitude needed to yield  this THD is -3.31 dBFS 

In order to calculate dynamic range we need to get into  FFT function.  For doing this

• In digital analyzer panel, select FFT spectrum analyzer. Set other parameters as shown below.
• Set the amplitude of Digital generator to -3.141 ( the 1% THD that was measured in previous step. 
• Hit F4, it writes this value in dBr A in Analog analyzer as a reference.
• Now change the amplitude of your signal to -60dB in digital Analyzer and turn on the outputs again. 
• Change the amplitude to Band Reject in Analog analyzer so it removes the -60db tone; the value you read is  Noise level for -60dB input.
• Add the reference (dBr A) to this value and this is your dynamic range, from above measurement for TAS2770 we get   DR of  88.23+17.71= 105.938.

SNR measurement in essence  is very similar to DR measurements with one defining characteristics: in  dynamic range, the ratio of the strongest to the weakest signal is measured where as for   (SNR), the ratio of a given signal to the noise in the system is measured.

• The dynamic range is limited at the lower end by the noise in the system and at the higher end by the level at which the greatest signal can be presented without distortion  (A 1% THD is assumed as standard level for measurement as described above)

• The SNR equals the dynamic range when a signal of the greatest possible amplitude is present and  is smaller than the dynamic range when a smaller signal is present.

Regards,

Arash