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##### Member level 2

In general, the total harmonic distortion (THD) is measured as:

input x(t)=2*sin(wt) is applied to the ADC, and output y(t) is measured. Then THD is calculated from y(t) as

THD(V/V) = (v_s)^2 / {(v_xh1)^2 + (v_xh2)^2 + ...} (eq.1)

where v_s: signal magnitude in voltage, v_xh1: harmonic magnitude in voltage, ...

Due to some reason, I need to measure the THD differently. Here is my procedure:

One at a time, 2 different sine inputs are applied to a flash ADC with +/-2v input range.

That is,

input x1(t) = sin(wt)+1 : this input swings from 0v to 2v, and output y1(t) was measured.

input x2(t) = sin(wt)-1 : this input swings from -2v to 0v, and output y2(t) was measured.

So, each input stimulates upper input range (0~2v) and lower input range(-2~0v) of the ADC.

Only using y1(t) and y2(t) outputs, the same overall THD, which was calculated in (eq.1), should be calculated.

For y1(t),

THD1(V/V) = (v_s1)^2 / {(v_x1h1)^2 + (v_x1h2)^2 + ...} (eq.2)

where v_s1: signal magnitude in voltage, v_x1h1: harmonic magnitude in voltage, ...

For y2(t),

THD2(V/V) = (v_s2)^2 / {(v_x2h1)^2 + (v_x2h2)^2 + ...} (eq.3)

where v_s2: signal magnitude in voltage, v_x2h1: harmonic magnitude in voltage, ...

I'm stuck at this status now.

Could you help to calculate the same THD shown in (eq.1), using (eq.2) and (eq.3)?